River channel large-section measurement method based on airborne laser radar and unmanned ship depth measurement

Abstract

The invention discloses a river channel large-section measurement method based on airborne laser radar and unmanned ship depth measurement. The unmanned aerial vehicle carries a laser radar to scan landforms on both banks, and the unmanned ship equipped with a single-beam depth finder is synchronously utilized to obtain underwater landforms; the data is subjected to space-time reference unification, point cloud calculation and classification and underwater data post-processing, fusion is carried out in a point cloud data processing system, and large-section data extraction and generation are carried out. Through man-machine cooperation, a 24 km river channel large-section task is completed in 3 days, and compared with a traditional RTK + manned ship depth finder, the efficiency is improved by 5 times. The method is suitable for large-scale river channel large-section measurement work, and is especially suitable for complex environments such as cliff steep banks, shoals, torrent and the like where manpower or manned ships cannot reach, the safety of operators is improved, and centimeter-level three-dimensional data is provided for water conservancy planning, flood control and disaster relief and engineering construction.

Description

TECHNICAL FIELD

[0001] The application relates to a river channel surveying method, in particular to a river channel large-section surveying method based on airborne laser radar and unmanned ship sounding. BACKGROUND

[0002] River channel large-section surveying and mapping is an indispensable basic data for river basin management, dike design, flood routing and ecological restoration. Influenced by factors such as water-land junction, coexistence of beach and channel and variable flow pattern, the traditional technology has long been facing the "three bottlenecks": first, low operation efficiency, total station and RTK need to measure point by point, which is labor-intensive, and it takes 15 days (2 people working, including internal drawing) for traditional RTK + manned ship sounding instrument to complete 24 km of river channel surveying; second, poor data integrity, sounding hammer and single-beam are limited by water depth and traffic conditions, and "blank zones" often appear in shallow beaches, steep banks and bridge areas; third, high safety risk, manual wading or riding a small boat for operation is prone to be threatened by floods, undercurrents and reefs, and accidents occur frequently.

[0003] In the past decade, the rise of remote sensing and unmanned platforms has provided a new way to solve the above problems. Airborne laser radar (LiDAR) can acquire high-density point clouds of single-side bank slope and dike in minutes with the advantages of collecting tens of thousands of points per second, centimeter-level elevation accuracy and non-contact measurement; combined with unmanned aerial vehicle platform, it is flexible in take-off and landing and controllable in flight path, and can quickly respond to emergency surveying and mapping needs. On the other hand, the unmanned ship sounding system integrates GNSS-RTK and multi-frequency sounder, and can autonomously navigate according to the preset section to achieve seamless coverage of underwater terrain "point to point", especially for shallow beaches, water grass areas, bridge holes and dangerous sections that are difficult for traditional ships to enter. When the two systems operate independently, the coordinate, time and precision references of the data on land and underwater are inconsistent, which leads to difficulties in direct splicing of the results, becoming a key technical obstacle to its engineering application.

[0004] Currently, domestic and foreign researches mainly focus on single data source processing algorithms, such as LiDAR filtering classification and multi-beam single-beam sounding sonar correction, but lack of spatio-temporal unified methods for air-water heterogeneous data, and traditional splicing methods often have error exceeding limit (such as elevation deviation > 10 cm); and there is still a lack of systematic solutions for spatio-temporal unification, precision matching and section generation of air-water heterogeneous data. Therefore, it is urgent to carry out research on integrated measurement technology of airborne laser radar and unmanned ship sounding, to build a safe, efficient and accurate new system for river channel large-section surveying and mapping by unifying spatio-temporal reference, optimizing joint adjustment, intelligently extracting sections and verifying precision, and to provide high-quality three-dimensional basic data for the construction of smart water conservancy and digital twin river basin. SUMMARY

[0005] The present application intends to provide a river large section measurement method based on airborne laser radar and unmanned ship sounding, so as to solve the problems of separation of onshore terrain and underwater terrain data, difficulty in splicing, low operation efficiency, high safety risk and insufficient result precision in the prior art. The present application realizes cm-level, efficient, low-risk and seamless connection of river large section measurement in complex environment, and provides high-quality three-dimensional basic data for digital twin watershed and intelligent water conservancy.

