A method for simulating nitrogen deposition in forest canopies based on drones

Abstract

The present invention discloses a method for simulating forest canopy nitrogen deposition based on an unmanned aerial vehicle, comprising the following steps: prospecting a sample plot to determine the scope and shape of the sample plot; selecting an unmanned aerial vehicle take-off and landing site based on the scope of the sample plot, measuring the sample plot through RTK technology to obtain the four-sided coordinates of the sample plot, and mapping the sample plot through the unmanned aerial vehicle to obtain a high-definition map of the sample plot; constructing a sample plot task with the four-sided coordinates of the sample plot, the unmanned aerial vehicle take-off and landing site, and the high-definition map of the sample plot, and importing the sample plot task into a remote controller; setting the simulated nitrogen deposition amount and deposition rate through the remote controller, and using the unmanned aerial vehicle to uniformly and precisely spray the sample plot, so as to overcome the problem that the current method of applying nitrogen under the forest cannot reflect important processes such as the adsorption, absorption, transformation and interception of natural nitrogen deposition by the forest canopy.

Description

Technical Field

[0001] The present invention belongs to the technical field of resources and environment, and particularly relates to a method for simulating nitrogen deposition in forest canopies based on unmanned aerial vehicles (UAVs). Background Art

[0002] As the main body of the terrestrial ecosystem, forests have a complex and tall canopy layer that directly bears atmospheric nitrogen deposition. Due to the lack of effective means to spray nitrogen fertilizers above the canopy layer, most of the existing forest simulated nitrogen deposition experiments are carried out by applying nitrogen under the forest, ignoring important processes such as the adsorption, absorption, transformation, and interception of nitrogen by the canopy layer during the natural nitrogen deposition process. It is impossible to evaluate the impact of nitrogen deposition on canopy biodiversity, and it will also overestimate the impact of nitrogen deposition on the understory vegetation system and soil conditions, resulting in great uncertainties in the research on the response and adaptation mechanisms of forest ecosystems to atmospheric nitrogen deposition. In the existing simulated forest canopy nitrogen deposition technologies, most of them involve laying pipelines in the forest and then regularly using power facilities to spray solutions from containers on the ground upward to above the forest canopy under pressure. Since this method requires construction and burying pipelines in the forest and erecting power supplies, the upfront investment in systems such as mechanical and electrical and control is relatively high, and the engineering facilities have a large destructive impact on the original forest vegetation and are not easy to replicate or promote in nature reserves. At the same time, due to the long pipelines, it is easy for the solution to remain inside the pipelines during the spraying process, making it difficult to accurately control the spraying quantity, and the residual liquid corrodes the inner wall of the pipelines, increasing the later maintenance cost. Summary of the Invention

[0003] The purpose of the present invention is to propose a method for simulating nitrogen deposition in forest canopies based on UAVs. Using the DJI T40 agricultural UAV to perform the spraying task, based on the aerial survey photos of the sample plot taken by the mapping UAV, the high-definition two-dimensional map of the sample plot reconstructed by the DJI Smart Mapping software, and the accurate four-corner position coordinates of the sample plot measured by RTK, according to specific research objectives and tasks, a spraying task is constructed freely, flexibly, and personalizedly and imported into the T40 intelligent remote controller. The flight task is regularly executed to make the DJI T40 agricultural UAV fly in imitation of the ground above the forest canopy layer of the forestry sample plot, and evenly and accurately spray nitrogen solutions with different concentrations above the canopy layer to completely simulate the natural nitrogen deposition process.

[0004] To achieve the above object, the present invention provides a method for simulating nitrogen deposition in forest canopies based on UAVs, including the following steps:

[0005] Explore and select a sample plot to determine the scope and shape of the sample plot;

[0006] Based on the scope of the sample plot, select a UAV takeoff and landing site, measure the sample plot through RTK technology to obtain the accurate four-corner coordinates of the sample plot, and obtain the high-definition map of the sample plot through UAV mapping of the sample plot;

[0007] Construct a plot task with the four - corner coordinates of the plot, the UAV take - off and landing site, and the high - definition map of the plot, and import the plot task into the remote controller;

[0008] Set the spraying parameters through the remote controller and spray the plot with the UAV.

