Systems and methods for determining a position of a location sensor in a vehicle

Abstract

A method for determining a position of a location sensor (402) in a vehicle (400) relative to a reference point in the vehicle comprises: receiving absolute position data measured by the location sens

Description

TECHNICAL FIELD The present disclosure relates to determining a position of a location sensor in a vehicle. Aspects of the invention relate to a method and system for determining a position of a location sensor in a vehicle, and to computer readable instructions which, when executed by one or more processors cause the one or more processors to performing the method for determining the position of the location sensor in the vehicle. BACKGROUND The present application relates to a location sensor in a vehicle. Manufacturing processes for vehicles involve vehicle testing, for example to test vehicle brakes and lane alignment systems. In brake testing, the vehicle brakes are applied, and the stopping distance is measured. When testing lane alignment systems, the location of the vehicle relative to a lane marking can be used to determine whether the lane assist mechanisms are triggering correctly. In examples such as this, the location of the vehicle (e.g., location of one or more wheels or axles of the vehicle) is used. SUMMARY OF THE INVENTION In certain scenarios, such as vehicle testing as described above, the precise location of a vehicle, and particularly the precise location of one or more reference points (e.g., components / features) of a vehicle is desirable. A Global Positioning System (GPS) sensor may be placed inside the vehicle during vehicle testing but since the GPS sensor only determines the location of the GPS sensor, not the location of the GPS sensor relative to the vehicle itself (e.g. relative to a reference point in the vehicle), the GPS sensor only provides an approximate position of the vehicle and reference point of the vehicle. For example, if the GPS sensor is placed in the boot of the vehicle, the location of the vehicle is approximated to be the location of the GPS sensor in the boot, and if the GPS sensor is placed in the front seat of the vehicle, the location of the vehicle is approximated to be the location of the GPS sensor in the front seat. This results in the measured location of the vehicle being approximately 2 metres apart, without the vehicle having moved position. Embodiments herein address some of these issues amongst others. According to an aspect of the present invention there is provided a method for determining a position of a location sensor in a vehicle relative to a reference point in the vehicle, the location sensor being fixed relative to the reference point. In methods herein, the relative offsets of the location sensor, as the vehicle moves through a predetermined set of manoeuvres, are measured. The offsets are used to determine the position of the location within the vehicle, relative to a reference point in the vehicle, such as e.g. the front wheel axle. The method comprises receiving absolute position data measured by the location sensor when the vehicle is aligned at each of a plurality of predetermined reference positions relative to a reference marker external to the vehicle, the absolute position data indicative of a plurality of absolute positions of the location sensor in a co-ordinate system independent of the vehicle; determining, based on the plurality of predetermined reference positions and on the plurality of absolute positions, the location of the location sensor relative to the reference point in the vehicle; and outputting a signal indicative of the location of the location sensor relative to the reference point in the vehicle. Advantageously, by determining the precise location of the location sensor relative to a reference point of the vehicle (e.g., such as the front or rear axle), it is possible to determine the location of the vehicle and / or the location of particular parts of the vehicle (such as e.g. the wheel position) more precisely from the location sensor data. Determining the location of the vehicle more precisely means that vehicle tests which require knowledge of the location of the vehicle, such as the aforementioned vehicle brake tests, and lane alignment tests, can be carried out more accurately. For example, lane alignment systems are arranged to ensure the vehicle is within the lane boundary markings on a road. Lane alignment tests test whether the lane alignment system of a vehicle correctly identifies when the vehicle is not within the lane boundary markings on the road. Accordingly, determining the location of the vehicle more precisely means that it is possible to determine when the lane alignment system of the vehicle is or is not within the lane boundary markings more accurately. The method may further comprise obtaining reference position data indicative of the plurality of predetermined positions of the vehicle relative to the reference marker external to the vehicle. Determining the location of the location sensor relative to the reference point in the vehicle may comprise: determining a distance between a first absolute position of the location sensor and a second absolute position of the location sensor; and determining a first co-ordinate of the location sensor based on the distance between the first and second absolute positions of the location sensor. Advantageously, a first co-ordinate (e.g., x-coordinate) of the location sensor relative to the reference point in the vehicle can be determined. Determining the location of the location sensor may comprise: determining a distance between a third absolute position of the location sensor and a fourth absolute position of the location sensor; and determining a second co-ordinate of the location sensor based on the distance between the third and fourth absolute positions of the location sensor. Advantageously, a second co-ordinate (e.g., y-coordinate) of the location sensor relative to the reference point in the vehicle can be determined. Determining the first co-ordinate of the location sensor may be carried out using the distance between the first and second positions of the location sensor and a first pre-determined dimension of the vehicle. The first predetermined dimension of the vehicle may for example be the wheelbase of the vehicle. Determining the second co-ordinate of the location sensor may be carried out using the distance between the third and fourth positions of the location sensor and a second pre-determined dimension of the vehicle. The second pre-determined dimension of the vehicle may for example be the trackwidth of the vehicle. The reference marker may be a straight line. Advantageously, by the reference marker being a straight line, the driver can easily position the vehicle in the required predetermined position, for example using a road marking on a vehicle track or marked line of a car parking space. As such, the method may be performed at any location where a straight line can be found such as a road marking or parking bay. Receiving position data measured