An unmanned aerial vehicle-based nautical chart coastline dynamic monitoring laser calibration device

Abstract

The utility model relates to a chart coast dynamic monitoring laser calibration device based on unmanned plane, include: unmanned plane flight platform, ground computer terminal, the unmanned plane flight platform includes unmanned plane body and the related equipment of carrying, the related equipment includes: flight control module, positioning and attitude measurement module, three -axis stabilizing holder, laser scanning range finder, multispectral camera, wireless transmission module, central control unit, the ground computer terminal, receive the data that unmanned plane platform returns and store and handle, include: data storage module, data processing module, image segmentation module, registration module, the data processing module includes three -dimensional coordinate solution unit, gross error elimination unit, binary image generation unit, binary image processing unit, reliability analysis unit. The utility model uses the elevation of mean spring high tide line, directly divides 3D point cloud data into water and land binary image, extracts chart coast.

Description

Technical Field

[0001] This utility model relates to the field of nautical chart shoreline calibration technology, and in particular to a laser calibration device for dynamic monitoring of nautical chart shorelines based on unmanned aerial vehicles. Background Technology

[0002] Current coastline monitoring mainly relies on satellite remote sensing and manual on-site measurements, which suffers from problems such as long revisit cycles, limited spatial resolution, and significant susceptibility to weather conditions. In recent years, manned aircraft-based nautical charting and coastline mapping systems equipped with lidar have emerged, but their operating costs are high, making high-frequency monitoring difficult, and low-altitude flight near the coast poses safety risks. Unmanned aerial vehicle (UAV)-based nautical charting and coastline mapping devices suffer from several problems: insufficient attitude accuracy; distortion of point clouds due to UAV attitude fluctuations caused by sea surface turbulence; drift of sensor installation parameters (pitch angle, roll angle, etc.) during flight due to mechanical vibration, lack of online calibration mechanisms; and high misjudgment rates of traditional image recognition methods due to tidal changes in the land-water boundary. Utility Model Content

[0003] This invention aims to address the shortcomings of existing technologies by providing a laser calibration device for dynamic monitoring of nautical charts and coastlines based on unmanned aerial vehicles (UAVs).

[0004] To achieve the above objectives, this utility model adopts the following technical solution: a laser calibration device for dynamic monitoring of nautical charts and coastlines based on unmanned aerial vehicles (UAVs), comprising: an UAV flight platform and a ground computer terminal;

[0005] The UAV flight platform includes the UAV body and related equipment, including: a flight control module, a positioning and attitude measurement module, a three-axis stabilization gimbal, a laser scanning rangefinder, a multispectral camera, a wireless transmission module, and a central control unit;

[0006] The flight control module is used to control the drone itself and enable it to fly autonomously along a predetermined flight path.

[0007] The positioning and attitude measurement module includes a satellite navigation system and an inertial navigation system, which are combined through a Kalman filter. The satellite navigation system provides the UAV with precise azimuth data, and the inertial navigation system provides the UAV with attitude data to form a navigation dataset.

[0008] The three-axis stabilization gimbal is installed below the UAV body, and the laser scanning rangefinder is installed at the center of the three-axis stabilization gimbal;

[0009] The laser scanning rangefinder uses a pulsed laser as the radiation source and a rotating mirror scanning unit to achieve lateral scanning of the laser beam. Combined with a MEMS micro-mirror array, it obtains a raw point cloud dataset. The raw point cloud dataset includes a series of discrete distance observations from the UAV to the observation point, azimuth angle, pitch angle, time information, and echo signal strength.

[0010] The multispectral camera is rigidly connected to the laser scanning rangefinder to capture orthophotos of the ground within the flight range of the UAV.

[0011] The wireless transmission module adopts a dual-link redundancy design, with the main link transmitting point cloud feature data and the backup link transmitting key status parameters.

[0012] The central control unit is electrically connected to the positioning and attitude measurement system, the three-axis stabilization gimbal, the laser scanning rangefinder, the digital camera, the information storage module, and the wireless transmission module, respectively.

