No-tide-gauge pelagic water depth calculation method based on airborne laser radar and related device

Abstract

The invention provides an airborne laser radar-based tide-gauge-free pelagic water depth calculation method and device, electronic equipment and a storage medium, and the method comprises the steps: obtaining laser point cloud data of a to-be-measured sea area, carrying out the preprocessing and classification of the laser point cloud data of the to-be-measured sea area, and obtaining the laser point cloud data of the to-be-measured sea area; outputting submarine topography geodetic high point cloud data under the earth ellipsoid reference; dTU21 global average sea surface model data are obtained, and average sea surface geodetic height data of the sea area to be measured are obtained through interpolation; determining a depth reference plane L value of the sea area to be measured; the water depth value is calculated according to the submarine topography geodetic high point cloud data, the average sea surface geodetic height data and the depth reference surface L value, model transmission errors are reduced, dependence on a tide gauge station is avoided, seamless splicing of water depths between different sea areas can be achieved, the tide gauge station does not need to be erected in an open sea area, and the cost is reduced. And the implementation difficulty and cost of airborne laser water depth measurement are greatly reduced.

Description

Technical Field

[0001] This invention relates to the field of water depth measurement technology, and in particular to a method, device, electronic equipment, and storage medium for calculating ocean depth without tide gauge based on airborne lidar. Background Technology

[0002] Water depth measurement is one of the most important tasks in hydrographic surveying. Traditional regional water depth measurement mainly relies on shipborne acoustic detection technologies, such as single-beam or multi-beam echo sounders. However, in shallow coastal areas, complex operating environments (such as shoals, silt, and reefs) pose high risks, low efficiency, and even inaccessibility for vessels, resulting in significant data gaps in nearshore waters. In recent years, airborne laser bathymetry has rapidly developed due to its advantages of high efficiency, high accuracy, and lack of access restrictions in shallow waters, becoming an important technical means for coastal water depth and seabed topography exploration. This technology emits dual-band lasers of 1064nm infrared light and 532nm green light towards the sea surface to acquire surface reflection signals and seabed reflection signals, respectively, and calculates water depth values ​​by combining the laser propagation time difference and the refractive index of the medium. However, existing methods have significant limitations in their application in open ocean areas: First, airborne laser bathymetry acquires instantaneous water depth values, which are affected by waves, tides, and currents. It requires data from synchronous tide gauge stations to convert the instantaneous sea level to mean sea level, a process that introduces observation and calculation errors. Second, open ocean areas typically lack the conditions for setting up tide gauge stations, resulting in the acquisition of only seabed topography and geodetic height data, making it impossible to calculate actual water depth. Furthermore, temporary tide gauge stations are susceptible to electromagnetic interference or poor GNSS signal quality, further reducing data accuracy. More importantly, relying on discrete tide gauge station data leads to inconsistencies in vertical reference between adjacent sea areas, making seamless stitching of water depth results difficult. Summary of the Invention

[0003] This invention provides a method, device, electronic equipment, and storage medium for calculating ocean depth without tide gauge based on airborne lidar, in order to solve the shortcomings of traditional airborne laser depth sounding technology, which relies on tide gauge data, resulting in difficulties in implementation, inconsistent benchmarks, error accumulation, and high costs in ocean measurements.

[0004] This invention provides a method for calculating ocean depth without tide gauge based on airborne lidar, comprising:

[0005] Acquire laser point cloud data of the sea area to be measured, preprocess and classify the laser point cloud data of the sea area to be measured, and output seabed topography geodetic height point cloud data under the Earth ellipsoid reference.

[0006] Obtain DTU21 global mean sea level model data, and interpolate to obtain the mean sea level geodetic height data of the sea area to be measured;

[0007] Determine the depth reference surface L value of the sea area to be measured;

[0008] The water depth is calculated based on the seabed topographic geodetic height cloud data, the mean sea surface geodetic height data, and the depth reference surface L value.

[0009] According to the present invention, the method for calculating ocean depth without tide gauge based on airborne lidar includes preprocessing and classifying the lidar point cloud data of the sea area to be measured, and outputting seabed topographic geodetic height point cloud data under the Earth ellipsoid reference, comprising:

[0010] The laser point cloud data of the sea area to be measured is subjected to data decoding and format conversion processing;

[0011] Perform geolocation on the converted point cloud data;

[0012] A point cloud classification algorithm based on intensity threshold and echo features is used to classify the geolocated point cloud data and obtain underwater point cloud data.

