Method for determining the height of water waves

Abstract

Method for determining the height of waves on a water surface (3), wherein the water surface (3) is scanned by means of radiation (8) directed from a sensor onto the water surface and reflected there, and a measurement of the distance between the sensor and the measuring points (9) on the water surface (3) is carried out, wherein, starting from the spatial position coordinates of the sensor, position coordinates of a plurality of measuring points (9) in three-dimensional space as well as the respective solid angle of the measuring points (9) to the sensor are determined and stored, wherein the measuring points (9) detected during the scanning of the water surface (3) form a measuring point cloud describing the water surface and the wave height is determined by forming the difference between the height coordinates (Z 10 , Z 11) of at least two automatically or manually selected measuring points (10, 11), characterized in that the measuring points (9) are predetermined starting from a reference object (12) located on the water surface (3) and moving on a spatial trajectory (4) in such a way that the measuring points (9) form a measuring point cloud at least partially containing the spatial trajectory (4) of the reference object.

Description

FIELD OF INVENTION

[0001] The present invention relates to a method for determining the height of waves on a water surface. The water surface is scanned using radiation directed from a sensor onto the water surface and reflected there, and the distance between the sensor and the measuring points on the water surface is measured. The invention also relates to the use of the method in surfing and to a device for implementing the method. STATE OF THE ART

[0002] Determining the height of ocean waves is not only necessary for forecasting weather events, but also for warning shipping or for warning coastal areas and structures exposed to wave activity in the event of extreme wave formations. This often involves measuring devices and sensors mounted on buoys or fixed points in the water, floating or on the seabed, or on land, such as Doppler profile current meters, pressure sensors, wave height sensors, or radar and lidar sensors.

[0003] DE 10 2013 002 127 A1 discloses a method for determining a wave elevation and / or velocity potential field in a wave-moving body of water, whereby measurement data are collected at at least two measuring locations located on a measuring surface oriented parallel to a still water level. Sensors used here include Doppler flow profilers.

[0004] JP 2014 232087 A discloses a method and a device for measuring wave height, in which a radar device arranged on land emits an electromagnetic wave directed towards the water surface and determines the wave height based on the intensity of the reflected wave.

[0005] In addition to its use for forecasting and warning, wave height measurement also has another, more enjoyable application, serving as a benchmark for sports competition. Since its Olympic debut in Tokyo in 2020, surfing has become an Olympic discipline. While the difficulty, type, and variety of surfers' maneuvers are evaluated by a jury in Olympic competitions, there is also growing public interest in "big wave surfing," and in particular, the spectacular surfing of the largest and highest waves possible.

[0006] The latter essentially involves documenting, comparing, and evaluating wave heights for a record attempt. In this area of ​​sport, wave height determination has so far been rather subjective, using methods such as the Hawaiian method, which estimates wave height from its backside, or the Bascom method, commonly used in the United States, which estimates the height available for surfing at the front of a wave.

[0007] Determining the height of water waves is fundamentally not trivial, as they are so-called gravity waves, whose propagation speed is dominated by the acceleration due to gravity. Water waves deviate from the theoretically symmetrical shape of a wave to a greater or lesser extent. In coastal areas, the wave height seen from the rear is also considerably lower than that seen from the front. Furthermore, an observer, such as a sailor standing in front of a wave in a trough, estimates its height to be approximately twice its amplitude.

[0008] All of this already makes it clear that, for the comparability of record attempts in big wave surfing, it is desirable to be able to determine wave heights more accurately than by estimation. On the other hand, expensive warning systems, such as those described above for forecasting and warning, which require significant infrastructure to implement, are not intended to document record attempts as a byproduct.

[0009] JP 2008 203 123 A discloses an aircraft for carrying out a method according to the preamble of claim 1. DESCRIPTION OF THE INVENTION

[0010] It is therefore an object of the invention to provide a wave height determination that is as accurate, comprehensible, documentable and objective as possible using measurement technology, which is independent of large and complex warning systems and can operate with simple means even without a large infrastructure of land- or sea-based measuring stations.

