Method and system for constructing three-dimensional map for coastal water environment inspection by using unmanned aerial vehicle

Abstract

A method and system for constructing a three-dimensional map for coastal water environment inspection by using an unmanned aerial vehicle includes the following steps: constructing an unmanned aerial vehicle navigation map, marking boundaries of a water environment area needing inspection in the unmanned aerial vehicle navigation map, and dividing square grids and surveying and mapping points corresponding to the square grids, the unmanned aerial vehicle navigation map is stored in the server, the surveying and mapping unmanned aerial vehicle and the unmanned aerial vehicle launching vehicle; and setting a square grid which is adjacent to the square grid where the boundary of the water environment area to be inspected is located and does not contain the boundary as an initial surveying and mapping grid, carrying out horizontal reference surveying and mapping, and uploading an initial surveying and mapping image obtained by surveying and mapping to a server for horizontal calibration. According to the method and the system provided by the invention, the manpower investment can be effectively reduced during use, the interference of a water surface natural environment on unmanned aerial vehicle surveying and mapping and communication can be avoided, and the three-dimensional map construction is autonomously completed by putting a plurality of unmanned aerial vehicles at one time.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of unmanned aerial vehicle control and mapping, and particularly relates to a method and system for constructing a three-dimensional map of a near-shore water environment for use in patrol inspection. BACKGROUND

[0002] China is the largest water user in the world, with abundant freshwater resources and a long coastline. In order to protect water resources and maintain maritime rights and interests, China has implemented the most stringent water resources management system and has invested a lot of resources in the maintenance of maritime rights and interests. Domestic rivers, lakes and sea areas are strictly monitored and managed, and water area monitoring work specifically includes ship monitoring, environmental monitoring, topography collection, special patrol of suspected areas, water environment monitoring, biodiversity monitoring, illegal detention ship monitoring, illegal sand and mud washing monitoring, etc., which requires periodic investment of manpower and equipment in related water environments for monitoring. The current water environment patrol commonly uses shore-based observation equipment monitoring, buoy monitoring, unmanned aerial vehicle patrol, and ship patrol monitoring. With the advancement of technology and the continuous refinement of detection content, water environment patrol, especially unmanned aerial vehicle patrol, increasingly needs to use three-dimensional maps for navigation and target marking and tracking, so the demand for constructing near-shore water environment maps is increasing.

[0003] The traditional three-dimensional map construction method is similar to the construction method of the panoramic map of the mobile navigation map software, that is, a manned vehicle (such as a car or a ship) equipped with a camera device is used to continuously shoot images in the area where the three-dimensional map needs to be constructed. After the images covering the entire area are shot, a three-dimensional map is constructed by image stitching. For example, the patent application “Unmanned aerial vehicle three-dimensional map construction method, device, computer equipment and storage medium” (publication number: CN110047142A) discloses a method for constructing a three-dimensional map using an unmanned aerial vehicle. However, the traditional three-dimensional map construction method has some drawbacks when constructing a water environment map, especially a near-shore water environment map. For example, the number of unmanned aerial vehicle pilots in China is currently small, and the traditional three-dimensional map construction method requires a large number of drivers to continuously drive the vehicle to shoot images. The wind speed on the sea is generally higher than that on land, which greatly interferes with the body of the unmanned aerial vehicle, which is mainly composed of small and medium-sized unmanned aerial vehicles. Due to the weight limit, the horizontal calibration instrument carried by the unmanned aerial vehicle has lower precision than the horizontal calibration instrument of large ground equipment, which makes it difficult to accurately calibrate the images shot by the unmanned aerial vehicle. The cloud and fog environment often encountered on the sea can seriously affect the shooting effect of the camera device. In addition, there are fewer communication base stations on the sea than on land, and the communication signal strength and communication distance of the unmanned aerial vehicle are greatly challenged. These drawbacks result in a long time-consuming, high labor consumption and low shooting accuracy when using the traditional method to construct a three-dimensional map of the near-shore water environment.

[0004] Therefore, in view of the defects in the prior art, there is a need to provide a method for constructing a near-shore water environment three-dimensional map with high shooting accuracy by relying on autonomous flight of a UAV and avoiding consumption of a large amount of manpower. SUMMARY

[0005] To solve the above problems in the prior art, the present application provides a method for constructing a near-shore water environment three-dimensional map using a UAV.