[0013] The underwater point cloud data is denoised, and the denoised underwater point cloud is converted to the WGS84 ellipsoid reference, and the seabed topographic geodetic height point cloud data under the WGS84 ellipsoid reference is output.

[0014] According to the present invention, the method for calculating deep-sea water depth without tide gauge based on airborne lidar includes the following: A point cloud classification algorithm based on intensity threshold and echo characteristics is used to classify the geolocated point cloud data to obtain underwater point cloud data.

[0015] Echo signal analysis was performed on the geolocated point cloud data to distinguish the reflection characteristics of lasers at different wavelengths:

[0016] Based on the intensity threshold, the laser reflection characteristics of different wavelengths are preliminarily classified to obtain candidate points on the seabed;

[0017] Verify whether the echo waveform characteristics of the candidate underwater points conform to the seabed reflection characteristics, and use the verified point cloud data as the underwater point cloud data.

[0018] According to the present invention, the method for calculating ocean depth without tide gauge based on airborne lidar, wherein acquiring DTU21 global mean sea level model data and interpolating it to obtain mean sea level geodetic height data of the sea area to be measured includes:

[0019] Download DTU21 global mean sea level model data;

[0020] Based on the coverage area of ​​the airborne laser bathymetry system, determine the boundary coordinates of the sea area to be interpolated;

[0021] Obtain the sea surface elevation of each DTU21 model grid data measurement point within the boundary coordinate range of the sea area to be interpolated;

[0022] Interpolation calculations are performed on the sea surface geodetic height at each measurement point location of the DTU21 model grid data to obtain the average sea surface geodetic height data of the sea area to be measured.

[0023] According to the method for calculating ocean depth without tide gauge based on airborne lidar provided by the present invention, the interpolation calculation of the sea surface geodetic height at the location of each DTU21 model grid data measurement point includes:

[0024] The sea surface geodetic height of each DTU21 model grid data measurement point is loaded into the geographic information processing software. Using the interpolation tool in the geographic information processing software, the interpolation method is selected and the corresponding interpolation parameters are set, and the interpolation is performed.

[0025] According to the method for calculating ocean depth without tide gauge based on airborne lidar provided by the present invention, determining the depth reference surface L value of the sea area to be measured includes:

[0026] When there are long-term tide gauge stations around the measurement area, obtain the depth reference surface L value provided by the tide gauge station;

[0027] Verify the temporal validity and spatial applicability of the depth datum L value. If the verification is successful, use the depth datum L value provided by the tide gauge station as the depth datum L value of the sea area to be measured.

[0028] When there is no long-term tide gauge data, nautical chart data is obtained from the national nautical chart publishing unit, and the depth datum information marked in the nautical chart data is extracted and used as the depth datum L value of the sea area to be measured.

[0029] According to the present invention, the method for calculating ocean depth without tide gauge based on airborne lidar, wherein the calculation of water depth based on the seabed topographic geodetic height cloud data, the mean sea surface geodetic height data, and the depth reference surface L value includes:

[0030] water depth H depth =H DTU21 -LH aero ;

[0031] Among them, H depth H represents the water depth at any point within the survey area. aero This is geodetic height cloud data for seafloor topography, with the reference plane pointing upwards as positive; H DTU21 The mean sea level geodetic height data is represented by a positive value pointing upwards; L is the depth reference surface L value.

[0032] The present invention also provides a device for calculating offshore water depth without tide gauge, comprising:

[0033] The first acquisition module is used to acquire laser point cloud data of the sea area to be measured, preprocess and classify the laser point cloud data of the sea area to be measured, and output seabed topography geodetic height point cloud data under the Earth ellipsoid reference.

[0034] The second acquisition module is used to acquire DTU21 global mean sea level model data and obtain the mean sea level geodetic height data of the sea area to be measured by interpolation.

[0035] The determination module is used to determine the depth reference surface L value of the sea area to be measured;

[0036] The calculation module is used to calculate the water depth value based on the seabed topographic geodetic height cloud data, the mean sea surface geodetic height data, and the depth reference surface L value.

[0037] The present invention also provides an electronic device, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the program to implement the above-described method for calculating ocean depth without tide gauge based on airborne lidar.

[0038] The present invention also provides a non-transitory computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the method for calculating ocean depth without tide gauge based on airborne lidar as described above.