[0013] The ground computer terminal receives, stores, and processes data transmitted from the UAV platform, including: a data storage module, a data processing module, an image segmentation module, and a registration module; the data processing module includes a three-dimensional coordinate calculation unit, a gross error removal unit, a binary image generation unit, a binary image processing unit, and a reliability analysis unit.

[0014] Furthermore, the central control unit is implemented based on a heterogeneous computing architecture and adopts the PTP precision clock protocol. It sends synchronization messages through the master node and the slave node response mechanism unifies the time axis of the positioning and attitude measurement module, the laser scanning rangefinder, and the multispectral camera.

[0015] Furthermore, the data storage module receives the navigation dataset, raw point cloud dataset, and digital image transmitted by the wireless transmission module, decodes them, and transmits them to the data processing module and the image segmentation module. The image segmentation module embeds training area samples to be calibrated and a classification algorithm.

[0016] Furthermore, the satellite navigation system uses a dynamic differential GNSS receiver.

[0017] Furthermore, the central control unit is also connected to an acceleration computing stick.

[0018] Furthermore, each of the three adjustment motors of the three-axis stabilization gimbal is connected to a magnetic encoder.

[0019] The beneficial effects of this invention are as follows: This invention uses the elevation of the mean high tide line to directly segment 3D point cloud data into a binary image of land and water, and extracts the coastline from the nautical chart; dynamic calibration reduces the ranging error of the lidar and improves the accuracy of coastline positioning; the three-axis gimbal has both fixing and adjusting functions, which can ensure the stability of the sensor's attitude during the mission; multispectral and lidar work together to overcome the limitations of traditional optical monitoring at night and in foggy weather, and can identify and map the missing parts of the coastline, reducing errors. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the structure of this utility model;

[0021] The accompanying drawings in this utility model are all schematic diagrams and their sizes do not represent actual dimensions.

[0022] The following will describe in detail the embodiments of this utility model with reference to the accompanying drawings. Detailed Implementation

[0023] The present invention will be further described below with reference to the accompanying drawings and embodiments:

[0024] like Figure 1 As shown, a laser calibration device for dynamic monitoring of nautical charts and coastlines based on unmanned aerial vehicles (UAVs) includes: an UAV flight platform and a ground computer terminal.

[0025] The UAV flight platform includes the UAV body and related equipment, including: a flight control module, a positioning and attitude measurement module, a three-axis stabilization gimbal, a laser scanning rangefinder, a multispectral camera, a wireless transmission module, and a central control unit;

[0026] The flight control module is used to control the drone itself and enable it to fly autonomously along a predetermined flight path; the optional drone model is Yunux Long Pro.

[0027] The positioning and attitude measurement module includes a satellite navigation system and an inertial navigation system, which are combined through a Kalman filter. The satellite navigation system provides the UAV with precise azimuth data, and the inertial navigation system provides the UAV with attitude data to form a navigation dataset; the optional model is NV-GI1000.

[0028] The three-axis stabilization gimbal is installed below the UAV body, and the laser scanning rangefinder is installed at the center of the three-axis stabilization gimbal;

[0029] The laser scanning rangefinder uses a pulsed laser as the radiation source and employs a rotating mirror scanning unit to achieve lateral scanning of the laser beam. Combined with a MEMS micro-mirror array, it obtains a raw point cloud dataset. The raw point cloud dataset includes a series of discrete distance observations from the UAV to the observation point, azimuth angle, pitch angle, time information, and echo signal strength. Optional models include the Hi-Target ARS-1000 series.

[0030] The multispectral camera is rigidly connected to the laser scanning rangefinder to capture orthophotos of the ground within the flight range of the UAV; a 20-megapixel global shutter camera is used in conjunction with a narrowband multispectral sensor (including five bands: 450nm, 560nm, 650nm, 720nm, and 850nm) to enhance the spectral features of the land-water boundary.