[0009] Optionally, conduct exploration on the plot to determine the plot range. Divide the plot into several spraying areas with different concentrations, and each area has the same size and specifications; refer to the average annual nitrogen deposition in the local area and set the control, low, medium, and high treatment areas according to 0, 1, 2, and 3 times the background value concentration.

[0010] Optionally, the conditions that the UAV take - off and landing site needs to meet are: a mesa or a small open space that meets the take - off height condition and a flat ground with less sand and gravel.

[0011] Optionally, the method for measuring the four - corner coordinates of the plot by RTK technology includes:

[0012] On the basis of determining the plot range and the UAV take - off and landing site, place the GNSS device at the four - corner positions of the plot, and measure the plot by RTK technology in the fixed - solution state to obtain the four - corner coordinates of the plot.

[0013] Optionally, the method for obtaining the high - definition map of the plot by UAV mapping includes: conduct photogrammetric 2D flight on the plot through UAV mapping to obtain the ortho - image and digital surface model of the plot, and perform two - dimensional reconstruction through DJI Terra software to obtain the high - definition map of the plot.

[0014] Optionally, the process of obtaining the high - definition map of the plot through two - dimensional reconstruction by DJI Terra software includes the following steps:

[0015] After opening the software, click "New Task" in the lower left corner. Subsequently, a task type selection will pop up on the main interface, and select "Two - Dimensional Map" for the reconstruction task;

[0016] Enter the reconstruction task name in the task name input box and click "OK";

[0017] Click the folder icon in the right - hand menu bar, and select the photo folder corresponding to the aerial photography task completed before mapping from the computer to add photos; click on the two - dimensional map bar and select "Low" for the resolution;

[0018] In the two - dimensional map bar, select "Farmland Scene" for the scene, "Agricultural Application" for the application, and click "Start Reconstruction" after selection.

[0019] Optionally, according to the research target features (terrain, tree height information), specific experimental purposes and contents, the spraying parameters are set through the remote controller, and the sample plot is sprayed by the UAV, where the spraying parameters include: takeoff / return speed, return height, UAV's task execution behavior, restricted maximum flight height, restricted maximum flight distance, horizontal avoidance, spraying system settings, joystick settings, aircraft RTK positioning, and network RTK.

[0020] Optionally, according to the preset simulated nitrogen deposition concentration, the UAV is equipped with a configured nitrogen solution, and the target spraying task is called through the remote controller, and the canopy nitrogen solution is quantitatively and evenly sprayed according to the optimal flight route intelligently planned by the remote controller.

[0021] Technical effects of the present invention:

[0022] 1. The present invention is an efficient, reliable, and easy-to-operate method. Compared with the traditional manual nitrogen application method under forest, it can more realistically, completely, and systematically simulate the impact mechanism of atmospheric nitrogen deposition on forest ecosystems, and has the characteristics of low cost and replicability, and can be widely promoted and applied to related experiments.

[0023] 2. The present invention executes the spraying task through the DJI T40 agricultural UAV. The DJI T40 model UAV has the advantages of large load, high efficiency, strong penetration, safety and reliability, and intelligent ease of use. The large-flow magnetic drive impeller pump equipped with it can completely isolate the internal solution from the motor and has the characteristics of corrosion resistance.

[0024] 3. The DJI T40 agricultural UAV selected in the present invention is equipped with a dual-atomization centrifugal nozzle, which can make the droplet size more uniform, ensure uniform spraying to the greatest extent, and improve the utilization rate of the sprayed solution; its effective spraying width is 11 meters, which can meet the requirements of spraying operations, with short time and high efficiency.

[0025] 4. The DJI T40 agricultural UAV selected in the present invention is equipped with a spatial intelligent perception system composed of binocular vision and phased array digital radar, which can realize full-autonomous three-dimensional continuous obstacle avoidance during the flight of the UAV, that is, meet the requirements of terrain-following flight; with the help of the terrain-following flight function, the UAV can adapt to different terrains, automatically generate a variable-height flight route according to the terrain of the surveyed area, and keep the ground resolution consistent, so as to obtain better data effects.