[0039] This invention provides a method, apparatus, electronic device, and storage medium for calculating ocean depth without tide checks based on airborne lidar. It acquires lidar point cloud data of the sea area to be measured, preprocesses and classifies the data, and outputs seafloor topography geodetic height point cloud data under an Earth ellipsoid reference. It also acquires DTU21 global mean sea level model data and interpolates it to obtain the mean sea level geodetic height data of the sea area to be measured. Finally, it determines the depth datum L value of the sea area to be measured. The water depth is calculated based on the seafloor topography geodetic height point cloud data, the mean sea level geodetic height data, and the depth datum L value. This invention does not require instantaneous sea surface parameters. Compared with water depth calculation, the measurement errors caused by wave correction and tide correction during the conversion between water depth and depth datum are reduced. The geodetic height of the mean sea level is obtained by interpolation using the DTU global mean sea level height model. In open sea areas, there is no need to use long-term tide gauge observation data to calculate the mean sea level, which reduces model propagation error and avoids dependence on tide gauges, realizing tide-free water depth measurement. Using the mean sea level model under a unified datum and seabed topography geodetic height data for water depth calculation, seamless splicing of water depth between different sea areas can be achieved. There is no need to set up tide gauges in open sea areas, which greatly reduces the implementation difficulty and cost of airborne laser water depth measurement. Attached Figure Description

[0040] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0041] Figure 1 This is one of the flowcharts of the method for calculating ocean depth without tide gauge based on airborne lidar provided by the present invention;

[0042] Figure 2 This is the second flowchart of the method for calculating ocean depth without tide gauge based on airborne lidar provided by the present invention.

[0043] Figure 3 This is a spatial relationship diagram between the elevation datum and the depth datum provided by the present invention;

[0044] Figure 4 This is a schematic diagram of the structure of the tide-free far-sea depth calculation device provided by the present invention. Detailed Implementation

[0045] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0046] Figure 1 A flowchart of the method for calculating ocean depth without tide gauge based on airborne lidar provided in an embodiment of the present invention is shown below. Figure 1 As shown, the method for calculating ocean depth without tide gauge based on airborne lidar provided in this embodiment of the invention includes:

[0047] Step 101: Obtain laser point cloud data of the sea area to be measured, preprocess and classify the laser point cloud data of the sea area to be measured, and output seabed topography geodetic height point cloud data under the Earth ellipsoid reference.

[0048] Step 102: Obtain DTU21 global mean sea level model data, and interpolate to obtain the mean sea level geodetic height data of the sea area to be measured;

[0049] Step 103: Determine the depth reference surface L value of the sea area to be measured;

[0050] Step 104: Calculate the water depth value based on the seabed topographic geodetic height cloud data, the mean sea surface geodetic height data, and the depth reference surface L value.

[0051] Traditional airborne laser bathymetry has significant limitations in its application in open ocean areas: First, it acquires instantaneous water depth values, which are affected by waves, tides, and currents. It requires data from synchronous tide gauge stations to convert the instantaneous sea level to mean sea level, introducing observation and calculation errors. Second, open ocean areas typically lack the facilities to set up tide gauge stations, resulting in only obtaining seabed topography and geodetic height data, and thus being unable to calculate actual water depth. Furthermore, temporary tide gauge stations are susceptible to electromagnetic interference or poor GNSS signal quality, further reducing data accuracy. More importantly, relying on discrete tide gauge data leads to inconsistencies in vertical reference between adjacent sea areas, making seamless stitching of water depth results difficult.

[0052] The present invention provides a method for calculating ocean depth without tides based on airborne lidar. This method acquires lidar point cloud data of the sea area to be measured, preprocesses and classifies the lidar point cloud data, and outputs seafloor topography geodetic height point cloud data under an Earth ellipsoid reference. It also acquires DTU21 global mean sea level model data and interpolates it to obtain the mean sea level geodetic height data of the sea area to be measured. Finally, it determines the depth datum L value of the sea area to be measured. The method calculates the water depth value based on the seafloor topography geodetic height point cloud data, the mean sea level geodetic height data, and the depth datum L value. This invention does not require instantaneous sea surface data for water depth calculation. This reduces measurement errors caused by wave and tidal corrections during the conversion between the laser and depth datum. The geodetic height of the mean sea level is obtained by interpolation using the DTU global mean sea level height model. In open ocean areas, there is no need to use long-term tide gauge observation data to calculate the mean sea level, reducing model propagation errors. Furthermore, it avoids dependence on tide gauges and achieves tide-free depth measurement. Using a mean sea level model under a unified datum and seafloor topography geodetic height data for depth calculation, seamless splicing of depths between different sea areas can be achieved. There is no need to set up tide gauges in open ocean areas, which greatly reduces the implementation difficulty and cost of airborne laser depth measurement.

