Method for designing airline of airborne laser radar of unmanned aerial vehicle in dense forest region based on canopy density estimation

Abstract

The invention belongs to the technical field of estimating an airborne laser radar route of an unmanned aerial vehicle in a dense forest region, and particularly relates to a method for designing an airborne laser radar route of an unmanned aerial vehicle in a dense forest region based on canopy density estimation, which comprises the following steps of: establishing an airborne laser radar route design model of the unmanned aerial vehicle based on canopy density estimation of a target region; according to the method, on the basis of canopy density estimation of the target area, an unmanned aerial vehicle airborne laser radar air route design model is established, and the pulse frequency, the reflectivity, the flight height, the air route spacing, the number of flight and the like of the laser radar are calculated and designed; therefore, the actually obtained point set density and the designed point set density are kept consistent, the specific large-scale topographic surveying and mapping requirements can be met, and the method is automatic in operation, simple and convenient to operate and very high in overall efficiency.

Description

Technical Field

[0001] The present invention relates to the technical field of estimating the airborne laser radar route of an unmanned aerial vehicle (UAV) in dense forest areas, and in particular to a method for designing the airborne laser radar route of an unmanned aerial vehicle (UAV) in dense forest areas based on canopy density estimation. Background Art

[0002] Large-scale topographic mapping in densely forested areas has always been a challenge in engineering surveys. First, densely forested areas are characterized by dense vegetation, rugged terrain, and difficulty accessing them. Traditional surveying methods often require significant manpower and material resources, resulting in high workload, long lead times, and high costs. Second, the use of drone-mounted LiDAR (lidar) cannot accurately estimate the density of the point cloud reaching the ground due to the dense vegetation cover and strong obstruction in dense forests, making it difficult to meet the requirements of large-scale topographic mapping.

[0003] Therefore, the accuracy and efficiency of large-scale topographic mapping in dense forest areas using existing technologies are not high enough. Therefore, based on the above technical problems, a method for designing UAV-mounted lidar routes in dense forest areas based on canopy density estimation was designed. Summary of the Invention

[0004] In order to remedy the problems of the existing technology, the present invention proposes a UAV airborne lidar route design method in dense forest areas based on canopy density estimation.

[0005] The technical solution adopted by the present invention to solve its technical problems is: a method for designing UAV airborne laser radar routes in dense forest areas based on canopy density estimation. Based on the canopy density estimation of the target area, a UAV airborne laser radar route design model is established. The laser radar pulse frequency, reflectivity, flight altitude, route spacing, number of flights, etc. are calculated and designed to obtain a designed route that meets the requirements of corresponding scale terrain mapping, including the following steps:

[0006] Step 1: Based on the high-spatial-resolution panchromatic images, multispectral remote sensing images, and field survey samples of the target area, supervised classification methods are used to estimate the canopy density.

[0007] Step 2: Select a suitable flight platform and aerial photography sensor based on the canopy density estimation results and existing geographic information (including DEM and DOM).

[0008] Step 3: Based on the flight platform and aerial photography sensor types obtained in step 2, establish the system route design model as follows:

[0009]

[0010] Where P is the ground point density;

[0011] n is the number of repeated flights;

[0012] C is the estimated canopy density;

[0013] μ is the laser pulse rate;

[0014] v is the ground speed of the UAV;

[0015] H is the relative altitude of the UAV;

[0016] θ is the laser scanning field of view (FOV).

[0017] Step 4: Based on the route design model obtained in step 3, the emission frequency, relative flight altitude, number of repeated flights, and FOV of the UAV-mounted lidar system are calculated according to the estimated canopy density and the scale requirements of the topographic map.

[0018] Step 5: Based on the route design parameters obtained in step 4, the flight route is laid out to obtain the three-dimensional track information of the aerial photography operation.

[0019] Step 6: Import the three-dimensional track information obtained in step 5 into the flight control system of the UAV, take off the UAV, and automatically acquire data based on the imported three-dimensional track information to obtain laser ranging files, image data, and airborne POS data; at the same time, set up a ground base station to obtain ground base station data.

[0020] Step 7: The actual ground point set density is obtained through joint solution and point cloud filtering, and compared with the designed point set density for verification.

[0021] Working Principle: LiDAR (Light Detection and Ranging) is an active remote sensing technology. Combined with attitude positioning technology (POS / IMU), it emits laser pulses and receives echoes to obtain three-dimensional point cloud data of the target object's surface. It boasts large data volumes, high measurement accuracy, and a certain degree of penetration. It is widely used in engineering surveys, natural resource surveys, urban planning, and emergency rescue. UAV-mounted LiDAR captures high point cloud density, allowing for flexible route design and operation planning, making it ideal for large-scale topographic mapping.

[0022] Canopy density refers to the ratio of the total projected area of ​​the tree crowns on the ground (canopy width) in direct sunlight to the total area of ​​the forest stand. It is a key factor reflecting forest structure and environment. Canopy density estimation using supervised classification methods based on panchromatic and multispectral satellite remote sensing imagery can effectively invert laser beam obstruction and penetration in dense forests.

