Tracking system and method of operation

Abstract

A method of operating a sports tracking system for tracking the positions of objects moving around a playing area includes the steps of: arranging at least three tracking devices around the playing area, each tracking device having a straight-line distance measuring unit; arranging a reference device at least at a first location; for each tracking device and the reference device, calculating a straight-line distance between said tracking device or the reference device and at least three other tracking devices and / or the reference device using the straight-line distance measuring unit to create a set of straight-line distance measurements; creating a device topology of the at least three tracking devices based on the set of straight-line distance measurements; and determining an arrangement of the device topology relative to the playing area based on the straight-line distance measurements to at least the first location and a known relationship between at least the first location and a first reference point.

Description

[Technical Field]

[0001] The present invention relates to a tracking system and method of operation for tracking the position of an object moving around a tracking area, and in particular to a sports tracking system for tracking the position of an object, such as a player or a ball, moving around a playing area, especially a sports field. [Background technology]

[0002] Many conventional tracking systems use a network of fixed or mobile tracking devices, commonly referred to as "anchors," to locate a number of mobile devices, commonly referred to as "tags." One example of such a tracking system is an ultra-wideband (UWB) tracking system, which uses an array of UWB anchors to track the location of one or more UWB tags using distance measurements possible using radio frequency messages. However, to accurately track the location of tags using anchor devices, the relative positions of the anchor devices, i.e., the device topology, must be known, and the absolute positions with respect to the coordinate system in which the tags are tracked must be known.

[0003] In many applications, a coordinate system for the tracking area is established using well-known surveying techniques and equipment. One such standard piece of surveying hardware is a total station, which can locate objects with millimeter or sub-millimeter accuracy. Once stationary UWB anchors are installed around the tracking area, a coordinate system is established using the total station, and the positions of the fixed anchors are determined relative to that coordinate system.

[0004] Once a coordinate system is established with high precision and the location of the anchors is known, the location of the tag relative to the established coordinate system can be calculated using several techniques well known to those skilled in the art, such as multilateration.

[0005] As an example, in sports applications, anchors are often installed in stadiums within stands, especially under I-beams supporting seating tiers. For these fixed installations, using a total station to determine anchor locations very accurately during installation is efficient because the procedure only needs to be performed once and the devices do not move for years. However, there are situations in which using a total station (or other equivalent surveying technology) is too costly, cumbersome, and restrictive. For example, in systems that must be transportable and capable of rapid deployment, such technology is impractical. Alternatively, anchors installed around training fields where field lines are regularly repainted also need to be periodically recalibrated, which is costly and operationally burdensome. Furthermore, if the anchor's location changes—for example, because the anchor is moved by maintenance workers or the fixture to which the anchor is attached is moved—the entire system must be recalibrated before it can be used again; otherwise, data will be compromised by inaccurate anchor locations.

[0006] Although UWB is specifically mentioned above, the same set of problems is applicable to camera tracking systems that use a combination of video and computer vision algorithms to track objects of interest. If the camera moves for any reason, the entire system needs to be recalibrated.

[0007] It is therefore desirable to provide a faster, more convenient and more cost-effective solution for operating a tracking system. Summary of the Invention

[0008] According to a first aspect of the present invention, there is provided a method of operating a tracking system, in particular a sports tracking system, for tracking the position of objects moving around a tracking area, in particular a playing area, the method comprising the steps of: arranging at least three tracking devices around the tracking area, each tracking device comprising a straight-line distance measuring unit; arranging a reference device at least at a first position, the reference device comprising the straight-line distance measuring unit, the at least first position having a known relationship to a first reference point in the playing area, the straight-line distance measuring unit being configured to enable straight-line distances between each tracking device or the reference device and the at least three other tracking devices and / or the reference device to be measured; for each tracking device and the reference device, calculating using the straight-line distance measuring unit the straight-line distances between said tracking device or the reference device and the at least three other tracking devices and / or the reference device to create a set of straight-line distance measurements; creating a device topology of the at least three tracking devices based on the set of straight-line distance measurements; and determining an arrangement of the device topology relative to the playing area based on the straight-line distance measurements to the at least first position and the known relationship of the at least first position to the first reference point.

[0009] This method uses linear distance measurement units located on the tracking devices themselves to establish the relative positions of the tracking devices and create a device topology. As described in more detail below, each linear distance measurement unit is typically a transmitter and / or receiver, allowing pairs of the linear distance measurement units to measure the linear distance between them. The device topology established using a set of linear distance measurements is fixed to a coordinate system by placing a reference device at a reference position within the tracking area and measuring the distance to the reference position, for example, using the linear distance measurement unit of the tracking device. In a particularly preferred embodiment, the device topology is created and then fixed relative to the playing area, although it is also possible to create the device topology within a reference frame already fixed to the playing area, i.e., by using a reference device in a starting set of devices when creating the topology. This technique prioritizes convenience over precision by having the tracking devices themselves contribute measurements used to establish the device topology and its position relative to the coordinate system in which the object is to be tracked. The result is a tracking system that is simple, cost-effective, and fast to set up and operate, allowing for rapid deployment and recalibration of large tracking systems.

[0010] The tracking device is typically placed at an unknown location, e.g., at any convenient location around the playing area (although this is not required). In contrast, the reference device is placed at least in part at a defined location such that there is a predetermined, known relationship between the location of the reference device and one or more reference points and / or reference directions within the playing area, as described in more detail below. In other words, the known relationship should be predetermined, i.e., known without straight-line distance measurements.

[0011] The present technology is preferably a method of operating a sports tracking system for tracking the positions of objects moving around a playing area, such as a sports field. However, the technology can also be used in other types of tracking systems, such as warehouses, music concerts, or television studios. In the sports tracking system, preferably, multiple tracking devices (most preferably each tracking device) are positioned outside the playing area, for example, outside the sports field. However, alternatively, the tracking devices may be positioned, for example, above the sports field.

[0012] The tracking devices herein each include a linear distance measurement unit that allows the linear distance between each tracking device or reference device and at least three other tracking devices and / or reference devices to be measured. It will be appreciated that the present invention may be used with more than three tracking devices (indeed, this is preferred), but in many setups, particularly around sports fields, where the devices can be assumed to be arranged in a single plane, three tracking devices are sufficient to establish a device topology and then track objects around the tracking area. When more than three tracking devices are used, typically each tracking device has a linear distance measurement unit that allows it to measure linear distances to each other and to the reference device, although the topology can still be established without measurements between each tracking device and all other devices. When the tracking devices are not arranged in the same plane, i.e., in the same plane as the tracked object on the playing field, at least four tracking devices are preferred, with each tracking device equipped with a linear distance measurement unit configured to allow linear distances to be measured to at least three, and preferably at least four, other tracking devices and / or reference devices, although again typically they measure linear distances to each other and to the reference device.

[0013] This technique also includes placing a reference device at at least a first location and using a linear distance measuring unit to measure the linear distance to the first location. As described above, the first location should be at least partially defined. For example, a user of the system may be instructed to place the reference device on a specific field marking or somewhere along one of the field lines of a sports field. This is because this step is used to obtain information about the device topology relative to the first reference point within the tracking area to establish the position of the tracking device relative to the coordinate system in which the object is tracked. Note that at least the first location has a predetermined "known relationship" with the first reference point, meaning that the location does not necessarily correspond to the first reference point but provides information about the location of the first reference point. For example, the first location may be on the first reference point or offset from the first reference point by a known distance, which may be taken into account when determining the placement of the device topology relative to the tracking area. Alternatively, if multiple reference devices are used, two reference devices may be positioned so that the first reference point is at a center point between the devices. This is why it is only required that at least the first position measured using the reference device has a known relationship to the first reference point; i.e., if there are more than only first positions, it may be these positions that have a known relationship to the first reference point.

[0014] By providing a reference device at a first location that has a known (predetermined) relationship with at least a first reference point within the tracking area, it may be possible to accurately map the device topology into the coordinate system of the tracking area.

[0015] In some particularly preferred embodiments, the setup is divided into two separate stages: the topology of the tracked devices is established in an arbitrary reference frame without a reference device, and then the placement of the device topology is determined relative to the tracking area using straight-line distance measurements calculated relative to the reference device. For example, the method includes the steps of: arranging at least three tracked devices around the tracking area, each tracked device comprising a straight-line distance measurement unit configured to measure straight-line distances to at least two other tracked devices among the at least three tracked devices; for each tracked device, calculating straight-line distances between the tracked device and the at least two other tracked devices using the straight-line distance measurement unit to create a set of straight-line distance measurements; creating a device topology for the at least three tracked devices based on the set of straight-line distance measurements; placing a reference device at at least a first position, the at least first position having a known relationship to a first reference point within the tracking area; calculating straight-line distances between each of the at least three tracked devices and the reference device at the first position to create a set of reference measurements; and determining the placement of the device topology relative to the tracking area based on the set of reference measurements.

[0016] It will be appreciated that the above generally describes a method of setting up or calibrating a sports tracking system. A method of operating a sports tracking system typically further comprises, after the steps defined above, the step of tracking one or more objects (preferably mobile electronic devices, i.e., tags) around a playing area using at least three tracking devices, preferably using the linear distance measuring units of the at least three tracking devices.

[0017] In some embodiments, one reference device may be all that is necessary to determine the placement of the device topology relative to the tracking area. For example, if the tracking area is circular with rotational symmetry around a center point, a single reference device may be placed on the center point to determine the placement of the device topology relative to the tracking area. This may require one or more assumptions, such as assuming that the tracking device is located in a plane parallel to the ground of the tracking area. In other embodiments, the reference device may include means for identifying the orientation of the reference device. For example, an embodiment is described below that enables orientation to be determined using phase difference of arrival (PDOA) or angle of arrival (AOA) using a UWB transceiver with multiple antennas. The reference device may then be configured to be placed at a location where the orientation of the reference device is aligned with one or more reference directions of the tracking area, and measurements of the linear distance to the reference device and the orientation of the reference device relative to the device topology can be used to determine the placement of the device topology relative to the tracking area. For example, if the tracking area is a running track, the reference device may be placed at the center of the running track and aligned with the longer dimension of the running track to enable the placement of the device topology relative to the running track to be determined.

[0018] While it may be possible in some scenarios to determine the placement of the device topology relative to the tracking area using only one reference device, most embodiments preferably include placing a reference device at each of at least a first location and a second location, which together have a known relationship to a first reference point within the tracking area and a second reference point or first reference direction within the tracking area, and determining the placement of the device topology relative to the playing area is based on straight-line distance measurements to the first location and the second location and the known relationship of the first location and the second location to the first reference point and the second reference point or the first reference direction. For example, this may include calculating the straight-line distance between each of at least three of the tracking devices and the reference device at the second location. This provides greater flexibility and accuracy for determining the placement of the device topology relative to the tracking area. As described below, if a reference device is required at the first location and the second location, this may include one reference device sequentially placed at the first location and the second location, or two reference devices placed at the first location and the second location, respectively.

[0019] Again, at least the first and second positions should be at least partially defined, and together may have a (predetermined) "known relationship" to the first and second reference points. The first and second positions preferably coincide with the first and second reference points, but there may again be a known offset. In one example, for a soccer pitch of known size, it may be specified that reference devices should be placed on two penalty spots so that the position of the tracking device relative to the field can be determined using measurements between the tracking device and the first and second reference points. Furthermore, at least the first and second positions may have a "known relationship" to a first reference direction. The devices may be spaced along the direction of the reference direction, for example, along one of the field lines, but may also be spaced at a known angle to the reference direction, for example, perpendicular to the field lines, if desired. In a second example, for a rugby field of known size, one reference device may be placed at one corner of the try line and touch line, and another reference device may be spaced from the first reference device along the touch line. This may provide information about the reference points, i.e. the corners of the try lines and touch lines, and the reference direction, i.e. the direction of the touch lines in which the two reference devices are spaced apart. These are just two examples given in a particular sports context, and it will be appreciated that any system of reference points for positioning device topology relative to a reference in a coordinate scheme for tracking may be used.