[0006] A method for constructing a near-shore water environment three-dimensional map using a UAV, characterized in that the method comprises the following steps: step S1: constructing a UAV navigation map, marking the boundary of the water environment area to be inspected in the UAV navigation map and dividing the square grid and its corresponding surveying points, and storing the UAV navigation map in a server, a surveying UAV and a UAV launching vehicle; step S2: setting the square grid adjacent to the square grid where the boundary of the water environment area to be inspected is located as an initial surveying grid, performing horizontal reference surveying, uploading the initial surveying image obtained by surveying to the server for horizontal calibration, embedding the surveying image in the UAV navigation map after calibration to obtain a reference surveying map; step S3: surveying the remaining square grids to obtain surveying images, matching the three-dimensional images of the obtained surveying images with the existing surveying images, and after successful matching, embedding the new surveying image in the existing reference surveying map according to the matching part of the new surveying image and the three-dimensional image of the existing reference surveying map, so that the new surveying image is also in a horizontal state in the existing reference surveying map; step S4: when all the square grids containing the surveying area in the reference surveying map are marked as surveyed grids, all the surveying UAVs are recovered to obtain a near-shore water environment three-dimensional map for inspection. Further, step S1 specifically comprises the following steps performed in sequence: step S11: using an existing two-dimensional electronic map as a UAV navigation map, and manually marking the boundary of the water environment area to be inspected in the UAV navigation map; step S12: dividing the UAV navigation map into square grids, and setting the length of each square grid as L, L being greater than or equal to 50% of the minimum working distance of the synthetic aperture radar used by the surveying UAV and less than or equal to 60% of the maximum working distance; step S13: marking all the square grids containing the water environment area as surveying areas; step S14: identifying and marking the center points of all the square grids in all the square grids in the surveying area of the UAV navigation map, setting surveying points above the natural terrain reference surface where each center point is located, and measuring and storing the satellite positioning data of each surveying point in the UAV navigation map; step S15: storing the processed UAV navigation map in the server, the surveying UAV and the UAV launching vehicle, and performing step S2. Further, in step S14, two surveying points with different heights are set in all the square grids in the surveying area.

[0007] Further, the step S2 specifically comprises the following steps performed in sequence: S21: the unmanned vehicle launching vehicle stops outside the boundary of the water environment area needing to be patrolled, opens the horizontal calibration mark on the unmanned vehicle launching vehicle, uses the level to level the horizontal calibration mark, measures the satellite positioning data of the horizontal calibration mark, marks the position of the horizontal calibration mark in the unmanned aerial vehicle navigation map, and releases the surveying unmanned aerial vehicle; S22: the surveying unmanned aerial vehicle flies to a surveying point of a square grid adjacent to the position of the unmanned vehicle launching vehicle, hovers at the surveying point, and performs three-dimensional map surveying towards the surveying unmanned vehicle launching vehicle direction, the surveying point is an initial surveying point, and the square grid where the initial surveying point is located is an initial surveying grid, an initial surveying image containing a clear horizontal calibration mark image is obtained, and the initial surveying image is uploaded to the server through the communication equipment of the surveying unmanned aerial vehicle; S23: in the server, the image quality of the initial surveying image is detected, the horizontal calibration mark surveyed in the initial surveying image is recognized, the initial surveying image is adjusted to a horizontal state according to the horizontal calibration mark, the initial surveying image is embedded in the unmanned aerial vehicle navigation map according to the satellite positioning data of the horizontal calibration mark, the initial surveying images in the square grids whose distance from the initial surveying point exceeds the maximum working distance of the synthetic aperture radar are all deleted, the initial surveying grid is marked as a surveyed grid in the unmanned aerial vehicle navigation map, a reference surveying map is obtained, and information of continuing surveying is sent to the surveying unmanned aerial vehicle and the unmanned vehicle launching vehicle, and step S3 is performed; if the image quality is lower than the surveying requirement, the initial surveying image is deleted, and information of re-surveying is sent to the surveying unmanned aerial vehicle and the unmanned vehicle launching vehicle, and step S21 is re-executed.