[0011] This object is achieved by a method having the features of claim 1. Advantageous embodiments and further developments are described in the respective dependent claims. A particular use of the method is described in claim 13. Furthermore, claim 14 discloses a device for carrying out the method.

[0012] According to the invention, based on the spatial position coordinates of a sensor, the position coordinates of a plurality of measuring points in three-dimensional space, as well as the respective solid angle of the measuring points relative to the sensor, are determined and stored. The measuring points acquired during the scanning of the water surface form a measurement point cloud describing the water surface, and the wave height is determined by calculating the difference between the height coordinates (Z coordinate) of at least two automatically or manually selected measuring points. The method according to the invention allows the actual, current, and local wave height for each wave to be determined using relatively simple means and independently of complex warning systems.

[0013] In a further development of the method according to the invention which facilitates digital processing in computing devices, position coordinates and solid angles are recorded and stored as digital values ​​and thus form a digital measurement point cloud.

[0014] According to the inventive method, the measuring points are specified starting from a reference object located on the water surface and moving on a spatial trajectory in such a way that the measuring points form a measuring point cloud that at least partially contains the spatial trajectory of the reference object.

[0015] Such a method makes it possible to determine the actual, current and local wave height as it is formed at or on the reference object, i.e. not at more or less distant points on the crest or at the foot of the wave, but where the reference object, for example a surfer, is moving on its path.

[0016] Such an assignment to the position of a reference object is further improved by a further development of the inventive method, in which the wave height is determined by forming the difference between the height coordinates (Z coordinate) of at least two measuring points located on the spatial trajectory curve.

[0017] By defining the measurement point cloud in this way and selecting the measurement points from it on the trajectory, the wave height is determined that is actually relevant on the trajectory or at the location of the reference object, i.e. the wave height that is “surfed” and not a wave height that is still building up behind the surfer.

[0018] With the method according to the invention, the investigation and evaluation of record attempts in “Big Wave Surfing” no longer requires the usual evaluation of image material or estimates.

[0019] One embodiment of the method according to the invention comprises arranging the sensor on an unmanned aerial vehicle, preferably on a remote-controlled multicopter or a drone. Since surfing, for example, is a highly dynamic and mobile activity, it is advantageous if the sensor is also correspondingly mobile. By arranging it on an unmanned aerial vehicle, i.e. attaching it to a drone or a remote-controlled multicopter, a carrier for the sensor is obtained that is movable during the measurement, can track the reference object, and can also be easily transported and deployed to any location. Such an unmanned aerial vehicle, e.g. a drone, can then be launched either from a boat or from the beach and positioned accordingly in relation to the surfer.

[0020] In principle, the method according to the invention can be used to measure any wave within the sensor's range. Depending on the radiation used, the sensor can also be mounted on fixed positions such as towers, masts, platforms, or similar. However, the influence of the radiation on objects or people within the field of influence must be taken into account, as well as the fact that accuracy decreases with the distance of the measurement point cloud from the sensor.

[0021] A further embodiment of the method according to the invention consists in controlling the unmanned aerial vehicle in such a way that it maintains a predetermined position relative to the reference object during its movement. Maintaining a predetermined position relative to the reference object, such as a surfer, facilitates the specification or definition of the measurement point cloud and the evaluation of the measurement points selected from it along the trajectory.

[0022] This also applies to a further embodiment of the method according to the invention, in which the aircraft is controlled such that it maintains a position above and, in the direction of movement, to the side of the reference object as well as above a wave crest located behind the reference object. The remote-controlled aircraft flies or hovers above the area of ​​the sea to be scanned or the wave front at a sufficient height above the area to be measured, i.e., above the wave ("follow-me" function). The water surface is continuously scanned in accordance with the method using the measurement point cloud. During the measuring process, i.e., while the surfer rides the wave, the position of the aircraft "above" and "in front of" the surfer is maintained, either via a "position hold function" in the aircraft's control system or by the pilot controlling it himself.