[0020] While the system may be set up with two reference devices in some situations, it is often preferable to use an additional reference device to extract information about the tracking area. Thus, preferably, the method includes placing a reference device at a third location, at least partially defined such that the first, second, and third locations are not along a straight line; preferably, the third location, together with the first and / or second locations, has a known relationship to a second reference direction within the tracking area; and determining the placement of the device topology relative to the playing area is based on linear distance measurements to the third location and the known relationship between the third location and the first and / or second locations and the second reference direction; preferably, determining the placement of the device topology relative to the tracking area is further based on the order of the first, second, and third locations. In many applications, measurements relative to the reference device at the third location are required to properly orient the device topology toward an area of interest, such as a sports field. For example, three locations that are not along a straight line can enable the system to identify a plane, such as the plane of a sports field, regardless of the placement of the device topology relative to this plane. Measurements relative to the reference device at the third location can also allow the system to identify a second reference direction within the tracking area. Continuing with the previous rugby field example, the third location could be located somewhere along the try line, such that the first location, along with the third location, is at the corner of the try line and the touch line, allowing the system to identify the direction of both the try line and the touch line. A series of three locations can also convey information through the order of the locations, for example, in a manner similar to the "right-hand rule." This could be used such that three locations are used to measure a plane, e.g., ground level, and the order of the locations is used to identify which direction is up in a direction perpendicular to the plane. Alternatively, note that the order of the tracking devices themselves can be used to determine the placement of the device topology relative to the tracking area.For example, each tracking device may be numbered and the setup may require the tracking devices to be placed clockwise around a sports field, with up being determined in a manner similar to the "right-hand rule."Again, in these examples, there may be a separate reference device placed at each location, or one or more reference devices may be moved sequentially between locations to measure location with fewer reference devices.

[0021] As described above, the first, second, and third positions preferably define a plane substantially parallel to the ground, e.g., a sports field, within the tracking area. This allows the system to identify the plane of the sports field. The or each reference device may, for example, be located substantially at ground level. Alternatively, one or more reference devices may be located at a known height above ground level. For example, one or more reference devices may be provided on a support, such as a tripod, having a known height. To identify ground level, the system may take the known height of the reference device into account when using measurements for the reference device.

[0022] In many embodiments, the first reference point is a point of interest in a coordinate system where the object is to be tracked. For example, the first reference point can be the intersection of the halfway line and the touchline on a rugby pitch. A preferred way of obtaining information about this reference point is to provide a first location with a known positional relationship to the first reference point, and most preferably, the first location substantially coincides with the first reference point. The reference device need not be physically located on the first reference point, although this is preferred. For example, if a game is currently in progress, the reference device may need to be located 5 meters from the reference point. However, if this offset is known, the reference point may still be identified using measurements to the reference device at the first location. Note that it is not necessary to locate a reference device with a known positional relationship to the first reference point. For example, two reference devices may be located at arbitrary intervals along the halfway line of a rugby field, and two reference devices may be located at arbitrary intervals along the touchline. In this case, the orientation of the two lines can be determined from the reference measurements, and therefore the reference position, i.e., the intersection of these two lines, can be determined from a combination of positions.

[0023] Regardless of how the reference device is positioned, preferably, a linear distance measurement to the reference position is further used to measure at least one dimension of the tracking area. Note that this may include linear distance measurements made between the reference devices at at least a first position and a second position. That is, the dimension may be measured either by linear distance measurement from the tracking device to the reference device, or based on direct linear distance measurements between the reference devices, or by some combination thereof. The dimension may be measured by ensuring that at least the first and second positions both have a (predetermined) "known relationship" with respect to the dimension to be measured. The dimension may then be determined by the distance between the positions used for the reference devices.

[0024] Further to the above, preferably, the second location has a known (predetermined) positional relationship to a second reference point within the tracking area, and preferably, the second location substantially coincides with the second reference point. Continuing with the rugby field example above, the second reference point may be the intersection of the same touchline and try line. Again, the reference device may be positioned to coincide with this reference point or may be spaced a known distance from the reference point. An advantage of a system requiring a user to position a reference device with a known positional relationship to two or more reference points is that it can conveniently determine at least one dimension of the tracking area based on a set of linear distance measurements. Continuing with the rugby field example, the system may then be able to measure the distance between the halfway line and the try line, and thus more accurately understand the tracking area. This is preferable, for example, to assuming standard field dimensions or requiring the user to separately input specific field measurements. In a further preferred embodiment, the third location has a known positional relationship to a third reference point within the tracking area, and preferably, the third location substantially coincides with the third reference point. Continuing with the rugby field example, this third reference point could be the intersection of the opposing touchline and the 22-meter line. This builds on the advantages discussed above and allows for additional measurements about the field during setup. Another alternative to placing reference devices at known positions relative to the reference points, as discussed above, is to rely on a combination of reference devices to provide information about one or more reference points along with a reference direction. For example, if pairs of reference devices are arbitrarily spaced along each field line, this would allow for the identification of reference points and the measurement of the distance between these reference points or field lines in order to measure the field. Thus, in a more general case, at least the first and second positions may have a (predetermined) "known relationship" with respect to the dimension being measured, as discussed above. However, this may require the use of reference devices at more positions to obtain the same information about the field.

[0025] As mentioned above, in addition to obtaining information about reference points within the tracking area, it may be desirable to identify a reference direction within the tracking area. One way this can be achieved is by having the first and second positions have a known (predetermined) angular relationship with the first reference direction, and preferably, the first and second positions define a line substantially parallel to the first reference direction. Note that a line parallel to the first reference direction is considered to include a line coinciding with the reference direction. For example, if the reference direction is considered to be defined by one of the touchlines, the first and second positions may be located along that touchline. Generally, it is easiest for a user to position the reference device along the reference direction, for example, along the field lines of a sports field. However, if the angle relative to the reference direction is known, this may provide sufficient information to identify the reference direction within the tracking area.

[0026] As is already clear from the above description, in the most preferred example, the reference points and reference directions correspond to field markings of the sports field within the tracking area. More generally, the first and / or second reference points (and / or any third or further reference points) may correspond to field markings on the sports field within the tracking area. Preferably, the first and / or second reference points (and / or any third or further reference points) correspond to the intersection of at least two field lines on the sports field, and / or the first reference direction corresponds to the direction of a field line on the sports field. Although the examples of reference points already given include the penalty spot on a soccer field or the intersection of the halfway line and the touchline on a rugby field, it will be clear that any field marking may be employed as a reference point when establishing a coordinate system in which the object should be tracked, and further, the direction of any field line can correspond to a reference direction in the coordinate system. Preferably, the set of straight-line distance measurements is further used to measure one or more dimensions of the sports field, for example, using straight-line distance measurements to the first and second positions.

[0027] In a particularly preferred example, the first location is at the intersection of at least two field lines on the sports field within the tracking area, and the second location is located along one of the two field lines from the first location, preferably the second location being at the intersection of a third field line with one of the at least two field lines, such that at least one dimension of the sports field can be determined based on straight-line distance measurements to the first and second locations. As already mentioned, the reference device may be located directly on the field or may be supported above the field, for example on a tripod. This represents a particularly convenient way of determining the placement of the device topology relative to the tracking area and obtaining measurements of one or more dimensions of the field, as it only requires the user to place the reference device at a specific position on the field lines, which is easy for the user to understand and implement.

[0028] As already briefly mentioned above, this technique may involve the use of any number of reference devices for the array of locations from which reference measurements are obtained. For example, a first reference device may be placed at a first location and a second reference device may be placed at a second location, or the first reference device may be placed at a first location, and then the linear distances between each of the at least three tracking devices and the first reference device at the first location may be calculated, and then the first reference device may be placed at a second location. The linear distances between each of the at least three tracking devices at the second location and the first reference device may then be calculated, and the linear distance measurement set may be updated. This principle may be extended to cases where additional locations are used, using anywhere between one reference device and as many reference devices as there are reference locations (i.e., one reference device for each location).

[0029] In particularly preferred embodiments, one or more of the or each reference device is an additional tracking device, and the method further includes the steps of positioning the or each reference device around the tracking area after obtaining linear distance measurements to the corresponding at least first location; calculating linear distances between the or each additional tracking device and the at least three tracking devices using one or more linear distance measurement units; and updating the device topology to include the or each additional tracking device. In these embodiments, the reference devices may each be used as tracking devices once they are used to determine the placement of the device topology relative to the tracking area. For example, the reference devices may be essentially the same hardware as the tracking devices. To do this, once linear distance measurements to the reference device locations are obtained, the device topology needs to be updated to include the reference devices; however, at this stage, the placement of the device topology relative to the tracking area is already known, and therefore the reference devices are no longer needed for their original function. It will be appreciated that the tracking function is enhanced by the additional tracking devices, and this embodiment makes the most efficient use of the hardware used to set up the tracking system. The reference device may be a further tracking device, but alternatively may be a "tag", ie a mobile device that is normally tracked by the tracking device.

[0030] In some embodiments, one or more of the tracking device and / or the reference device comprises a GNSS receiver configured to perform GNSS positioning of the device, and determining the placement of the device topology relative to the tracking region is further based on the GNSS positioning. Using the GNSS positioning has various advantages. For example, the GNSS positioning data may be used for initial coarse alignment of the device topology with the tracking region, or the data may be fused with linear distance measurement data to provide a more accurate coordinate system.

[0031] The method may be performed by a controller, and measurements from each tracked device and / or reference device may be communicated to the controller, which may then calculate straight-line distances, create a device topology, and determine the placement of the device topology relative to the tracking area based on measurements received from the tracked devices (and reference devices).

[0032] One problem with conventional tracking systems is that if one of the tracking devices is moved, the entire system needs to be recalibrated before it can be used again, otherwise data will be corrupted due to tracking inaccuracies in device positions. Therefore, preferably, the method includes the steps of: after creating a device topology, detecting movement of one of the at least three tracking devices (preferably at least four tracking devices) relative to the other tracking devices of the at least three (preferably at least four) tracking devices; recalculating the straight-line distances between the moved tracking device and each of the at least two (preferably at least three) other tracking devices using a straight-line distance measuring unit; and updating the device topology to take into account the movement of the moved tracking device based on the recalculated straight-line distances between the moved tracking device and each of the at least two (preferably at least three) other tracking devices of the at least three (preferably at least four) tracking devices. That is, in this system, because the tracking devices can measure the distances between each other, the device topology can be automatically updated without the need to use surveying equipment again, as in conventional systems. This part of the method is typically performed after an initial calibration, e.g., after the reference device has been removed, and therefore, in order to most accurately reposition a moved tracking device, the method preferably includes at least four tracking devices.