[0006] To achieve the above object, the present application provides the following technical scheme: a river large section measurement method based on airborne laser radar and unmanned ship sounding, comprising the following steps:

[0007] S1, scanning the terrain on both banks of the river by using an airborne laser radar system carried by a drone, and acquiring laser point cloud data of both banks above the water surface;

[0008] S2, measuring the underwater terrain of the river along a preset section route by using an unmanned ship sounding system configured with a single-beam depth sounder or a multi-beam sounding system, and acquiring water depth point data distributed along the center line of the section;

[0009] S3, processing the laser point cloud data and the single-beam water depth data respectively: the point cloud data processing includes point cloud solving, data resampling, point cloud denoising and point cloud classification; the water depth data processing includes selection of spatial reference, data quality inspection and depth correction;

[0010] S4, performing coordinate conversion and section line matching of the processed ground point point cloud and the post-processed water depth point data under the unified spatial and temporal reference, realizing seamless splicing of the terrain points and the water depth points, and forming a complete large section elevation point sequence;

[0011] S5, directly generating a river large section map based on the elevation point sequence, and outputting the map in DXF, LAS or three-dimensional section model format, wherein the underwater part is only represented as discrete points or polylines along the section line.

[0012] Specifically, the airborne laser radar system comprises a laser scanner, a GNSS positioning module and an inertial navigation system (INS), which are used to acquire three-dimensional coordinate data of the laser point cloud in real time.

[0013] Specifically, the unmanned ship sounding system comprises a sound wave depth sounder, a GNSS positioning device and an autonomous navigation control system, which are used to automatically complete water depth measurement and data acquisition.

[0014] Specifically, the laser point cloud data is preprocessed, including selection of spatial reference and solving of point cloud data.

[0015] Specifically, the fusion of data in step S4 is realized by LiDAR360 or other professional software, including extracting ground point cloud data and water depth data on the section line, and generating a complete river channel large section drawing.

[0016] Specifically, after the completion of the section drawing generation, the precision verification includes: using RTK measurement or single-beam review method to randomly select 10 sections for RTK review, and the average error of the onshore elevation is 2.3 cm, and the average error of the underwater error is 4.7 cm, ensuring that the onshore elevation error is within 5 cm.

[0017] Specifically, the unmanned aerial vehicle flying height of the airborne laser radar system is 120 m, the flight speed is 8 m / s, and the section scanning is completed in a single trip; the plane and elevation accuracy of the laser radar at 120 m flight height can reach 5 cm and 4 cm respectively.

[0018] Specifically, the unmanned ship depth measurement system uses the Guangdong Continuous Operation Reference Station System for positioning, and completes the water depth measurement by autonomously navigating along the preset section design route.

[0019] Specifically, the method is suitable for all scenes, especially for complex environment measurement in shoal, rapids, steep bank, bridge area and dense water area; remote operation in the whole process avoids personnel contact with dangerous environments such as flood and dark current, and the unmanned ship carries millimeter wave radar and binocular vision system to realize autonomous obstacle avoidance, improving the safety of equipment and personnel.

[0020] The principle and beneficial effects of the technical solution are as follows:

[0021] The technical solution is based on the technical idea of air-water integrated collaborative measurement, which quickly obtains high-precision laser point cloud data above the water surface of both banks of the river channel through the unmanned aerial vehicle airborne laser radar system, and simultaneously uses the unmanned ship to automatically collect underwater terrain data along the preset section. Two types of data are jointly processed and adjusted under a unified space-time reference (such as the provincial CORS system), and point cloud classification, data fusion and section line accurate matching are realized by means of LiDAR360 platform, and finally seamless spliced river channel large section results are generated.

