An airborne LiDAR acquisition mobile calibrator for sequential detection of weak surface changes

Abstract

The present invention relates to the field of geological disasters, and discloses an airborne LiDAR acquisition mobile calibrator for detecting weak surface change sequences, comprising: a laser reflection device and a GPS device for measuring the position of the laser reflection device. The laser reflection device includes: a spherical lens, a signal reflection base, and a base. The spherical lens and the signal reflection base are both located on the base. The signal reflection base is used to reflect the laser signal converged by the spherical lens. The GPS device is located on the top of the base. With this solution, stable point clouds can be collected through the laser reflection device, and at the same time, high-precision positioning information corresponding to the point clouds can be obtained through the GPS base station, so that the ground data collected by subsequent airborne LiDAR can be error-suppressed based on the point clouds, and thus weak changes in ground objects can be detected.

Description

Technical Field

[0001] The present invention relates to the field of geological disasters, and particularly to an airborne LiDAR acquisition mobile calibrator for detecting sequential weak changes on the ground surface. Background Art

[0002] Airborne LiDAR, as an active remote sensing technology, combines traditional radar technology and modern laser ranging technology, and can perform high-precision observations on objects such as terrain, seabed, vegetation, etc., and is widely used in many fields such as ecology, volcanology, glaciology, geomorphology, etc. In recent years, with the continuous update of airborne LiDAR technology, airborne LiDAR data (ALS) has become increasingly rich, making it gradually possible for application scenarios such as detection of ground object changes. Especially in the field of geological disasters, airborne LiDAR technology can obtain ground surface point cloud data after filtering vegetation, providing the most intuitive regional observation data for mountainous areas with undulating terrain and steep vegetation. Airborne LiDAR technology has been applied to the identification of landslide hazards in mountainous areas with high-density vegetation coverage. In addition, in addition to using single-phase airborne LiDAR data to identify the location and volume of landslide hazards, change detection technology based on multi-phase data has been applied to application scenarios such as continuously tracking the evolution process of landslides and the volume of sliding masses.

[0003] An airborne LiDAR system is a multi-sensor integrated system composed of multiple components such as a global positioning system (GPS), an inertial measurement system (IMS), and a laser ranging system. The measurement accuracy will be affected by the coupling of multiple internal and external factors such as each independent component within the system, the material of the ground object target, and the flight route. Scholars Okyay et al. (2019) classified the error sources affecting the observation accuracy when using ALS data for multi-phase change detection into two categories: one is the error caused by positioning reasons, and the other is the error caused by classification reasons. Zhang Xiaohong (2007) further subdivided the measurement error of ALS data into positioning error, angle measurement error, ranging error, dynamic time delay error, second-class elevation error, scanning angle error, systematic error generated by the laser beam divergence angle, and system integration error. According to the research summary of scholars James and Robson (2012), the measurement accuracy of ALS data is 0.05 - 0.2 m (vertical) and 0.2 - 0.6 m (horizontal). When using ALS data for multi-phase change detection, the error accumulation between different-phase ALS data will greatly affect the final settlement accuracy, and may make it difficult for the final analysis results to effectively observe ground object targets with minor changes.

[0004] To effectively suppress errors and improve the accuracy of multi-period ALS data observations, one of the current mainstream research approaches is to optimize airborne LiDAR hardware to mitigate errors during ALS data collection. This includes building several evenly distributed base stations within the survey area to mitigate GPS dynamic positioning errors, mitigating IMS measurement errors by rationally planning aircraft routes (such as lowering flight altitude / speed), and regularly calibrating laser scanning equipment to reduce ranging errors.

