EXCAVATION PIT SURVEYING

Description

[0001] The invention relates to the surveying of a water-filled structure, in particular the base and / or walls of the structure. The structure may be, for example, a pit or other depth-oriented structures such as a shaft or chamber. The surveying may include the measurement of the base and / or walls of the structure. Such excavations are, for example, dug for the construction of hydraulic engineering structures. The excavation may, for instance, be a lock chamber for the passage of watercraft.

[0002] Surveying the base and walls of an excavation, for example, is essential for inspection purposes, specifically for examining the ground and walls for damage. Like the excavation itself, the survey must be carried out underwater. The base can be surveyed during excavation to determine if the pit has reached the desired depth. After excavation, the base of the excavation is often concreted. It is crucial that the concrete layer reaches a precise thickness. This must be done while the excavation is water-filled, as a defective concrete layer can crack and break when the pit is drained. Repairing any resulting damage is only possible while the excavation is water-filled, as otherwise further damage, particularly hydraulic failure, can occur.

[0003] Surveys of the bottom of a water-filled excavation pit are nowadays usually carried out manually by one or more divers. However, this is very unreliable and not reproducible. In particular, difficulties arise in assigning the measurement data collected by the diver to a specific position on the excavation pit floor. Underwater surveying is also known in principle using measuring rods mounted on floating buoys, which measure the bottom of the excavation pit by means of underwater sensors. Such measuring rods are known, for example, from JP 2001 343 237 A and JP 2001 280 957 A. The position of such measuring rods can be determined relatively accurately, especially using GPS, which improves the surveying. However, the positional accuracy can be further improved.

[0004] The publication by Hesse, Holste, Neumann et al. on the topic of 3D hydromappers in the June 2019 issue of Hydrographic News explains the surveying of a structure near water using a surveying device mounted on a ship. Prior to the survey, a route is determined based on preliminary information such as rough as-built plans or 3D data. The surveying device is then moved along this route relative to the structure from the ship for the subsequent survey.

[0005] CN 109131742 A describes a rotating, vessel-side mounted survey system with a rotating underwater instrument mounting platform. The system comprises a water instrument mounting platform, a satellite positioning system, data acquisition, and an instrument rotation control terminal. The water instrument mounting platform is attached to the top of the side mounting pole, while the rotating underwater instrument mounting platform is installed at the bottom. The satellite positioning system is used to obtain real-time position information for the survey vessel. The data acquisition and instrument rotation control terminal is used for data acquisition, post-processing, and to control the rotation of the underwater instrument mounting platform. The system is used for marine research and seabed exploration.

[0006] US patent 20180031685 A1 describes the use of a floating target marker, such as those known on land for referencing terrestrial laser scans, to improve the positioning of a ship-based underwater survey using a laser scanner or echo sounder. The target marker consists of an above-water and an underwater portion. The georeferencing described in US patent 20180031685 A1 is referred to as "indirect referencing" via externally determined target markers near the object's surface and, for 3D surveys, always requires at least three simultaneously determined target markers for a closed-loop solution. This is not the case with the present invention for measuring depth-oriented structures.

[0007] US Patent 20120125077 A1 relates to a calibration device for a drill head for vertical drilling in solid ground, designed to compensate for sensor drift of magnetometers and accelerometers due to high temperatures in the borehole. Within the device, inertial sensors are rotated around three orthogonal axes or planes or moved by means of a gimbal to determine the calibration values. The acquired measurements are used to determine the position of the drill head.

[0008] The invention is based on the objective of enabling the surveying of a water-filled structure, in particular a water-filled excavation pit, with higher positional accuracy.

[0009] The invention solves the problem by means of a system according to claim 1 or 2, by means of a method according to claim 12 or 13.

[0010] Advantageous embodiments are the subject of the dependent claims, the description, and the figures.