by the location sensor when the vehicle is aligned at each of the plurality of predetermined reference positions relative to the reference marker external to the vehicle may comprise: receiving position data measured by the location sensor: when a front axle of the vehicle is aligned with the straight line; when a rear axle of the vehicle is aligned with the straight line; when a left side of the vehicle is aligned with the straight line; and when a right side of the vehicle is aligned with the straight line. In orderto align the front axle of the vehicle with the straight line (or any other reference marker external to the vehicle), the driver may drive the vehicle such that the front axle of the vehicle is aligned with the straight line (or other reference marker). To align the rear axle of the vehicle with the straight line (or other reference marker), the driver may drive the vehicle such that the rear axle of the vehicle is aligned with the straight line (or other reference marker). To align the left side of the vehicle with the straight line (or other reference marker), the driver may drive the vehicle such that the left side of the vehicle is aligned with the straight line (or other reference marker). To align the right side of the vehicle with the straight line (or other reference marker), the driver may drive the vehicle such that the right side of the vehicle is aligned with the straight line. The driver may be instructed to carry out such manoeuvres. Advantageously, the driver of the vehicle is able to easily position the vehicle at each of the plurality of predetermined reference positions because the front axle is aligned with the front wheels of the vehicle and the rear axle is aligned with the rear wheels of the vehicle, and the left and right sides of the vehicle are visible from the exterior of the vehicle, allowing the driver or a person situated outside the vehicle to easily and accurately guide the vehicle to the plurality of predetermined reference positions. The method may further comprise receiving an indication when the vehicle is aligned at one or more predetermined reference positions of the plurality of predetermined reference positions. Advantageously, this allows a driver to identify when the vehicle is correctly aligned at one or more of the plurality of predetermined reference positions. The absolute position data may be a bearing. The location sensor may be a global positioning system navigation device. The method may further comprise determining an error in the position of the location sensor relative to the reference point in the vehicle based on a bearing error and vehicle misalignment error. Advantageously, the determined error of the determined position of the location sensor relative to the reference point in the vehicle can be taken into account when using the determined position of the location sensor relative to the reference point, for example when testing vehicle brakes and wheel alignment systems. The signal indicative of the location of the location sensor may comprise a calibration signal configured to calibrate a measurement of a position of the vehicle based on the location of the location sensor relative to the reference point of the vehicle. Advantageously, the calibration signal provides an accurate position of the vehicle taking into account where in the vehicle the location sensor is situated. According to a further aspect of the present invention, there is provided computer readable instructions which, when executed by one or more processors, cause the one or more processors to perform the method described above. According to yet a further aspect of the present invention, there is provided a system for determining a position of a location sensor in a vehicle relative to a reference point in the vehicle, the system comprising: an input configured to receive absolute position data measured by the location sensor when the vehicle is aligned at each of a plurality of predetermined reference positions relative to a reference marker external to the vehicle, the absolute position data indicative of a plurality of absolute positions of the location sensor in a co-ordinate system independent of the vehicle; a processor configured to determine, based on the plurality of predetermined reference positions and on the plurality of absolute positions, the location of the location sensor relative to the reference point in the vehicle; and an output for outputting a signal indicative of the position of the location sensor relative to the reference point in the vehicle. The processor may be configured to: determine a distance between a first absolute position of the location sensor and a second absolute position of the location sensor; and determine a first co-ordinate of the location sensor based on the distance between the first and second absolute positions of the location sensor. Alternatively or additionally, the processor may be configured to determine a distance between a third absolute position of the location sensor and a fourth absolute position of the location sensor; and determine a second co-ordinate of the location sensor based on the distance between the third and fourth absolute positions of the location sensor. Within the scope of this application it is expressly intended that the various aspects, embodiments, examples and alternatives set out in the preceding paragraphs, in the claims and / or in the following description and drawings, and in particular the individual features thereof, may be taken independently or in any combination. That is, all embodiments and / or features of any embodiment can be combined in anyway and / or combination, unless such features are incompatible. The applicant reserves the right to change any originally filed claim or file any new claim accordingly, including the right to amend any originally filed claim to depend from and / or incorporate any feature of any other claim although not originally claimed in that manner. BRIEF DESCRIPTION OF THE DRAWINGS One or more embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 shows a schematic representation of a computer node, according to an embodiment of the present invention; Figure 2 shows a schematic representation of a system for determining a position of a location sensor comprising an input, a processor, and an output; Figure 3 shows a method for determining a position of a location sensor in a vehicle relative to a reference point in accordance with an embodiment of the present invention; Figure 4a shows a vehicle in predetermined reference positions relative to a reference marker according to an embodiment of the invention; Figure 4b shows a vehicle in predetermined reference positions relative to a reference marker according to an embodiment of the invention; Figure 5 shows a vehicle comprising a location sensor according to an embodiment of the invention; Figure 6a shows a vehicle in predetermined reference positions aligned with a reference marker and misaligned with the reference marker; Figure 6b shows a vehicle in predetermined reference positions aligned with a reference marker