[0053] Based on any of the above embodiments, the preprocessing and classification of the laser point cloud data of the sea area to be measured, and the output of seabed topographic geodetic height point cloud data under the Earth ellipsoid reference, includes:

[0054] Step 201: Perform data decoding and format conversion on the laser point cloud data of the sea area to be measured;

[0055] Step 202: Geolocation of the converted point cloud data;

[0056] Step 203: Use a point cloud classification algorithm based on intensity threshold and echo features to classify the geolocated point cloud data and obtain underwater point cloud data.

[0057] Step 204: Denoise the underwater point cloud data, convert the denoised underwater point cloud to the WGS84 ellipsoid reference, and output the seabed topographic geodetic height point cloud data under the WGS84 ellipsoid reference.

[0058] This invention utilizes various airborne laser bathymetry systems to acquire airborne laser bathymetry point cloud data of the surveyed sea area. Specifically, by integrating laser ranging, GPS positioning, and IMU attitude measurement data, and based on the laws of light propagation and spatial geometry, the geodetic height of the seabed points is directly derived. All input parameters in this method come from direct measurements by the system's own sensors (laser time, GPS position, IMU attitude) or known constants (speed of light, refractive index). Mathematical relationships are directly established through the laws of light propagation (speed = distance / time) and spatial geometry (vertical projection), without relying on external elevation models or complex transformations, ultimately directly outputting the geodetic height of the seabed points. The calculation formula is as follows:

[0059]

[0060] Wherein: H 水底 Target result, i.e., the geodetic height of the bottom point (unit: m);

[0061] H 平台 The elevation of the platform (in meters) is directly measured by the airborne GPS (WGS84 coordinate system).

[0062] c: The speed of laser propagation in air (approximately equal to the speed of light in a vacuum, 3 × 10⁸ m / s, a constant);

[0063] θ: Measured directly by the IMU, it is the zenith angle between the laser beam and the vertical direction (unit: radians, used to correct the projection of the slant distance to the vertical distance);

[0064] t1: Measured directly by the laser receiver, it is the time it takes for the laser to travel to and from the water surface (unit: s, usually in nanoseconds).

[0065] Δt: Calculated directly from t2-t1 (t2 is the time for the laser to travel to and from the bottom of the water), reflecting the round-trip propagation time of the laser in the water (unit: s);

[0066] n: Refractive index of water (freshwater ≈ 1.33, seawater ≈ 1.34, which can be obtained through on-site calibration or empirical values; a known parameter).

[0067] This invention enables the unification of spatiotemporal references. GPS positioning provides the platform's absolute position (longitude, latitude, and geodetic height) in the WGS84 coordinate system, serving as the spatial reference for all measurements. IMU attitude (θ) measures the platform's pitch / roll angle in real time during laser emission, projecting the laser slant range onto the vertical direction to eliminate geometric errors caused by platform sway. Laser timing, GPS positioning, and IMU attitude must be strictly synchronized to ensure data temporal consistency. All sensor data is unified within the same spatiotemporal framework, avoiding reference conversion errors introduced by step-by-step processing in traditional methods.

[0068] Furthermore, laser ranging calculates the distance from the water surface to the platform using the water surface reflection time t1, and then uses GPS geodetic height to infer the water surface elevation. The water refractive index (n) is used to accurately calculate the actual propagation distance of the laser in the water (rather than simply c·Δt / 2) by utilizing the round-trip time difference Δt of the laser at the bottom of the water and combining it with the known refractive index n. The IMU attitude angle (θ) corrects the projection of the slant range to the vertical distance (cosθ), avoiding an underestimation of the elevation due to non-perpendicular laser incidence. Through the joint calculation of light speed, refractive index, and geometric projection, a physical closed loop from time measurement to spatial coordinates is achieved, without relying on external water depth or tidal models.

[0069] The embodiments of the present invention improve the robustness of the system in complex environments (such as waves and turbid water) by mutual verification between sensors.