[0023] A further development of the method consists in that the unmanned aircraft is controlled with the aid of a position determination by a GPS system, or differential GPS system using permanently measured reference stations, preferably using an additional attitude sensor of the aircraft, wherein, starting from the position of the aircraft, ie the sensor, the absolute position coordinates of the measuring points are determined in all three spatial directions.

[0024] Determining such absolute coordinates, namely the coordinates for the absolute positions of the measurement points, enables clear and reliable comparability at any location. This simplifies the unambiguous determination and comparability of wave heights. Determining such absolute position coordinates can be achieved with a differential GPS system, in which the signal travel times for each GPS satellite can be determined very precisely using permanently surveyed reference stations.

[0025] A further embodiment of the method according to the invention involves using a lidar or radar sensor as the sensor. Such measurement systems, which operate with laser beams or electromagnetic radiation, are extremely precise and can now be used as compact modules and sensors for a wide variety of applications. Lidar sensors are already being used for various applications in the automotive sector. Lidar sensors scan their surroundings using laser beams, thus generating a digital point cloud with sampled measurement points.

[0026] A further development of the method involves taking a video recording of the water surface while measuring the distance between the sensor and the measurement points. This video recording includes the reference object moving along a spatial trajectory and the surface associated with the measurement points. This allows a camera on the remotely piloted aircraft to record the video recordings for later review of the data in the measurement point cloud.

[0027] In a further development of the method, the data from the distance measurement and / or the video recording are sent via a telemetry system and in real time to a stationary evaluation unit, for example to a stationary receiving station, in which a higher computing power is available for storage and evaluation than in the remote-controlled aircraft or in the drone.

[0028] In a further development of the method, the distance measurement data and / or video recordings are stored on board the aircraft and subjected to a delayed evaluation. This simplifies the design of the aircraft or drone by eliminating the need for a transmission unit, such as a transmitter, and an evaluation unit requiring high computing power.

[0029] As already explained, an advantageous application of the method according to the invention is to determine the wave height at a sporting event, with the reference object being a surfer moving along a curved trajectory on the front of a wave. Such an application allows for an exact, comparable measurement of the wave height to be provided at any location, for example, on particularly remote beaches with high waves.

[0030] A further aspect of the invention relates to a device for carrying out the method, designed as an unmanned aerial vehicle provided with a measuring device, wherein the measuring device has one or more lidar and / or radar sensors for measuring a distance between the respective sensor and measuring points on the water surface.

[0031] In the following, the invention is described with reference to the exemplary embodiment shown in the figure.

[0032] This shows Fig. 1 shows a schematic diagram of two developed waves 1 and 2 on a water surface 3. Waves 1 and 2 are drawn in a sectional view and have formed over a bottom 5 of a beach area not shown in detail here. On the front side of wave 2, a surfer 12 can be seen moving along a curved path 4, namely, gliding diagonally down the front side of the wave, thus "riding" the wave.

[0033] To determine the wave height below and relative to the position of the surfer 12, a remote-controlled multicopter 6 is provided, which is controlled by a pilot (not shown here) in such a way that it maintains a predetermined position relative to the surfer 12 during the movement of the reference object 12, here the surfer, namely laterally in front of the surfer 12 in the direction of movement and above the wave crest 7 located behind the surfer 12.

[0034] The multicopter 6 is equipped with a lidar sensor (not shown in detail here), which emits a laser beam 8 directed at the water surface, here the front of the shaft 2, and reflected there, thus measuring the distance between the lidar sensor and the measuring points 9 on the water surface forming a measuring point cloud.

[0035] The measuring points 9 are specified, here starting from the surfer 3 moving on the spatial trajectory 4 on the water surface as a reference point or reference object in such a way that the measuring points 9 form a measuring point cloud which contains the spatial trajectory 4 of the reference object / surfer 12.