[0011] The system according to the invention comprises a surveying device for surveying a water-filled structure, in particular the bottom of a water-filled excavation, a holding device located on land next to the structure, and a total station, wherein the surveying device comprises a rod-shaped sensor carrier with a first end arranged below the water surface in the operating state of the surveying device and a second end arranged above the water surface in the operating state of the surveying device, wherein at least one surveying sensor is arranged at the first end of the sensor carrier for surveying the structure, in particular the bottom of the excavation, by acquiring surveying data, wherein the surveying device further comprises an accelerometer and a GNSS receiver for receiving GNSS signals from satellites of a global navigation satellite system.wherein the total station is located on land and pointed towards the surveying device, wherein the system further comprises a control unit configured to determine a current position and / or orientation of the surveying device based on measurement data from the accelerometer, on the basis of GNSS signals received by the GNSS receiver and on the basis of measurement data acquired by the total station, and to assign this to the surveying data, wherein the holding device is configured to hold the surveying device in the operating state.

[0012] In an alternative to the method according to the invention, which is preferably used when GNSS reception is poor, the measuring device is alternatively or additionally equipped with a prism unit, preferably a 360° prism. The total station is pointed at the prism unit to determine the position of the measuring device. In this configuration, the total station is positioned via GNSS measurement points in the global coordinate system. Starting from its absolute position, the total station then measures the relative position of the prism unit, so that the entire measurement can be transformed into the global coordinate system.

[0013] The inventive method for surveying a water-filled structure, in particular the bottom of a water-filled excavation, using such a system comprises the following steps: placing the surveying device in an operational state in which the first end of the sensor carrier is arranged below the water surface; surveying the structure, in particular the bottom of the excavation, by means of the at least one surveying sensor by acquiring survey data; determining a current position and / or orientation of the surveying device based on measurement data from the accelerometer, on the basis of the GNSS signals received by the GNSS receiver, and on the basis of the measurement data of a tachymeter located on land and directed towards the surveying device; assigning the current position and / or orientation of the surveying device to the survey data, wherein the surveying device is maintained in the operational state from land.

[0014] An alternative or additional embodiment of the method, which is used, for example, but not exclusively, when the measuring device has poor GNSS reception, involves determining the position of the total station using GNSS measurement points in the global coordinate system. The total station is then pointed at a prism unit, preferably a 360° prism, on the measuring device. This allows the measuring device to be located within a global coordinate system.

[0015] In the event of shadowing or complete absence of GNSS signals, the referencing of, for example, the rotation circle, its surface normal, and the center of rotation over water can be carried out using an automatically tracking and measuring total station. Due to its high local measurement accuracy, this total station can also be used to improve signal quality and to bridge GNSS signal interruptions, for example, when the system is cable-supported and the GNSS reception is disrupted by the cables.

[0016] Since measurements with accelerometers and inertial measurement units (IMUs) are ideally performed in a global, space-fixed coordinate system (e.g., WGS84) and not in a local, position-based system (as is typical with total stations, where the station point is 0,0,0 and the Z-axis is coaxial with the local gravity vector), the total station is first established in the WGS84 system. For this purpose, at least three, ideally five to six, control points are sequentially determined using GNSS and the total station within a GNSS-measurable area, such as outside the hall or the shaded area. A seven-parameter transformation is then used to transform the total station into the global coordinate system, allowing the position of the prism unit to be determined within the GNSS coordinate system.

[0017] The prism unit can be used simultaneously with GNSS, but also independently. It can be mounted on the side of the crossbeam opposite the GNSS antenna or below the antenna. Even with two GNSS antennas, the prism can, of course, be mounted below the crossbeam, thus improving redundancy and fault tolerance.

[0018] An offset to the axis of rotation of the rod is calibrated during the evaluation, but - just like with the GNSS antenna - it can be introduced as a target condition to increase accuracy.

[0019] The evaluation uses X, Y, Z coordinates, allowing the prism unit, which rotates instead of or simultaneously with the GNSS antenna, to be used like a GNSS antenna. Due to the system's movement, all measurements must be time-referenced very precisely. For this purpose, the total station is synchronized with GNSS time (UTC) or atomic time via a measurement computer.

[0020] The prism unit can, of course, be shaded; if mounted under the crossbeam, this will happen twice per revolution of the measuring rod. However, the total station is able to regain its position even during movement and resume the measurement after a short time.