[0005] Since the above-mentioned hardware-level error correction methods are not always feasible during actual data collection, some scholars have proposed a variety of software algorithm-level error correction methods. However, when collecting multi-period ALS data, the working status of the equipment, the climatic conditions during the aircraft flight, and the status of the ground objects vary due to different collection times. When conducting a comprehensive analysis of the subtle changes in the ground objects, it is still difficult to effectively ensure the accurate separation of the subtle change information of the ground objects from other noise errors by relying solely on the error control of the airborne LiDAR equipment itself. Therefore, for the highly difficult application scenario of using multi-period ALS data to detect subtle changes in ground objects, it is necessary to introduce an external calibration method based on standardized hardware equipment for multi-period ALS data on the basis of the existing error correction algorithm, so as to maximize the change detection accuracy based on the airborne LiDAR system and help expand the application scenarios of airborne LiDAR technology in the field of geoscience. Summary of the Invention

[0006] The present invention aims to provide an airborne LiDAR acquisition mobile calibrator for the time-series detection of subtle changes in the surface, so as to solve the problem that the working state of the equipment, the climatic conditions during the flight of the aircraft, and the state of the ground objects will cause differences in multi-period ALS data, making it difficult to detect subtle changes in ground objects using multi-period ALS data.

[0007] To achieve the above-mentioned objectives, the present invention adopts the following technical solution: an airborne LiDAR acquisition mobile calibrator for time-series detection of weak surface changes, comprising: a laser reflecting device and a GPS device for determining the position of the laser reflecting device, the laser reflecting device comprising: a spherical lens, a signal reflecting base and a base, the spherical lens and the signal reflecting base are both located on the base, the signal reflecting base is used to reflect the laser signal converged by the spherical lens, and the GPS device is located on the top of the base.

[0008] Principle of this solution: According to the selected data acquisition method before airborne LiDAR acquisition, based on the planned flight route and the road conditions on site, initially select the positions where the laser reflection devices are to be arranged during single - flight - leg base - borne LiDAR data acquisition, and adjust and optimize the flight route according to the on - site survey situation to ensure that the laser reflection devices can be effectively deployed in key areas during data acquisition. Before each airborne LiDAR data acquisition, after installing the device on the top of a vehicle on site, the vehicle moves in advance to the selected position for deploying the laser reflection device, and then the height coordinate information of this laser reflection device is measured by a GPS base station. Subsequently, carry out the current airborne LiDAR data acquisition work. After completing the acquisition of this flight leg, repeat the steps of moving the laser reflection device, measuring with the GPS device, and airborne LiDAR data acquisition until all the acquisition work is completed to obtain the point cloud.

[0009] Advantages of this solution:

[0010] 1. Due to the characteristics of the spherical lens, the laser reflection device can effectively reflect incident lasers in different directions within a certain angle range, ensuring that stable point cloud data can be collected at the positions where the laser reflection devices are arranged during airborne LiDAR data acquisition.

[0011] 2. For airborne LiDAR data acquisition work under certain extreme terrain conditions (such as large height differences and limited areas for arranging laser reflection devices), the size and arrangement method of the laser reflection device can be adjusted to be compatible with acquisition scenarios with large changes in heading and flight altitude.

[0012] 3. By carrying the laser reflection device to the set position by a vehicle, it is not necessary to pre - arrange the laser reflection device at each position, which can save costs and is also convenient for adjusting the size and arrangement method of the laser reflection device.

[0013] 4. Stable point cloud can be collected through the laser reflection device, and at the same time, high - precision positioning information corresponding to this point cloud can be obtained through the GPS base station. Thus, the ALS data collected by subsequent airborne LiDAR can be error - suppressed according to this point cloud, reducing the errors of ALS data caused by factors such as the working state of the equipment, the climate conditions during aircraft flight, and the states of ground objects, and thus weak changes in ground objects can be detected.

[0014] Preferably, as an improvement, the spherical lenses and signal reflection bases are evenly distributed in groups on the side surface of the base. In this way, in the case where flight is restricted at the positions where some laser reflection devices are arranged, data can be collected through the spherical lenses and signal reflection bases on the other surfaces, and the data of the laser reflection devices here can be made more accurate through the data collected in multiple directions.

[0015] Preferably, as an improvement, the base is conical, and a connecting device is connected to the bottom of the base. The connecting device can be used to reduce damage to the base and prevent the inclination of the base from affecting the acquisition of point cloud data.

[0016] Preferably, as an improvement, the connecting devices are symmetrically arranged on the base. The connecting device includes a connecting block, and the connecting block is connected to the base. Symmetrical arrangement can make the laser reflection device more stable after being installed on other devices.