[0023] The present invention is beneficial in that:

[0024] 1. Based on the estimation of the canopy density of the target area, the present invention establishes a UAV-mounted lidar route design model. The laser radar pulse frequency, reflectivity, flight altitude, route spacing, number of flights, etc. are calculated and designed, so that the actual point set density is kept consistent with the designed point set density, which can meet the specific large-scale terrain mapping requirements. In addition, this method is automated, easy to operate, and has very high overall efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0026] Figure 1 It is the overall flow chart of the present invention;

[0027] Figure 2 Schematic diagram of the three-dimensional trajectory designed for the UAV route of the Han River Diversion Project;

[0028] Figure 3 This is a schematic diagram of the three-dimensional flight trajectory of the UAV in the Han River Diversion Project. DETAILED DESCRIPTION

[0029] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention. The specific equipment, technical parameters and uses used in this embodiment are as follows:

[0030]

[0031] Example 1:

[0032] A UAV airborne LiDAR route design method based on canopy density estimation is proposed. The canopy density of the target area is estimated, and a UAV airborne LiDAR route design model is established. The pulse frequency, reflectivity, flight altitude, route spacing, and number of flights of the LiDAR are calculated and designed to obtain a designed route that meets the requirements of terrain mapping at the corresponding scale. Figure 1 As shown, the following steps are included:

[0033] Step 1: Based on the high-resolution panchromatic imagery, multispectral remote sensing imagery, and field survey samples of the target area, a supervised classification method was used to estimate the canopy density of the target area to be 75%;

[0034] Step 2: Based on the canopy density estimation results and existing geographic information, including digital elevation models and scale requirements, the UAV platform was determined to be the Yunying Feiyang C200 vertical take-off and landing UAV platform, and the sensor was determined to be the RIEGL_VUX-1LR 1350 laser scanning system;

[0035] Step 3: Based on the flight platform and aerial photography sensor types obtained in step 2, establish the system route design model as follows:

[0036]

[0037] Where P is the ground point density;

[0038] n is the number of repeated flights;

[0039] C is the estimated canopy density;

[0040] μ is the laser pulse rate;

[0041] v is the ground speed of the UAV;

[0042] H is the relative altitude of the UAV;

[0043] θ is the laser scanning field of view (FOV);

[0044] According to the requirements of 75% canopy density and 1:2000 topographic mapping, the flight altitude of the UAV is calculated to be 100 meters, the laser frequency is 100 Hz, and the number of repeated flights is 3. The flight route is laid out to obtain the three-dimensional track information of the aerial photography operation. Step 3, as shown in Figure 3 As shown;

[0045] Step 4: Import the three-dimensional track information obtained in step 3 into the flight control system of the UAV, take off the UAV, and automatically acquire data based on the imported three-dimensional track information to obtain laser ranging files, image data, and airborne POS data; at the same time, set up a ground base station to obtain ground base station data. Step 5: The actual ground point density is obtained through joint calculation and point cloud filtering. It is verified that the actual point density is consistent with the designed point density, both of which are 0.5 points / m 2 .

[0046] Throughout this specification, references to terms such as "one embodiment," "example," or "specific example" indicate that the specific features, structures, materials, or characteristics described in conjunction with that embodiment or example are included in at least one embodiment or example of the present invention. In this specification, schematic representations of these terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0047] The basic principles, main features, and advantages of the present invention are shown and described above. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions are merely illustrative of the principles of the present invention. Various changes and modifications may be made to the present invention without departing from the spirit and scope of the present invention, and such changes and modifications fall within the scope of the invention as claimed.

Claims

1. A method for designing UAV-mounted LiDAR flight paths in dense forest areas based on canopy density estimation. Based on the canopy density estimation of the target area, a UAV-mounted LiDAR flight path design model is established to obtain a designed flight path that meets the requirements of terrain mapping at a corresponding scale. The method specifically includes the following steps: Step 1: Based on high-spatial-resolution panchromatic images, multispectral remote sensing images, and field survey samples of the target area, supervised classification methods are used to estimate canopy density. Step 2: Select a flight platform and an aerial sensor based on the canopy density estimation results and existing geographic information data, including DEM and DOM. Step 3: Based on the flight platform and aerial sensor type selected in step 2, a route design model for the system is established; Step 4: Based on the route design model obtained in step 3, the emission frequency, relative flight altitude, number of repeated flights, and FOV of the UAV-mounted lidar system are calculated according to the estimated canopy density and the scale requirements of the topographic map. Step 5: Lay out the flight route according to the route design parameters obtained in step 4 to obtain the three-dimensional track information of the aerial photography operation; Step 6: Import the 3D track information obtained in step 5 into the UAV's flight control system, take off the UAV, and automatically acquire data based on the imported 3D track information to obtain laser ranging files, image data, and airborne POS data; at the same time, set up a ground base station to acquire ground base station data; Step 7: The actual ground point set density is obtained through joint solution and point cloud filtering, and compared with the designed point set density for verification.

2. The method for designing a UAV-mounted LiDAR route in dense forest areas based on canopy density estimation according to claim 1, characterized in that: In step 3, a route design model is established based on the estimated canopy density to obtain the UAV airborne lidar route design parameters.

3. The method for designing a UAV-mounted LiDAR route in dense forest areas based on canopy density estimation according to claim 2, characterized in that: The route design model is established based on the estimated canopy density, and the route design model of the system is established as follows: Where P is the ground point density; n is the number of repeated flights; C is the estimated canopy density; μ is the laser pulse rate; v is the ground speed of the UAV; H is the relative altitude of the UAV; θ is the laser scanning field of view (FOV).

Images