A method for determining the overlap rate of mountain aerial photography by an unmanned aerial vehicle in a region

Abstract

The present invention discloses a method for determining the mountain overlap rate in UAV regional aerial photography, which includes: by superimposing the DEM data of the aerial photography area and the elevation and overlap degree data of the expected take-off location, for elevation points higher than the take-off point, calculate the overlap rate of each point one by one. For areas where the overlap rate is lower than the threshold required by the UAV data processing software, give a warning and dynamically adjust the overlap rate of the flight path so that all areas meet the overlap rate required by the processing software; it solves the technical problems in UAV regional aerial photography, such as when it is impossible to reach the highest area of the area, or the cost of reaching the highest area is relatively high, the aerial photography photos are insufficient and need to be retaken in the later stage, or the overlap rate is set too high, resulting in waste of aerial photography battery and time, etc.

Description

Technical Field

[0001] The present invention belongs to the field of UAV aerial photography technology, and particularly relates to a method for determining the overlap rate of mountain bodies in UAV regional aerial photography. Background Art

[0002] At present, the overlap rate displayed by the ground station software used in UAV regional aerial photography for producing orthophotos is based on the elevation of the take-off point. This has led to the situation that for workers engaged in regional aerial photography, in order to meet the overlap rate of the entire area, they have to choose the highest point in the entire area as the take-off point. However, this has also increased the complexity and danger of the operation because they have to climb to the highest point or a position similar to the highest point to take off. At this time, they can only estimate by experience whether the mountain bodies higher than the take-off point can meet the coverage rate. After aerial photography, through the software, low-resolution images are quickly generated, and the test results are checked to see if they meet the requirements. If not, the areas with insufficient overlap rate need to be reshot.

[0003] Its general process steps are as follows:

[0004] 1. Understand and photograph the situation of the aerial photography area. If there are accurate boundaries, the shooting vector area can be outlined in advance and imported into the ground station software such as DJI GS PRO;

[0005] 2. Plan the layout positions of control points and preliminarily determine the take-off point position according to the terrain and road conditions;

[0006] 3. Set up control point targets on site and measure the accurate positions of the control points;

[0007] 4. Find the highest or second-highest point in the area and determine the final take-off point;

[0008] 5. Plan the flight path, set the heading and side overlap rate according to the take-off point position. If the take-off point position is near the highest point, the overlap rate can be set lower. If the take-off point position is at a lower position, the overlap rate can be set higher;

[0009] 6. Start aerial photography. After collecting all the aerial photography data, import all the data into the software for quick inspection and processing to check whether all the photos meet the overlap rate required by the software. If not, reshooting is required;

[0010] 7. If the photos meet the requirements, the field work is completed, and the data will be processed with high precision indoors later.

[0011] One drawback of the ground station software widely used in the market is that in areas with large topographic undulations in mountainous regions, when the takeoff point is set to meet the required overlap rate and there are peaks much higher than the takeoff point, the overlap rate of the mountain body may not meet the requirements, resulting in the need for additional shooting or voids in the final results later. Although it is known that the higher the mountain body is above the takeoff point, the lower the overlap rate, there is no reference data provided by the ground station software on what height difference is acceptable. This leads to setting the overlap rate as high as possible based on experience. On the one hand, if the overlap rate is set too high, the flight time will be too long, which may delay the project progress and waste valuable operation time. On the other hand, if the overlap rate is set too low, the higher mountain bodies may not meet the overlap rate requirements. Summary of the Invention

[0012] The technical problem to be solved by the present invention is to provide a method for determining the overlap rate of mountain bodies in UAV regional aerial photography, so as to solve the technical problems in UAV regional aerial photography, such as when the highest area of the area cannot be reached, or the cost of reaching the highest area is relatively high, the aerial photos are insufficient, resulting in the need for additional shooting in the later stage, or the overlap rate is set too high, resulting in waste of aerial photography batteries and time.