[0017] Preferably, as an improvement, an equipment skeleton is further included. The equipment skeleton includes a cross brace and brackets. The brackets are X-shaped, and both ends of the brackets are respectively slidably connected to the symmetrically arranged cross braces. The connecting block is connected to the brackets. When the equipment is installed on a vehicle, by using the sliding connection between the cross brace and the brackets, the brackets can be moved, and the position of the laser reflection device can be quickly changed.

[0018] Preferably, as an improvement, grooves are provided inside the cross brace, and bumps corresponding to the grooves are provided on the brackets. This can limit the sliding direction of the brackets.

[0019] Preferably, as an improvement, an installation mechanism is further included. The installation mechanism includes: an upper fixed base, a lower fixed base, a first rotary fixing bolt, and a second rotary fixing screw. The first rotary fixing bolt passes through the upper fixed base and is threadedly connected to the lower fixed base. The first rotary fixing bolt is threadedly connected to the upper fixed base. The cross brace is located between the upper fixed base and the lower fixed base. The second rotary fixing bolt horizontally passes through the lower fixed base, and the second rotary fixing bolt is threadedly connected to the lower fixed base.

[0020] By adjusting the first rotary fixing bolt, the distance between the upper fixed base and the lower fixed base can be changed, so that the upper fixed base and the lower fixed base can clamp and fix the cross brace. This method is convenient for installation and disassembly; the installation mechanism as a whole is connected to the roof rack of the vehicle through the second rotary fixing bolt. By adjusting the second rotary fixing bolt, the installation mechanism can be quickly installed and disassembled, realizing the rapid installation and deployment of the laser reflection device.

[0021] Preferably, as an improvement, a power supply is further included. The power supply is used to supply power to the GPS device. This ensures that the overall device can be quickly deployed to any area where vehicles can pass, improving the applicability of the device under complex on-site working conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a side view of the laser reflection device according to an embodiment of the present invention.

[0023] Figure 2 It is a top view of the laser reflection device according to an embodiment of the present invention.

[0024] Figure 3 It is the top view of the device skeleton of the embodiment of the present invention.

[0025] Figure 4 It is the side view of the device skeleton and the installation mechanism of the embodiment of the present invention.

[0026] Figure 5 It is the structural schematic diagram of the embodiment of the present invention. Specific Embodiments

[0027] The following is a further detailed description through specific embodiments:

[0028] The reference numerals in the drawings of the specification include: spherical lens 1, reflection base 2, conical base 3, connecting device 4, cross brace 5, bracket 6, upper fixed base 7, first rotating fixing bolt 8, second rotating fixing bolt 9, lower fixed base 10, GPS base station 11.

[0029] Embodiment:

[0030] An airborne LiDAR acquisition mobile calibrator for detecting weak surface change sequences includes: a laser reflection device, a device skeleton, and an installation mechanism. As shown in the attached drawings, the laser reflection device includes: a spherical lens, a signal reflection base, and a base. The spherical lens and the signal reflection base are both located on the base. The signal reflection base is used to reflect the laser signal converged by the spherical lens. As shown in the attached drawings, the spherical lens is used to change the incident angle of the laser, and the signal reflection base reflects the incident laser back to the spherical lens. In this way, it is possible to achieve that the laser is reflected back to the laser emission device (i.e., airborne LiDAR) in the same direction after incidence, so as to obtain accurate data of a point on the ground. By collecting data at multiple deployment locations of the laser reflection device, a stable point cloud (without change, i.e., a standard point cloud) can be obtained. Taking this point cloud as a reference, the error suppression of the subsequent ground data collected by the airborne LiDAR can be continued, thereby improving the detection accuracy and detecting weak surface changes. Figure 1 Figure 5

[0031]

[0032] The base is conical, and both the upper surface and the lower surface of the base are circular. The spherical lens is placed on the signal reflection base, and the signal reflection base is provided with an arc-shaped groove matching the spherical lens, which is convenient for placing the spherical lens on the signal reflection base. The signal reflection base is an arc-shaped block, so that the signal reflection base contacts the base more closely.

[0032] As shown in the attached drawings Figure 2As shown, the spherical lenses and signal reflectors are evenly distributed in groups on the sides of the base. In this embodiment, there are four sets of spherical lenses and signal reflectors, evenly distributed in a circular pattern on the sides of the base. This allows data to be collected from the remaining spherical lenses and signal reflectors in situations where the placement of certain laser reflectors is restricted. This multi-directional data collection allows for more accurate data from the laser reflectors.