[0008] Further, in step S21, the number of unmanned vehicle launching vehicles is at least one.

[0009] Further, the step S21 further comprises: releasing a relay communication unmanned aerial vehicle for relaying communication between the surveying unmanned aerial vehicle and the server.

[0010] Further, the step S3 specifically comprises the following steps executed in sequence: S31: after receiving the information of continuing mapping from the mapping unmanned aerial vehicle and the unmanned aerial vehicle launching vehicle, the mapping unmanned aerial vehicle flies to a square grid adjacent to the mapped grid and belonging to the mapping area; S32: the mapping unmanned aerial vehicle hovers at a mapping point in the square grid, maps the surrounding environment to obtain a new mapping image, the mapping point is a new mapping point, the square grid where the new mapping point is located is a new mapping grid, and the new mapping image is uploaded to the server through the communication device of the mapping unmanned aerial vehicle; S33: in the server, the image quality of the new mapping image is detected, the new mapping image is matched with the three-dimensional image of the existing reference mapping map, after successful matching, the new mapping image is embedded in the reference mapping map, the new mapping images in the square grids with a distance exceeding the maximum working distance of the synthetic aperture radar from the new mapping point are all deleted, the new mapping image is embedded in the existing reference mapping map according to the matched part of the new mapping image and the three-dimensional image of the existing reference mapping map, so that the new mapping image is also in a horizontal state in the existing reference mapping map, the new mapping grid is marked as a mapped grid in the reference mapping map, and then information of continuing mapping is sent to the mapping unmanned aerial vehicle and the unmanned aerial vehicle launching vehicle, and the step S31 is executed in sequence.

[0011] Further, before the step S31 in the step S3, the step S30 of releasing at least one mapping unmanned aerial vehicle by the unmanned aerial vehicle launching vehicle again is included.

[0012] Further, the step S4 specifically comprises the following steps executed in sequence: S41: the mapping unmanned aerial vehicle flies to a specified position at a specified time, and the unmanned aerial vehicle launching vehicle recovers the mapping unmanned aerial vehicle; S42: all square grids and mapping points in the reference mapping map are deleted to obtain a three-dimensional map for nearshore water environment inspection.

[0013] The application also provides a system for constructing a three-dimensional map for nearshore water environment inspection using unmanned aerial vehicles, which is characterized in that the system comprises at least one unmanned aerial vehicle launching vehicle, at least one mapping unmanned aerial vehicle, at least one relay communication unmanned aerial vehicle and a server, the unmanned aerial vehicle launching vehicle is provided with a horizontal calibration mark, a communication device and a satellite positioning device; the mapping unmanned aerial vehicle is provided with a synthetic aperture radar, a communication device and a satellite positioning device; the relay communication unmanned aerial vehicle is provided with a relay communication device and a satellite positioning device; and the system for constructing a three-dimensional map for nearshore water environment inspection executes the above method.

[0014] Compared with the prior art, the method and system provided by the present application can effectively reduce the labor input when used, and the staff only needs to drive the unmanned aerial vehicle launching vehicle to the appropriate position, lay out the large horizontal calibration mark, and after releasing the unmanned aerial vehicle, the unmanned aerial vehicle only needs to perform autonomous flight, synthetic aperture radar imaging and data transmission, and the image fusion and automatic calibration are performed by the background. The method can also avoid the interference of the natural environment of the water surface on the unmanned aerial vehicle surveying and mapping and communication, and the three-dimensional map construction is autonomously completed by one-time deployment of multiple unmanned aerial vehicles. BRIEF DESCRIPTION OF DRAWINGS

[0015] Figure 1 is a flowchart of the method for constructing a three-dimensional map for nearshore water environment inspection using an unmanned aerial vehicle according to the present application;

[0016] Figure 2 is a flowchart of the specific steps in step S1 of the method according to the present application;

[0017] Figure 3 is a flowchart of the specific steps in step S2 of the method according to the present application;

[0018] Figure 4 is a flowchart of the specific steps in step S3 of the method according to the present application;

[0019] Figure 5 is a schematic diagram of the map surveying process in the embodiment of the method according to the present application. DETAILED DESCRIPTION

[0020] In order to make the purpose, technical scheme and advantages of the present application clearer, the technical scheme in the present application will be described clearly and completely below in combination with the drawings in the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0021] As Figures 1 to 5 shown, the embodiment of the present application provides a method for constructing a three-dimensional map for nearshore water environment inspection using an unmanned aerial vehicle. In the embodiment, the method is executed in the following steps:

[0022] Step 1: Preparation work before surveying.