and misaligned with the reference marker; Figure 7 shows an error margin of a location sensor in a vehicle in predetermined reference positions; Figure 8 shows a vehicle in accordance with an embodiment of the invention. DETAILED DESCRIPTION In brief, in embodiments herein, the location of a location sensor (e.g., a GPS sensor) in a vehicle relative to a feature of a vehicle (e.g. a front or rear axle) is determined by measuring an absolute position of the location sensor when the vehicle is positioned, in turn, at a plurality of predetermined reference positions relative to a reference marker outside the vehicle (e.g. such as a marked line on the ground). The position of the location sensor relative to said feature of the vehicle is then calculated based on the measured absolute positions of the location sensor at the plurality of predetermined reference positions. For example, if the reference marker is a straight line (e.g., painted on the surface of a car park), the location of the location sensor may be determined by receiving position data from the location sensor indicating the position of the location sensor when the vehicle is at a first position relative to the straight line (e.g., with the front axle of the vehicle aligned with the straight line), receiving position data from the location sensor indicating the position of the location sensor when the vehicle is at a second position relative to the straight line (e.g., with the rear axle of the vehicle aligned with the straight line), determining a distance between the first position and second position, and using this distance to determine a first co-ordinate (e.g., x-co-ordinate) of the location sensor relative to a reference point in the vehicle (e.g., the centre point of the rear axle). A second co-ordinate (e.g., a y-co-ordinate) may be determined by receiving position data from the location sensor indicating the position of the location sensor when the vehicle is at a third position relative to the straight line (e.g., with the left side of the vehicle aligned with the straight line), receiving position data from the location sensor indicating the position of the location sensor when the vehicle is at a fourth position relative to the straight line (e.g., with the right side of the vehicle is aligned with the straight line, determining a distance between the third position and fourth position and calculating the second co-ordinate based on the distance between the distance between the third and fourth positions. In this way, by looking at the relative offsets in the recorded locations of the location sensor when the vehicle is placed in the first, second, third and fourth positions, and by knowing e.g. the wheel axle length of the vehicle, the position of the location sensor relative to other parts of the vehicle can be determined. The coordinates / location of the reference marker do not need to be specified or known in the methods herein. The reference marker is used as an aid for the driver to perform their manoeuvres correctly by eye. As such, the method can be performed anywhere, at any time, without the need for specialist equipment or the like. Advantageously, by determining the precise location of the location sensor relative to the reference point of the vehicle (e.g., the front or rear axle), it is possible to determine the location of the vehicle more precisely. Determining the location of the vehicle more precisely means that vehicle tests which require the location of the vehicle, such as vehicle brake tests, and lane alignment tests, can be carried out more accurately. Turning now to Figure 1, embodiments herein may be computer implemented. Figure 1 shows a computer node 100. A node 100 may generally be configured (e.g. operative) to perform any of the methods and functions described herein, such as the method 300 described below. A node 100 comprises a processor 102, a memory 104 and set of instructions 106. The memory 104 holds instruction data (e.g. such as compiled code) representing set of instructions 106. The processor 102 may be configured to communicate with the memory 104 and to execute the set of instructions 106. The set of instructions 106, when executed by the processor 102, may cause the processor to perform any of the methods herein, such as the method 300 described below. The processor (e.g. processing circuitry or logic) 102 may be any type of processor, such as, for example, a central processing unit (CPU), a Graphics Processing Unit (GPU), a Neural Processing Unit (NPU), or any other type of processing unit. Processor 102 may comprise one or more sub-processors, processing units, multi-core processors or modules that are configured to work together in a distributed manner to control the node in the manner described herein. The node 100 may comprise a memory 104. In some embodiments, the memory 104 of the node 100 can be configured to store program code or instructions that can be executed by the processor 102 of the node 100 to perform the functionality described herein. The memory 104 of the node 100, may be configured to store any data or information referred to herein, such as for example, requests, resources, information, data, signals, or similar that are described herein. The processor 102 of the node 100 may be configured to control the memory 104 of the node 100 to store such information. In some embodiments, the node 100 may be a virtual node, e.g. such as a virtual machine or any other containerised computer node. In such embodiments, the processor 102 and the memory 104 may be portions of larger processing and memory resources respectively. In some embodiments herein, as illustrated in Fig. 2, there is provided a system for determining a position of a location sensor in a vehicle relative to a reference point in the vehicle. The system 200 comprises an input 202, a processor 204 as described with respect to Fig. 1, and an output 206. The input 202 comprises an input mechanism for receiving data from other computing modules or nodes. The input mechanism is configured to receive, for example, the absolute position data measured by the location sensor when the vehicle is aligned at each of a plurality of predetermined reference positions relative to the reference marker external to the vehicle. The input mechanism may for example be a receiver or transceiver. The output 206 comprises an output mechanism for sending data, such as the relative position of the location sensor in the vehicle, to other computing modules. The output mechanism may for example be a transceiver or transmitter. Briefly, in both embodiments above, the processor 102; 204 is configured to perform the method described herein. In brief, the processor 102; 204 is configured to receive absolute position data measured by the location sensor when the vehicle is aligned at each of a plurality of predetermined reference positions relative to a reference marker external to the vehicle. The absolute position data is indicative of a plurality of absolute positions of the location sensor in a co-ordinate system independent of the vehicle. The processor is further