[0021] The method according to the invention can be carried out using the system according to the invention. The system according to the invention is therefore suitable for carrying out the method according to the invention. The measuring device according to the invention can be part of the system and used for the method. The system, method, and measuring device are explained together below, and these explanations apply accordingly to all embodiments.

[0022] In the operational state of the surveying device, i.e., with the first end of the sensor carrier inserted into the water surrounding the structure, the structure, in particular its foundation and / or walls, can be surveyed using the at least one survey sensor. In principle, the entire water contact area of ​​the structure can be surveyed. According to the invention, the rod-shaped sensor carrier is held in this operational state from land, as will be explained later. The rod-shaped sensor carrier can, for example, have a length of 50 m, preferably a length between 10 m and 25 m, and in particular a length between 10 m and 22 m or between 15 m and 22 m. The at least one survey sensor can thus be lowered to a depth of, for example, 22 m. Therefore, a survey 5 m above ground can, for example, measure an excavation pit with a depth of approximately 27 m.For surveying the structure, the at least one survey sensor can be rotated, as will be explained later. During the survey, the most accurate possible knowledge of the current position of the surveying device and thus of the survey sensor is essential, as this is the only way to precisely locate the survey data acquired by the at least one survey sensor. The same applies to the orientation of the surveying device or the survey sensor. The invention allows a position to be assigned to the survey data, particularly with an accuracy of up to 5 cm. The control unit can ensure this, especially in real time. For this purpose, the invention provides a combination of a GNSS receiver, an accelerometer, and a total station. The accelerometer can, in particular, be part of an inertial measurement unit.Using the accelerometer, and in particular the inertial measurement unit (IMU), not only the position but also the spatial orientation of the measuring device can be determined. Such an inertial measurement unit is also called an IMU (". inertial measurement unit(referred to as ""). An IMU is known per se and has a spatial combination of several initial sensors, for example, accelerometers and / or gyroscopes. The accelerometer, in particular, can detect movement of the surveying device. The control unit takes this into account to determine the current position or orientation of the surveying device. GNSS signals are also used in the position determination. GNSS is known to be the abbreviation for Global Navigation Satellite System, which can be, for example, GPS, Galileo, GLONASS, Beidou, or QZSS. The GNSS receiver can, in particular, be located at the second end of the sensor carrier, i.e., above the water surface when the surveying device is in use. In particular, two GNSS receivers can be provided for more precise position determination.The position of the surveying device, and thus of at least one surveying sensor, can be determined relatively accurately by correlating the GNSS signals with the measurement data from the accelerometer or IMU. However, GNSS reception can be interrupted, or the data quality of the GNSS signals can be limited. This negatively impacts the accuracy of the position determination. In particular, drift of the accelerometer or IMU can occur, which can no longer be stabilized by the GNSS.

[0023] According to the invention, in addition to the accelerometer or IMU and the GNSS receiver, a total station is provided for determining the position of the surveying device. In particular, the orientation of the surveying device can also be determined more precisely using the total station, for example, the inclination of the sensor carrier. The total station is arranged on land next to the excavation and directed towards the surveying device, especially towards the second end of the sensor carrier located above the water surface. The total station determines the position of the surveying device in space in a manner known per se. For example, the total station can be directed towards a prism arranged on the surveying device or detect an optically unambiguous point on the surveying device using a camera arranged in the total station. By combining the GNSS signals, the measurement data of the accelerometer or IMU, and the GNSS receiver, the total station can determine the position of the surveying device.The IMU and the tachymeter's measurement data enable particularly precise position determination and orientation of the surveying device. By matching this position and orientation data to the survey data acquired by the at least one survey sensor, the survey data can be precisely localized. This results in a highly accurate survey. For example, if the measuring device has poor GNSS signal reception, its position can be determined using reference points, and the measuring device can be measured with the tachymeter using a prism unit.

[0024] The total station can be used, in particular, to fill gaps in position or orientation data that arise due to potential GNSS signal attenuation. If the GNSS provides insufficient data, the position can be determined using the GNSS signals with reduced accuracy. If the GNSS signals are not received at all, the position can only be determined using the accelerometer / IMU measurement data and the total station measurement data. However, if there is no line of sight to the total station, the position can at least be determined using the accelerometer / IMU measurement data and the GNSS signals.