[0022] The scheme has the following beneficial effects:

[0023] 1. Overall improve operation efficiency: air-water synchronous acquisition and automatic processing greatly shorten the field and office time, and the efficiency is improved by more than five times compared with the traditional manual measurement method;

[0024] 2. Ensure personnel operation safety: remote operation in the whole process effectively avoids water, steep bank operation and ship measurement risk, and is especially suitable for dangerous or complex water areas;

[0025] 3. High data precision and good consistency: through unified reference and fusion processing, cm-level precision connection onshore and underwater is realized, meeting the needs of high-standard engineering applications;

[0026] 4. Adapt to complex environment measurement: capable of penetrating vegetation, covering shallow shoals, rapids, bridge areas and other areas that traditional methods are difficult to measure, with no measurement blind area;

[0027] 5. Support for intelligent water conservancy construction: the generated standardized cross-section results can be directly used in digital twin watershed, flood simulation, dike design and other information systems, promoting the digital transformation of water conservancy. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 It is a working principle diagram of airborne laser radar;

[0029] Figure 2 It is a working diagram of unmanned ship;

[0030] Figure 3 It is a working flowchart of airborne laser radar and unmanned ship depth measurement integration technology;

[0031] Figure 4 It is a present situation diagram of the research area of this embodiment;

[0032] Figure 5 It is an effect diagram of this embodiment after laser point cloud fusion underwater data;

[0033] Figure 6 It is a comparison diagram of traditional measurement method and new technology integrated cross section of this embodiment. DETAILED DESCRIPTION

[0034] The application will be further described in detail in combination with the drawings and embodiments:

[0035] I. System composition and technical principle

[0036] 1. Airborne acquisition unit: taking unmanned aerial vehicle as carrier, airborne laser radar system is carried. The system integrates laser scanner (frequency 80-240 kHz), high-precision GNSS receiver (built-in RTK module) and inertial measurement unit (IMU), which can obtain three-dimensional coordinates and attitude information of ground objects in real time during flight. Its working principle is to actively emit laser pulse and receive echo, accurately measure the distance between sensor and target ground object by calculating the flight time of laser, and solve and generate high-density three-dimensional laser point cloud (point density ≥200 pts / m 2 ) combined with instantaneous high-precision POS data.

[0037] 2. Underwater acquisition unit: Based on an unmanned ship, it integrates key sensors such as single-beam echo sounder, positioning module, and sound velocity profiler. Its working principle is based on acoustic ranging: the transducer of the echo sounder vertically emits acoustic pulses to the river bottom and receives the reflected signals. By measuring the round-trip time of the acoustic wave in water and combining with the sound velocity value measured by the sound velocity profiler (SSP data), the water depth is accurately calculated. The GNSS-RTK module synchronously provides the horizontal coordinates and elevation of the antenna center of the unmanned ship (the accuracy can reach ±8mm in plane and ±15mm in elevation), and through coordinate conversion and draft correction, the three-dimensional coordinates of the river bottom points are finally obtained.

[0038] 3. Data fusion processing unit: This is the key to realize "air-water seamless splicing". The system takes the Guangdong Continuous Operation Reference Station System (GDCORS) as the unified time and space reference, providing real-time differential services of CGCS2000 coordinate system and 1985 national height datum. The data processing relies on professional software platforms: DJI ZhiTu is used for initial solution of laser point cloud data, and then imported into LiDAR360 for denoising, filtering, and fine classification (separation of ground, vegetation, buildings, etc.); underwater data is collected and monitored by HimaxE, and corrected for tide, sound velocity, attitude, and GNSS data joint adjustment. Finally, all data are unified in coordinates, data registration and fusion modeling in the LiDAR360 platform.

[0039] II. Implementation process and key technologies

[0040] 1. Preliminary preparation and reference unification:

[0041] 1.1 Collect topographic maps and hydrological data in the survey area, design unmanned aerial vehicle flight lines (flight height 120m, speed 8m / s, heading overlap 80%) and unmanned ship sounding lines (section line spacing 10m).

[0042] 1.2 Set up GNSS image control points and check points along the coast in the survey area, and use RTK to measure their accurate coordinates as the basis for data solution and accuracy verification.

[0043] 1.3 Set the GNSS receivers of the unmanned aerial vehicle and unmanned ship to receive VRS differential signals from GDCORS, to ensure that all collected data is unified in CGCS2000 coordinate system and 1985 national height datum from the source, which is the fundamental prerequisite for subsequent seamless data splicing.