[0023] First, prepare the unmanned aerial vehicle navigation map. The existing two-dimensional electronic map can be used as the unmanned aerial vehicle navigation map, for example, use the two-dimensional electronic map provided by the electronic map company. Manually mark the boundary of the water environment area to be inspected in the unmanned aerial vehicle navigation map, which is generally the coastline and river embankment, so as to clearly define the water area involved in the unmanned aerial vehicle surveying and future inspection. Figure 5In the map, the boundary of the water environment region is the coastline, and the inland region is not shown.

[0024] Then, the UAV navigation map is preprocessed, that is, rasterization processing, and the surveying and mapping positions involved in the surveying and mapping of the UAV navigation map are demarcated. The UAV navigation map is divided into square grids, and the length of each square grid is greater than or equal to 50% of the minimum working distance of the synthetic aperture radar used by the surveying and mapping UAV and less than or equal to 60% of the maximum working distance. The minimum working distance of the synthetic aperture radar used for surveying and mapping is generally more than 500 meters, and the maximum working distance is generally about 8 km. This grid division method can enable the UAV to survey the entire environment within a grid and survey most of the environment in the eight grids around the grid.

[0025] Then, according to the boundary of the water environment region that has been marked, all square grids containing the water environment region are manually marked as surveying and mapping regions, and the surveying and mapping regions are the regions where the UAV will conduct map surveying in the future.

[0026] Then, in all square grids in the surveying and mapping region of the UAV navigation map, the center points of all square grids are identified and marked, two positions with different heights directly above the natural terrain reference surface of each center point are set as surveying and mapping points, and the satellite positioning data of each surveying and mapping point is measured and stored in the UAV navigation map. In future UAV surveying, the UAV surveys the surrounding environment at two surveying and mapping points in each square grid to generate a three-dimensional environment map.

[0027] After the above steps are completed, the processed UAV navigation map is stored in the server, the surveying and mapping UAV, and the UAV launch vehicle. At this time, step one is completed, and step two can be prepared for execution.

[0028] Step two is the UAV surveying step. In step two, first, at least one UAV launch vehicle is driven to stop outside the boundary of the water environment region that needs to be inspected, that is, on the shore of the water area, which is shown as the position of the black triangle in the figure. When there are multiple UAV launch vehicles, a large distance of multiple square lengths can be maintained between each two UAV launch vehicles, so that multiple UAV launch vehicles can survey simultaneously and in parallel, improving the surveying speed. The staff opens the large horizontal calibration marker on the UAV launch vehicle, which is a horizontal and vertical marker in this embodiment. The staff uses a level to level the horizontal calibration marker, measures the satellite positioning data of the horizontal calibration marker using a satellite positioning device, marks the position of the horizontal calibration marker in the UAV navigation map, and releases the surveying and mapping UAV. When the surveying range is too large and the UAV has difficulty in long-distance wireless communication with the server, a relay communication UAV is released for relay communication between the surveying and mapping UAV and the server. At this time, map surveying can be started.

[0029] The UAV first carries out initial benchmark surveying to establish a benchmark image, and subsequent surveying is all matched with the benchmark image. The UAV flies to a surveying point of the adjacent square grid to the position of the UAV launching vehicle, which is the position of the black dot in the figure, hovers at the surveying point, and carries out three-dimensional map surveying in the direction of the surveying UAV launching vehicle to ensure that the horizontal calibration mark is within the surveying range. The surveying point is an initial surveying point, and the square grid where the initial surveying point is located is an initial surveying grid, and an initial surveying image containing a clear horizontal calibration mark image is obtained, and the initial surveying image is uploaded to the server through the communication equipment of the surveying UAV. After uploading, the UAV temporarily hovers at the surveying point, waits for the server to receive and process the image, and waits for the server to issue further instructions.