[0026] 5. The DJI T40 agricultural UAV selected in the present invention is equipped with a brand-new ultra-high-definition FPV camera, whose gimbal pitch is adjustable and the field of view is stable, enabling the UAV to autonomously collect plot images; after collecting the terrain, local offline mapping can be carried out through the brand-new intelligent remote controller of DJI T40, and the optimal flight route can be automatically calculated.

[0027] 6. The present invention measures the four boundaries coordinates of the sample plot through RTK measurement. The selected RTK (Real Time Kinematic) real-time dynamic measurement technology is a real-time differential GPS (RTDGPS) technology based on carrier phase observation, which consists of a reference station receiver, a data link, and a rover receiver. RTK is a breakthrough in the development mileage of measurement technology and has many advantages such as a wide range of applications, high precision, and single-unit field operation compared with traditional GPS operations.

[0028] 7. The RTK measurement method selected by the present invention can obtain high-precision data (centimeter-level positioning results) that meet the experimental requirements; compared with the UAV measurement point method and the remote control measurement point method, RTK measurement is more suitable for measuring the four boundaries positions of field sample plots and can accurately measure the coordinates of fixed points, with an error of only ±2 cm; while the UAV cannot accurately stay at the fixed four boundaries positions, and the remote control measurement point method cannot simultaneously meet the measurement conditions of achieving high-precision measurement and aligning with the four boundaries field positions in forest sample plots. Therefore, the flight path planning based on RTK measurement is the most accurate.

[0029] 8. The present invention provides a new idea for nitrogen deposition experiments. By spraying nitrogen solution on the forest canopy, it fully considers the response of the forest canopy to atmospheric nitrogen deposition and the different response mechanisms of forest vegetation structure in nitrogen deposition simulation, avoiding the neglect of the important functions and roles of the canopy during nitrogen deposition, and avoiding the direct exposure of understory vegetation and soil to nitrogen deposition. From the perspectives of ecosystem integrity, systematicness, and complexity, it studies the overall impact of natural nitrogen deposition on forest ecosystems. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The drawings constituting a part of this application are used to provide a further understanding of this application. The schematic embodiments of this application and their descriptions are used to explain this application and do not constitute an improper limitation to this application. In the drawings:

[0031] Figure 1 is a schematic flow chart of the method for spraying nitrogen on the forest canopy based on UAV in the embodiment of the present invention;

[0032] Figure 2 is Figure 1 a schematic diagram of the high-definition map of the sample plot in

[0033] Figure 3 a schematic diagram of the main interface of the Dajiang Zhitu software;

[0034] Figure 4-1 is the step (1) of establishing a high-definition map of the sample plot in the Dajiang Zhitu software, where the reconstruction task selects "two-dimensional map";

[0035] Figure 4-2 is the step (2) of establishing a high-definition map of the sample plot in the Dajiang Zhitu software, where the reconstruction task name is input;

[0036] Figure 4-3 Steps to create a high-definition map of the sample plot in the Dajiang Zhitu software: (3) Open the task aerial survey photos and select "low" resolution;

[0037] Figure 4-4 Steps to create a high-definition map of the sample plot in the Dajiang Zhitu software: (4) Set the scene and application;

[0038] Figure 5-1 Steps to import the four boundaries coordinates of the sample plot into the Dajiang Zhitu software: (1) Select the application scenario;

[0039] Figure 5-2 Steps to import the four boundaries coordinates of the sample plot into the Dajiang Zhitu software: (2) Enter the task name;

[0040] Figure 5-3 Steps to import the four boundaries coordinates of the sample plot into the Dajiang Zhitu software: (3) Farmland planning dotting guide;

[0041] Figure 5-4 Steps to import the four boundaries coordinates of the sample plot into the Dajiang Zhitu software: (4) Enter the longitude and latitude of the four boundaries coordinates of the sample plot one by one in sequence;

[0042] Figure 5-5 Steps to import the four boundaries coordinates of the sample plot into the Dajiang Zhitu software: (5) Enter the coordinates of the sample plot center point;

[0043] Figure 5-6 Steps to import the four boundaries coordinates of the sample plot into the Dajiang Zhitu software: (6) Save the task after the coordinate entry is completed;