[0025] In one embodiment, a suspension system is provided by means of which the surveying device can be brought into its operational state. The surveying device can thus be suspended in the water-filled structure such that the first end of the rod-shaped sensor carrier is below the water surface and the second end of the rod-shaped sensor carrier, opposite the first end, is above the water surface. The surveying device, and in particular the rod-shaped sensor carrier, can, for example, be arranged on a measuring platform, which is positioned above the excavation pit by means of the suspension system. An operator can, for example, be located on the measuring platform. In one embodiment, the suspension system can be a gimbal suspension. The surveying device, and in particular the sensor carrier, can thus be held particularly stably.This makes it possible to use the surveying device even at great depths in windy and choppy conditions.

[0026] According to one embodiment, the system includes a holding device located on land next to the structure, designed to hold the surveying device in its operational state. In particular, the holding device can include a boom that can be positioned above the water's surface, allowing the sensor carrier to be lowered into the water-filled structure with its first end. In this embodiment, the surveying device is not mounted on a floating platform. Rather, it rests on land. The holding device can be, for example, a platform located on land or a land vehicle such as a crane or lifting device. Such a system is particularly practical for water-filled structures accessible from land, especially excavation pits, as it eliminates the need for a floating platform, such as a ship or boat.The surveying device can thus be held particularly stable and is less dependent on currents or movements on the water's surface. The land vehicle can pivot the boom over the excavation, thereby moving the surveying device, which is mounted on the boom's suspension, over the excavation. The surveying device, especially the sensor carrier, can then be lowered into the excavation so that the first end of the sensor carrier breaks the water surface to the desired depth. With this type of suspension, the height of the surveying device, particularly the sensor carrier, can be adjusted. Thus, depending on the depth of the excavation, the surveying device can be inserted to varying depths by lowering it accordingly.

[0027] To survey the structure, particularly its foundation, the at least one surveying sensor can rotate, as already mentioned. In one embodiment, this can be achieved, in particular, by designing the sensor carrier to rotate about its longitudinal axis. A suitable rotating device can be provided, for example, a turntable rotatable via a cable pull. A cable pull sensor can be arranged on the turntable to detect the rotational position or movement. The surveying sensor can, in particular, measure in a plane, whereby a circular area of ​​the foundation can be measured by rotating the surveying sensor through 360°.

[0028] In one embodiment, the measuring device includes additional sensors, in particular sensors for detecting inclination, rotation, and / or bending of the sensor carrier. An inclination or bending of the sensor carrier can cause a position assigned to the upper, second end of the measuring device to not accurately reflect the position of the measuring sensor located at the lower, second end of the sensor carrier. For example, the bending can result in an offset between the first and second ends of the sensor carrier, such as by 10 cm. In one embodiment, an inclination, rotation, and / or bending relative to the longitudinal axis of the sensor carrier is taken into account when assigning the position and / or orientation to the measurement data. This compensates for such an error. For example, strain gauges can be used to determine the bending of the sensor carrier.These sensors can, for example, detect flow-induced bending of the sensor carrier caused by a current in the water. Taking the bending of the sensor carrier into account during the evaluation is particularly important when the measurement is carried out while the sensor is rotating.

[0029] The measuring plane of the surveying sensor passes over each point on the seabed twice: once during a 180° rotation and again during a further 180° rotation. Due to any curvature of the sensor mount, this can lead to a significant error in the localization of the survey data. With the aforementioned 10 cm offset, the rotation could result in a localization that is off by 20 cm. This error can be compensated for by calibrating the surveying device. The curvature could be determined, for example, by measuring the sensor mount on land, and then taken into account for subsequent analysis, particularly for assigning the determined position and / or orientation to the survey data.

[0030] In one embodiment, the control unit is further configured to use the GNSS receiver to temporally synchronize the measurement data from the accelerometer, particularly the inertial measurement unit, the tachymeter measurement data, and the GNSS signals. The method can therefore incorporate temporal synchronization. Such temporal synchronization is particularly useful when the GNSS receiver receives insufficient GNSS signals. This synchronization can be achieved, in particular, via a clock in the GNSS receiver. Alternatively, the GNSS signals received by the GNSS receiver can include a time signal, and temporal synchronization can be performed based on this time signal. Temporal synchronization enables real-time position determination of the surveying device and thus accelerates data processing.