configured to determine, based on the plurality of predetermined reference positions and on the plurality of absolute positions, the location of the location sensor relative to the reference point in the vehicle. The processor is then configured to output a signal indicative of the position of the location sensor relative to the reference point in the vehicle. It will be appreciated that the system 200 may comprise other components to those illustrated in Fig. 2. For example, the system 200 may comprise a power supply (e.g. mains or battery power supply). The system 200 may further comprise a wireless transmitter and / or wireless receiver to communicate wirelessly with other computing nodes. In some embodiments, the system 200 may have a wired connection with which to communicate with other computing nodes. In some embodiments, the system 200 may further comprise a user input device such as a mouse, keyboard, or touch pad, for receiving input user data. In some embodiments, the system 200 may further comprise a display for displaying any of the data described herein, such as for example, any of the outputs (or intermediate data products) of any of the methods described herein. Turning now to Fig. 3, there is a method 300 for determining a position of a location sensor in a vehicle relative to a reference point in the vehicle. The method can be performed by the computer node 100 described above. It will also be appreciated that the method 300 can be embodied in computer code (e.g., such as in the instructions 106). The method 300 is used to determine the position of a location sensor in a vehicle, relative to a reference point in the vehicle. In embodiments herein, the vehicle is fitted with a location sensor. The location sensor may be fitted at any point to the interior or exterior of the vehicle. Herein the location sensor can be any type of location sensor. For example, the location sensor may be a sensor of a positioning system such as but not limited to a Global Positioning System (GPS), a global navigation satellite system (GNSS), land-based positioning transmitters and local positioning system (LPS). The location sensor may comprise any number of components configured to determine the position of the location sensor, such as but not limited to a gyroscope, magnetometer, and a differential GPS antenna. The location sensor will provide / measure what is referred to herein as “absolute position” data. Absolute position data refers to location data in a co-ordinate system independent of the vehicle (e.g. relative to a GPS co-ordinate system or bearing). The reference point in the vehicle may comprise any fixed feature of the vehicle with a known position within the vehicle. The reference point may for example be, but is not limited to, the centre of the vehicle’s front or rear axle, the centre point of the vehicle, and / or the centre of the steering wheel. In some examples, the method can be used to determine the location of a GPS sensor relative to the centre of a front or rear axle of the vehicle. In a first step, the method comprises receiving 302 absolute position data measured by the location sensor when the vehicle is aligned at each of a plurality of predetermined reference positions relative to the reference marker external to the vehicle, the absolute position data indicative of a plurality of absolute positions of the location sensor in a co-ordinate system independent of the vehicle. In a second step the method comprises determining 304, based on the plurality of predetermined reference positions and on the plurality of absolute positions position data, the location of the location sensor relative to the reference point in the vehicle from the absolute positions of the location sensor at the predetermined reference positions. In a third step the method comprises outputting 306 a signal indicative of the location of the location sensor relative to the reference point in the vehicle. In more detail, the step 302 comprises receiving absolute position data measured by the location sensor when the vehicle is aligned at each of a plurality of predetermined reference positions relative to a reference marker external to the vehicle, the absolute position data indicative of a plurality of absolute positions of the location sensor in a co-ordinate system independent of the vehicle. Absolute position data may comprise the absolute position, or simply the position, of the location sensor. Absolute position may refer to an absolute or fixed value of the location. The absolute position data is indicative of a plurality of absolute positions of the location sensor (i.e., at the plurality of reference positions) in a co-ordinate system independent of the vehicle. The co-ordinate system independent of the vehicle may for example refer to a geographic co-ordinate system. It will be appreciated that the absolute position data could take all manner of forms. For example, the absolute position data may be in terms of longitude and latitude measurements, x and y co-ordinates, a bearing, heading, angle relative to true north or magnetic north, or any other data that can be used by a location sensor to report its position. When the absolute position data is a heading or bearing, the location sensor may, for example, determine the heading or bearing by fusing data from magnetometers, gyroscopes, and differential GPS antennas. The reference marker external to the vehicle may refer to a marking outside the vehicle that the driver of the vehicle can position the vehicle relative to. The marking may be located on a surface the vehicle can be driven on (e.g., ground / road / floor). The reference marker may for example comprise but is not limited to a straight or curved line, a square, a rectangle, or box. The reference marker may for example comprise a road marking (e.g. a painted line on the road). As noted above, the coordinates / location of the reference marker do not need to be specified or known in advance in the methods herein. The reference marker is used as an aid for the driver to perform their manoeuvres correctly by eye. As such, the method can be performed anywhere, at any time, (e.g. the method cab be performed with respect to any line or box) without the need for specialist equipment, or the like. The plurality of predetermined reference positions refer to positions the vehicle is positioned (e.g., manoeuvred) to relative to the reference marker. For example, if the reference marker is a straight line, the driver may drive the vehicle such that it is aligned in various orientations relative to the straight line. The driver may for example manoeuvre the vehicle, in any order, such that the front, rear, left and right of vehicle is aligned with the straight line. The plurality of predetermined reference positions may comprise positions of the vehicle when each of these alignment manoeuvres has been carried out. Readings of the absolute position of the location sensor may be taken when the vehicle is at each of these predetermined reference positions. It will be appreciated that in some embodiments, the method 300 may comprise