[0044] Figure 6-1 In the steps to export the sample plot spraying area task in the Dajiang Zhitu software: (1) Save the task as another file,

[0045] Figure 6-2 In the steps to export the sample plot spraying area task in the Dajiang Zhitu software: (2) Enter the sample plot name as the file name to be saved;

[0046] Figure 6-3 In the steps to export the sample plot spraying area task in the Dajiang Zhitu software: (3) The task export process displays a progress bar;

[0047] Figure 7-1 Steps to import the spraying area task into the drone remote controller: (2) Click the "Task Operation Management" icon;

[0048] Figure 7-2 Steps to import the spraying area task into the drone remote controller: (3) "Plot" drop-down menu;

[0049] Figure 7-3 Steps to import the spraying area task into the drone remote controller: (3) Select "Prescription Map";

[0050] Figure 7-5 shows the list display of the imported task data in step (3) of importing the spraying area task into the drone remote controller;

[0051] Figure 8-1 For step (1) of setting the drone spraying parameters in the DJI T40 remote controller, enter "Job Task Management" and click "Call";

[0052] Figure 8-2 For step (2) of setting the drone spraying parameters in the DJI T40 remote controller, set the parameters in the left menu bar;

[0053] Figure 9-1 For selecting the last icon "Settings" in the function area of the DJI T40 remote controller;

[0054] Figure 9-2 For entering the general parameter setting interface in the DJI T40 remote controller;

[0055] Figure 9-3 For step (1) of setting the general flight parameters of the drone in the DJI T40 remote controller, set the takeoff / return speed and return altitude;

[0056] Figure 9-4 For step (2) of setting the general flight parameters of the drone in the DJI T40 remote controller, turn on the "Takeoff Altitude" switch;

[0057] Figure 9-5 For step (3) of setting the general flight parameters of the drone in the DJI T40 remote controller, set the drone's task execution behavior;

[0058] Figure 9-6 For step (4) of setting the general flight parameters of the drone in the DJI T40 remote controller, set the maximum flight altitude and the maximum flight distance of the drone;

[0059] Figure 9-7 For step (5) of setting the general flight parameters of the drone in the DJI T40 remote controller, turn on the "Horizontal Avoidance" switch;

[0060] Figure 9-8 For step (6) of setting the general flight parameters of the drone in the DJI T40 remote controller, turn on the spraying system switch;

[0061] Figure 9-9 For step (7) of setting the general flight parameters of the drone in the DJI T40 remote controller, select "Joystick Settings";

[0062] Figure 9-10 For step (8) of setting the general flight parameters of the drone in the DJI T40 remote controller, "RTK Settings". Specific implementation method

[0063] It should be noted that, without conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0064] It should be noted that the steps shown in the flowchart of the accompanying drawings can be executed in a computer system such as a set of computer-executable instructions, and although the logical order is shown in the flowchart, in some cases, the steps shown or described can be executed in an order different from that here.

[0065] As Figure 1 shown, in this embodiment, a method for simulating forest canopy nitrogen deposition based on an unmanned aerial vehicle is provided, including the following steps:

[0066] Explore the sample plot to determine the scope of the sample plot;

[0067] Based on the scope of the sample plot, select a takeoff and landing site for the unmanned aerial vehicle, measure the sample plot through RTK technology to obtain the four-direction coordinates of the sample plot, and map the sample plot through the unmanned aerial vehicle to obtain a high-definition map of the sample plot;

[0068] Construct a sample plot task with the four-direction coordinates of the sample plot, the takeoff and landing site of the unmanned aerial vehicle, and the high-definition map of the sample plot, and import the sample plot task into the remote controller;

[0069] Set the spraying parameters through the remote controller, and spray the sample plot through the unmanned aerial vehicle.

[0070] First, before selecting the sample plot and the experimental area, it is necessary to conduct a field survey of the site to fully understand the background information such as the basic terrain, vegetation status, and climate characteristics of the sample plot; it is also necessary to consider the site selection conditions. For the nitrogen deposition experimental sample plot, natural forest land that has not been artificially damaged should be selected as much as possible, and buildings such as houses or temples or roads in the forest land should be avoided.