[0031] In one embodiment, the control unit is designed to correct drift in the accelerometer, particularly in the inertial measurement unit (IMU), using GNSS signals and tachymeter data. This allows the drift occurring in such IMUs—that is, an undesirable deviation of the IMU sensors—to be corrected via the GNSS signals. Specifically, this embodiment also performs such correction using the tachymeter, enabling particularly reliable correction even when no GNSS signal is available.

[0032] According to the invention, the orientation of the surveying device can also be assigned to the survey data, as explained. In one embodiment, the total station can be configured to determine the orientation of the surveying device. In particular, the total station can include a camera with which the current orientation of the surveying device can be determined. The orientation of the surveying device, especially the inclination of the sensor carrier, is also relevant for the survey data.

[0033] According to one embodiment, at least one surveying sensor is selected from the following set: camera, in particular a thermal camera or a multispectral camera; laser scanner; echo sounder, in particular a multibeam echo sounder; 3D, area, or line sensor. The multibeam echo sounder is also called a multibeam. If several surveying sensors are provided, they can comprise any combination of the aforementioned sensors.

[0034] One embodiment of the invention is explained below with reference to figures. These show: Figure 1 shows a system according to the invention consisting of a surveying device inserted into an excavation pit by means of a crane and a tachymeter in a side view; Figure 2 shows a perspective view of the surveying device and the excavation pit. Figure 1 Figure 3 shows a surveying device according to the invention, inserted into an excavation pit by means of a platform standing at the edge of the pit in a side view, Figure 4A shows legs of a surveying device according to the invention, inserted into a vertical or inclined excavation pit by means of a lifting device in a side view, and Figure 5 shows a surveying device according to the invention in a further embodiment.

[0035] Unless otherwise stated, the same reference symbols refer to the same objects.

[0036] Figure 1Figure 1 shows a system according to the invention comprising a surveying device 10 and a total station 40. The surveying device 10 comprises a rod-shaped sensor carrier 12 with a first end 12a and a second end 12b opposite the first end. A surveying sensor 14 configured as a multibeam is arranged at the first end 12a, while a heading with two GNSS receivers 16 is arranged at the second end 12b. Depending on the selected configuration, the GNSS receiver 16 can also additionally or exclusively comprise a prism unit, which, for example, is configured as a 360° prism and is measured by the total station. The surveying device 10 further comprises an inertial measurement unit 28, hereinafter referred to as IMU. The IMU 28 comprises at least one accelerometer and can include further sensors, in particular gyroscopes.The system's task is to create a comprehensive 3D map of vertical or inclined structures, shafts, and other structures, as well as inclined or horizontal tunnels located underwater that are inaccessible or extremely difficult to reach from the surface. Entrances to these structures may be in the open air, inside buildings / halls / tunnels, or in environments with poor GNSS reception (forests, under bridges, in steep urban canyons). For this purpose, a 2D area-based survey sensor and / or a thermal sensor is moved rotatingly or oscillatingly along a long sensor pole. Depending on the sensor technology, this pole can be stably positioned above the object or moved / pendulum from a hook or cable. The length of the sensor pole is not limited (e.g., 50 m).

[0037] The measuring device 10 is rotatably mounted on a measuring platform 18, so that the sensor carrier 12 can be rotated about its longitudinal axis L. The measuring platform 18 has an opening 19 through which the sensor carrier 12 projects, as shown in particular Figure 2The measuring platform 18, and thus the surveying device 10, is arranged on a suspension 20 of a boom 22 of a crane vehicle 24. The surveying device 10 can be pivoted over the boom 22 across an excavation 30 and lowered into the excavation 30. In this operating state of the surveying device 10, as shown in the figures, the first end 12a of the sensor carrier 12 is located below the water surface W, so that the bottom 32 of the excavation 30 can be examined with the surveying sensor 14. The second end 12b is located above the water surface W, and in particular also above the excavation 30, as also shown in the figures. To secure the measuring platform 18, it is fixed to the ground surrounding the excavation 30 by means of guy wires 26. The excavation pit can have a stabilizing stiffener 34, which can extend between opposing walls of the excavation pit 30, as shown. Figure 2 to be taken.