further steps, for example, step 302 may comprise sending an instruction to a user of driver of the vehicle, instructing the driver to manoeuvre the vehicle into each predetermined reference position. The driver may be given the option to indicate (e.g. via an application or app) when the vehicle is in the predetermined position relative to the marker. The method 300 may thus further comprise receiving an indication (e.g. user input) when the vehicle is in each of the predetermined positions. An example is shown in Figs. 4a and 4b. In this example, the location sensor is a GPS sensor at a position 402 in the vehicle 400 and the reference marker is a straight line 404. In this example there are four predetermined reference positions: a first reference position where the front axle 406 is aligned with the straight line 404, a second reference position where the rear axle 408 is aligned with the straight line 404, a third reference position where the left side 410 of the vehicle 400 is aligned with the straight line 404 and a fourth reference position the right side 412 of the vehicle 400 is aligned with the straight line 404. Fig. 4a shows the vehicle when the front axle 406 is aligned with the straight line 404 and when the rear axle 408 is aligned with the straight line 404 (e.g. the first and second reference positions). Fig. 4b shows the vehicle when the left side 410 of the vehicle 400 is aligned with the straight line 404 and when the right side 412 of the vehicle 400 is aligned with the straight line 404 (e.g. the third and fourth reference positions). The GPS sensor 402 (or other location sensor) measures the absolute position data when the vehicle 400 is positioned in each of the four orientations. In step 302, the absolute position data output by the location sensor 402 when the vehicle 400 is positioned in each of the four orientations is received e.g. at the input 202. It will be appreciated that although a line has been indicated, this example (and the equations described below with respect to Figs 4b, 5, 6 and 7) apply equally to an example where the reference marker is a box. As noted above, at step 304, the method comprises determining, based on the plurality of predetermined reference positions and on the plurality of absolute positions position data, the location of the location sensor relative to the reference point in the vehicle from the absolute positions of the location sensor at the predetermined reference positions. Determining the location of the location sensor relative to the reference point in the vehicle may comprise determining a distance between a first absolute position of the location sensor and a second absolute position of the location sensor and determining a first co-ordinate of the location sensor based on the distance between the first and second absolute positions of the location sensor. The first co-ordinate may for example comprise an x co-ordinate relative to the reference point in the vehicle, or the distance the location sensor is from the reference point in an x direction, with the reference point acting as the origin point of the co-ordinate system. The first absolute position of the location sensor may refer to the absolute position of the location sensor when the vehicle is aligned at a first predetermined position of the plurality of predetermined reference positions relative to the reference marker. The second absolute position of the location sensor may refer to the absolute position of the location sensor when the vehicle is aligned at a second predetermined position of the plurality of predetermined reference positions relative to the reference marker. The distance between the first and second absolute positions of the location sensor may for example be measured using geometry. Alternatively, or additionally, determining the location of the location sensor relative to the reference point in the vehicle may comprise determining a distance between a third position of the location sensor and a fourth position of the location sensor; and determining a second co-ordinate of the location sensor based on the distance between the third and fourth positions of the location sensor (e.g. the relative offset of the location sensor between the third and fourth positions). The second co-ordinate may for example comprise a y coordinate relative to the reference point in the vehicle, or the distance the location sensor is from the reference point in an y direction, with the reference point acting as the origin point of the co-ordinate system. The third absolute position of the location sensor may refer to the absolute position of the location sensor when the vehicle is aligned at a third predetermined position of the plurality of predetermined reference positions relative to the reference marker. The fourth absolute position of the location sensor may refer to the absolute position of the location sensor when the vehicle is aligned at a fourth predetermined position of the plurality of predetermined reference positions relative to the reference marker. The distance between the third and fourth absolute positions of the location sensor may for example be measured using geometry. It will be appreciated that the geometric relationships between the first, second, third and fourth absolute positions and the location of the sensor within the vehicle will depend on the predetermined positions that are selected, the shape of the reference point, and the order in which the different orientations / positions of the vehicle are recorded. As such, a wide range of possible combinations are possible, subject to design choices of the skilled person. It will be appreciated that different geometric relationships will be used dependent on the set-up chosen. Additionally, or alternatively, the step of determining the first co-ordinate of the location sensor may be carried out using the determined distance between the first and second positions of the location sensor and a first pre-determined dimension of the vehicle. The first pre-determined dimension of the vehicle may refer to a known vehicle dimension, such as but not limited to the wheelbase or track width of the vehicle. Additionally, or alternatively, the step of determining the second co-ordinate of the location sensor may be carried out using the determined distance between the first and second positions of the location sensor and a second pre-determined dimension of the vehicle. The second pre-determined dimension of the vehicle may refer to a known vehicle dimension, such as but not limited to the wheelbase or track width of the vehicle. Returning to the example shown in Fig. 4a and 4b, when the predetermined reference positions are as shown in Fig. 4a and 4b, the step of determining 304 the location of the location sensor relative to the reference point in the vehicle may comprise using the following equations: Equation 1: wheelbase—b 2 Equation 2: track width—d y =-------- -7 2 Where x is the x-co-ordinate indicating the position of the location sensor relative to the reference point (the centre point of the rear axle in the example shown in