[0071] Second, after completing the site survey, the basic scope of the experimental sample plot can be determined, and different concentration spraying areas can be planned. Each area is set as a sample square of 30m×30m, and each sample square needs to be separated by more than 10 meters (the effective spraying width of the DJI T40 agricultural unmanned aerial vehicle is 11 meters) to avoid mutual influence between sample squares during spraying treatment.

[0072] Third, measure the four-direction coordinates of the sample plot by RTK, select a takeoff and landing site, and draw a high-definition map of the sample plot.

[0073] When selecting a drone take-off and landing site, considering that the allowable take-off height of agricultural drones is 30 meters (based on the take-off point), and the distance of drones will be limited when flying at low altitudes, there should be a terrace or a small open space near the selected sample plot that meets the take-off conditions as the drone take-off and landing point; at the same time, in order to improve the operation efficiency, the spraying area should not be too far from the take-off and landing point. In addition to considering the above-mentioned height and space conditions, you should also try to choose a flat ground with less sand and stones, which is conducive to the smooth take-off and landing of the drone and safe landing.

[0074] After determining the scope of the sample site and the take-off and landing site, place the GNSS device at the four-point position of the sample site, and use the point measurement function of the RTK technology to accurately measure the four-point coordinates of the sample site to obtain its longitude and latitude. The steps for RTK coordinate measurement are: (1) Turn on the host and handheld device, open the handheld device software, create a new project, select the coordinate system, and select the data link (CORS); (2) Enter the point measurement interface, measure the four-point coordinates of the sample site in the fixed solution state and save them; (3) Export the measured coordinates.

[0075] Since the base map data provided by the agricultural drone remote control software is not accurate (for example, the clarity is not high and the surface data is inaccurate), and the exact boundaries of the forestry sample plot cannot be entered on the remote control, it is necessary to reconstruct a high-definition map of the sample plot for mission planning.

[0076] Through the surveying and mapping drone to perform 2D photogrammetry flight, we can obtain the orthophotos and digital surface models of the sample sites, and use the DJI Zhitu software to perform 2D reconstruction to generate a high-definition map of the sample sites (orthophotos, digital surface models). Figure 2 It should be noted that any brand and model of surveying drones that meet the requirements can be selected for the surveying sample site, but data processing must be performed through the DJI Zhitu software, because only this software can export tasks to the T40 remote controller selected by the present invention. The main interface of the DJI Zhitu software is as follows Figure 3 shown.

[0077] The specific steps for creating a high-definition map using DJI Intelligent Mapping (taking the DJI Phantom 4RTK aerial survey drone as an example) are as follows: (1) After opening the software, click "New Task" in the lower left corner. Then the main interface will pop up a task type selection. For the reconstruction task, select "2D Map". Figure 4-1 (2) Enter the reconstruction task name in the task name input box and click "OK". Figure 4-2 (3) Click the folder icon in the right menu bar and select the photo folder corresponding to the aerial photography task (i.e., surveying drone aerial survey) completed before map construction from the computer to add photos; click the 2D map bar and select "Low" for resolution, as shown in the figure below. Figure 4-3 (4) In the 2D map column, select "Farmland Scene" for the scene and "Agricultural Application" for the application. After making your selections, click "Start Reconstruction". Figure 4-4As shown, the software starts two-dimensional map reconstruction.

[0078] After the map reconstruction is completed, the longitude and latitude of the coordinates of the four boundaries of the sample plot obtained by RTK measurement need to be entered into the high-definition map of the sample plot. You can continue to operate in the Dajiang Zhitu software. The operation steps are as follows: (1) Select "Applications" in the right-side menu bar and click the second item "Agricultural Applications", as Figure 5-1 shown; (2) Enter the task name in the pop-up input box and select "OK", as Figure 5-2 shown; (3) Read the "Farmland Planning Pointing Guide" in the pop-up box and select "Got it", as Figure 5-3 shown; (4) At any position in the high-definition map interface of the sample plot, click the left mouse button, and a corresponding menu bar will appear on the right. There are "Longitude", "Latitude" and corresponding input boxes below "Operation Planning". Enter the coordinates of the four boundaries of the sample plot one by one in order (currently, the software does not support batch import of coordinates), as Figure 5-4 shown; (5) After completing the entry of the four boundaries, select the icon in the lower left corner of "Operation Planning" (the second one from the left in the horizontal row) and enter the coordinates of the center point of the quadrat in order, as Figure 5-5 shown; (6) After all the coordinates are entered, click the save button in the upper left corner of the right-side menu bar. A menu bar will appear on the left and display "Task saved successfully", as Figure 5-6 shown.