[0038] A control unit (not shown) of the system evaluates measurement data from the IMU 28 and the total station 40, which is directed at the surveying device 10, as well as GNSS signals received from a satellite 42 by the GNSS receivers 16, to determine the current position and orientation of the surveying device 10. The control unit then assigns the position and orientation thus determined to the survey data output by the survey sensor 14. This survey data contains information about the surveyed ground 32 of the excavation 30 and is acquired by rotating the survey sensor 14 about the longitudinal axis L of the sensor carrier 12. For a meaningful survey of the ground 32 of the excavation 30, the most precise possible localization of this survey data is necessary. According to the invention, this is achieved by the aforementioned combination of the GNSS signals, the measurement data from the IMU, and the measurement data from the total station.

[0039] Instead of using a crane vehicle, the surveying device can also be brought into operation, for example, using a 24' land-based platform or a 24" land-based lifting device, as shown in the Figures 3 or 4. In Figure 3 A part of the platform 24', which can be understood as a boom 22, projects over the excavation pit 30, with the sensor carrier 12 of the surveying device 10' projecting vertically downwards into the water through a floor opening in the boom 22. Figure 4 A suitably designed boom 22 is held above the excavation 30 by means of an arm of the lifting vehicle 24", which carries a surveying device 10". By moving the arm of the lifting vehicle 24", the surveying device 10 can be easily adjusted in height and the surveying sensor 14 can be lowered to the desired depth in the excavation. The surveying device 10 can also be removed from the Figure 1 and 2could be moved into and held in the operating position by means of the 24' platform or the 24" lifting vehicle. Similarly, the 10' and 10" surveying devices could also be moved via a suspension and a crane vehicle as in Figure 1 be positioned.

[0040] The surveying devices 10', 10" differ from the surveying device 10 from the Figure 1 and 2 by a receiving unit 45 for receiving further sensors, including a rotation sensor 46 and a tilt sensor 48, as well as by strain gauges 50 arranged on the sensor carrier 12, as shown in Figure 5This figure shows a prism 44 towards which the total station is directed. The surveying devices 10 can also incorporate such a prism. The tilt sensor 48 enables the determination of an inclination of the sensor carrier 12, i.e., a tilting of its longitudinal axis L relative to the vertical. The rotation sensor 46 determines a rotational position or movement of the sensor carrier 12 about its longitudinal axis. The strain gauges 50 can detect a bending of the sensor carrier relative to its longitudinal axis L. An inclination, rotation, and / or bending determined by these sensors can be taken into account for assigning the position and / or orientation to the survey data.

[0041] An inclination or bend in the sensor carrier 12 can cause a position assigned to the upper, second end 12b of the sensor carrier to not allow a correct conclusion to be drawn about the position of the surveying sensor 14 located at the lower, second end 12a of the sensor carrier 12. For example, the bend can cause an offset between the first end 12a and the second end 12b of the sensor carrier, by 10 cm. Such an error can be compensated for by taking the inclination or bend into account. Considering the bend of the sensor carrier during the evaluation is particularly important when the survey is carried out while the surveying sensor is rotated. In this case, the measuring plane of the surveying sensor passes over each point on the ground twice: once during a 180° rotation and a second time during a further 180° rotation.In this case, bending of the sensor carrier can lead to an even greater error in the localization of the survey data. With the aforementioned offset of 10 cm, rotation can result in a localization that is off by 20 cm. Compensating for this error is particularly important.

[0042] Figure 5 Figure 60 also shows a central computer 60 that communicates with the sensors of the surveying device 10'. This central computer 60 can serve as a central control unit that performs the localization of the survey data and, in particular, a time synchronization symbolically represented at reference numeral 62. The surveying device 10 can, of course, also communicate with a central computer. The receiving unit 45 also serves as a suspension point for the surveying device on the boom 22, as shown. Figure 5 to be taken.