[0033] A connecting device is provided at the bottom of the base. This device can be used to reduce damage to the base and prevent tilting that could affect point cloud data collection. The connecting device is symmetrically positioned on the base and includes connecting blocks. This symmetrical arrangement ensures greater stability when the laser reflector is mounted on other equipment.

[0034] Also includes equipment skeleton, such as attached Figure 3 As shown, the device framework consists of a cross brace and a bracket. The bracket is X-shaped, with each end slidingly connected to a symmetrical cross brace. The cross brace has grooves on its inner side, and the bracket has corresponding bumps. This restricts the bracket's sliding direction. The connecting block is connected to the bracket. Once the device is mounted on a vehicle, the bracket can be moved using the sliding connection between the cross brace and bracket, allowing for quick repositioning of the laser reflector.

[0035] Also includes mounting mechanism, such as attached Figure 4 As shown, the mounting mechanism includes an upper fixed base, a lower fixed base, a first rotating fixing bolt, and a second rotating fixing screw. The first rotating fixing bolt passes through the upper fixed base and is threadedly connected to the lower fixed base. The first rotating fixing bolt is also threadedly connected to the upper fixed base. The cross brace is located between the upper and lower fixed bases. By adjusting the first rotating fixing bolt, the distance between the upper and lower fixed bases can be changed, thereby ensuring a stable connection between the upper and lower fixed bases and the cross brace, which facilitates installation and removal.

[0036] A second rotating fixing bolt passes horizontally through the lower fixing base and is threadedly connected to the lower fixing base. This second rotating fixing bolt secures the entire mounting mechanism to the vehicle's roof rack. Adjusting the second rotating fixing bolt allows for quick installation and removal of the mounting mechanism, enabling rapid deployment of the laser reflector.

[0037] The thickness of the lower fixed base is greater than that of the upper fixed base, which can reduce the weight of the installation mechanism without affecting the connection stability of the upper fixed base, the lower fixed base and the cross brace.

[0038] It also includes a GPS device for measuring the position of the laser reflection device. The GPS device is located on the top of the base and is fixed to the base by bolts. It also includes a power supply for powering the GPS device, which is a vehicle-mounted power supply in this embodiment, ensuring that the overall device can be quickly deployed to any area accessible by vehicles and improving the applicability of the device under complex on-site working conditions.

[0039] The specific implementation process is as follows:

[0040] First, select a suitable laser reflection device according to the data acquisition plan selected before the airborne LiDAR acquisition. Mainly adjust the geometric dimensions and layout methods of the conical base and the laser reflection component in the laser reflection device according to the flight route parameters (route design, flight altitude, etc.) and the main parameters of the LiDAR head (tilt angle, etc.).

[0041] Select and process the laser reflection device. According to the selected flight route and the road access situation on-site, preliminarily select the positions where the laser reflection device is to be arranged during a single flight of airborne LiDAR data acquisition, and adjust and optimize the flight route according to the on-site survey situation to ensure that the laser reflection device can be effectively deployed in key areas during data acquisition.

[0042] Determine the device deployment plan. Before each flight of airborne LiDAR data acquisition, after installing the device on the top of an available vehicle on-site, the vehicle moves to the selected position in advance, and the high-precision coordinate information of this position is calculated through the GPS base station. Subsequently, carry out the airborne LiDAR data acquisition work for this flight. After completing the acquisition for this flight, repeat the above steps to deploy the device to the next designated position. After obtaining the high-precision coordinate information of this position through the GPS base station, carry out the next flight of airborne LiDAR acquisition work. Repeat the above steps until all acquisition work is completed.

[0043] Perform post-processing on the ALS data obtained by the airborne LiDAR. Use the point cloud collected by the laser reflection device and the corresponding high-precision coordinate information to perform error calibration and correction on the overall point cloud data.