[0070] Existing technologies often employ sonar depth sounding or fail to consider dynamic refractive index calibration. This invention, however, precisely calculates the underwater propagation path using laser time difference and refractive index. Regarding measurement accuracy, the laser round-trip time difference and dynamic refractive index calibration enable accurate calculation of the underwater propagation path, effectively overcoming the errors caused by the fixed refractive index assumption in traditional sonar depth sounding. Especially in sea areas with significant variations in salinity and temperature, measurement accuracy can reach the centimeter level. Furthermore, lasers have stronger penetrating power in turbid waters, maintaining stable performance in complex waters such as estuaries and nearshore areas. In terms of operational efficiency, the integrated design of GPS, IMU, and laser ranging systems allows for real-time synchronous processing of all sensor data, directly outputting the geodetic height of the seabed point based on the WGS84 coordinate system, completely eliminating reliance on tide gauge stations. Regarding applicability, the globally unified coordinate reference ensures seamless integration with various satellite data, facilitating multi-source data fusion applications. Whether for high-precision mapping in shallow waters, operations in the open ocean without tide gauges, or measurements in complex aquatic environments, this technology provides reliable data support.

[0071] In this embodiment of the invention, the airborne laser bathymetry point cloud data acquired using various types of airborne laser bathymetry systems is saved as a .las format bathymetry point cloud. Using professional software such as Base Editor, ArcGIS, GlobalMapper, and Terrasolid, the .las format bathymetry point cloud data is loaded, the 40th type of seabed point is selected, and the required resolution, interpolation method, and sampling range parameters are set. An elevation grid is created, and a digital elevation model (DEM) of the seabed topography is generated through rasterization, thereby obtaining the seabed topographic geodetic height data, which is then exported and saved.

[0072] Based on any of the above embodiments, the step of using a point cloud classification algorithm based on intensity threshold and echo features to classify the geolocated point cloud data and obtain underwater point cloud data includes:

[0073] Step 301: Perform echo signal analysis on the geolocated point cloud data to distinguish the laser reflection characteristics of different wavelengths:

[0074] Step 302: Based on the intensity threshold, perform preliminary classification of the laser reflection characteristics of different wavelengths to obtain candidate points on the seabed;

[0075] Step 303: Verify whether the echo waveform characteristics of the candidate underwater points conform to the seabed reflection characteristics, and use the verified point cloud data as the underwater point cloud data.

[0076] The embodiments of the present invention can be applied in offshore waters with complex electromagnetic interference and poor GNSS quality, without relying on tide gauge observation data, thus avoiding errors caused by poor observation data quality.

[0077] Based on any of the above embodiments, the step of acquiring DTU21 global mean sea level model data and obtaining the mean sea level geodetic height data of the sea area to be measured by interpolation includes:

[0078] Step 401: Download DTU21 global mean sea level model data;

[0079] Step 402: Determine the boundary coordinates of the sea area to be interpolated based on the coverage area of ​​the airborne laser bathymetry system;

[0080] Step 403: Obtain the sea surface elevation of each DTU21 model grid data measurement point within the boundary coordinate range of the sea area to be interpolated;

[0081] Step 404: Perform interpolation calculation on the sea surface geodetic height at the location of each DTU21 model grid data measurement point to obtain the average sea surface geodetic height data of the sea area to be measured.

[0082] This invention provides a free online download of DTU21 global mean sea level model data via the internet. Since tidal information extracted from satellite altimetry data in open sea areas can achieve an accuracy of 2-3 cm, the accuracy and stability of the DTU21 global tidal model in offshore areas meet measurement requirements. The spatial reference coordinate system is a WGS84 ellipsoid with a resolution of 1′×1′, containing a total of 10800 latitude cells * 21602 longitude cells.

[0083] The embodiments of the present invention use the DTU global mean sea level height model to interpolate the geodetic height of the mean sea level. In open sea areas, there is no need to use long-term tide gauge observation data to calculate the mean sea level, which reduces the dependence on tide gauges and realizes tide-free water depth measurement.

[0084] In this embodiment of the invention, the interpolation calculation of the sea surface geodetic height at the location of each DTU21 model grid data measurement point includes:

[0085] The sea surface geodetic height of each DTU21 model grid data measurement point is loaded into the geographic information processing software. Using the interpolation tool in the geographic information processing software, the interpolation method is selected and the corresponding interpolation parameters are set, and the interpolation is performed.

[0086] In this embodiment of the invention, the conversion for any water depth point is performed according to the following steps:

[0087] Airborne laser sounding systems measure seabed topography and geodetic height data at any point; the mean sea level height model is loaded into professional geographic information processing software such as Base Editor, ArcGIS, and Global Mapper; the interpolation tools in the software are used to select the interpolation method and set the corresponding interpolation parameters, and the interpolation is performed to obtain the mean sea level geodetic height data.