[0043] If the measuring system cannot be fixed in a rigid position (such as on a crane), an inertial measurement unit (IMU) is used to determine the time-referenced deviations dX, dY, dZ, as well as the rotation angles about the X, Y, and Z axes from the initial axis of rotation of the sensor rod. In conjunction with GNSS, the coordinates of the gimbal joint above water are also determined. If the device is used in flowing water or if the rod is so long that it bends statically (i.e., is no longer linear), the bending of the rod can be determined and computationally accounted for using multiple strain gauges along its length. For higher accuracy, the rotation angle about Z can also be determined using a cable-operated sensor attached to the top of the rod's gimbal mount. This sensor determines the rod's rotation by tracking the unwinding of the sensor's cable with a known unwinding radius.As an alternative to the cable-operated sensor, a rotary encoder / angle encoder or lateral displacement encoder can also be attached to the rotating circle. This significantly improves the accuracy of the object coordinates determined by the survey sensor, since at greater measurement distances (due to the intercept theorem), a lateral error from incorrect / inaccurate rotation angles has a greater impact than a positional error of the rod. For unstable and long rods, the accelerometer can also be replaced by an inertial measurement unit (IMU) at the bottom of the rod. For unstable rods that do not have a constant axis of rotation, in addition to the underwater IMU, a second IMU can be used above water near the GNSS antenna to measure and compensate for the unknown bending / kinking of the rod as well as the unknown variation of the axis of rotation. List of reference symbols

[0044] 10 Surveying device 12 Sensor carrier 11 Sensor mount 12a First end 12b Second end 14 Survey sensor 16 Two GNSS receivers 16 GNSS measurement points 18 Surveying platform 19 Opening 20 Suspension 22 Boom 24 Crane vehicle 24 Platform on land 24 Lifting device 26 Guy wires 28 Inertial measurement unit (IMU) 30 Excavation 32 Ground 34 Stiffener 40 Total station 42 Satellite 44 Prism 45 Recording unit 46 Rotation sensor 48 Tilt sensor 50 Strain gauges 60 Central computer 62 Time synchronization Water surface Llongitudinal axis

Claims

1. A system consisting of a measuring device (10) for measuring a water-filled structure (30), a holding device (24, 24', 24") located on land next to the structure (30), and a tachymeter (40), wherein the measuring device (10) comprises a rod-shaped sensor support (12) having a first end (12a) arranged below the water surface (W) in the state of use of the measuring device (10) and a second end (12b) arranged above the water surface (W) in the state of use of the measuring device (10), wherein at least one measuring sensor (14) is arranged at the first end (12a) of the sensor support (10) for measuring the structure (30) by recording measuring data, wherein the measuring device (10) further comprises an acceleration sensor (28) and a GNSS receiver (16) for receiving GNSS signals from satellites (42) of a global navigation satellite system (42), wherein the tachymeter (40) is located on land and is directed towards the measuring device (10), wherein the system further comprises a control unit which is designed to ascertain a current position and / or orientation of the measuring device (10) on the basis of measurement data of the acceleration sensor (28), on the basis of the GNSS signals received by the GNSS receiver (16), and on the basis of measurement data recorded by the tachymeter (40) and to assign said current position and / or orientation to the measuring data, wherein the holding apparatus is designed to hold the measuring device (10) in the state of use.

2. A system consisting of a measuring device (10) for measuring a water-filled structure (30), a holding device (24, 24', 24") located on land next to the structure, and a tachymeter (40), wherein the measuring device (10) comprises a rod-shaped sensor support (12) having a first end (12a) arranged below the water surface (W) in the state of use of the measuring device (10) and a second end (12b) arranged above the water surface (W) in the state of use of the measuring device (10), wherein at least one measuring sensor (14) is arranged at the first end (12a) of the sensor support (10) for measuring the structure (30) by recording measuring data, wherein the measuring device (10) further comprises an acceleration sensor (28) and a prism unit (16') for the tachymeter (40), wherein the tachymeter (40) is located on land, is directed towards the measuring device (10), and is determined in its position via GNSS measuring points that are designed to receive GNSS signals from satellites of a global navigation system (42), wherein the system further comprises a control unit which is designed to ascertain a current position and / or orientation of the measuring device (10) on the basis of measurement data of the acceleration sensor (28), on the basis of the GNSS signals received by the GNSS measuring points (16'), and on the basis of measurement data recorded by the tachymeter (40) and to assign said current position and / or orientation to the measuring data, wherein the holding device is designed to hold the measuring device (10) in the state of use.