[0036] Using the lidar sensor on the multicopter 6, the absolute position coordinates of the measuring points 9 are determined in all three spatial directions x, y and in the height direction z. The current wave height relevant for the surfer 12 is then determined by calculating the difference between the height coordinates Z 10 and Z 11 at least two automatically selected measuring points 10 and 11. Here, two measuring points 10 and 11 are selected, which are also located on trajectory curve 4.

[0037] The position of the Multicopter 6 is determined by a differential GPS system, whereby the multicopter has an additional position sensor.

Claims

[1] Method for determining the height of waves on a water surface (3), wherein the water surface (3) is scanned by means of radiation (8) directed from a sensor onto the water surface and reflected there, and a measurement of the distance between the sensor and measuring points (9) on the water surface (3) is carried out, wherein, starting from the spatial position coordinates of the sensor, position coordinates of a plurality of measuring points (9) in three-dimensional space as well as the respective solid angle of the measuring points (9) to the sensor are determined and stored, wherein the measuring points (9) recorded during the scanning of the water surface (3) form a measuring point cloud describing the water surface and the wave height is determined by forming the difference between the height coordinates (Z 10 , Z 11 ) of at least two automatically or manually selected measuring points (10, 11), characterized bythat the measuring points (9) are predetermined starting from a reference object (12) located on the water surface (3) and moving on a spatial trajectory (4) in such a way that the measuring points (9) form a measuring point cloud at least partially containing the spatial trajectory (4) of the reference object. [2] Method according to claim 1, characterized by that the position coordinates and solid angles are recorded and stored as digital values ​​and form a digital measurement point cloud. [3] Method according to claim 1 or 2, characterized by that the wave height is determined by forming the difference of the height coordinates (Z 10 , Z 11 ) of at least two measuring points (10, 11) located on the spatial trajectory curve. [4] Method according to one of claims 1 to 3, characterized bythat the sensor is arranged on an unmanned aerial vehicle (6), preferably on a remote-controlled multicopter (6) or on a drone, further comprising: - Controlling the aircraft (6) so that it maintains a predetermined position relative to the reference object (12) during the movement of the reference object. [5] Method according to claim 4, characterized by that the aircraft (6) is controlled in such a way that it maintains a position above and laterally in front of the reference object (12) in the direction of movement and above a wave crest (7) located behind the reference object (12). [6] Method according to one of claims 4 or 5, characterized bythat the aircraft (6) is controlled with the aid of a position determination by a GPS system or differential GPS system, preferably using an additional position sensor of the aircraft (6), wherein the absolute position coordinates of the measuring points (9) are determined in all three spatial directions based on the position of the aircraft (6) and the sensor provided there. [7] Method according to one of claims 1 to 6, characterized by that during the measurement of the distance between the sensor and the measuring points, a video recording of the water surface is made, which contains the reference object (12) moving on a spatial trajectory (4) and the measuring points (9). [8] Method according to one of claims 1 to 7, characterized by that the distance measurement data is sent via a telemetry system and in real time to a stationary evaluation unit. [9] Method according to one of claims 4 to 7, wherein claim 7 refers back exclusively to one of claims 4 to 6, characterized by that the distance measurement data are stored on board the aircraft (6) and subjected to a time-delayed evaluation. [10] Method according to claim 7, characterized by that the data from the distance measurement and the video recording or the data from the video recording are sent via a telemetry system and in real time to a stationary evaluation unit. [11] Method according to claim 7, wherein claim 7 refers back exclusively to one of claims 4 to 6, characterized by that the data of the distance measurement and the video recording or the data of the video recording are stored on board the aircraft (6) and subjected to a time-delayed evaluation. [12] Method according to one of claims 1 to 11, characterized bythat a lidar or radar sensor is provided as the sensor. [13] Use of the method according to one of claims 1 to 12 for determining the wave height at a sporting event, wherein the reference object (12) is a surfer moving on a trajectory curve on the front side of a wave. [14] Device for carrying out the method according to one of claims 4 to 12, designed as an unmanned aerial vehicle (6) provided with a measuring device, wherein the measuring device has one or more lidar and / or radar sensors for measuring a distance between the sensor and measuring points (9) on the water surface (3).

Images