[0044] 2. Synchronous acquisition of air and water data:

[0045] 2.1 Air scanning: The unmanned aerial vehicle automatically flies according to the preset flight lines, and the airborne LiDAR system quickly scans the terrain, embankment, vegetation, etc. on both sides of the river, and records laser point cloud data and POS data in real time.

[0046] 2.2 Underwater measurement: The unmanned ship autonomously sails along the cross-section line (ship speed 2.5 m / s), the single-beam depth sounder collects water depth data at a frequency of 20 Hz, GNSS-RTK records the plane and elevation position in real time, and the sound velocity profiler periodically measures the sound velocity profile for sound velocity correction.

[0047] 2.3 Synchronization control: Hardware synchronization is achieved through PPS (Pulse Per Second) and GPRMC time messages, ensuring that the time error between the laser radar and the depth sounding system is less than 1 millisecond, laying the foundation for space-time matching.

[0048] 3. Data preprocessing and fine processing:

[0049] 3.1 Laser point cloud processing: The laser point cloud data is processed using DJI ZhiTu to solve the point cloud, and the solved results LAS are imported into LiDAR360. The point cloud is denoised (removing flying points and noise), and then automatically classified through algorithms to extract high-precision "ground point" point cloud. This part of data truly represents the river bank and beach surface elevation.

[0050] 3.2 Water depth data processing: In HimaxE software, import tide observation data, sound velocity profile data and unmanned ship attitude data, and perform a series of corrections on the original water depth data to eliminate errors caused by waves, tides, sound velocity changes and ship body shaking, and generate high-precision water bottom terrain point set (XYZ).

[0051] 4. Air-water data fusion and cross-section generation:

[0052] 4.1 Coordinate unification and registration: Import the processed laser ground point cloud (LAS format) and underwater terrain point set into LiDAR360. Although the reference has been unified, fine tuning is still needed through "same point registration method", such as selecting bridge, embankment fixed points as control points, and using iterative closest point (ICP) algorithm to ensure that the two banks and underwater data perfectly match at the joint.

[0053] 4.2 Data fusion and modeling: Fuse the registered onshore point cloud and underwater point cloud to generate a complete three-dimensional terrain data set covering "water on-water under" integration. Then, cut the three-dimensional model along the preset cross-section line to extract all elevation points on the cross-section line, forming a continuous elevation sequence from one river bank to the other.

[0054] 4.3 Result output: Based on the elevation point sequence, the river cross-section drawing conforming to industry standards can be automatically generated (output as DXF format), and can also be output as LAS point cloud, TIN irregular triangle mesh or three-dimensional cross-section model (such as OBJ format), meeting the needs of different application scenarios.

[0055] 5. Precision verification and quality control:

[0056] 5.1 Throughout the entire process. During the field, real-time monitoring of UAV POS solution quality and unmanned ship sounding data anomalies, found over the limit (such as height mutation > 10cm) immediately re-measurement.

[0057] 5.2 After the processing of the industry, the RTK is used to re-measure the shore feature points, which are compared with the laser point cloud to verify the plane and elevation accuracy (in this case, the error is 2.3cm and 4.7cm respectively); the underwater review points are compared with the fusion results to ensure the reliability of the final section data, and the overall accuracy requirements of the "Water Conservancy and Hydropower Engineering Measurement Specification" (SL 197-2013) are met.

[0058] Embodiment:

[0059] 1. Test area profile and measurement target

[0060] As shown in Figure 4 , this embodiment selects the Dongjiang River main stream garden section (center coordinates: 23°07'N, 113°58'E) as the test area, and the river section is about 8.2km long. The terrain of this river section is complex, the river width is 250-420m in the dry season, the maximum water depth of the main channel is about 11.8m, the obstacles such as shoals, deep pools, sharp bends, bridges and culverts coexist in the river, the hydrological conditions are complex, the water level daily variation amplitude is 0.3-0.6m, and the flow rate changes between 0.2-0.9m / s. It is difficult to implement and high risk for traditional measurement means.