[0031] The wireless transmission module adopts a dual-link redundancy design, establishing a wireless local area network with the ground computer terminal to achieve rapid data transmission; the main link transmits point cloud feature data, and the backup link transmits key status parameters.

[0032] The central control unit is electrically connected to the positioning and attitude measurement system, the three-axis stabilization gimbal, the laser scanning rangefinder, the digital camera, the information storage module, and the wireless transmission module; the central control unit can be a Raspberry Pi4 Model B.

[0033] The ground computer terminal receives, stores, and processes data transmitted from the UAV platform, including: a data storage module, a data processing module, an image segmentation module, and a registration module; the data processing module includes a three-dimensional coordinate calculation unit, a gross error removal unit, a binary image generation unit, and a binary image processing unit.

[0034] Specifically, the 3D coordinate calculation unit converts the original point cloud dataset into a geodetic coordinate system and a national elevation datum based on the navigation dataset; the gross error removal unit removes erroneous data such as high points, low points, and isolated point clouds; the average spring tide height of the calibrated area is calculated based on the tidal data of the calibrated area, and the elevation of the nautical chart coastline is determined as the average spring tide height plus the sea level height under the national elevation datum; the binary image generation unit assigns a value of 0 to point clouds with an elevation higher than the nautical chart coastline elevation, and assigns a value of 1 to point clouds with an elevation lower than the nautical chart coastline elevation; the binary image processing unit removes small discontinuous pseudo-targets from the binary image, then performs morphological processing on the binary image by first dilation and then erosion, and finally performs edge detection on the binary image to extract the nautical chart coastline.

[0035] The central control unit is implemented based on a heterogeneous computing architecture and adopts the PTP precision clock protocol. Synchronization messages are sent by the master node, and the timelines of the positioning and attitude measurement module, laser scanning rangefinder, and multispectral camera are unified through the slave node response mechanism. Using timestamp-based positioning, the navigation dataset, raw point cloud dataset, and digital image are registered. The target point's position is transformed from a device-centric spherical coordinate system to three-dimensional coordinates in a global coordinate system, calculating a 3D point cloud dataset. Each point contains its three-dimensional coordinates and additional attributes, resulting in a digital image aligned with the coordinates.

[0036] The data storage module receives the navigation dataset, point cloud dataset, and digital imagery transmitted by the wireless transmission module. After decoding, it transmits them to the data processing module and the image segmentation module. The image segmentation module embeds training area samples to be calibrated and a classification algorithm. Image segmentation technology is used to segment the acquired image data into different pixels. Similar pixels are merged into the current region using region growing. After manual classification, the segmented modules are used to establish training areas for automatic image segmentation and classification. This can assist in the classification and recognition of land and sea, and in the manual supplementation and mapping of nautical charts and coastlines.

[0037] The satellite navigation system uses a dynamic differential GNSS receiver. The dynamic differential GNSS receiver is used to determine the spatial position of the UAV. It can receive satellite data to determine the UAV's spatial position in real time, and also perform differential calculations with ground base stations through data analysis to accurately calculate the flight trajectory.

[0038] The central control unit is also connected to an acceleration computing stick. The Intel Movidius NCS computing stick is configured to accelerate computation.

[0039] Each of the three adjustment motors of the three-axis stabilization gimbal is connected to a magnetic encoder. The magnetic encoders provide real-time feedback on the angle of each axis of the three-axis stabilization gimbal, and the attitude compensation is calculated using the centroid offset of the laser point cloud.

[0040] The working principle of this utility model is as follows: After the UAV takes off, it determines the preset altitude based on GPS, activates the laser scanning rangefinder, and autonomously flies along the predetermined flight path. The satellite navigation system provides the UAV's real-time azimuth information, the inertial navigation system provides the UAV's attitude data, and the GNSS receiver receives the calibration signal from the ground base station to calculate the installation parameter deviation in real time. The above data is transmitted back to the ground computer terminal through the wireless transmission module, where it is spatiotemporally aligned to generate a 3D point cloud dataset. Based on the average high tide height of the sea area, the point cloud dataset is converted into a binary image, and the coastline of the nautical chart is extracted. The multispectral image is segmented, and the point cloud and image features are matched for manual interpretation and mapping, ultimately calibrating the coastline of the nautical chart.