[0013] The technical solution of the present invention is as follows:

[0014] A method for determining the overlap rate of mountain bodies in UAV regional aerial photography, which includes: by superimposing the DEM data of the aerial photography area and the elevation and overlap degree data of the expected takeoff location, for elevation points higher than the takeoff point, calculate the overlap rate of each point one by one. For areas where the overlap rate is lower than the required threshold of the UAV data processing software, give a warning and dynamically adjust the overlap rate of the flight route so that all areas meet the overlap rate requirements of the processing software.

[0015] The method for calculating the overlap rate of all areas is as follows:

[0016] Assume that the lens field of view angle is 2α, the flight altitude set at the takeoff point is H, the mountain body height is h, the side overlap rate is β, and the overlap width of two photos at the mountain body height is y'. Then, at the takeoff point height, the ground width covered by the photo is:

[0017] x = 2Htan(α)

[0018] The photo overlap width is:

[0019] x' = βx = 2βHtan(α)

[0020] The width of the photo coverage on the mountain body is:

[0021] y = 2(H - h)tan(α)

[0022] Then, according to the relationship between the sides and angles of the triangle, it can be obtained that:

[0023]

[0024] where δ = 90° + α, η = 90° - α - arctan(2h / x');

[0025] Thus, the

[0026] Finally, the new overlap rate of the mountain body is obtained as:

[0027]

[0028] The method for dynamically adjusting the overlap rate of the flight path is as follows: Provide a software slider to simulate precise adjustment of the overlap rate. If a certain value can just make the overlap rate of the entire area meet the requirements, then this value is the minimum overlap rate that needs to be set at a certain take-off point.

[0029] Advantages of the present invention:

[0030] The present invention is to solve the problem that when conducting aerial photography of an area by an unmanned aerial vehicle (UAV), when it is unable to reach the highest area of the area, or the cost of reaching the highest area is relatively high, and it has to choose a take-off point with a lower altitude, to check whether the designed overlap rate meets the requirements. The main method is to superimpose data such as DEM data of the aerial photography area, the elevation of the planned take-off location, and the overlap degree. For elevation points higher than the take-off point, calculate the overlap rate of each point one by one. For areas where the overlap rate is lower than the threshold required by the UAV data processing software, perform red marking warnings, so as to dynamically adjust the overlap rate of the flight path, making the overlap rate of all areas meet the requirements of the processing software.

[0031] The advantages of the present invention are that it changes the previous way of qualitatively estimating the mountain overlap rate by the take-off point to a way of quantitatively calculating the overlap rate of all areas in the region. This can avoid operations such as re-shooting due to insufficient aerial photography photos in the later stage, or waste of aerial photography batteries and time caused by setting the overlap rate too high, saving manpower and material resources; according to the DEM data of the region, the present invention realizes the adjustment of the overlap rate from qualitative adjustment to quantitative adjustment, can ensure that the overlap rate of all areas meets the requirements of software processing, and can see the high and low overlap rates of all areas.

[0032] It solves technical problems such as when conducting aerial photography of an area by an unmanned aerial vehicle, when it is unable to reach the highest area of the area, or the cost of reaching the highest area is relatively high, insufficient aerial photography photos leading to operations such as re-shooting in the later stage, or waste of aerial photography batteries and time caused by setting the overlap rate too high. Description of the Drawings

[0033] Figure 1 It is a schematic diagram of the calculation principle of the mountain overlap rate of the present invention;

[0034] Figure 2 Schematic diagram of the aerial photography process in the specific embodiment of the present invention Specific embodiment

[0035] The purpose of the present invention is to solve the problem that when conducting aerial photography in a drone area, when it is impossible to reach the highest area of the area, or the cost of reaching the highest area is relatively high, and a takeoff point with a lower altitude has to be selected, it is used to check whether the overlap rate of the design meets the requirements. The main method is to superimpose data such as the DEM data of the aerial photography area, the elevation of the expected takeoff location, and the overlap degree. For elevation points higher than the takeoff point, the overlap rate of each point is calculated point by point. For areas where the overlap rate is lower than the threshold required by the drone data processing software, they are marked in red for warning, so that the overlap rate of the flight path can be dynamically adjusted to make all areas meet the overlap rate required by the processing software.