[0033] The method may include, for each tracking device, periodically recalculating the linear distance between the tracking device and at least two other (preferably at least three) tracking devices using a linear distance measurement unit, and detecting movement of one of the at least three tracking devices based on a change in the detected linear distance between the moved tracking device and the at least two other tracking devices after the recalculation. In other words, the tracking device constantly checks the linear distance to the other tracking devices to identify when one device has moved. This can be seen in the data, as one device detects movement of all other devices it is measuring, while the other devices detect only movement of that one tracking device. Additionally or alternatively, each tracking device may further include one or more of an accelerometer, a gyroscope, and a magnetometer, and detecting movement of one of the at least three tracking devices relative to the other tracking devices is based on readings from the accelerometer, gyroscope, and / or magnetometer. Note that including these sensors in tracking devices has other advantages. For example, in some applications, it may be desirable to identify north-south direction as part of a coordinate system, and a magnetometer makes this possible. These sensors also enable a form of dead reckoning to update the location of a device in the topology even when measurements to other tracked devices are blocked, such as when line of sight is blocked.

[0034] The linear distance measurement unit can generate a particularly accurate device topology when the positions of the tracking devices vary in three-dimensional space, i.e., when they are not all substantially in the same plane, resulting in multiple measurements being taken for each device from significantly different directions. Similarly, the linear distance measurement unit can generate an accurate device topology when all tracking devices are located in a single plane, for example, all at the same height above a sports field. However, it is very common for there to be small elevation differences between tracking devices due to infrastructure surrounding the tracking area, which can introduce significant inaccuracies into the device topology. For example, if the tracking devices are all located in approximately the same plane but have elevation differences of up to, for example, one meter, this elevation difference can be very difficult to accurately identify and incorporate into the device topology when linear distances are measured at, for example, 200 meters. Therefore, preferably, each tracking device further includes a pressure sensor configured to measure air pressure at the location of the tracking device, and the method further includes calculating a relative altitude of each tracking device based on the measured air pressure at the location of each tracking device, and creating the device topology is further based on the calculated relative altitude of each tracking device. The or each reference device may also further comprise a pressure sensor configured to measure air pressure at the location of the reference device, in this embodiment, relative height can be estimated reasonably accurately from air pressure measurements at the tracking device.

[0035] The method may further include determining the absolute height of each of the tracking devices. In practice, this may involve providing one or more tracking devices (or reference devices) with known altitudes, and then comparing the pressure readings of each tracking device with the pressure readings of the known devices to determine the absolute altitude of each device.

[0036] Preferably, the one or more reference devices further comprise a pressure sensor configured to measure air pressure at the location of the reference device, and determining the placement of the device topology relative to the tracking region is further based on the pressure measurements of the tracked device and the pressure measurements of the one or more reference devices. Alternatively, altitude may be determined between the tracked devices relative to each other such that the device topology reflects changes in height, and then only the device topology determined relative to the reference device using straight-line distance measurements to the reference location.

[0037] It should be noted that in the above embodiment, pressure naturally varies over time, which affects the pressure measurements made by the devices. Therefore, it may be preferable to take each pressure reading over the same, preferably known, time interval, e.g., two minutes. For example, the readings of one device (or an average of multiple devices), preferably with a known altitude, over the time interval may then be subtracted from the pressure readings of each tracking device to remove natural fluctuations in atmospheric pressure, leaving only the difference caused by altitude differences between the tracking devices.

[0038] The use of pressure sensors is preferably provided in a method comprising positioning at least four tracking devices around the tracking area, each tracking device being positioned in substantially the same plane within a tolerance of 10 meters, preferably within a tolerance of 5 meters, more preferably within a tolerance of 2 meters, and most preferably within a tolerance of 1 meter, and preferably the tracking devices are positioned at least 50 meters, preferably at least 70 meters, more preferably at least 100 meters apart. That is, the use of pressure sensors becomes more beneficial as the different heights between the tracking devices become smaller, i.e., more difficult to measure from straight-line distance measurements, and as the distance between the tracking devices becomes greater, i.e., therefore, the effect on distance caused by height variations has a smaller proportional effect on the total distance measured.

[0039] In many embodiments, the linear distance measuring unit of each tracking device is further configured to enable linear distances between each tracking device and one or more mobile electronic devices moving about the tracking area to be measured. Such a system is particularly advantageous because it makes dual use of the linear distance measuring unit.

[0040] The linear distance measurement unit of each tracking device preferably includes an ultra-wideband (UWB) transmitter and / or receiver, including the use of a UWB transceiver. Preferably, each tracking device includes a UWB transmitter and receiver so that each tracking device can measure the linear distance to each other tracking device. Other examples of suitable linear distance measurement devices include, for example, lidar, ultrasonic, and laser rangefinder units. A UWB transmitter and / or receiver is one example of a linear distance measurement unit that can also measure the distance to a corresponding electronic device that may move through the tracking area.

[0041] Preferably, the linear distance measurement unit of at least one tracking device includes at least a first antenna and a second antenna used in making linear distance measurements, and the method further includes calculating a relative orientation of the at least one tracking device using linear distance measurements obtained using the first antenna and the second antenna. Preferably, multiple tracking devices, preferably each tracking device, each include at least a first antenna and a second antenna, so that an angular orientation can be determined for each of the tracking devices. As described above, the reference device may be configured identically to the tracking device, and therefore one or more, preferably each, reference device may have at least a first antenna and a second antenna, and the method may include calculating the angular orientation of the reference device or each reference device relative to one or more tracking devices. This orientation of the reference device may be used in determining the placement of the device topology relative to the tracking area. The use of at least two antennas may enable orientation to be determined using, for example, the phase difference of arrival (PDOA) or angle of arrival (AOA) of measurements made using the linear distance measurement unit. Two antennas may allow angular orientation to be determined in two-dimensional space, for example, if all devices are known to be located in the same plane. Three antennas may be preferred to allow orientation to be determined in three-dimensional space.

[0042] While an antenna may be preferred for determining orientation, in other embodiments, at least one tracking device includes multiple linear distance measuring units, and the method further includes calculating a linear distance between each of the multiple linear distance measuring units on the at least one tracking device and at least one other tracking device, and calculating a relative orientation of the at least one tracking device based on the difference in the calculated linear distances. Again, preferably, multiple tracking devices, preferably each tracking device, include multiple linear distance measuring units, so that an orientation can be determined for each of the tracking devices. Again, the reference device may be configured in the same way to enable their orientation to be determined. In this case, the orientation is determined based on the difference in linear distance measurements. For example, if a first linear distance measuring unit of one of the tracking devices is measured to be closer to another tracking device than a second linear distance measuring unit on that tracking device, it can be determined that the tracking device is oriented so that the first linear distance measuring unit is closer to the other tracking device. Again, two linear distance measuring units on each tracking device may enable orientation to be determined in two-dimensional space, for example, if all devices are known to be arranged in the same plane as their linear distance measuring units. However, it may be preferable to provide each tracking device with three linear distance measuring units to allow orientation to be determined in three-dimensional space.

[0043] In another example, one or more tracking devices include a camera for optically tracking the position of an object moving around the tracking area. The use of several cameras to track objects in three-dimensional space is known, particularly in various sports. In these embodiments, the distance between the tracking devices must still be measured using a linear distance measurement unit, such as an UWB transmitter and / or receiver. It is particularly preferred if the tracking devices include a camera that allows the orientation of the tracking device to be determined relative to the other tracking devices, for example, using the techniques described above. This is because object tracking with cameras typically requires knowledge of the orientation of each camera. Therefore, if one or more tracking devices include a camera, preferably each of those tracking devices with a camera includes a linear distance measurement unit with at least a first antenna and a second antenna, or at least two linear distance measurement units.

[0044] Preferably, distributing the at least three tracking devices around the tracking area includes stationary disposing of each tracking device around the tracking area. This is in contrast to systems that use UWB transmitters and / or receivers attached to objects, such as players or sports balls, that move around the tracking area. For example, the tracking devices may be attached to an infrastructure around the tracking area or may be provided on a fixed support structure, such as a tripod, that remains in place throughout the tracking process. Preferably, each of the at least three tracking devices remains stationary during one or more subsequent steps of tracking the positions of objects moving around the playing area.

[0045] As mentioned above, preferably, more than three tracking devices are used to improve the accuracy of the tracking process and introduce redundancy with respect to the number and location of the tracking devices. Preferably, the method includes the step of arranging at least four tracking devices, preferably at least six tracking devices, more preferably at least ten tracking devices around the tracking area, and preferably each tracking device is equipped with a linear distance measuring unit configured to enable it to measure the linear distance to at least three other tracking devices. A system with four tracking devices measuring the distance to three other tracking devices is particularly useful when the tracked object is not essentially limited to a single plane, such as a player on a sports field. While more tracking devices still only need to measure the distance to three other tracking devices, typically each tracking device is equipped with a linear distance measuring unit configured to enable it to measure the linear distance to each other tracking device.

[0046] When four or more tracking devices are used, creating a device topology of at least four tracking devices based on the set of linear distance measurements preferably includes identifying a starting set of three tracking devices and / or reference devices based on the magnitude of the linear distance measurements and the difference between the linear distance measurements within the set of linear distance measurements, defining a coordinate system using the linear distance measurements between each of the tracking devices and / or reference devices of the starting set, and then placing the fourth tracking device or reference device within the coordinate system defined for the starting set of tracking devices and / or reference devices based on the linear distance measurements between the fourth tracking device or reference device and each tracking device and / or reference device in the starting set of tracking devices and / or reference devices. Typically, it is desirable to identify a starting set of three tracking devices and / or reference devices that define a relatively large, approximately equilateral triangle, identifiable from the magnitude of the linear distance measurements and the difference between the linear distance measurements. From this starting set, additional tracking devices and / or reference devices can be relatively accurately incorporated into the topology from a robust starting set of tracking devices and / or reference devices. When operating in three-dimensional space, as opposed to tracked and / or reference devices that are all in approximately the same plane, a starting set should be selected based on the magnitude of the linear distance measurements and the differences between the linear distance measurements that define a tetrahedron, and then further tracked and / or reference devices are measured relative to the starting set and incorporated into the device topology.

[0047] Preferably, creating a device topology for at least four tracked devices includes creating a preliminary device topology using each of a plurality of different starting sets of at least three tracked devices and / or reference devices, preferably each possible starting set of at least three tracked devices and / or reference devices, and creating a device topology using the plurality of preliminary device topologies, preferably by averaging the preliminary device topologies. Calibration using the above method is vulnerable to error propagation if only one starting set of devices contains measurement errors. To prevent this, the device topology may be created several times from several different starting sets, as described, and then averaged. This reduces the effect of measurement errors in the starting set. Note that the average may be the average or median position of each device, with the median being more resilient to measurement errors.

[0048] In a particularly preferred embodiment, the method includes comparing preliminary device topologies created from each starting set, disregarding one or more preliminary device topologies, one or more device positions within the one or more preliminary device topologies, or one or more linear distance measurements based on the results of the comparison, and creating a device topology using the remaining multiple preliminary device topologies. In this embodiment, different preliminary device topologies are compared, and discernible measurement errors are taken into account. In particular, an entire topology containing measurement errors may be disregarded, individual device positions within the device topology may be disregarded, or it may be determined which linear distance measurements led to erroneous device positions, the measurements may be disregarded, and the preliminary device topology may be recalculated. For example, most preliminary device topologies can match relative device positions within a relatively small tolerance, and thus, for example, any preliminary device topology that includes one or more device positions that differ from the average device position or device positions of multiple other preliminary device topologies by more than a threshold amount, e.g., 30 cm, preferably 20 cm, more preferably 10 cm, and even more preferably 5 cm, may be ignored, or the device positions in that preliminary device topology may be ignored, or problematic straight-line distance measurements may be ignored to remove measurement error from the calibration process.