[0088] The embodiments of the present invention use the DTU global mean sea level height model to interpolate the geodetic height of the mean sea level. In open sea areas such as the open ocean and uninhabited islands and reefs, it is not necessary to use the observation data of short-term tide gauge stations and temporary tide gauge stations to determine the mean sea level through the transfer method, thus reducing the model transfer error.

[0089] Based on any of the above embodiments, determining the depth reference surface L value of the sea area to be measured includes:

[0090] When there are long-term tide gauge stations around the measurement area, obtain the depth reference surface L value provided by the tide gauge station;

[0091] Verify the temporal validity and spatial applicability of the depth datum L value. If the verification is successful, use the depth datum L value provided by the tide gauge station as the depth datum L value of the sea area to be measured.

[0092] When there is no long-term tide gauge data, nautical chart data is obtained from the national nautical chart publishing unit, and the depth datum information marked in the nautical chart data is extracted and used as the depth datum L value of the sea area to be measured.

[0093] Based on any of the above embodiments, such as Figure 2 As shown, the specific steps for calculating offshore water depth without tide gauge provided in this embodiment of the invention include:

[0094] (1) Obtain global or regional sea surface height observation data to establish mean sea surface model.

[0095] (2) Use LiDAR technology to obtain high-precision seabed topography data of nearshore or specific sea areas to supplement the blind spots of satellite data.

[0096] (3) Use the DTU21 mean sea surface model (or other versions) to grid the discrete sea surface height of the satellite altimetry data to form a continuous mean sea surface (MSS).

[0097] (4) Combine the sea surface topography retrieved by satellite altimetry and the airborne laser bathymetry data to calculate the geodetic height (ellipsoidal height) of the seabed topography relative to the reference ellipsoid.

[0098] (5) Determination of depth datum (L value): The depth datum (such as the lowest astronomical tide level LAT) is usually determined by tidal models or tide gauge data.

[0099] (6) Model the vertical deviation (i.e., L value) between the geodetic height and the depth reference surface and establish the conversion relationship.

[0100] In this embodiment of the invention, the spatial relationship between the elevation datum and the depth datum is as follows: Figure 3 As shown, the water depth value is calculated based on the seabed topographic geodetic height cloud data, the mean sea surface geodetic height data, and the depth reference surface L value, including:

[0101] water depth H depth =H DTU21 -LH aero ;

[0102] Among them, H depth H represents the water depth at any point within the survey area. aero This is geodetic height cloud data for seafloor topography, with the reference plane pointing upwards as positive; H DTU21 The mean sea level geodetic height data is represented by a positive value pointing upwards; L is the depth reference surface L value.

[0103] The embodiments of the present invention use a mean sea surface model and seabed topographic geodetic height data under a unified benchmark to calculate water depth, which can achieve seamless splicing of water depth between different sea areas; it does not require the instantaneous sea surface to participate in the water depth calculation, reducing the measurement errors caused by wave correction and tide correction during the conversion between the sea surface and the depth benchmark.

[0104] The present invention provides a method for calculating ocean depth in open waters without tide gauges based on airborne lidar. This method acquires sounding point cloud data using multiple sensors. In open sea areas, tidal information extracted from satellite altimetry data achieves an accuracy of 2-3 cm. The average sea level in the open sea is interpolated using the DTU21 global mean sea level model, meeting the accuracy requirements while reducing reliance on tide gauge stations. This enables tide-free ocean depth measurement based on airborne laser sounding technology. This method effectively reduces the acquisition and observation errors of control data during airborne laser sounding in open seas, improves the mathematical accuracy of calculated water depth values ​​in the measurement area, and reduces the difficulty and cost of measurement implementation. It effectively reduces the dependence on tide gauge station data during airborne laser depth measurement in open seas and uninhabited island / reef areas, achieving tide-free ocean depth measurement.

[0105] The following describes the tide-free far-sea depth calculation device provided by the present invention. The tide-free far-sea depth calculation device described below can be referred to in correspondence with the tide-free far-sea depth calculation method based on airborne lidar described above.