[0079] Fourth, in the Dajiang Zhitu software, save and export the constructed spraying area task of the sample plot, and you can get a planar flight task composed of the accurate four boundaries of the experimental forestry sample plot. You can continue to operate in the Dajiang Zhitu software. The specific steps are as follows: (1) In the save and parallel menu bar on the right side of the interface, select the third "Save As" icon in the upper right corner, as Figure 6-1 shown; (2) Enter the name of the sample plot in the file name to be saved, click "Save", and a planar flight task composed of the accurate four boundaries of the forestry sample plot will be saved. The file extension is DJITILE, as Figure 6-2 shown; (3) A save progress bar will pop up, as Figure 6-3 shown; While saving the above file, the software will also save a folder corresponding to the input file name, which contains four files, all of which are high-definition map files of the sample plot (orthophoto image, digital surface model).

[0080] Fifth, export the saved spraying area task of the sample plot to the Dajiang T40 remote controller. The specific steps are as follows: (1) Copy the task file (file extension is DJITILE and the folder corresponding to the file name) to the "rouse" folder of the TF card of the remote controller. After putting the TF into the drone remote controller, when the remote controller is powered on and the software is opened, the task will be automatically called; (2) Click the first "Operation Task Management" icon in the function area in the upper left corner of the remote controller interface to enter the plot management interface, asFigure 7-1 as shown; (3) In the "plot" drop-down menu (such as Figure 7-2 ), select "prescription map" (such as Figure 7-3 ), and the task data imported into the TF card will be displayed in the list. Double-click on the task to call it, as Figure 7-4 shown.

[0081] Sixth, before performing a flight mission, it is necessary to set the drone spraying parameters in the "operation task management" interface of the remote controller. The steps for setting the spraying parameters are as follows: (1) After entering the "operation task", click "Call" in the lower right corner, as Figure 8-1 shown; (2) Set the operation parameters in the menu bar that appears on the left side of the interface, as Figure 8-2 shown; After the main parameters are set, a green prompt "RTK positioning normal" will appear in the status bar in the upper left corner. Then click "Execute" to achieve autonomous spraying during the takeoff and landing of the drone.

[0082] Seventh, at the same time, the general flight parameters of the drone should be adjusted according to the actual geographical and meteorological conditions. The steps for setting the general parameters of the drone are as follows: After the remote controller is turned on, click the last icon "Settings" in the function area in the upper left corner, as Figure 9-1 shown, to enter the general parameter setting interface, as Figure 9-2 shown. It is recommended to set the following parameters: (1) Departure / Return speed (7 m / s), Return height (29 m), as Figure 9-3 shown; (2) Select the "Departure height" switch to be turned on, as Figure 9-4 shown; (3) Set the behavior of the drone during the task execution, such as "Return after spraying is completed", "Return after the operation is completed", "Return after the aircraft loses contact", as Figure 9-5 shown; (4) Limit the maximum flight height (30 m), limit the maximum flight distance (2000 m), as Figure 9-6 shown; (5) In the "Perception settings", turn on the "Horizontal avoidance" switch, as Figure 9-7 shown; (6) In the "Spraying system settings", turn on the "Spraying and broadcasting system" and "Real-time data of the spraying system" switches, as Figure 9-8 shown, so that the spraying status can be observed in real time through the remote controller; (7) The "Joystick settings" can be selected according to the personal operation habits of the drone pilot, as Figure 9-9 shown; (8) In the "RTK settings", turn on the "Aircraft RTK positioning" switch, and in the "RTK signal source", select "Network RTK", as Figure 9-10 shown.