[0049] According to a second aspect of the present invention, there is provided a method of operating a sports tracking system for tracking the position of an object moving around a playing area, the method comprising the steps of: fixedly positioning at least three tracking devices around the playing area, each tracking device comprising a linear distance measurement unit configured to enable a linear distance between each of the at least three tracking devices and at least two other tracking devices to be measured, the at least three tracking devices having a known device topology; detecting movement of one of the at least three tracking devices relative to the other of the at least three tracking devices; calculating, using the linear distance measurement unit, a linear distance between the moved tracking device and each of the at least two other tracking devices; and updating the device topology based on the calculated linear distances between the moved tracking device and each of the at least two other tracking devices of the at least three tracking devices to take into account the movement of the moved tracking device.

[0050] Compared to the first aspect of the present invention, this may involve calibrating the system using conventional techniques, such as the use of a total station. However, in this case, if one of the tracking devices is moved, there is no need to recalibrate the system; the device topology is automatically updated. In this case, tracking accuracy may degrade over time, and recalibration may still be required periodically, but this technique prevents significantly inaccurate tracking results due to inaccuracies in the tracking device's position.

[0051] The preferred features described above in relation to the first aspect apply equally to this aspect of the invention, for example this is also preferably a method of operating a sports tracking system for tracking the position of objects moving about a playing area such as a sports field, preferably using more than three tracking devices configured to measure the straight line distance to each other, preferably using straight line distance measurement units in the form of ultra-wideband (UWB) transmitters and / or receivers.

[0052] In this embodiment, each tracking device is fixedly positioned around the tracking area. For example, the tracking devices may be attached to a base structure around the tracking area or may be mounted on a fixed support structure such as a tripod. This is in contrast to tags, which may be attached to objects moving around the tracking area, such as players moving around a sports field. Indeed, in a sports tracking system, each tracking device is preferably positioned outside the playing area, e.g., outside the sports field. In conventional tracking systems, fixed tracking devices are not expected to move, and therefore any change in the position of one of these fixed anchors would corrupt the tracking data. This is addressed in this embodiment by detecting movement of one of the at least three tracking devices and updating the device topology accordingly. This method may be performed simultaneously with one or more steps of tracking the position of objects moving around the playing area.

[0053] The technique for updating the device topology in consideration of movement of one of the tracking devices is the same as described above. Preferably, detecting movement of one of the at least three tracking devices includes, for each tracking device, periodically calculating the linear distance between the tracking device and at least two other tracking devices (preferably each of them) using a linear distance measuring unit, and detecting movement of one of the at least three tracking devices based on changes in the detected linear distances between the moved tracking device and the at least two other tracking devices after the calculation. In other words, the tracking device constantly checks the linear distances to the other tracking devices to identify when one device has moved. This can be seen in the data, as one device detects movement of all other devices it is measuring, while the other devices only detect movement of that one tracking device. Additionally or alternatively, each tracking device may further include one or more of an accelerometer, a gyroscope, and a magnetometer, and detecting movement of one of the at least three tracking devices relative to the other tracking devices is based on readings from the accelerometer, gyroscope, and / or magnetometer.

[0054] Also as mentioned above, each tracking device preferably further comprises a pressure sensor configured to measure air pressure at the location of the tracking device, and the method further includes calculating a relative altitude of each tracking device based on the measured air pressure at the location of each tracking device, and updating the device topology is further based on the calculated relative altitude of each tracking device. This can be particularly useful when device movement includes raising or lowering a tracking device relative to other devices, especially when the tracking devices are in approximately the same plane.

[0055] According to a third aspect of the present invention, there is provided a method of operating a sports tracking system for tracking the position of objects moving around a playing area, the method comprising the steps of: arranging at least three tracking devices around the tracking area, each tracking device comprising a straight-line distance measuring unit configured to enable a straight-line distance between each tracking device and at least two other tracking devices of the at least three tracking devices to be measured, and a pressure sensor configured to measure air pressure at a location of the tracking device; for each tracking device, calculating a straight-line distance between said tracking device and the at least two other tracking devices using the straight-line distance measuring unit to create a set of straight-line distance measurements; calculating a relative altitude of each tracking device based on the measured air pressure at the location of each tracking device; and creating a device topology of the at least three tracking devices based on the set of straight-line distance measurements and the calculated relative altitude of each tracking device.

[0056] Again, the preferred features discussed above in relation to the first aspect apply equally to this aspect of the invention, for example this is also preferably a method of operating a sports tracking system for tracking the position of objects moving about a playing area such as a sports field, preferably using more than three tracking devices configured to measure the straight line distance to each other, preferably using straight line distance measuring units in the form of ultra-wideband (UWB) transmitters and / or receivers.

[0057] Compared to the first aspect of the present invention, this technique uses both linear distance measurements and pressure measurements to establish the device topology, however the position of the device topology relative to the tracking area, e.g. a sports field, may be determined in any known manner, including the use of a calibration device such as a total station.

[0058] As in the first aspect, the method may further include determining the absolute height of each of the tracking devices, for example by providing one or more tracking devices (or reference devices) with known altitudes, and then comparing the pressure readings of each tracking device with pressure readings of known devices to determine the absolute altitude of each device.

[0059] Again, it is preferable to take each pressure reading over the same time interval, preferably a known time interval, for example 2 minutes, and then subtract the reading of one device (or an average of multiple devices), preferably the known device, over the time interval, and then to remove natural fluctuations in atmospheric pressure, one may subtract one from the pressure reading of each tracked device over the time interval, leaving only the difference caused by the altitude difference of the tracked devices.

[0060] As mentioned above, preferably the method includes positioning at least four tracking devices around the tracking area, each tracking device positioned in substantially the same plane within a tolerance of 10 metres, preferably within a tolerance of 5 metres, more preferably within a tolerance of 2 metres, and most preferably within a tolerance of 1 meter, and preferably the tracking devices are positioned at least 50 metres, preferably at least 70 metres, more preferably at least 100 metres apart.

[0061] According to a fourth aspect of the present invention, there is provided a sports tracking system for tracking positions of objects moving around a playing area, the system comprising: at least three tracking devices configured to be arranged around the playing area, each tracking device comprising a straight-line distance measuring unit; a reference device comprising a straight-line distance measuring unit configured to enable a straight-line distance between each tracking device or the reference device and at least three other tracking devices and / or the reference device to be measured; and a data processing unit configured to create a device topology of the at least three tracking devices based on a set of straight-line distance measurements calculated for each tracking device and the reference device between said tracking device or the reference device and the at least three other tracking devices and / or the reference device using the straight-line distance measuring unit, the set of straight-line distance measurements comprising straight-line distance measurements calculated for each tracking device and the reference device, wherein the data processing unit is further configured to receive straight-line distance measurements to the reference device arranged at least at a first position, the at least first position having a known relationship to a first reference point within the playing area, and the data processing unit is further configured to determine a placement of the device topology relative to the playing area based on the straight-line distance measurements to the at least first position and the known relationship between the at least first position and the first reference point.

[0062] This corresponds to a system suitable for use with the method of the first aspect of the invention, and therefore all preferred features discussed above in relation to the first aspect apply equally to a system according to this aspect.

[0063] According to a fifth aspect of the present invention, there is provided a sports tracking system for tracking the position of objects moving around a playing area, the system comprising: at least three tracking devices configured to be arranged around a playing area having a known device topology, each tracking device comprising a straight-line distance measurement unit configured to enable measuring straight-line distances between each tracking device and at least two other tracking devices of the at least three tracking devices to produce a set of straight-line distance measurements; and a data processing unit configured to detect movement of one of the at least three tracking devices relative to the other tracking devices of the at least three tracking devices, and to update the device topology to take into account movement of the moved tracking device based on the set of straight-line distance measurements.

[0064] This corresponds to a system suitable for use with the method of the second aspect of the invention, and again all of the preferred features discussed above apply equally to this system.

[0065] According to a sixth aspect of the present invention there is provided a sports tracking system for tracking the position of an object moving around a playing area, the system comprising at least three tracking devices configured to be positioned around the tracking area, each tracking device comprising a straight line distance measuring unit configured to enable measuring straight line distances between each tracking device and at least two other tracking devices of the at least three tracking devices to produce a set of straight line distance measurements, and a pressure sensor configured to measure air pressure at the location of the tracking device.

[0066] This corresponds to a system suitable for use with the method of the third aspect of the invention, and again all of the preferred features discussed above apply equally to this system.

[0067] Preferably, the system further comprises a data processing unit configured to calculate the relative altitude of each tracking device based on the measured barometric pressure at the location of each tracking device, and to create a device topology of the at least three tracking devices based on the set of straight-line distance measurements and the estimated relative altitude of each tracking device, which may operate as described above in relation to the third aspect of the invention.

[0068] The present invention will now be described with reference to the accompanying drawings. [Brief explanation of the drawings]

[0069] [Figure 1] 1 is a schematic diagram of the arrangement of elements of a sports tracking system around a sports field during setup. [Figure 2] 1 is a schematic diagram of the structure of a tracking device of a sports tracking system. FIG. [Figure 3] 1 is a schematic diagram of the structure of certain elements of a sports tracking system. [Figure 4] 1 is a flow chart illustrating the setup of a sports tracking system. [Figure 5] 1 is a flow chart illustrating the operation of the sports tracking system. [Figure 6] FIG. 1 is a schematic diagram of creating a tracking device topology for a sports tracking system. [Figure 7] FIG. 10 is another schematic diagram of creating a tracking device topology for a sports tracking system. [Figure 8] FIG. 1 is a schematic diagram of determining the placement of a tracking device topology relative to a sports field. [Figure 9] FIG. 10 is another schematic diagram of determining the placement of tracking device topology relative to a sports field. [Figure 10] FIG. 10 is yet another schematic diagram of determining the placement of tracking device topology relative to a sports field. DETAILED DESCRIPTION OF THE INVENTION

[0070] FIG. 1 shows elements of a sports tracking system during setup. The sports tracking system is installed on a rugby field 10. As previously mentioned, the technology is applicable to other sports fields or playing areas, including non-sports situations such as tracking objects in warehouses, music concerts, or television studios. The tracking system comprises an array of tracking devices 100. The tracking devices are positioned around the sports field 10 outside the field markings. For example, the tracking devices 100 may be fixed to convenient infrastructure around the sports field or supported on a fixed support, such as a tripod, positioned outside the field markings. In this embodiment, twelve tracking devices are used, although any number of tracking devices greater than three is possible. Generally, more tracking devices improve the tracking capabilities of the system and provide redundancy for tracking devices in the event of any malfunction or failure. The tracking devices 100 are distributed relatively evenly around the sports field, which also improves the tracking capabilities of the system.

[0071] FIG. 2 shows the structure of tracking device 100. Tracking device 100 includes an ultra-wideband (UWB) transceiver 110 that functions as a linear distance measurement unit. This UWB transceiver preferably includes three spaced antennas used to transmit and receive UWB signals, with the antennas arranged in a triangle, although the tracking device could alternatively include three separate UWB transceivers that are also not arranged in a straight line. The tracking device also includes a communications module for communicating with central computer 300, shown in FIG. 3. The communications module may be any means of transferring data to central computer 300, including Wi-Fi, a wired Ethernet port, Bluetooth, or the like. In some embodiments, a UWB transceiver can be used to transfer data to central computer 300, in which case a dedicated communications module 120 is not required. Tracking device 100 also includes a GNSS receiver, such as a GPS receiver, configured to obtain position measurements using GNSS. In some embodiments, the tracking device may include a camera 140, and tracking is intended to be optical tracking of objects on sports field 10. Tracking systems often utilize high-speed cameras, although any camera may be used in this context. Finally, the tracking devices include a series of micro-electromechanical systems (MEMS) sensors 150, including a pressure sensor 151, an accelerometer 152, a gyroscope 153, and a magnetometer 154. Each tracking device may be battery-powered (not shown in FIG. 2), preferably using a rechargeable battery, for convenient portability. Alternatively, the tracking devices may include a connector cable for powering them by an external power source, such as mains power.