[0041] The present invention has been described above with reference to the accompanying drawings. Obviously, the specific implementation of the present invention is not limited to the above-described manner. Any improvements made using the inventive concept and technical solution of the present invention, or direct application to other situations without modification, are all within the protection scope of the present invention.

Claims

1. A laser calibration device for dynamic monitoring of nautical charts and coastlines based on unmanned aerial vehicles (UAVs), characterized in that, include: Unmanned aerial vehicle (UAV) flight platform and ground computer terminal; The UAV flight platform includes the UAV body and related equipment, including: a flight control module, a positioning and attitude measurement module, a three-axis stabilization gimbal, a laser scanning rangefinder, a multispectral camera, a wireless transmission module, and a central control unit; The flight control module is used to control the drone itself and enable it to fly autonomously along a predetermined flight path. The positioning and attitude measurement module includes a satellite navigation system and an inertial navigation system, which are combined through a Kalman filter. The satellite navigation system provides the UAV with precise azimuth data, and the inertial navigation system provides the UAV with attitude data to form a navigation dataset. The three-axis stabilization gimbal is installed below the UAV body, and the laser scanning rangefinder is installed at the center of the three-axis stabilization gimbal; The laser scanning rangefinder uses a pulsed laser as the radiation source and a rotating mirror scanning unit to achieve lateral scanning of the laser beam. Combined with a MEMS micro-mirror array, it obtains a raw point cloud dataset. The raw point cloud dataset includes a series of discrete distance observations from the UAV to the observation point, azimuth angle, pitch angle, time information, and echo signal strength. The multispectral camera is rigidly connected to the laser scanning rangefinder to capture orthophotos of the ground within the flight range of the UAV. The wireless transmission module adopts a dual-link redundancy design, with the main link transmitting point cloud feature data and the backup link transmitting key status parameters. The central control unit is electrically connected to the positioning and attitude measurement system, the laser scanning rangefinder, the digital camera, the information storage module, and the wireless transmission module, respectively. The ground computer terminal receives, stores, and processes data transmitted from the UAV platform, including: a data storage module, a data processing module, an image segmentation module, and a registration module; the data processing module includes a three-dimensional coordinate calculation unit, a gross error removal unit, a binary image generation unit, a binary image processing unit, and a reliability analysis unit.

2. The laser calibration device for dynamic monitoring of nautical charts and coastlines based on unmanned aerial vehicles (UAVs) according to claim 1, characterized in that, The central control unit is implemented based on a heterogeneous computing architecture and adopts the PTP precision clock protocol. It sends synchronization messages through the master node and the slave node response mechanism unifies the time axis of the positioning and attitude measurement module, the laser scanning rangefinder, and the multispectral camera.

3. The laser calibration device for dynamic monitoring of nautical charts and coastlines based on unmanned aerial vehicles (UAVs) according to claim 2, characterized in that, The data storage module receives the navigation dataset, raw point cloud dataset, and digital image transmitted by the wireless transmission module, decodes them, and transmits them to the data processing module and the image segmentation module. The image segmentation module embeds training area samples to be calibrated and a classification algorithm.

4. The laser calibration device for dynamic monitoring of nautical charts and coastlines based on unmanned aerial vehicles (UAVs) according to claim 3, characterized in that, The satellite navigation system uses a dynamic differential GNSS receiver.

5. A laser calibration device for dynamic monitoring of nautical charts and coastlines based on unmanned aerial vehicles (UAVs) according to claim 3, characterized in that, The central control unit is also connected to an accelerator computing stick.

6. The laser calibration device for dynamic monitoring of nautical charts and coastlines based on unmanned aerial vehicles (UAVs) according to claim 3, characterized in that, The three adjustment motors of the three-axis stabilization gimbal are all connected to magnetic encoders.

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