[0061] This measurement task needs to strictly follow the requirements of the "Water Conservancy and Hydropower Engineering Measurement Specification" (SL 197-2013), and complete a total of 20 river channel section measurement work (section spacing about 0.5km) according to the scale of 1:500. The technical requirements are: the elevation accuracy error of the shore terrain points is ≤5cm, the elevation accuracy error of the underwater terrain points is ≤10cm, and the total construction period requirement is to complete all field data collection and industry processing work within 3 days.

[0062] 2. Technical route and implementation scheme

[0063] This project adopts an integrated technical route, and the specific process is shown in Figure 3 .

[0064] 2.1 Unified space-time reference: VRS differential signals broadcasted by Guangdong Continuous Operation Reference Station System (GDCORS) are used throughout the process to unify the spatial reference of all collected data to CGCS2000 coordinate system and 1985 national height datum, which fundamentally ensures the premise of air-water data fusion.

[0065] 2.2 Air data acquisition: The UAV airborne laser radar system is used to scan the river water and the terrain of the 100m range of the bank slope.

[0066] 2.3 Underwater data acquisition: The underwater topography is measured by the unmanned boat sounding system (from the shore boundary 0m isobath to the river bottom about 12m deep), and ensure that there is a ≥5m overlap with the water bank topography, which is used for subsequent accurate splicing.

[0067] 2.4 Real-time data processing and correction on site: During the field work, GNSS difference, attitude, sound velocity profile and tide correction are completed synchronously on site to ensure the quality of data sources.

[0068] 2.5 Pipeline processing: The professional software chain composed of DJI ZhiTu + HimaxE + LiDAR360 is used for data processing, and finally the river section map is generated.

[0069] 3. Equipment integration and configuration

[0070] 3.1 Airborne acquisition unit

[0071] Unmanned aerial vehicle platform: DJI M350 RTK quadcopter, maximum load 2.7kg, endurance time 55 minutes.

[0072] Laser radar system: Zenith L2 airborne laser radar, laser frequency 80-240kHz, field of view 70.4°. Its ranging accuracy is ±1cm, and at 120m flight height, the plane and elevation accuracy can reach 5cm and 4cm respectively. Synchronously integrated 1 inch 2000 million pixel camera for true color coloring.

[0073] 3.2 Underwater acquisition unit

[0074] Unmanned boat platform: iBoat BS12 catamaran, length 1.2m, draft depth only 0.18m, strong maneuverability.

[0075] Sounding system: NORBIT iWBMS 400kHz multi-beam and Odom CV100 single-beam are used to form a double-redundant sounding system; among them, Odom CV100 at 200kHz scale has a nominal accuracy of 0.01m+ / –0.1% water depth, and the overall accuracy of the system is affected by GNSS / INS, sound velocity and installation factors.

[0076] Positioning system: integrated Trimble SPS855 GNSS-RTK module, providing positioning accuracy of plane ±8mm+1ppm, elevation ±15mm+1ppm.

[0077] Auxiliary sensor: integrated AML SVP30 sound velocity profiler to measure sound velocity in real time; equipped with millimeter wave radar and binocular vision system to realize autonomous obstacle avoidance.

[0078] 3.3 Synchronization and communication system

[0079] PPS pulse signal and GPRMC time message are used for hardware synchronization to ensure the time error between laser radar and sounding system is less than 1ms.

[0080] 2.4GHz / 5.8GHz integrated link is used for remote monitoring and data transmission, supporting breakpoint resume.

[0081] 4. Field implementation process

[0082] 4.1 Layout of photo control points and check points

[0083] 12 planar photo control points and 12 elevation check points are laid along the river bank.

[0084] Trimble I5 GNSS-RTK receiver is used for three-measurement observation to ensure the plane and elevation mean error is ≤1cm, providing absolute reference for data solution and precision verification.

[0085] 4.2 Airborne laser radar aerial photography

[0086] The flight height is set to 120m, the flight speed is 8m / s, and the heading and lateral overlap rates are 80% and 60% respectively.

[0087] A single flight can completely cover a section, with a laser point cloud density >200pts / m 2 , and a lateral point distance of about 2.4cm.