[0072] As also shown in FIG. 1 , the sports tracking system includes a plurality of mobile electronic devices, or tags, positioned on the field 10. If the tracking devices are intended to track objects using UWB transceivers 110, the tags 50 may include corresponding UWB transceivers for communicating with the tracking devices. While FIG. 2 shows only two tags 50 on the field, it will be understood that more tags may be used (e.g., if each player wears a tag 50) or only one may be used (e.g., if the system is intended only to track the ball during play). Note also that if tracking is optical, using, for example, cameras 140, there may not be a tag 50 required for the tracking system to operate.

[0073] 1 also shows three reference devices 200 placed on the sports field. In particular, a first reference device 200a is placed at the intersection of the halfway line and one of the touchlines, a second reference device 200b is placed at the intersection of the same touchline and one of the trylines, and a third reference device 200c is placed at the intersection of the opposite touchline and the 22-meter line between the halfway line and the same tryline. In a preferred embodiment, the reference devices are configured identically to the tracking device 100 shown and described with respect to FIG. 2.

[0074] Figure 3 shows a portion of a sports tracking system similar to that shown in Figure 1. In particular, this figure shows how a central computer 300 (not shown in Figure 1) and two tracking devices 100 communicate with each other. In this embodiment, each tracking device includes only a UWB transceiver 110, a communication module 120, and a MEMS sensor 150. It should be noted that while Figure 3 shows the interaction of two tracking devices 100, the reference device 200 is preferably configured identically to the tracking devices, so the illustrated communication applies equally to communication between a tracking device 100 and a reference device 200.

[0075] As shown in FIG. 3 , the UWB transceiver 110 of each tracking device 100 is configured to communicate with the UWB transceivers of each other tracking device 100, although only two are shown in FIG. 3 . This communication between the UWB transceivers 110 of each tracking device 100 allows the distance between the two tracking devices to be established, for example, using time-of-flight (TOF) or time-difference-of-arrival (TDOA). The relative orientation of the tracking devices may also be determined using phase-difference-of-arrival (PDOA) or angle-of-arrival (AOA), as measured using three separate antennas on each UWB transceiver. The tracking devices also collect data using their respective MEMS sensors 150. Data from the UWB transceivers and MEMS sensors of each tracking device 100 is communicated to a central computer 300 via their respective communication modules 120. The central computer 300 includes a controller 310 and a communication module 320. The communications module 320 receives UWB and MEMS sensor data from the tracking devices and passes it to the controller 310. The controller is responsible for interpreting the data received from all tracking devices during system calibration and operation, as described below.

[0076] FIG. 4 illustrates a method for setting up and calibrating a tracking system. First, in step S100, tracking devices 100 are positioned around the perimeter of the tracking area. In this step, the tracking devices 100 should be positioned in the locations they are intended to occupy during operation of the tracking system. However, as described below, the system may be configured to account for movement of the tracking devices 100 after calibration. In the example of FIG. 1, the tracking devices are positioned around the sports field, each located outside the sports field. The tracking devices should be positioned so that each has a clear line of sight with at least two other tracking devices, preferably at least three other tracking devices, and more preferably at least four other tracking devices. In the most preferred case, each tracking device 100 has a clear line of sight with each other tracking device. Step S100 depends on the particular area to be tracked. For example, in a sports field with closely spaced stands, one or more tracking devices may need to be positioned within or above the stands. Other tracking devices 100 may be placed on support structures, such as tripods, intended to be positioned around the tracking area. As will be explained further below, three of the tracking devices 100 are preferably arranged to define a large, approximately equilateral triangle, which may be taken into consideration when positioning the tracking devices. As mentioned above, to ensure good tracking capabilities, the tracking devices are also preferably arranged relatively evenly around the sports field, for example, with at least two on each side of the sports field.

[0077] In step S110, the straight-line distance between each of the tracking devices 100 is calculated using their UWB transceivers 110. For example, each of the tracking devices 100 may transmit a TOF signal to each of the other tracking devices using their UWB transceivers 110. From this TOF data transmitted from the tracking devices 100 to the computer 300 using the communication modules, the controller 310 may calculate the straight-line distance between each of the tracking devices.

[0078] In step S120, air pressure is measured at each tracking device over a two-minute interval using the respective pressure sensor 151. Note that although step S120 is shown as occurring after step S110, these steps may occur at least partially simultaneously or may be reversed. The pressure measurements from each tracking device are then passed to computer 300 using communication modules 120, 320.

[0079] Although the illustrated method uses only straight-line distance and pressure measurements, the method may also include collecting GNSS position data using the GNSS receiver 130 of each tracking device and transmitting this to the controller 310.

[0080] In step S130, the controller 310 uses the received data to create a device topology that reflects the location of the tracking device 100 around the sports field 10. In this embodiment, the device topology is based on both linear distance measurements and pressure data calculated from the UWB TOF data. Figures 6 and 7 illustrate this process of creating the device topology.

[0081] The first part of this step may involve determining the relative height difference of the tracking devices 100 based on the measured pressure. This may involve first comparing the pressure readings of each tracking device 100 to a first tracking device or several tracking devices placed at a known height. This may require the height of the device to be measured, or the tracking device may be placed on a tripod at a known height, for example. The measured pressure readings at this first tracking device over a two-minute period may then be subtracted from the pressure readings of the other tracking devices over the same two-minute period to remove natural fluctuations in atmospheric pressure. The resulting difference in the measured pressure of each tracking device can then be converted to a height difference of the tracking devices.

[0082] The controller 310 may then begin constructing a device topology by selecting a starting set of three tracking devices 100 for this substantially two-dimensional arrangement of tracking devices. An ideal starting set of tracking devices 100 is a large, approximately equilateral triangle. This may be identified from straight-line distance measurements. In particular, a set of three tracking devices with large straight-line distance measurements between themselves, as well as straight-line distances between themselves with low variance, is preferred. FIG. 6 shows a suitable starting set of tracking devices in this particular example, with dashed lines indicating the distance measurements of this starting set. Here, two tracking devices are selected adjacent to one touchline of the rugby field 10, located at either end of the touchline, and a third tracking device is selected adjacent to the opposite touchline at the same height as the halfway line.

[0083] Once these three tracking devices 100 are selected, one of the tracking devices may be designated as the origin P0, and the position P1 of one of the remaining devices may be selected to define the x-axis. The position of the third device may be asserted to be in the y-direction from the tracking device designated as the origin. The unit vector for x may then be found as follows:

number

number

number

number

number

number

[0084] Once the first three tracking devices have been placed within the coordinate system, additional tracking devices may now be added to the coordinate system. Any one of the remaining tracking devices 100 may then be selected for incorporation into the device topology, as shown in FIG. 7 . FIG. 7 illustrates the straight-line distance measurements between the starting set of tracking devices 100 with solid lines, and the straight-line distance measurements between each of these tracking devices in the starting set and the next tracking device to be added with dashed lines. Once a coordinate system has been established and three straight-line distance measurements from the starting set of tracking devices 100 have already been placed in the coordinate system, the location of the next tracking device can be determined in the same way as finding the intersection of three circles centered on each of the tracking devices 100 in the starting set, with radii defined as the straight-line distances measured to the next tracking device.

[0085] This step may be repeated for subsequent tracking devices until all tracking devices are located within the defined coordinate system. It will be appreciated that each additional tracking device 100 may be incorporated to help prevent error propagation based solely on straight-line distance measurements relative to the starting set, or to any three tracking devices already located within the coordinate system, or to more than three tracking devices for further certainty of position.

[0086] Optionally, the method may repeat the above process for generating a device topology for each possible starting set of tracked devices. This generates as many device topologies (referred to in this context as preliminary device topologies) as there are unique starting sets of tracked devices. Each of these preliminary device topologies may then be compared to account for measurement errors in the starting set. The position of each device in each preliminary device topology may be compared to the average position of that device determined from all other device topologies. If the position of any device in any preliminary device topology differs from the average position by, for example, more than 5 cm, that preliminary device topology may be ignored, or the device position in that preliminary device topology may be ignored. Alternatively, the comparison may be used to identify which one or more linear distance measurements resulted in an erroneous calculated device position, and those measurements may be ignored. In this case, the preliminary device topology may need to be updated. Once each preliminary device topology has been evaluated in this manner, the device topology to be used in the remainder of the method may be established, for example, by averaging the device positions in the remaining preliminary device topologies. This process may also be performed as a random sample consensus where the process iteratively repeats the steps of estimating device locations based on preliminary device topology, for example by taking the average (e.g., median), and ignoring information associated with any outliers that deviate from the estimated device location by a threshold amount. This iterative process gradually refines the estimation until all remaining data matches within the threshold amount.

[0087] Once the position of each of the tracked devices has been established within the device topology, the orientation of each of those tracked devices can be set relative to one another. As described above, the relative orientation of the tracked devices may be determined using PDOA or AOA, as determined by measurements made with the three antennas of each UWB transceiver.

[0088] With device positions and orientations calculated using only linear distance measurements, their height can be optimized by incorporating pressure data. The calculated positions define a new topology that can be compared to the set of UWB measurements originally acquired. These topologies can be represented as two matrices of inter-device measurements. If the UWB measurements are accurate, the device's calculated position will be accurate, and the two matrices will be identical. However, due to measurement noise and normal variability, the calculated position will not be exact. At this stage, a stochastic optimization algorithm can be used to optimize the position so that the calculated topology matches both the original UWB measurements and the pressure sensor data, while incorporating pressure sensor data to ensure the correct relative height difference between anchors. This can be achieved by minimizing an objective function:

[0089] It will be understood that the above example is considered two-dimensional in nature. However, the technique applies equally to a three-dimensional arrangement of tracking devices. Instead of identifying a starting set of three tracking devices that define an equilateral triangle, a starting set of four tracking devices that define a tetrahedron with sides of approximately equal length is required. A coordinate system is defined in essentially the same manner as described above for the three starting sets, and a fourth device is added as the solution of the intersection of three spheres centered on the first three tracking devices and with a radius determined by the measured distance to the fourth tracking device. Additional tracking devices can then be incorporated again by the intersection of four or more spheres. This may be repeated for each starting set in the same manner as described above.

[0090] Once all tracking devices have been placed in the coordinate system initially defined for the starting set of tracking devices, a device topology is known that indicates the relative position in space of each tracking device 100. However, at this stage the location of these devices relative to the area to be tracked, i.e. the sports field 10, is not known.

[0091] Once the device topology is created, three reference devices 200 are placed within the tracking area in step S140. While step S140 is described as occurring after steps S100-S130, this step can also be performed before or during any of the preceding steps. As noted above, the reference devices may be configured identically to the tracked devices 100.

[0092] As mentioned above, in this embodiment, the first reference device 200a is placed at the intersection of the halfway line and one of the touchlines of the rugby field 10, the second reference device 200b is placed at the intersection of the same touchline and one of the trylines, and the third reference device 200c is placed at the intersection of the opposite touchline and the 22 metre line between the halfway line and the same tryline on which the second reference device is placed. These reference devices may be placed directly on the field or on tripods, for example at a known height above the field.