[0106] Figure 4 This is a schematic diagram of the tide-free offshore water depth calculation device provided in an embodiment of the present invention, as shown below. Figure 4 As shown, the tide-free offshore water depth calculation device provided in this embodiment of the invention includes:

[0107] The first acquisition module 401 is used to acquire laser point cloud data of the sea area to be measured, preprocess and classify the laser point cloud data of the sea area to be measured, and output seabed topography geodetic height point cloud data under the Earth ellipsoid reference.

[0108] The second acquisition module 402 is used to acquire DTU21 global mean sea level model data and obtain the mean sea level geodetic height data of the sea area to be measured by interpolation.

[0109] The determination module 403 is used to determine the depth reference surface L value of the sea area to be measured;

[0110] The calculation module 404 is used to calculate the water depth value based on the seabed topographic geodetic height cloud data, the mean sea surface geodetic height data, and the depth reference surface L value.

[0111] The tidal-free far-sea depth calculation device provided in this invention acquires laser point cloud data of the sea area to be measured, preprocesses and classifies the laser point cloud data of the sea area to be measured, and outputs seafloor topographic geodetic height point cloud data under the Earth ellipsoid reference; acquires DTU21 global mean sea level model data, and obtains the mean sea level geodetic height data of the sea area to be measured through interpolation; determines the depth datum L value of the sea area to be measured; and calculates the water depth value based on the seafloor topographic geodetic height point cloud data, the mean sea level geodetic height data, and the depth datum L value. This invention does not require instantaneous sea level to participate in the water depth calculation, reducing... The measurement errors introduced during wave and tidal corrections during the conversion between the laser depth datum and the depth datum are obtained by interpolating the mean sea level using the DTU global mean sea level height model. In open ocean areas, there is no need to use long-term tide gauge observation data to calculate the mean sea level, reducing model propagation errors and avoiding dependence on tide gauges, thus achieving tide-free depth measurement. Using a mean sea level model under a unified datum and seafloor topography geodetic height data for depth calculation, seamless splicing of depths between different sea areas can be achieved. There is no need to set up tide gauges in open ocean areas, which greatly reduces the implementation difficulty and cost of airborne laser depth measurement.

[0112] This invention also provides an electronic device, which may include a processor, a communication interface, a memory, and a communication bus, wherein the processor, communication interface, and memory communicate with each other via the communication bus. The processor can call logical instructions in the memory to execute a method for calculating ocean depth without tides based on airborne lidar. This method includes: acquiring lidar point cloud data of the sea area to be measured; preprocessing and classifying the lidar point cloud data of the sea area to be measured; outputting seafloor topography geodetic height point cloud data under an Earth ellipsoidal reference; acquiring DTU21 global mean sea level model data; obtaining mean sea level geodetic height data of the sea area to be measured through interpolation; determining the depth datum L value of the sea area to be measured; and calculating the water depth value based on the seafloor topography geodetic height point cloud data, the mean sea level geodetic height data, and the depth datum L value.

[0113] On the other hand, the present invention also provides a non-transitory computer-readable storage medium storing a computer program thereon. When executed by a processor, the computer program implements the above-described method for calculating ocean depth without tides based on airborne lidar. The method includes: acquiring laser point cloud data of the sea area to be measured; preprocessing and classifying the laser point cloud data of the sea area to be measured; outputting seafloor topographic geodetic height point cloud data under the Earth ellipsoid reference; acquiring DTU21 global mean sea level model data; obtaining mean sea level geodetic height data of the sea area to be measured through interpolation; determining the depth datum L value of the sea area to be measured; and calculating the water depth value based on the seafloor topographic geodetic height point cloud data, the mean sea level geodetic height data, and the depth datum L value.

[0114] The device embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the modules can be selected to achieve the purpose of this embodiment according to actual needs. Those skilled in the art can understand and implement this without any creative effort.

[0115] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for calculating ocean depth without tide gauge based on airborne lidar, characterized in that, include: Acquire laser point cloud data of the sea area to be measured, preprocess and classify the laser point cloud data of the sea area to be measured, and output seabed topography geodetic height point cloud data under the Earth ellipsoid reference. Obtain DTU21 global mean sea level model data, and interpolate to obtain the mean sea level geodetic height data of the sea area to be measured; Determine the depth reference surface L value of the sea area to be measured; The water depth is calculated based on the seabed topographic geodetic height cloud data, the mean sea surface geodetic height data, and the depth reference surface L value.