3. The system according to claim 1 or 2, characterized by a suspension (20) by means of which the measuring device (10) can be brought into the state of use.

4. The system according to claim 3, characterized in that the suspension (20) is a gimbal.

5. The system according to claim 1, characterized in that the holding apparatus (24, 24', 24") comprises a boom (22) which can be positioned above the water surface and which makes it possible to lower the sensor support (12) by the first end (12a) into the water-filled structure (30).

6. The system according to one of the preceding claims, characterized in that the sensor support (12) can be rotated about its longitudinal axis (L).

7. The system according to one of the preceding claims, characterized in that the control unit is further designed to temporally synchronize the measurement data of the acceleration sensor (28), the measurement data of the tachymeter (40), and the GNSS signals with one another using the GNSS receiver (16).

8. The system according to claim 7, characterized in that the control unit is designed, for the temporal synchronization, to use a time signal received via the GNSS receiver (16) of the tachymeter (40) and / or to provide the measurement data received from the tachymeter (40) with a time stamp upon receipt.

9. The system according to one of the preceding claims, characterized in that the acceleration sensor is part of an inertial measuring unit (28).

10. The system according to claim 9, characterized in that the control unit is designed to correct a drift of the inertial measuring unit (28) by means of the GNSS signals and the measurement data of the tachymeter (40).

11. The system according to one of the preceding claims, characterized in that the at least one measuring sensor (14) is selected from the following set: camera, in particular a thermal camera or multispectral camera, a laser scanner, an echo sounder, in particular a multi-beam echo sounder, a 3D area sensor, or a line sensor.

12. A method for measuring a water-filled structure (30) by means of a system according to one of the preceding claims, comprising the steps of: bringing the measuring device (10) into a state of use, in which the first end (12a) of the sensor support (10) is arranged below the water surface; measuring the structure (30) by means of the at least one measuring sensor (14) by recording measuring data; ascertaining a current position and / or orientation of the measuring device (10) on the basis of measurement data of the acceleration sensor (28), on the basis of the GNSS signals received by the GNSS receiver (16), and on the basis of the measurement data of a tachymeter (40) located on land and directed towards the measuring device (40); assigning the current position and / or orientation of the measuring device (10) to the measuring data, wherein the measuring device is held in the state of use from on land.

13. A method for measuring a water-filled structure (30) by means of a system according to one of the preceding claims, comprising the steps of: bringing the measuring device (10) into a state of use, in which the first end (12a) of the sensor support (10) is arranged below the water surface; measuring the structure (30) by means of the at least one measuring sensor (14) by recording measuring data; ascertaining a current position and / or orientation of the measuring device (10) on the basis of measurement data of the acceleration sensor (28), on the basis of the GNSS signals for the position of a tachymeter received by GNSS measuring points (16'), and on the basis of measurement data of the tachymeter (40) located on land and directed towards prism apparatuses; assigning the current position and / or orientation of the measuring device (10) to the measuring data, wherein the measuring device is held in the state of use from on land.

14. The method according to claim 12 or 13, characterized by temporal synchronization of the measurement data of the acceleration sensor (28), of the measurement data of the tachymeter (40), and of the GNSS signals with one another using the GNSS receiver (16), at least when the GNSS receiver (16) receives inadequate GNSS signals.

15. The method according to one of claims 12 to 14, characterized by bringing the measuring device (10) into the state of use by means of a holding apparatus (24, 24', 24") located on land next to the structure (30).

16. The method according to claim 15, characterized by bringing the measuring device (10) into the state of use by positioning a boom (22) of the holding apparatus (24, 24', 24") located on land, on which boom the measuring device (10) is arranged, above the structure (30) and lowering the sensor support (12) by the first end (12a) into the structure (30).

17. The method according to one of claims 12 to 16, characterized by taking into account an inclination and / or a rotation and / or a bending of the sensor support (12) when assigning the position and / or orientation to the measuring data.