[0030] Then, in the server, the initial surveying image sent by the UAV is received, and whether the image quality of the initial surveying image meets the surveying standards and requirements is detected. When the image quality meets the surveying standards and requirements, the horizontal calibration mark surveyed in the initial surveying image is recognized, the initial surveying image is adjusted to a horizontal state according to the horizontal plane and the vertical plane on the horizontal calibration mark, and the horizontal calibration mark is overlapped with the position of the satellite positioning data of the initial surveying mark marked in the UAV navigation map according to the satellite positioning data of the horizontal calibration mark, so that the initial surveying image is embedded in the UAV navigation map. All initial surveying images with a distance between the initial surveying point exceeding the maximum working distance of the synthetic aperture radar and being lower than the minimum working distance are deleted. The initial surveying grid is marked as a surveyed grid in the UAV navigation map, and a benchmark surveying map is obtained, and the subsequent image splicing work is all based on the benchmark surveying map. At this time, the server completes the image processing work, sends information of continuing surveying to the surveying UAV and the UAV launching vehicle, and executes step three. If the image quality is lower than the surveying requirements, the UAV surveying fails this time, the initial surveying image is deleted in the server, and information of re-surveying is sent to the surveying UAV and the UAV launching vehicle, re-surveying is carried out in the surveying point, and the image uploading and processing steps are repeated until the surveying is successful.

[0031] Step three is then executed, at this time, the benchmark surveying map surveying has been completed, and the UAV can continue to survey in the adjacent square grid, in the figure, the UAV flies from the black dot to the adjacent square grid pointed by the arrow, and then matches the newly surveyed image with the benchmark surveying map. To improve the surveying efficiency, the UAV launching vehicle can release at least one surveying UAV for simultaneous operation again at this time, and the newly launched UAV does not need to execute the benchmark surveying step. The UAV launching vehicle can be folded at this time, and the staff can drive to the predetermined UAV recovery position, and the remaining surveying work is all completed by the UAV under the instruction of the server.

[0032] Then, after receiving the information of continuing mapping from the mapping unmanned aerial vehicle and the unmanned aerial vehicle launching vehicle, the mapping unmanned aerial vehicle flies to the square grid adjacent to the mapped grid and belonging to the mapping area, and gradually expands the mapping range with the initial mapping grid as the center.

[0033] Then, the mapping unmanned aerial vehicle hovers at the mapping point in the square grid, maps the surrounding environment to obtain a new mapping image, the mapping point is a new mapping point, the square grid where the new mapping point is located is a new mapping grid, and the new mapping image is uploaded to the server through the communication device of the mapping unmanned aerial vehicle.

[0034] In the server, the image quality of the initial mapping image also needs to be detected. When the image quality meets the standard, the new mapping image is matched with the three-dimensional image of the existing benchmark mapping map, and after the matching is successful, the new mapping image in the square grid whose distance from the new mapping point exceeds the maximum working distance of the synthetic aperture radar is all deleted. According to the part of the new mapping image matched with the three-dimensional image of the existing benchmark mapping map, the new mapping image is embedded in the existing benchmark mapping map, and the new mapping image is also in a horizontal state in the existing benchmark mapping map. At this time, the mapping work of the new mapping grid is completed, the new mapping grid is marked as a mapped grid in the benchmark mapping map, then the information of continuing mapping is sent to the mapping unmanned aerial vehicle and the unmanned aerial vehicle launching vehicle, and then step three is repeatedly executed in turn until the square grids containing the mapping area in the benchmark mapping map are all marked as mapped grids, and step four is executed; if the image quality is lower than the mapping requirement or the matching fails, this mapping fails, the new mapping image is deleted, and the information of re-mapping is sent to the mapping unmanned aerial vehicle and the unmanned aerial vehicle launching vehicle, and the execution starts from the step of mapping at the new mapping point of the unmanned aerial vehicle in turn until the unmanned aerial vehicle successfully maps at the new mapping point.

[0035] In step four, the square grids containing the mapping area in the benchmark mapping map are all marked as mapped grids, at this time, all the mapping work has been completed, the mapping unmanned aerial vehicle flies to the designated unmanned aerial vehicle recovery position at a specified time, and the unmanned aerial vehicle launching vehicle recovers the mapping unmanned aerial vehicle. At this time, all the square grids and mapping points in the benchmark mapping map that are useless can be deleted to obtain the final three-dimensional map for near-shore water environment inspection.