[0088] 4.3 Unmanned ship sounding operation

[0089] The unmanned ship autonomously navigates along the preset section line, with a speed controlled at 2.5m / s and a line spacing of 10m.

[0090] The single-beam opening angle is 120°, and the water depth data sampling frequency is 20Hz. Each section is measured back and forth once, with a total of about 450,000 valid water depth points collected.

[0091] During the field work, the AML SVP30 sound velocity profiler is used to measure the sound velocity profile every 2 hours, and the tide station automatically records the tide data every 10 minutes for real-time correction.

[0092] 4.4 Real-time quality control

[0093] Drone end: Real-time monitoring of POS solution status and point cloud density to ensure data acquisition quality.

[0094] Unmanned ship end: Real-time comparison of GNSS-RTK antenna elevation and sounding value to alarm and trigger re-measurement immediately for abnormal water depth value (mutation >±10cm) to ensure the reliability of raw data.

[0095] 5. Data processing and fusion

[0096] 5.1 Laser Point Cloud Processing

[0097] DJI Terra was used to perform precise calculations on POS data.

[0098] Import the data into LiDAR360 for point cloud denoising, filtering, and fine classification (separating ground, vegetation, buildings, etc.).

[0099] The classified ground points are thinned out, and elevation points are extracted at 1m intervals along each cross-section line.

[0100] 5.2 Water Depth Data Processing

[0101] After the raw data is acquired by HimaxE, the following operations are performed sequentially during data post-processing:

[0102] Tide level correction, sound velocity correction, attitude correction, and joint adjustment of GNSS data were performed sequentially to eliminate various errors.

[0103] The processed water depth points were sampled at 2-meter intervals, and the data were exported in DAT and DXF formats.

[0104] 5.3 Air-water data fusion and cross-section generation

[0105] like Figure 5 As shown, this is a map of data collected on-site by an unmanned surface vessel. Radar data is presented at the same height on the water surface. Elevation points on both sides of the river channel are retained, while redundant points are removed. The removed radar data and underwater data are then fused and plotted. A large-section map is created using the elevation data from the map. The image shows the effect of fusing laser point clouds with underwater data in LiDAR360 software.

[0106] 6.1 Quality Assessment

[0107] Through project experiments, this integrated technology demonstrated a higher level of intelligence and more accurate built-in algorithms, significantly reducing manual intervention. After data fusion was completed, a typical cross-section was randomly selected and verified using RTK combined with single-beam echo sounding. The comparison results are as follows: Figure 6 As shown in the figure. Analysis indicates that the results obtained by the two methods are highly consistent, and the cross-section generated by the integrated technology is richer in detail, especially in terms of topographic relief and slope changes. The elevation difference at the same location point is controlled within ±5cm, indicating that the integrated technology has high measurement accuracy. The onshore topographic data reaches centimeter-level accuracy, and the underwater topographic data also meets the requirements of engineering applications. The advantages of the integrated technology in terms of data quality are mainly reflected in the following three points:

[0108] (1) It has strong terrain adaptability and can effectively obtain measurement data in areas that are difficult for humans to reach;

[0109] (2) With the powerful active scanning capability of laser radar, high-density and high-precision terrain point cloud can be obtained, making the cross-section shape closer to the actual terrain;

[0110] (3) The automatic acquisition process strictly follows the preset route, avoiding data deviation caused by manual operation or ship deviation, and ensuring the consistency and reliability of the cross-section data.

[0111] 6.2 Efficiency improvement

[0112] Compared with traditional measurement methods, the integrated technology has achieved significant improvement in operation efficiency: traditional RTK + manned ship depth sounder takes 15 days to complete 24 km of river measurement (2 people working, including internal drawing), while the invention achieves 3 days to complete 24 km through air-water collaborative operation (2 people working, including internal drawing), with 5 times efficiency improvement, meeting the timeliness requirements of emergency mapping and large-scale river measurement.

[0113] 6.3 Safety

[0114] The technology realizes automatic data acquisition through preset route, and the operator does not need to enter the dangerous area for point-by-point measurement, which fundamentally avoids safety risks such as bank collapse, cliff falling, bee stings, drowning and ship overturning, significantly improving the safety guarantee level of field operation.