[0083] Eighth, after completing all the above steps, load the configured nitrogen solution into the water tank of the UAV, check the status of the UAV and the battery. If the takeoff conditions are met, the target spraying task can be called through the T40 remote controller, and the T40 agricultural UAV will perform the uniform spraying task of the canopy nitrogen solution according to the optimal flight path intelligently planned by the remote controller.

[0084] As described above, the above are only the preferred specific embodiments of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the technical field of the present application within the technical scope disclosed in the present application should be covered by the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A method for simulating nitrogen deposition in forest canopies based on drones, characterized in that, It includes the following steps: Explore and select a sample plot to determine the scope and shape of the sample plot; Explore the sample plot to determine its scope, where the sample plot is divided into several spraying areas with different concentrations, and each area has the same size and specifications; referring to the average annual nitrogen deposition in the local area, set four treatment areas of control, low, medium, and high according to the background values of 0, 1, 2, and 3 times the concentration; Based on the scope of the sample plot, select a takeoff and landing site for the drone. Measure the sample plot through RTK technology to obtain the precise coordinates of the four boundaries of the sample plot, and obtain a high-definition map of the sample plot through drone mapping; Construct a sample plot task with the coordinates of the four boundaries of the sample plot, the takeoff and landing site of the drone, and the high-definition map of the sample plot, and import the sample plot task into the remote controller; Set the spraying parameters through the remote controller and spray the sample plot through the drone.

2. The method for simulating nitrogen deposition in forest canopy based on unmanned aerial vehicle according to claim 1, wherein The conditions that the selected takeoff and landing site of the drone needs to meet are: a mesa or a small open space that meets the takeoff height conditions and a flat ground with less sand and gravel.

3. The method for simulating nitrogen deposition in forest canopies based on unmanned aerial vehicles according to claim 1, wherein The method of measuring the sample plot through RTK technology to obtain the coordinates of the four boundaries of the sample plot includes: On the basis of determining the scope of the sample plot and the takeoff and landing site of the drone, place the GNSS device at the four positions of the sample plot, and measure the sample plot through RTK technology in the fixed solution state to obtain the coordinates of the four boundaries of the sample plot.

4. The method for simulating nitrogen deposition in forest canopy based on unmanned aerial vehicle according to claim 1, characterized in that, The method of obtaining a high-definition map of the sample plot through drone mapping includes: conducting photogrammetric 2D flight on the sample plot through the drone mapping to obtain the orthophoto image and digital surface model of the sample plot, and performing two-dimensional reconstruction through the DJI Terra software to obtain the high-definition map of the sample plot.

5. The method for simulating forest canopy nitrogen deposition based on an unmanned aerial vehicle according to claim 4, wherein The process of performing two-dimensional reconstruction through the DJI Terra software to obtain the high-definition map of the sample plot includes the following steps: After opening the software, click "New Task" in the lower left corner. Subsequently, a task type selection will pop up on the main interface, and select "Two-dimensional Map" for the reconstruction task; Enter the name of the reconstruction task in the task name input box and click "OK"; Click the folder icon in the right menu bar, and select the photo folder corresponding to the aerial photography task completed before mapping from the computer to add photos; click on the two-dimensional map column, and select "Low" for the resolution; In the two-dimensional map column, select "Farmland Scene" for the scene, select "Agricultural Application" for the application, and click "Start Reconstruction" after selection.

6. The method for simulating nitrogen deposition in forest canopies based on unmanned aerial vehicles according to claim 1, wherein According to the characteristics of the research target, specific experimental purposes and contents, set the spraying parameters through the remote controller and spray the sample plot through the drone, where the spraying parameters include: takeoff / return speed, return height, behavior of the drone performing tasks, restricted maximum flight height, restricted maximum flight distance, horizontal avoidance, spraying system settings, joystick settings, aircraft RTK positioning, and network RTK; the target characteristics include terrain and tree height information.

7. The method for simulating forest canopy nitrogen deposition based on an unmanned aerial vehicle according to claim 6, wherein According to the preset simulated nitrogen deposition concentration, the drone is carried with a configured nitrogen solution, and the target spraying task is called through the remote controller, and the nitrogen solution is quantitatively and evenly sprayed on the canopy according to the optimal flight route intelligently planned by the remote controller.

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