[0036] The present application is described with reference to flowcharts and / or block diagrams of the method product according to the embodiments of the present application. It should be understood that each flow and / or block in the flowcharts and / or block diagrams, and the combination of the flows and / or blocks in the flowcharts and / or block diagrams can be realized by computer program instructions. These computer program instructions can be provided to the processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing devices to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing devices generate a machine that realizes the functions described in the flowcharts and / or block diagrams.Figure 1 apparatuses that implement the functions specified in the flowchart Figure 1 block or blocks.

[0037] These computer program instructions can also be stored in a computer readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer readable memory produce an article of manufacture including instructions which implement the Figure 1 apparatuses that implement the functions specified in the flowchart Figure 1 block or blocks.

[0038] These computer program instructions can also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions that are executed on the computer or other programmable apparatus provide steps for implementing the Figure 1 apparatuses that implement the functions specified in the flowchart Figure 1 block or blocks.

[0039] Obviously, the above-described embodiments are only examples for clearly illustrating the present application and are not intended to limit the present application. Based on the above description, those skilled in the art can make other different forms of changes or modifications. Here, it is not necessary or possible to enumerate all the embodiments. The obvious changes or modifications derived therefrom are still within the protection scope of the present application.

Claims

1. A method for constructing a three-dimensional map for nearshore water environment inspection using unmanned aerial vehicles (UAVs), characterized in that, The following method includes the following steps: Step S1: Construct a drone navigation map, mark the boundaries of the water environment area to be inspected in the drone navigation map and divide it into square grids and their corresponding survey points, and store the drone navigation map in the server, surveying drone and drone launch vehicle; Step S2: Set the square grids adjacent to the boundary of the water environment area to be inspected, which do not contain the boundary, as the initial mapping grids, perform horizontal benchmark mapping, upload the obtained initial mapping image to the server for horizontal calibration, and embed the mapping image into the UAV navigation map to obtain the benchmark mapping map. Step S3: Map the remaining square grids and match the obtained map image with the 3D image of the existing map image. After successful matching, embed the new map image into the existing reference map based on the matching part between the new map image and the 3D image of the existing reference map, so that the new map image is also in a horizontal state on the existing reference map. Step S4: When all the square grids containing the survey area in the baseline mapping map are marked as surveyed grids, retrieve all the surveying drones to obtain a three-dimensional map for nearshore water environment inspection.

2. The method for constructing a three-dimensional map for nearshore water environment inspection using a drone according to claim 1, characterized in that, Step S1 specifically includes the following steps performed sequentially: Step S11: Use an existing two-dimensional electronic map as the drone navigation map, and manually mark the boundaries of the water environment area to be inspected on the drone navigation map; Step S12: Divide the entire UAV navigation map into square grids, with the side length of each square grid set to L. L is greater than or equal to 50% of the minimum working range of the synthetic aperture radar used by the surveying UAV and less than or equal to 60% of the maximum working range. Step S13: Mark all square grids containing water environment areas as the mapping area; Step S14: In all square grids in the UAV navigation map survey area, identify and mark the center point of all square grids, set a survey point directly above the natural terrain reference plane where each center point is located, and measure and store the satellite positioning data of each survey point in the UAV navigation map; Step S15: Store the processed UAV navigation map in the server, the mapping UAV, and the UAV launch vehicle, and then execute step S2.

3. The method for constructing a three-dimensional map for nearshore water environment inspection using a drone according to claim 2, characterized in that, In step S14, two survey points with different heights are set in all square grids within the survey area.