[0093] Note that this placement of the reference devices allows for the dimensions of the field to be measured. In particular, the distance between the first and second reference devices indicates the distance between the try line and the halfway line. The perpendicular distance between the third reference device and the line connecting the first and second reference devices indicates the distance between the opposing touch lines. These distances can be determined directly using measurements between the reference devices, as they have UWB transceivers themselves, or can be determined using distance measurements between the tracking device 100 and the reference devices, or some combination. It will also be appreciated that additional combinations of reference devices can be used to determine more dimensions of the pitch, if desired. In this embodiment, opposing halves of the pitch are assumed to be the same size, but this can also be confirmed with additional reference devices 200.

[0094] In step S150, the straight-line distance between each tracking device 100 and each reference device 200 is calculated using their UWB transceivers 110. For example, each tracking device 100 may transmit a TOF signal to each reference device using their UWB transceiver 110. From this TOF data transmitted from the tracking device 100 to the computer 300 using the communication module, the controller 310 may calculate the straight-line distance between each tracking device 100 and each reference device 200.

[0095] It should also be noted that this method may include pressure data being acquired at the reference device 200 and the tracking device 100. The pressure data for the reference device may be acquired simultaneously with the tracking devices, i.e., in step S120, if all devices are positioned at that stage, or pressure data may be collected for all devices again after step S140. This pressure data may be used again in subsequent steps to determine the height difference between the reference device and the tracking device, as described above.

[0096] Finally, in step S160, the method includes determining a placement of the created device topology relative to the sports field based on the linear distance measurements and based on any pressure measurements taken by the reference device. Figures 8-10 illustrate this process.

[0097] Figure 8 shows a first reference device 200a positioned in a coordinate system relative to the tracking device 100. While Figure 8 shows straight-line distance measurements between four of the tracking devices 100 and the reference device 200a with dashed lines, it will be understood that straight-line distance measurements from all tracking devices 100 could be used if such measurements were available. Based on these straight-line distance measurements, the controller can establish the position of each tracking device relative to the intersection of the halfway line and touchline of the rugby field. This reference point may be designated the origin of the coordinate system, although alternatively, the origin may be arbitrarily set relative to this reference point.

[0098] Knowing the relative position of the tracking device topology with respect to one point on the field is not sufficient to fix the sports field in a coordinate system. For example, the sports field can rotate in the coordinate system around this fixed reference point and still satisfy the measured distance between the tracking device 100 and the first reference device 200a. Therefore, at least a second reference device is required to fix the sports field in the coordinate system.

[0099] FIG. 9 shows a second reference device 200b positioned in a coordinate system relative to the tracking device 100. The figure shows measurements relative to the first reference device 200a with solid lines representing that this point is fixed in the coordinate system at this point, and dashed lines showing straight-line distance measurements between four of the tracking devices 100 and the second reference device 200b. Again, straight-line distance measurements from all tracking devices 100 are preferably used, but these are not shown in the figure for clarity. Based on these straight-line distance measurements, the controller 310 can establish the position of each tracking device 100 relative to the intersection of the try lines and touchlines of the rugby field 10. Note also that the controller can determine a reference direction in the coordinate system, i.e., the direction of the touchlines of the rugby field, based on these measurements.

[0100] In some embodiments, fixing two such reference points within a coordinate system may be sufficient to fix the rugby field 10 within the coordinate system. For example, an assumption may be made that the plane of the tracking device is the same as the plane of the rugby field. However, in this embodiment, measurements relative to a third reference device are used to fix the rugby field 10 within the coordinate system.

[0101] FIG. 10 shows a third reference device 200c positioned in a coordinate system relative to the tracking devices 100. The figure shows measurements for the first and second reference devices 200a, 200b with solid lines representing that these points are fixed in the coordinate system at this point, and dashed lines showing straight-line distance measurements between four of the tracking devices 100 and the third reference device 200c. Again, straight-line distance measurements from all tracking devices 100 are preferably used, but these are not shown in the figure for clarity. Based on these straight-line distance measurements, the controller 310 can establish the position of each tracking device 100 relative to the intersection of the 22-meter line and the touchline of the rugby field 10. Note also that the controller can determine a second reference direction in the coordinate system based on these measurements, namely the direction of the halfway line, try line, and 22-meter line of the rugby field.

[0102] Note that even if these three reference points are fixed within the coordinate system of the tracking device, the vertical direction may still be unknown, i.e., it may not be known which side of the flat sports field the game will be played on. Again, this can be resolved, for example, by making assumptions about the height of the tracking device relative to the height of the reference devices. However, the reference devices may be numbered sequentially, and the order of the reference devices on the field may be used to ascertain the vertical direction. For example, the reference devices may need to be positioned sequentially counterclockwise from above the sports field to convey this information.

[0103] Once the topology of the tracking device has been established relative to a coordinate system and the sports field is fixed within this coordinate system, the tracking system is now calibrated and is able to track the movement of objects such as tags 50 within the tracking system's coordinate system.

[0104] It should also be noted that the reference device 200 here can be moved outside the sports field 10 and used to function as an additional tracking device after calibration has been performed. In this case, the location of the reference device 200 (in its role as a tracking device) needs to be incorporated into the tracking device topology. This may be achieved by placing the reference device 200 at a desired location around the sports field 10 and then adding the reference device to the device topology in the same manner as described above with respect to FIG. 7. In particular, the straight-line distance measurements between any of the existing tracking devices 100 and each reference device may be used to place the reference device in a coordinate system in the same manner as finding the intersection of a circle centered on the existing tracking device 100, with its radius defined as the straight-line distance measured to the reference device that will be used as a tracking device.

[0105] While the above method is described as generating a device topology using only tracked devices and then using measurements relative to reference devices to fix the topology to the coordinate system of the sports field, the method can also build a combined device topology for all tracked devices and reference devices in a single process. That is, steps 110-130 may be performed while treating the reference devices identically to tracked devices and measuring the linear distances between the reference devices and other tracked devices and / or reference devices to determine a topology including both sets of devices. In this case, the placement of the device topology relative to the playing area can be determined as soon as the reference devices are included in the device topology, because the positions of those reference devices provide knowledge of the reference points within the playing area. For example, if the reference devices constitute a starting set, the placement of the tracked devices relative to the playing area may be known because the tracked devices are included in the device topology. The reference devices can then be removed from the device topology at the end of the process, leaving only tracked devices with known placement relative to the playing area.

[0106] As mentioned above, a problem with this type of tracking system is that any movement of the tracking device can corrupt the tracking data. Figure 5 shows a method for addressing this problem.

[0107] The method of Figure 5 begins with a sports tracking system that has been set up and calibrated. This method may follow the calibration steps just described, or may be used after any other calibration technique, including those described in the Background section above.

[0108] In step S200, the tracking system monitors and detects movement of one of the tracking devices. Movement of the tracking device can be detected in several ways.

[0109] A first way in which movement can be detected is based on distance measurements taken between tracking devices in a tracking system. That is, the system may be configured to periodically use the UWB transceiver 110 of each tracking device 100 to transmit a TOF signal to each other tracking device 100. From this TOF data transmitted from the tracking device 100 to the computer 300 using the communication module, the controller 310 may check the straight-line distance between each tracking device. Movement of one of the tracking devices may be identified from this data, i.e., based on changes in the measured straight-line distance. Movement of one of the tracking devices relative to the other tracking devices is typically identifiable because the moved tracking device will see a straight-line distance measurement change until substantially all of the other tracking devices see a change in the straight-line distance measurement of the moved tracking device, while substantially all of the other tracking devices see a change in the straight-line distance measurement of the moved tracking device while the others remain substantially the same.

[0110] An alternative way in which movement may be detected is by using measurements from one or more of the MEMS sensors: pressure sensor 151 (for vertical movement), accelerometer 152, gyroscope 153, and magnetometer 154. Again, the controller may monitor data from these sensors to identify when the tracking device has moved.

[0111] If movement is detected, the straight line distance between the moved tracking device and each other tracking device is calculated in step S210, in the same manner as described above for step S110.

[0112] In optional step S220, the barometric pressure of each tracking device is measured, again in a manner similar to step S120. This step allows the system to be updated to reflect any changes in the height of the tracking device 100 that has been moved.

[0113] Finally, in step S230, the position of the moved tracking device within the device topology is updated based on the measured linear distance and any pressure measurements. This process is similar to the process described above, particularly with reference to Figure 7. That is, the new position of the moved tracking device 100 can be determined in the same way as finding the intersection of circles centered on each of the other tracking devices and whose radius is defined as the linear distance measured to the moved tracking device.

[0114] The present invention may be further understood with reference to the following numbered clauses:

[0115] Clause 1. A method of operating a tracking system for tracking a position of an object moving around a tracking area, the method comprising: arranging at least three tracking devices around the tracking area, each tracking device comprising a straight-line distance measurement unit configured to measure a straight-line distance to at least two other tracking devices of the at least three tracking devices; for each tracking device, calculating a straight-line distance between said tracking device and the at least two other tracking devices using the straight-line distance measurement unit to create a set of straight-line distance measurements; creating a device topology of the at least three tracking devices based on the set of straight-line distance measurements; placing a reference device at at least a first location, the at least first location having a known relationship to a first reference point within the tracking area; calculating a straight-line distance between each of at least three of the tracking devices and the reference device at the first location to create a set of reference measurements; and determining an arrangement of the device topology relative to the tracking area based on the set of reference measurements.

[0116] Clause 2. The method of clause 1, comprising the step of placing a reference device at each of at least a first location and a second location, both of which have a known relationship to a first reference point within the tracking area and a second reference point or a first reference direction within the tracking area, and further comprising the step of calculating a straight-line distance between each of at least three of the tracking devices and the reference device at the second location to create a set of reference measurements.

[0117] Clause 3. The method of clause 2, comprising the steps of placing a reference device at a third position such that the first, second and third positions are not along a straight line, the third position having a known relationship, together with the first and / or second positions, to a second reference direction within the tracking area; and using a straight-line distance measuring unit to calculate straight-line distances between each of at least three of the tracking devices at the third position and the reference device to create a set of reference measurements, preferably wherein the step of determining the placement of the device topology relative to the tracking area is further based on the order of the first, second and third positions.

[0118] Clause 4. The method of clause 3, wherein the first, second and third positions define a plane substantially parallel to the sports field within the tracking area.

[0119] Clause 5. The method of any preceding clause, wherein the first location has a known positional relationship to a first reference point within the tracking region, and preferably the first location substantially coincides with the first reference point.

[0120] Clause 6. The method of clause 5, when citing at least clause 2, wherein the second position has a known positional relationship with a second reference point within the tracking region, and preferably the second position substantially coincides with the second reference point.

[0121] Clause 7. The method of clause 6, when referencing at least clause 3, wherein the third position has a known positional relationship with a third reference point within the tracking region, and preferably the third position substantially coincides with the third reference point.

[0122] Clause 8. The method of at least clause 2, wherein the first and second positions have a known angular relationship with a first reference direction, and preferably the first and second positions define a line that is substantially parallel to the first reference direction.

[0123] Clause 9. The method of any of the preceding clauses, wherein the first reference point corresponds to a field marking on the sports field within the tracking area, preferably wherein the first reference point corresponds to an intersection of at least two field lines on the sports field.

[0124] Clause 10. The method of at least clause 2, wherein the first reference direction corresponds to a direction of a field line on a sports field within the tracking area.