Figs. 4A and 4B) in the x axis, or distance between the location sensor and reference point in the x direction, b is the distance between the first and second absolute positions of the location sensor, the wheelbase 414 is the distance between the front and rear axles of the vehicle, y is the y-co-ordinate indicating the position of the location sensor relative to the reference point in the y axis or distance between the location sensor and reference point in the y direction, the track width 416 is the distance between the centreline of two wheels on the same axle (of the front or rear axle) and d is the distance between the third and fourth absolute positions of the location sensor. Alternatively, or additionally, the y co-ordinate may be determined by the following equation assuming the centre of the rear axle is the same as the centre of the track width: Equation 3: y = Where y is the y-co-ordinate indicating the position of the location sensor relative to the reference point in the y direction, or distance between the location sensor and reference point in the y direction, the track width 416 is the distance between the centreline of two wheels on the same axle of the front or rear axle and d is the distance between the third and fourth absolute positions of the location sensor. Fig. 5 shows the distances b and d from a second perspective. Distance b is the distance between first and second absolute positions of the location sensor and distance d is the distance between the third and fourth absolute positions of the location sensor. The rectangular box 500 shown overlaying the vehicle 400 has a length and a width. The length corresponds to the wheelbase 414 and the width corresponds to the track width 416. Turning now to step 306, the method 300 comprises outputting a signal indicative of the position of the location sensor relative to the reference point in the vehicle. The position of the location sensor relative to the reference point in the vehicle may take all manner of forms. For example, the position may be provided as one or more co-ordinates (e.g., with the reference point acting as the origin of the co-ordinate system), a distance to the reference point, or as any other positional information relative to the vehicle. The signal may for example be transmitted to a computer node or user device internal or external to the vehicle. The location of the location sensor may for example be sent in a calibration signal for calibrating a measurement of a position of the vehicle based on the location of the location sensor relative to the reference point of the vehicle. In other words, one or more offsets may be determined and output for use in converting the absolute location measurements from the location sensor into positional information of e.g. each wheel of the vehicle. Turning now to Figure 6a, which is a diagram showing how an error of the determined position of the location sensor relative to the reference point in the vehicle may be calculated. During the calibration process described above with respect to Figures 4a and 4b, the driver may not always rotate the vehicle perfectly 180 degrees between manoeuvres (e.g., when repositioning the vehicle from a reference position when the front axle of the vehicle is aligned with the reference marker to a reference position when the rear axle of the vehicle is aligned with the reference marker, and when repositioning the vehicle from a reference position when the left side of the vehicle is aligned with the reference marker to a reference position when the right side of the vehicle is aligned with the reference marker). Not aligning the vehicle perfectly with the reference marker, or otherwise not rotating the vehicle perfectly 180 degrees between manoeuvres, may result in an error to the measurement of the position of the position sensor relative to the reference point. In Figure 6a, distance b is the distance between first and second absolute positions of the location sensor, this is due to the location sensor being offset relative to the centre of the vehicle, and depends on the position of the location sensor within the vehicle (as described above). Distance h is the hypotenuse of the triangle formed by distance b and distance a. Distance a is the offset due to the movement of the vehicle along the reference marker (which is a line in this example). The parameter a thus goes to 0 if the vehicle is rotated and positioned in exactly the same footprint (albeit rotated by 180 degrees) when rotated between the first and second predetermined positions. Figure 6b shows the offset between the location sensor when the vehicle is moved through the third and fourth predetermined positions illustrated in Figure 4b. Distances a and c are affected by i) how far along the line / reference marker the driver positions the vehicle (after each manoeuvre), and ii) how far the location sensor is from the centre line of the car (lateral direction). If the driver uses the exact same part of the line for every manoeuvre and the GPS is mounted along the centre line of the car, then as noted above, a and c would be zero. Distances a and c are not used when calculating the X and Y position of the location sensor, however they are used when calculating the error due to heading misalignment. The larger a and c are, the more the heading error (if any) gets amplified. Figure 6a shows how a is used to help calculate the heading misalignment of the two manoeuvres in Figure 4a. Figure 6b shows how c is used to help calculate the heading misalignment of the two manoeuvres in Figure 4b. If the absolute position data is a heading or bearing, the arc error may be calculated using the following equation. Equation 4: arcerror = 2nh '2^1222^^ Where, as noted above, h is the hypotenuse and calculated from a and b; or c and d, depending on whether it is the error in the X or Y co-ordinate that is being determined. The heading error (heading error) may be the reported heading or bearing inaccuracy of the location sensor, which may be a GPS device. If the device is not capable of outputting its estimated error in real time, it may be assumed to be constant and gathered from the datasheet of the device. The heading misalignment (headingmisaiignment) may refer to the error induced by the driver performing the calibration having not rotated the vehicle perfectly 180 degrees between manoeuvres (e.g., when repositioning the vehicle from a reference position when the front axle of the vehicle is aligned with the reference marker to a reference position when the rear axle of the vehicle is aligned with the reference marker, and when repositioning the vehicle from a reference position when the left side of the vehicle is aligned with the reference marker to a reference position when the right side of the vehicle is aligned with the reference marker). For example, if the heading of the vehicle is 0 degrees (with the vehicle facing North) when placing the front axle of the vehicle on the reference marker (e.g., the straight line), and the heading of the vehicle is 181 degrees (the vehicle is facing approximately South) when