[0036] The calculation process of the overlap rate of the present invention is as follows:

[0037] Based on the photo overlap rate at the original altitude (taking the side overlap rate as an example for calculation here, because the side overlap rate is generally set lower than the forward overlap rate), the photo overlap rate at the mountain height is deduced. The schematic diagram of the calculation principle is as Figure 1 , and the derivation process is as follows:

[0038] Assume that the lens field of view angle is 2α, the flight altitude set at the takeoff point is H, the mountain height is h, the side overlap rate is β, and the overlap width of two photos at the mountain height is y'. Then, at the takeoff point, the ground width covered by the photo is:

[0039] x = 2Htan(α)

[0040] The photo overlap width is:

[0041] x' = βx = 2βHtan(α)

[0042] The width covered by the photo on the mountain is:

[0043] y = 2(H - h)tan(α)

[0044] Then, according to the relationship between the sides and angles of the triangle, we get:

[0045]

[0046] where δ = 90° + α, η = 90° - α - arctan(2h / x').

[0047] Thus, it is solved that

[0048] Finally, the new overlap rate of the mountain is obtained as:

[0049]

[0050] Based on the calculated results of the mountain overlap rate, the latest overlap rate of any elevation point within the area can be obtained. Therefore, the latest process during field operations is (see Figure 2 ):

[0051] When the take-off point is not near the highest area, if the area overlap rate is set according to the overlap rate requirement of the software at this time, it may cause the overlap rate of some parts of the mountain to fail to meet the minimum requirement of the software, let alone the quality. According to the solution of this patent, in this case, the overlap rate of all areas can be calculated based on the DEM (Digital Elevation Model) data of the area (with a maximum resolution of 12.5 meters globally) and the elevation of the take-off point. Highlight the areas that cannot meet the overlap rate requirement, and at the same time provide a software slider to simulate and precisely adjust the overlap rate. If a certain value can just make the overlap rate of the entire area meet the requirement when reaching a certain value, then this value is the minimum overlap rate that needs to be set at a certain take-off point. At this time, input this value into the ground station software to complete the setting, and then the aerial photography can start.

[0052] The heading overlap rate described in the present invention refers to the ratio of the overlapping length of two photos along the flight direction of the flight line to the length of a single photo.

[0053] The side overlap rate described in the present invention refers to the ratio of the overlapping width of two adjacent photos in adjacent flights to the width of a single photo.

[0054] The DEM described in the present invention refers to the Digital Elevation Model, which is data representing the terrain height.

Claims

1. A method for determining the overlap rate of mountain bodies in aerial photography of an unmanned aerial vehicle area, characterized in that: It includes: By superimposing the DEM data of the aerial photography area and the elevation and overlap degree data of the planned take-off location, for elevation points higher than the take-off point, calculate the overlap rate of each point one by one. For areas where the overlap rate is lower than the threshold required by the UAV data processing software, give a warning and dynamically adjust the overlap rate of the flight path so that all areas meet the overlap rate required by the processing software; The method for calculating the overlap rate of all areas is: Assume that the lens field of view angle is 2α, the set flight altitude at the take-off point is H, the mountain height is h, the side overlap rate is β, and the overlap width of two photos at the mountain height is y'. Then, at the take-off point height, the ground width covered by the photo is: x = 2Htan(α) The photo overlap width is: x′ = βx = 2βHtan(α) The width covered by the photo on the mountain is: y = 2(H - h)tan(α) Then, according to the relationship between the sides and angles of the triangle, we get: where δ = 90° + α, η = 90° - α - arctan(2h / x’); Thus, the calculation is carried out to obtain Finally, the new overlap rate of the mountain is obtained as: The method for dynamically adjusting the overlap rate of the flight path is: provide a software slider to simulate precise adjustment of the overlap rate. If a certain value can just make the overlap rate of the whole area meet the requirements, then this value is the minimum overlap rate that needs to be set at a certain take-off point.

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