4. The method for constructing a three-dimensional map for nearshore water environment inspection using a drone according to claim 1, characterized in that, Step S2 specifically includes the following steps executed sequentially: S21: The UAV launcher vehicle stops outside the boundary of the water environment area to be inspected, opens the horizontal calibration mark on the UAV launcher vehicle, uses a level to level the horizontal calibration mark, the UAV vehicle measures the satellite positioning data of the horizontal calibration mark, marks the location of the horizontal calibration mark on the UAV navigation map, and releases the mapping UAV at the same time. S22: The mapping drone flies to the mapping point of the square grid adjacent to the location of the drone launch vehicle, hovers at the mapping point, and performs three-dimensional map mapping in the direction of the mapping drone launch vehicle. This mapping point is the initial mapping point, and the square grid where the initial mapping point is located is the initial mapping grid. The initial mapping image containing clear horizontal calibration mark images is obtained, and the initial mapping image is uploaded to the server through the communication equipment of the mapping drone. S23: In the server, the image quality of the initial survey image is detected, the horizontal calibration marks in the initial survey image are identified, the initial survey image is adjusted to a horizontal state according to the horizontal calibration marks, the initial survey image is embedded into the UAV navigation map according to the satellite positioning data of the horizontal calibration marks, all initial survey images in square grids whose distance from the initial survey point exceeds the maximum working distance of the synthetic aperture radar are deleted, the initial survey grids are marked as surveyed grids in the UAV navigation map, the baseline survey map is obtained, and the information to continue surveying is sent to the surveying UAV and the UAV launcher, and step S3 is executed; if the image quality is lower than the surveying requirements, the initial survey image is deleted, and the information to re-survey is sent to the surveying UAV and the UAV launcher, and step S21 is executed again.

5. The method for constructing a three-dimensional map for nearshore water environment inspection using a drone according to claim 4, characterized in that, In step S21, the number of drone launch vehicles is at least one.

6. The method for constructing a three-dimensional map of nearshore water environment inspection using a drone according to claim 4, characterized in that, Step S21 further includes: releasing a relay communication drone for use in mapping relay communication between the drone and the server.

7. The method for constructing a three-dimensional map for nearshore water environment inspection using a drone according to claim 1, characterized in that, Step S3 specifically includes the following steps executed sequentially: S31: After receiving the message to continue mapping, the mapping drone and the drone launcher will fly to the square grid that is adjacent to the already mapped grid and belongs to the mapping area. S32: The surveying drone hovers over the surveying point in the square grid, performs map surveying of the surrounding environment, and obtains a new surveying image. This surveying point is the new surveying point, and the square grid where the new surveying point is located is the new surveying grid. The new surveying image is uploaded to the server through the communication equipment of the surveying drone. S33: In the server, the image quality of the new survey image is detected. The new survey image is matched with the 3D image of the existing reference survey map. If the match is successful, the new survey image is embedded into the reference survey map. All new survey images in square grids whose distance from the new survey point exceeds the maximum working distance of the synthetic aperture radar are deleted. Based on the part of the new survey image that matches the 3D image of the existing reference survey map, the new survey image is embedded into the existing reference survey map, so that the new survey image is also in a horizontal state in the existing reference survey map. The new survey grid is marked as a surveyed grid in the reference survey map. Then, the surveying drone and drone launcher are sent with the message to continue surveying. This process is executed sequentially starting from step S31. When all square grids in the reference survey map containing the survey area are marked as surveyed grids, step S4 is executed. If the image quality is lower than the surveying requirements or the match fails, the new survey image is deleted, and the surveying drone and drone launcher are sent with the message to re-survey. This process is executed sequentially starting from step S32.

8. The method for constructing a three-dimensional map for nearshore water environment inspection using a drone according to claim 1, characterized in that, Before step S31 in step S3, step S30 is included: The drone launcher released at least one more mapping drone.

9. The method for constructing a three-dimensional map for nearshore water environment inspection using a drone according to claim 1, characterized in that, Step S4 specifically includes the following steps performed sequentially: S41: The mapping drone flies to the designated location at the designated time, and the drone launcher recovers the mapping drone; S42: Delete all square grids and survey points in the baseline mapping map to obtain a three-dimensional map for nearshore water environment inspection.

10. A system for constructing a three-dimensional map of nearshore water environment inspection using unmanned aerial vehicles (UAVs), characterized in that: The system comprises at least one UAV launch vehicle, at least one mapping UAV, at least one relay communication UAV, and a server. The UAV launch vehicle is equipped with horizontal calibration marks, communication devices, and satellite positioning devices. The mapping drone is equipped with synthetic aperture radar, communication devices, and satellite positioning devices. The relay communication UAV is equipped with a relay communication device and a satellite positioning device; The nearshore water environment inspection three-dimensional map construction system performs the method according to any one of claims 1-9.

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