2. The method for calculating ocean depth without tide gauge based on airborne lidar according to claim 1, characterized in that, The process of preprocessing and classifying the laser point cloud data of the sea area to be measured, and outputting seabed topographic geodetic height point cloud data under the Earth ellipsoid reference, includes: The laser point cloud data of the sea area to be measured is subjected to data decoding and format conversion processing; Perform geolocation on the converted point cloud data; A point cloud classification algorithm based on intensity threshold and echo features is used to classify the geolocated point cloud data and obtain underwater point cloud data. The underwater point cloud data is denoised, and the denoised underwater point cloud is converted to the WGS84 ellipsoid reference, and the seabed topographic geodetic height point cloud data under the WGS84 ellipsoid reference is output.

3. The method for calculating ocean depth without tide gauge based on airborne lidar according to claim 2, characterized in that, The point cloud classification algorithm based on intensity threshold and echo features is used to classify the geolocated point cloud data and obtain underwater point cloud data, including: Echo signal analysis was performed on the geolocated point cloud data to distinguish the reflection characteristics of lasers at different wavelengths: Based on the intensity threshold, the laser reflection characteristics of different wavelengths are preliminarily classified to obtain candidate points on the seabed; Verify whether the echo waveform characteristics of the candidate underwater points conform to the seabed reflection characteristics, and use the verified point cloud data as the underwater point cloud data.

4. The method for calculating ocean depth without tide gauge based on airborne lidar according to claim 1, characterized in that, The acquisition of DTU21 global mean sea level model data, and the interpolation to obtain the mean sea level geodetic height data of the sea area to be measured, includes: Download DTU21 global mean sea level model data; Based on the coverage area of ​​the airborne laser bathymetry system, determine the boundary coordinates of the sea area to be interpolated; Obtain the sea surface elevation of each DTU21 model grid data measurement point within the boundary coordinate range of the sea area to be interpolated; Interpolation calculations are performed on the sea surface geodetic height at each measurement point location of the DTU21 model grid data to obtain the average sea surface geodetic height data of the sea area to be measured.

5. The method for calculating ocean depth without tide gauge based on airborne lidar according to claim 4, characterized in that, The interpolation calculation of the sea surface geodetic height at each DTU21 model grid data measurement point location includes: The sea surface geodetic height of each DTU21 model grid data measurement point is loaded into the geographic information processing software. Using the interpolation tool in the geographic information processing software, the interpolation method is selected and the corresponding interpolation parameters are set, and the interpolation is performed.

6. The method for calculating ocean depth without tide gauge based on airborne lidar according to claim 1, characterized in that, Determining the depth reference surface L value of the sea area to be measured includes: When there are long-term tide gauge stations around the measurement area, obtain the depth reference surface L value provided by the tide gauge station; Verify the temporal validity and spatial applicability of the depth datum L value. If the verification is successful, use the depth datum L value provided by the tide gauge station as the depth datum L value of the sea area to be measured. When there is no long-term tide gauge data, nautical chart data is obtained from the national nautical chart publishing unit, and the depth datum information marked in the nautical chart data is extracted and used as the depth datum L value of the sea area to be measured.

7. The method for calculating ocean depth without tide gauge based on airborne lidar according to claim 1, characterized in that, The calculation of water depth based on the seabed topographic geodetic height cloud data, mean sea surface geodetic height data, and the depth reference surface L value includes: water depth H depth =H DTU21 -LH aero ; Among them, H depth H represents the water depth at any point within the survey area. aero This is geodetic height cloud data for seafloor topography, with the reference plane pointing upwards as positive; H DTU21 The mean sea level geodetic height data is represented by a positive value pointing upwards; L is the depth reference surface L value.

8. A device for calculating offshore water depth without tide gauge, characterized in that, include: The first acquisition module is used to acquire laser point cloud data of the sea area to be measured, preprocess and classify the laser point cloud data of the sea area to be measured, and output seabed topography geodetic height point cloud data under the Earth ellipsoid reference. The second acquisition module is used to acquire DTU21 global mean sea level model data and obtain the mean sea level geodetic height data of the sea area to be measured by interpolation. The determination module is used to determine the depth reference surface L value of the sea area to be measured; The calculation module is used to calculate the water depth value based on the seabed topographic geodetic height cloud data, the mean sea surface geodetic height data, and the depth reference surface L value.

9. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the program, it implements the method for calculating ocean depth without tide gauge based on airborne lidar as described in any one of claims 1 to 7.

10. A non-transitory computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor, it implements the method for calculating ocean depth without tide gauge based on airborne lidar as described in any one of claims 1 to 7.

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