[0125] Clause 11. A method as described in at least clause 2, wherein a first position is at an intersection of at least two field lines on a sports field within a tracking area, and a second position is located along one of said two field lines from the first position, preferably the second position is at an intersection of a third field line with one of said at least two field lines, such that at least one dimension of the sports field can be determined based on a set of reference measurements.

[0126] Clause 12. A method as described in at least clause 2, wherein a first reference device is placed at a first location and a second reference device is placed at a second location, or wherein the first reference device is placed at the first location and then the first reference device is placed at the second location after calculating the straight-line distance between each of the at least three tracking devices and the first reference device at the first location.

[0127] Clause 13. The method of any of the preceding clauses, wherein the or each reference device is a further tracking device comprising a linear distance measuring unit configured to measure linear distances to at least two of the at least three tracking devices, and further comprising the steps of: after creating the corresponding sets of reference measurements, positioning the or each reference device around the tracking area; calculating, using the one or more linear distance measuring units, linear distances between at least two of the at least three tracking devices and the further or each reference device; and updating the device topology to include each reference device.

[0128] Clause 14. The method of any of the preceding clauses, wherein one or more of the tracked device and / or reference device comprises a GNSS receiver configured to perform GNSS position measurements of said device, and wherein the step of determining the placement of the device topology relative to the tracking area is further based on the GNSS position measurements.

[0129] Clause 15. The method of any of the preceding clauses, further comprising the steps of: after creating the device topology, detecting a movement of one of the at least three tracking devices relative to the other tracking devices of the at least three tracking devices; recalculating the straight-line distance between the moved tracking device and each of the at least two other tracking devices using a straight-line distance measuring unit; and updating the device topology to take into account the movement of the moved tracking device based on the recalculated straight-line distance between the moved tracking device and each of the at least two other tracking devices of the at least three tracking devices.

[0130] Clause 16. The method of clause 15, comprising the step of, for each tracking device, periodically recalculating a straight-line distance between said tracking device and at least two other tracking devices using a straight-line distance measuring unit, and wherein detecting a movement of one of the at least three tracking devices is based on a change in the detected straight-line distance between said moved tracking device and said other at least two other tracking devices after said recalculation.

[0131] Clause 17. The method of clause 15 or clause 16, wherein each tracking device further comprises one or more of an accelerometer, a gyroscope and a magnetometer, and wherein detecting movement of one of the at least three tracking devices relative to the other tracking devices is based on readings from the accelerometer, gyroscope and / or magnetometer.

[0132] Clause 18. The method of any of the preceding clauses, wherein each tracking device further comprises a pressure sensor configured to measure air pressure at the location of the tracking device, and further comprising calculating a relative altitude of each tracking device based on the measured air pressure at the location of each tracking device, and wherein creating the device topology is further based on the calculated relative altitude of each tracking device.

[0133] Clause 19. A method according to clause 18, comprising the step of positioning at least four tracking devices around the tracking area, each tracking device being positioned in substantially the same plane within a tolerance of 10 metres, preferably within a tolerance of 5 metres, more preferably within a tolerance of 2 metres, and most preferably within a tolerance of 1 meter, and preferably one or more of the tracking devices being positioned at least 50 metres apart, preferably at least 70 metres apart, more preferably at least 100 metres apart.

[0134] Clause 20. The method of any of the preceding clauses, wherein the linear distance measuring unit of each tracking device is further configured to measure linear distances to one or more mobile electronic devices moving around the tracking area.

[0135] Clause 21. The method of any of the preceding clauses, wherein the linear distance measurement unit of each tracking device comprises an ultra-wideband (UWB) transmitter and / or receiver.

[0136] Clause 22. The method of any of the preceding clauses, wherein the linear distance measurement unit of at least one tracking device comprises at least a first antenna and a second antenna for use in making linear distance measurements, and further comprising the step of calculating a relative orientation of said at least one tracking device using linear distance measurements obtained using the first and second antennas.

[0137] Clause 23. The method of any of the preceding clauses, wherein at least one tracking device comprises a plurality of linear distance measuring units, and further comprising the steps of calculating a linear distance between each of the plurality of linear distance measuring units on said at least one tracking device and at least one other tracking device, and calculating a relative orientation of said at least one tracking device based on a difference in the calculated linear distances.

[0138] Clause 24. A method according to any of the preceding clauses, wherein the one or more tracking devices comprise a camera for optically tracking the position of an object moving about a tracking area.

[0139] Clause 25. The method of any of the preceding clauses, wherein the step of disposing at least three tracking devices around the tracking area includes the step of disposing each tracking device fixedly around the tracking area.

[0140] Clause 26. A method according to any of the preceding clauses, comprising the step of distributing at least four tracking devices, preferably at least six tracking devices, more preferably at least ten tracking devices around the tracking area, preferably each tracking device comprising a straight line distance measuring unit configured to measure straight line distances to at least three other tracking devices.

[0141] Clause 27. The method of clause 26, wherein the step of creating a device topology of at least four tracking devices based on the set of straight-line distance measurements includes the steps of identifying a starting set of three tracking devices based on the magnitudes of the straight-line distance measurements and differences between the straight-line distance measurements in the set of straight-line distance measurements, defining a coordinate system using the straight-line distance measurements between each of the tracking devices in the starting set, and then locating the fourth tracking device within the coordinate system defined for the starting set of tracking devices based on the straight-line distance measurements between the fourth tracking device and each tracking device in the starting set of tracking devices.

[0142] Clause 28. A method of operating a tracking system for tracking the position of an object moving around a tracking area, the method comprising the steps of: fixedly arranging at least three tracking devices around the tracking area, each tracking device comprising a linear distance measurement unit configured to measure a linear distance to at least two other tracking devices of the at least three tracking devices, the at least three tracking devices having a known device topology; detecting movement of one of the at least three tracking devices relative to the other tracking devices of the at least three tracking devices; calculating, using the linear distance measurement unit, a linear distance between the moved tracking device and each of the at least two other tracking devices; and updating the device topology to take into account the movement of the moved tracking device based on the calculated linear distances between the moved tracking device and each of the at least two other tracking devices of the at least three tracking devices.

[0143] Clause 29. The method according to clause 28, wherein the step of detecting movement of one of the at least three tracking devices includes the steps of: for each tracking device, periodically calculating a straight-line distance between said tracking device and at least two other tracking devices using a straight-line distance measuring unit; and detecting movement of one of the at least three tracking devices based on a change in the detected straight-line distance between said moved tracking device and said at least two other tracking devices after said calculation.

[0144] Clause 30. The method of clause 28 or clause 29, wherein each tracking device further comprises one or more of an accelerometer, a gyroscope and a magnetometer, and wherein detecting movement of one of the at least three tracking devices relative to the other tracking devices is based on readings from the accelerometer, gyroscope and / or magnetometer.

[0145] Clause 31. The method of any of clauses 28 to 30, wherein each tracking device further comprises a pressure sensor configured to measure air pressure at the location of the tracking device, and further comprising a step of calculating a relative altitude of each tracking device based on the measured air pressure at the location of each tracking device, and wherein the step of updating the device topology is further based on the calculated relative altitude of each tracking device.

[0146] Clause 32. A method of operating a tracking system for tracking the position of an object moving around a tracking area, the method comprising the steps of: arranging at least three tracking devices around the tracking area, each tracking device comprising a straight-line distance measuring unit configured to measure a straight-line distance to at least two other tracking devices of the at least three tracking devices, and a pressure sensor configured to measure air pressure at a location of the tracking device; for each tracking device, calculating the straight-line distance between said tracking device and the at least two other tracking devices using the straight-line distance measuring unit to create a set of straight-line distance measurements; calculating a relative altitude of each tracking device based on the measured air pressure at the location of each tracking device; and creating a device topology of the at least three tracking devices based on the set of straight-line distance measurements and the calculated relative altitude of each tracking device.

[0147] Clause 33. A tracking system for tracking a position of an object moving around a tracking area, comprising: at least three tracking devices configured to be arranged around the tracking area, each tracking device comprising a straight-line distance measurement unit configured to measure straight-line distances to at least two other tracking devices of the at least three tracking devices to create a set of straight-line distance measurements; a data processing unit configured to create a device topology of the at least three tracking devices based on the set of straight-line distance measurements; and at least one reference device configured to be arranged at least at a first position having a known relationship to a first reference point within the tracking area, wherein the data processing unit is further configured to receive the set of reference measurements, the set of reference measurements including straight-line distance measurements between each of the at least three tracking devices and the reference device at the first position, and the data processing unit is further configured to determine a placement of the device topology relative to the tracking area based on the set of reference measurements.

[0148] Clause 34. A tracking system for tracking a position of an object moving around a tracking area, the tracking system comprising: at least three tracking devices configured to be arranged around the tracking area having a known device topology, each tracking device comprising a straight line distance measurement unit configured to measure straight line distances to at least two other tracking devices of the at least three tracking devices to produce a set of straight line distance measurements; and a data processing unit configured to detect movement of one of the at least three tracking devices relative to the other tracking devices of the at least three tracking devices, and to update the device topology to take into account movement of said moved tracking device based on the set of straight line distance measurements.

[0149] Clause 35. A tracking system for tracking the position of an object moving around a tracking area, the tracking system comprising at least three tracking devices configured to be positioned around the tracking area, each tracking device comprising a straight line distance measuring unit configured to measure straight line distances to at least two other tracking devices of the at least three tracking devices to produce a set of straight line distance measurements, and a pressure sensor configured to measure air pressure at the location of the tracking device.

[0150] Clause 36. The tracking system of clause 35, further comprising a data processing device configured to calculate a relative altitude of each tracking device based on the measured barometric pressure at the location of each tracking device, and to create a device topology of the at least three tracking devices based on the set of straight-line distance measurements and the estimated relative altitude of each tracking device.

Claims

1. 1. A method of operating a sports tracking system for tracking the position of an object moving about a playing area, comprising: placing at least three tracking devices around the playing area, each tracking device comprising a linear distance measuring unit; placing a reference device at least at a first location, said reference device comprising a linear distance measuring unit, said at least first location having a known relationship to a first reference point within said playing area; the linear distance measuring unit is configured to enable linear distances between each tracking device or reference device and at least three other tracking devices and / or reference devices to be measured; - for each tracking device and reference device, using the linear distance measurement unit to calculate linear distances between said tracking device or reference device and at least three other tracking devices and / or reference devices to produce a set of linear distance measurements; creating a device topology for the at least three tracked devices based on the set of linear distance measurements; determining a placement of the device topology relative to the playing field based on a straight-line distance measurement to the at least first location and the known relationship between the at least first location and the first reference point; A method comprising:

2. placing a reference device at each of at least the first and second locations, both of which have a known relationship to the first reference point within the playing area and a second reference point or first reference direction within the playing area; 2. The method of claim 1, wherein determining the placement of the device topology relative to the playing area is based on straight-line distance measurements to the first and second locations and known relationships of the first and second locations to the first and second reference points or first reference directions.

3. 3. The method of claim 2, comprising the steps of placing a reference device at each of the first location, the second location, and a third location such that the first, second, and third locations are not along a straight line, the third location having a known relationship, together with the first and / or second location, to a second reference direction within the playing area, and determining the placement of the device topology relative to the playing area is based on straight-line distance measurements to the third location and the known relationship, together with the first and / or second location, of the third location to the second reference direction, and preferably, determining the placement of the device topology relative to the playing area is further based on an order of the first, second, and third locations.