[0044] The laser reflection device of this solution can effectively reflect incident lasers in different directions within a certain angle range, ensuring that stable point cloud data can be collected at the position where the laser reflection device is arranged during airborne LiDAR data collection (within a certain flight route direction and flight altitude range); for the airborne LiDAR data collection requirement scenarios under certain extreme terrain conditions (such as large height differences and limited areas where the device can be arranged), by adjusting the geometric dimensions of the conical base of the laser reflection device, the geometric dimensions and arrangement methods of the laser reflection components, it can better accommodate the collection scenarios with large changes in flight route direction and flight altitude; the device skeleton and installation mechanism have modular attributes and are easy to process, facilitating on-site installation and having good compatibility with different sizes of car roof luggage racks. It can be quickly installed and deployed on the car roof under limited on-site conditions, thus achieving rapid device deployment during airborne LiDAR data collection; in addition, the power supply required for the GPS base station can be effectively guaranteed through devices such as vehicle power supplies, further ensuring that the overall device can be quickly deployed to any area accessible by cars, enhancing the applicability of the device under complex on-site working conditions; by arranging the laser reflection device on-site and combining it with the GPS base station arranged on the device, it can be ensured that stable laser point clouds can be collected at the position where the device is arranged during airborne LiDAR collection. At the same time, high-precision positioning information corresponding to the point clouds can be obtained through the GPS base station, so as to use these point clouds as high-precision calibration points to suppress the errors of the ground data collected by airborne LiDAR, reducing the errors caused by factors such as the working state of the equipment, the climate conditions during aircraft flight, and the state of ground objects, and thus detecting weak changes in ground objects.

[0045] The above are only embodiments of the present invention. Specific technical solutions and / or common knowledge such as characteristics well known in the art are not described in detail herein. It should be noted that for those skilled in the art, without departing from the technical solution of the present invention, several modifications and improvements can be made. In the present invention, unless otherwise clearly defined and limited, terms such as "installation", "connection", "connection", "fixation" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be directly connected, or indirectly connected through an intermediate medium, and it can be the connection of two components inside. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations. The scope of protection required by this application should be based on the content of its claims, and the specific implementation manners described in the specification can be used to interpret the content of the claims.

Claims

1. A mobile airborne LiDAR calibrator for detecting subtle surface changes in time series, characterized by: include: A laser reflecting device and a GPS device for determining the position of the laser reflecting device. The laser reflecting device includes: a spherical lens, a signal reflecting base and a base. The spherical lens and the signal reflecting base are both located on the base. The signal reflecting base is used to reflect the laser signal converged by the spherical lens. The GPS device is located on top of the base. The spherical lens and the signal reflecting base are evenly distributed in groups on the side of the base.

2. The mobile airborne LiDAR calibrator for detecting subtle surface changes in time series according to claim 1, characterized in that: The base is conical, and the bottom of the base is connected with a connecting device.

3. The mobile airborne LiDAR calibrator for detecting subtle surface changes in time series according to claim 2, characterized in that: The connecting device is symmetrically arranged on the base, and the connecting device includes a connecting block, and the connecting block is connected to the base.

4. The mobile airborne LiDAR calibrator for detecting subtle surface changes in time series according to claim 3, characterized in that: It also includes an equipment frame, which includes a cross brace and a bracket. The bracket is X-shaped, and both ends of the bracket are slidingly connected to the symmetrically arranged cross braces, and the connecting block is connected to the bracket.

5. The mobile airborne LiDAR calibrator for detecting subtle surface changes in time series according to claim 4, characterized in that: A groove is provided on the inner side of the cross brace, and a convex block corresponding to the groove is provided on the bracket.

6. The mobile airborne LiDAR calibrator for detecting subtle surface changes in time series according to claim 4, characterized in that: It also includes an installation mechanism, which includes: an upper fixed base, a lower fixed base, a first rotating fixing bolt and a second rotating fixing bolt, the first rotating fixing bolt passes through the upper fixed base and is threadedly connected to the lower fixed base, the first rotating fixing bolt is threadedly connected to the upper fixed base, the cross brace is located between the upper fixed base and the lower fixed base, the second rotating fixing bolt passes horizontally through the lower fixed base, and the second rotating fixing bolt is threadedly connected to the lower fixed base.

7. The mobile airborne LiDAR calibrator for detecting subtle surface changes in time series according to claim 1, characterized in that: Also included is a power supply for powering the GPS device.

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