placing the rear axle of the vehicle on the reference marker (e.g., the straight line), the heading misalignment would be 1 degree. Turning to the example shown in Figs. 4a and 4b, if a driver parks the front axle of the vehicle on the straight line reference marker and the absolute position data indicates the vehicle heading (or bearing) is 20 degrees clockwise from magnetic north, the driver then parks the rear axle of the vehicle on the straight line reference marker, and the absolute position data indicates the vehicle heading (or bearing) is 202 degrees clockwise from magnetic north, since the vehicle should have been rotated 180 degrees, the heading misalignment is (202-20) -180= 2 degrees. If the driver parks the left side of the vehicle on the straight line reference marker and the absolute position data indicates the vehicle heading (or bearing) is 25 degrees clockwise from magnetic north, the driver then parks the right side of the vehicle on the straight line reference marker and the absolute position data indicates the vehicle heading (orbearing) is 207 degrees clockwise from magnetic north, since the vehicle should have been rotated 180 degrees, the heading misalignment in this case is (207-25) -180 = 2 degrees. The total heading misalignment, which may be headingmisaiignment in Equation 4 is the average of the two misalignments calculated in this example (the average of the heading misalignments calculated for each 180-degree rotation of the vehicle). In this example, the total heading misalignment is therefore 2 degrees (— = 2). The error margin of the location sensor (e.g. GPS sensor) may also be taken into account when determining the position of the location sensor relative to a reference point in the vehicle. To do this, the reported accuracy (as outputted from the location sensor) at the time each manoeuvre is completed (i.e., each time the vehicle is positioned at a reference position of the plurality of reference positions) may be recorded. The average of each of the reported accuracies (i.e., reported errors) may be averaged to determine an average positional error. The final error of the determined position of the location sensor relative to the reference point in the vehicle may be calculated using Equation 5. Equation 5: Total Error = arcerror + average positional error Equations 4 and 5 are calculated twice, once for each direction. The first calculation is performed for the maneuverers in Figure 4a (as shown in Figure 6a) and the second calculation is performed forthe manoeuvres in Figure 4b (as shown in Figure 6b). When using equations 4 and 5 on the predetermined positions shown in Figure 4a, this gives the arc_error and total_error in the xdirection. Using the same equations again forthe predetermined positions in Figure 4b gives the arc_error and total_error in the Y direction. When using Equations 4 and 5 forthe predetermined positions in Figure 4b, equation 5 would use D and C instead of A and B forthe hypotenuse (h). In this way therefore, the error in both the X and Y directions can be calculated. Figure 7 shows a vehicle arranged in two reference positions of the plurality of reference positions, namely with the front axle aligned with the reference marker 404 and the rear axle aligned with the reference marker 404. The dotted line 700 surrounding the location sensor 402 represents the error margin of the location sensor. The total error may be taken into account when making use of the determined position of the location sensor relative to the reference point in the vehicle, for example during the testing of braking and lane alignment systems. The error may further be used to prompt the user to re-position the vehicle and / or to re-take one or more of the measurements if the error is above a threshold error. Figure 7 shows a passenger vehicle 400 according to some embodiments herein. The location sensor 402 may be fitted in such a vehicle and the described method, system, and computer readable instructions used to determine the location of said location sensor relative to a reference point (e.g. relative to the wheels, front or rear wheel axle) within said vehicle. It will be appreciated that various changes and modifications can be made to the present invention without departing from the scope of the present application. Turning now to other embodiments, it will be appreciated that the method 300 may be embodied in a computer program. The method 300 may be performed by an application (“app”) installed on a mobile device, such as a phone, tablet, laptop computer or other wireless connected device. A computer program product may comprise a computer readable medium, the computer readable medium having computer readable code embodied thereon. The computer readable code can be configured such that, on execution by a suitable computer or processor, the computer or processor is caused to perform the method or methods described herein (such as the method 300). A computer program may take different forms, for example, source code, compiled code, executable code, or any other type of code. It will be appreciated that the source code of computer programs may be written in a wide variety of different programming languages, and may take different architectural designs. For example, the functionality described herein may be split across various different sub-routines. Furthermore, the skilled person will appreciate that many different ways of splitting the functionality between the different sub-routines will be possible. The sub-routines may be stored together in one executable file to form a self-contained program. Furthermore, computer programs may call external and / or standard libraries of computer code for performing certain sub-tasks associated with the functionality described herein. In another embodiment, there is a computer program product comprising non-transitory computer readable media, having stored thereon a computer program as described above. Examples of computer readable media include, but are not limited to: ROM, such as a CD ROM, a semi-conductor ROM or a magnetic recording medium such as a hard disk. In another embodiment, there is a carrier containing a computer program. Examples of carriers include but are not limited to an electronic signal, optical signal, radio signal, computer storage medium, or similar. The carrier of a computer program may be any entity or device (e.g. hardware) capable of carrying the program. As an example, a carrier may be a computer readable media as described above. In other examples a carrier may be a transmissible carrier such as an electronic or optical signal, which may be conveyed via electrical or optical cable or by radio or other means. Variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure and the appended claims. In the claims, the word “comprising” does not exclude other elements or steps, and the indefinite article “a” or “an” does not exclude a plurality. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these claims cannot be used to advantage. Any reference signs in the claims should not be construed as limiting the scope.