[0115] 6.4 Application prospect

[0116] The successful application of the integrated technology in river cross-section measurement provides a new technical means and solution for water conservancy engineering, geological disaster investigation, water environment monitoring and other fields. With the continuous optimization of related sensor technology, positioning accuracy and algorithm model, the technology is expected to carry out high-precision measurement in more complex water and land environments, and play a more important role in smart water conservancy, digital twin watershed, ecological restoration and other major projects, promoting the technological transformation and upgrading of the industry.

[0117] 7. Conclusion

[0118] This study verifies that the technology system has the advantages of high precision and high efficiency through the systematic application of airborne laser radar and unmanned ship depth integration technology in river cross-section measurement, and is suitable for large-scale river mapping and treatment engineering. The experimental results show that the integrated technology can obtain accurate and continuous terrain data on land and underwater, providing reliable data support for river comprehensive regulation planning, water resource fine management and watershed ecological environment protection.

[0119] The above are only embodiments of the present application, and common technical solutions or characteristics in the scheme are not described in detail. For those skilled in the art, without departing from the technical solutions of the present application, a number of modifications and improvements can be made, which should also be considered as the protection scope of the present application, and these will not affect the effect and practicality of the present application. The protection scope claimed in the present application should be subject to the content of its claims, and the specific implementation mode and the like recorded in the specification can be used to explain the content of the claims.

Claims

1. A river channel large section measurement method based on airborne laser radar and unmanned ship sounding, characterized in that, The method comprises the following steps: S1, using an unmanned aerial vehicle to carry an airborne laser radar system to scan the terrain on both sides of the river, and obtaining laser point cloud data on both sides above the water surface; S2, using an unmanned ship equipped with a single-beam depth sounder or a multi-beam depth sounding system to measure the underwater terrain of the river along the preset section line, and obtaining water depth point data distributed along the center line of the section; S3, processing the laser point cloud data and single-beam water depth data respectively: point cloud data processing includes point cloud solving, data resampling, point cloud denoising, and point cloud classification; water depth data processing includes selection of spatial reference, data quality inspection, and depth correction; S4, performing coordinate conversion and section line matching of the processed ground point point cloud and the post-processed water depth point data under the unified spatial and temporal reference, realizing seamless splicing of the terrain points and the water depth points, and forming a complete large-section elevation point sequence; S5, based on the elevation point sequence, directly generating a large-section map of the river, and outputting in DXF, LAS or three-dimensional section model format, wherein the underwater part is only represented as discrete points or polylines along the section line.

2. The method of claim 1, wherein: The airborne laser radar system comprises a laser scanner, a GNSS positioning module and an inertial navigation system (INS), which are used to obtain three-dimensional coordinate data of the laser point cloud in real time.

3. The method of claim 1, wherein: The unmanned ship depth sounding system comprises a sound wave depth sounder, a GNSS positioning device and an autonomous navigation control system, which are used to automatically complete water depth measurement and data acquisition.

4. The method of claim 1, wherein: The laser point cloud data is preprocessed, including selection of spatial reference and solving of point cloud data.

5. The method of claim 1, wherein: The data fusion in step S4 is realized by professional software such as LiDAR360, including extracting ground point cloud data and water depth data on the section line, and generating a complete large-section map of the river.

6. The method of claim 1, wherein: After completing the section map generation, precision verification is performed, including using RTK measurement or single-beam review method to spot check the fused section elevation points, to ensure that the onshore elevation error is within 5 cm.

7. The method of claim 1, wherein: The unmanned aerial vehicle carrying the airborne laser radar system flies at a height of 120 m and a speed of 8 m / s, and completes the section scanning in a single trip.

8. The method of claim 1, wherein: The unmanned ship depth sounding system uses the Guangdong Continuous Operation Reference Station System for positioning, and autonomously navigates along the preset section design route to complete water depth measurement.

9. The method of claim 1, wherein: The method is suitable for most scenarios, and is particularly suitable for measurement in complex environments such as shoals, rapids and steep banks.

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