4. The method of claim 3 , wherein the first, second, and third locations define a plane substantially parallel to a sports field within the playing area.

5. 5. The method of claim 1, wherein the first position has a known positional relationship to the first reference point within the playing area, and preferably the first position substantially coincides with the first reference point.

6. The method of claim 5 when relying on at least claim 2, wherein the second position has a known positional relationship to the second reference point within the playing area, and preferably the second position substantially coincides with the second reference point.

7. The method of claim 6 when relying on at least claim 3, wherein the third position has a known positional relationship with a third reference point within the playing area, and preferably the third position substantially coincides with the third reference point.

8. A method according to claim 2, or any of claims 3 to 7 when relying on claim 2, wherein the first and second positions have a known angular relationship with the first reference direction, preferably wherein the first and second positions define a line that is substantially parallel to the first reference direction.

9. 9. The method according to any of the preceding claims, wherein said first reference point corresponds to a field marking on a sports field within said playing area, preferably wherein said first reference point corresponds to an intersection of at least two field lines on said sports field.

10. The method of claim 2 or any of claims 3 to 9 when relying on claim 2, wherein the first reference direction corresponds to the direction of a field line on a sports field within the playing area.

11. 11. The method of claim 2, or any of claims 3 to 10 when relying on claim 2, wherein the first location is at the intersection of at least two field lines on a sports field within the playing area, and the second location is located along one of the two field lines from the first location, preferably the second location is at the intersection of a third field line and one of the at least two field lines, such that at least one dimension of the sports field can be determined based on straight-line distance measurements to the first and second locations.

12. The method of claim 2 or any of claims 3 to 11 when claim 2 is recited, wherein a first reference device is placed at the first position and a second reference device is placed at the second position, or a first reference device is placed at the first position, and then the first reference device is placed at the second position after the linear distances between each of the at least three tracking devices and the first reference device at the first position are calculated.

13. 13. The method of any preceding claim, wherein the or each reference device is a further tracking device, further comprising the steps of: positioning the or each reference device around the playing area after obtaining straight-line distance measurements to the corresponding at least first location; calculating, using the straight-line distance measuring unit, straight-line distances between the or each further tracking device and at least three of the at least three tracking devices; and updating the device topology to include the or each further tracking device.

14. 14. The method of any of claims 1 to 13, wherein one or more of the tracking devices and / or reference devices comprise a GNSS receiver configured to provide GNSS position measurements of the devices, and wherein determining the placement of the device topology relative to the playing field is further based on the GNSS position measurements.

15. 15. The method of claim 1, further comprising the steps of: after creating the device topology, detecting a movement of one of the at least three tracking devices relative to other tracking devices of the at least three tracking devices; using the linear distance measuring unit to recalculate a linear distance between the moved tracking device and each of the at least two other tracking devices; and updating the device topology to take into account the movement of the moved tracking device based on the recalculated linear distances between the moved tracking device and each of the at least two other tracking devices of the at least three tracking devices.

16. 16. The method of claim 15, comprising: for each tracking device, periodically recalculating a straight-line distance between the tracking device and at least two other tracking devices using the straight-line distance measuring unit; and detecting a movement of one of the at least three tracking devices based on a change in the detected straight-line distance between the moved tracking device and the other at least two other tracking devices after the recalculation.

17. 17. The method of claim 15 or claim 16, wherein each tracking device further comprises one or more of an accelerometer, a gyroscope, and a magnetometer, and wherein detecting movement of one of the at least three tracking devices relative to the other tracking devices is based on readings from the accelerometer, gyroscope, and / or magnetometer.

18. 18. The method of any preceding claim, wherein each tracking device further comprises a pressure sensor configured to measure air pressure at the location of the tracking device, and further comprising calculating a relative altitude of each tracking device based on the measured air pressure at the location of each tracking device, and wherein creating the device topology is further based on the calculated relative altitude of each tracking device.

19. 19. A method according to claim 18, comprising the step of positioning at least four tracking devices around the playing area, each tracking device being positioned in substantially the same plane within a tolerance of 10 metres, preferably within a tolerance of 5 metres, more preferably within a tolerance of 2 metres, and most preferably within a tolerance of 1 meter, and preferably one or more of the tracking devices being positioned at least 50 metres apart, preferably at least 70 metres apart, more preferably at least 100 metres apart.

20. 20. The method of any preceding claim, wherein the linear distance measuring unit of each tracking device is further configured to enable linear distances between each tracking device and one or more mobile electronic devices moving around the playing area to be measured.

21. A method according to any preceding claim, wherein each linear distance measuring unit comprises an ultra-wideband (UWB) transmitter and / or receiver.

22. 22. The method of any of claims 1 to 21, wherein the linear distance measurement unit of at least one tracking device comprises at least a first antenna and a second antenna for use in making the linear distance measurements, and further comprising the step of calculating a relative orientation of the at least one tracking device using the linear distance measurements obtained using the first and second antennas.

23. 23. The method of any of claims 1 to 22, wherein at least one tracking device comprises a plurality of linear distance measuring units, and further comprising the steps of: calculating a linear distance between each of the plurality of linear distance measuring units on the at least one tracking device and at least one other tracking device; and calculating a relative orientation of the at least one tracking device based on a difference in the calculated linear distances.

24. A method according to any preceding claim, wherein one or more tracking devices comprise cameras for optically tracking the positions of objects moving around the playing area.

25. The method of any preceding claim, wherein disposing at least three tracking devices around the playing area comprises disposing each tracking device fixedly around the playing area.

26. A method according to any preceding claim, comprising the step of positioning at least four tracking devices, preferably at least six tracking devices, more preferably at least ten tracking devices around the playing area, preferably each tracking device comprising a straight line distance measuring unit configured to enable the straight line distance to at least three other tracking devices to be measured.

27. 27. The method of claim 26, wherein creating a device topology of the at least four tracked devices based on the set of linear distance measurements comprises: identifying a starting set of three tracked and / or reference devices based on magnitudes of the linear distance measurements and differences between the linear distance measurements in the set of linear distance measurements; defining a coordinate system using the linear distance measurements between each of the tracking and / or reference devices of the starting set; and then locating a fourth tracked or reference device within the coordinate system defined for the starting set of tracked and / or reference devices based on the linear distance measurements between the fourth tracked or reference device and each tracking and / or reference device in the starting set of tracked and / or reference devices.

28. 28. The method of claim 26 or 27, wherein creating a device topology for the at least four tracked devices comprises: creating a preliminary device topology using each of a plurality of different starting sets of at least three tracked devices and / or reference devices, preferably each possible starting set of at least three tracked devices and / or reference devices; and creating the device topology using the plurality of preliminary device topologies, preferably by averaging the preliminary device topologies.

29. 29. The method of claim 28, comprising: comparing the preliminary device topologies created from each starting set; disregarding one or more preliminary device topologies, the positions of one or more devices within one or more preliminary device topologies, or one or more straight-line distance measurements based on results of the comparison; and creating the device topology using a plurality of remaining preliminary device topologies.

30. 1. A method of operating a sports tracking system for tracking the position of an object moving about a playing area, comprising: fixedly arranging at least three tracking devices around the playing area, each tracking device comprising a straight-line distance measuring unit configured to enable a straight-line distance between each tracking device and at least two other tracking devices of the at least three tracking devices to be measured, the at least three tracking devices having a known device topology; detecting movement of one of the at least three tracking devices relative to another of the at least three tracking devices; calculating a straight-line distance between the moved tracking device and each of at least two other tracking devices using the straight-line distance measuring unit; updating the device topology to account for the movement of the moved tracking device based on the calculated straight-line distances between the moved tracking device and each of at least two other tracking devices of the at least three tracking devices; A method comprising:

31. 31. The method of claim 30, wherein detecting the movement of one of the at least three tracking devices includes: for each tracking device, periodically calculating a straight-line distance between the tracking device and at least two other tracking devices using the straight-line distance measuring unit; and detecting the movement of one of the at least three tracking devices based on a change in the detected straight-line distance between the moved tracking device and the at least two other tracking devices after the calculation.

32. 32. The method of claim 30 or claim 31, wherein each tracking device further comprises one or more of an accelerometer, a gyroscope, and a magnetometer, and wherein detecting movement of one of the at least three tracking devices relative to the other tracking devices is based on readings from the accelerometer, gyroscope, and / or magnetometer.

33. 33. The method of any of claims 30 to 32, wherein each tracking device further comprises a pressure sensor configured to measure air pressure at the location of the tracking device, and further comprising calculating a relative altitude of each tracking device based on the measured air pressure at the location of each tracking device, and wherein updating the device topology is further based on the calculated relative altitude of each tracking device.

34. 1. A method of operating a sports tracking system for tracking the position of an object moving about a playing area, comprising: placing at least three tracking devices around the playing area, each tracking device comprising a linear distance measuring unit configured to enable a linear distance between each tracking device and at least two other tracking devices of the at least three tracking devices to be measured, and a pressure sensor configured to measure air pressure at the location of the tracking device; for each tracking device, calculating a straight-line distance between said tracking device and at least two other tracking devices using said straight-line distance measurement unit to produce a set of straight-line distance measurements; calculating a relative altitude of each tracking device based on the measured air pressure at the location of each tracking device; creating a device topology for the at least three tracked devices based on the set of straight-line distance measurements and the calculated relative altitude of each tracked device; A method comprising:

35. 1. A sports tracking system for tracking the position of an object moving around a playing area, comprising: at least three tracking devices configured to be positioned around the playing area, each tracking device comprising a linear distance measuring unit; A reference device comprising a linear distance measuring unit, a reference device, wherein the linear distance measurement unit is configured to enable linear distances between each tracking or reference device and at least three other tracking and / or reference devices to be measured; a data processing device configured to use the linear distance measurement unit to create a device topology of the at least three tracked devices based on a set of linear distance measurements comprising linear distance measurements calculated for each tracked device and reference device between the tracked device or reference device and at least three other tracked devices and / or reference devices; Equipped with the data processing device is further configured to receive straight-line distance measurements to the reference device located at at least a first location, the at least first location having a known relationship to a first reference point within the playing area, and the data processing device is further configured to determine a placement of the device topology relative to the playing area based on the straight-line distance measurements to the at least first location and the known relationship between the at least first location and the first reference point. Sports tracking system.

36. 1. A sports tracking system for tracking the position of an object moving around a playing area, comprising: at least three tracking devices configured to be arranged around a playing area having a known device topology, each tracking device comprising a straight-line distance measurement unit configured to enable measuring straight-line distances between each tracking device and at least two other tracking devices of the at least three tracking devices to produce a set of straight-line distance measurements; a data processing device configured to detect movement of one of the at least three tracking devices relative to other tracking devices of the at least three tracking devices, and to update a device topology to take into account the movement of the moved tracking device based on the set of linear distance measurements; A sports tracking system comprising:

37. 1. A sports tracking system for tracking the position of an object moving around a playing area, comprising: At least three tracking devices configured to be positioned around a playing area, each tracking device comprising: a linear distance measurement unit configured to enable measuring linear distances between each tracking device and at least two other tracking devices of the at least three tracking devices to produce a set of linear distance measurements; and a pressure sensor configured to measure air pressure at the location of the tracking device. A sports tracking system comprising:

38. 38. The sports tracking system of claim 37, further comprising a data processing device configured to calculate a relative altitude of each tracking device based on the measured air pressure at the location of each tracking device, and to create a device topology of the at least three tracking devices based on the set of straight-line distance measurements and the estimated relative altitude of each tracking device.

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