Claims

1. A method for determining a position of a location sensor in a vehicle relative to a reference point in the vehicle, the location sensor being fixed relative to the reference point, the method comprising:receiving absolute position data measured by the location sensor when the vehicle is aligned at each of a plurality of predetermined reference positions relative to a reference marker external to the vehicle, the absolute position data indicative of a plurality of absolute positions of the location sensor in a co-ordinate system independent of the vehicle;determining, based on the plurality of predetermined reference positions and on the plurality of absolute positions, the location of the location sensor relative to the reference point in the vehicle; and outputting a signal indicative of the position of the location sensor relative to the reference point in the vehicle.

2. A method as in claim 1 wherein determining the location of the location sensor relative to thereference point in the vehicle comprises:determining a distance between a first absolute position of the location sensor and a second absolute position of the location sensor; anddetermining a first co-ordinate of the location sensor based on the distance between the first and second absolute positions of the location sensor.

3. A method as in claim 1 or 2 wherein determining the location of the location sensor comprises:determining a distance between a third absolute position of the location sensor and a fourth absolute position of the location sensor; anddetermining a second co-ordinate of the location sensor based on the distance between the third and fourth absolute positions of the location sensor.

4. A method as in claim 2 or claim 3 when dependent on claim 2, wherein determining the firstco-ordinate of the location sensor is carried out using the distance between the first and second positions of the location sensor and a first pre-determined dimension of the vehicle.

5. A method as in claim 3, wherein determining the second co-ordinate of the location sensor iscarried out using the distance between the third and fourth positions of the location sensor and a secondpre-determined dimension of the vehicle.

6. A method as in any preceding claim, wherein the reference marker is a straight line.

7. A method as in claim 6 wherein receiving position data measured by the location sensor whenthe vehicle is aligned at each of the plurality of predetermined reference positions relative to the reference marker external to the vehicle comprises: receiving position data measured by the location sensor: when a front axle of the vehicle is aligned with the straight line;when a rear axle of the vehicle is aligned with the straight line;when a left side of the vehicle is aligned with the straight line; andwhen a right side of the vehicle is aligned with the straight line.

8. A method as in any preceding claim, further comprising receiving an indication when the vehicle is aligned at one or more predetermined reference positions of the plurality of predetermined reference positions.

9. A method as in any preceding claim, wherein the absolute position data is a bearing.

10. A method as in any preceding claim, wherein the location sensor is a global positioning systemnavigation device.

11. A method as in claim 9, further comprising determining an error in the position of the locationsensor relative to the reference point in the vehicle based on a bearing error and vehicle misalignment error.

12. A method as in any preceding claim, wherein the signal indicative of the location of the locationsensor comprises a calibration signal configured to calibrate a measurement of a position of the vehicle based on the location of the location sensor relative to the reference point of the vehicle.

13. Computer readable instructions which, when executed by one or moreprocessors, cause the one or more processors to perform the method according to any of Claims 2 to 12.

14. A system for determining a position of a location sensor in a vehicle relative to a referencepoint in the vehicle, the system comprising:an input configured to receive absolute position data measured by the location sensor when the vehicle is aligned at each of a plurality of predetermined reference positions relative to a reference marker external to the vehicle, the absolute position data indicative of a plurality of absolute positions of the location sensor in a co-ordinate system independent of the vehicle;a processor configured to determine, based on the plurality of predetermined reference positions and on the plurality of absolute positions, the location of the location sensor relative to the reference point in the vehicle; andan output for outputting a signal indicative of the position of the location sensor relative to the reference point in the vehicle.

15. The system of claim 14, wherein the processor is configured to:determine a distance between a first absolute position of the location sensor and a second absolute position of the location sensor; anddetermine a first co-ordinate of the location sensor based on the distance between the first and second absolute positions of the location sensor;and / ordetermine a distance between a third absolute position of the location sensor and a fourth absolute position of the location sensor; anddetermine a second co-ordinate of the location sensor based on the distance between the third and fourth absolute positions of the location sensor.

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