An unmanned aerial vehicle based shelterbelt layered leaf area index measuring device and method

Abstract

The application provides a kind of forest belt layering leaf area density measuring device and method based on unmanned aerial vehicle, belongs to the technical field of forestry and ecology, device includes: unmanned aerial vehicle, camera holder, motion camera and fish eye lens;The upper surface of unmanned aerial vehicle is fixedly connected with camera holder, motion camera is fixedly connected on camera holder, fish eye lens is fixedly installed on motion camera, adjust camera holder so that fish eye lens is vertically upward, wireless control device is connected with the control system of unmanned aerial vehicle and the control system of motion camera;The application can flexibly, efficiently, non-destructive measure forest belt layering leaf area density, provide important parameters for farmland shelter forest aerodynamics research, and provide basis for scientific construction and management of farmland shelter forest.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of forestry and ecology, and particularly relates to a device and method for measuring layered leaf area density of shelter forest belt based on a UAV. BACKGROUND

[0002] The shelter forest is a kind of public welfare forest, which is mainly used for disaster prevention and reduction, improvement of regional environmental conditions, and protection of people's living and production environment safety. Among them, the farmland shelter forest is one of the most common shelter forests, which is mainly arranged in the form of a belt (forest belt) around the farmland, and changes the behavior of the wind in the farmland area and reduces the wind speed through its own structure similar to a fence, so as to form a local microclimate condition conducive to agricultural production and ensure stable and increased crop yield. The function of the farmland shelter forest to reduce the wind speed depends on its three-dimensional structural characteristics, and quantitative evaluation of the structural characteristics of the forest belt and clear relationship between the structural characteristics and the windproof function of the forest belt are the key to design, construction and operation of efficient farmland shelter forests. The three-dimensional structural characteristics of the forest belt include internal characteristics and external characteristics, wherein the internal characteristics are mainly determined by the leaf area density (LAD, defined as the total leaf area per unit space at a certain height, with the unit of m 2 / m 3 ) and its vertical distribution. Due to the difficulty in measuring the layered leaf area density of the forest belt, the average leaf area density obtained by dividing the leaf area index (LAI, defined as the sum of the area of the leaves per unit area, with the unit of m 2 / m 2 ) by the length of the canopy is often used as a substitute based on the assumption that the leaf area density is uniformly distributed in the canopy. However, the actual leaf area density of the forest belt is not uniformly distributed in the canopy, and is an important structural parameter in the process of aerodynamic action of the forest belt, so it is necessary to accurately measure the layered leaf area density of the forest belt.

[0003] Among the existing vegetation leaf area density measurement methods, there are mainly two methods of direct measurement and indirect measurement. The direct measurement method generally refers to the method of using a movable tower to collect leaf blades at different heights, or completely felling the sample trees and measuring the leaf area of the leaf blades collected in different height layers, and then converting into leaf area density and its vertical distribution. This method uses destructive sampling, and the operation is complicated, laborious and difficult to implement. The indirect measurement method includes using hemispherical photography technology, laser sensing technology, laser radar technology, and measuring at different heights of vegetation. This method generally needs to use auxiliary equipment such as probe rods, telescopic rods, support towers, lifting frames, etc. to lift the sensor equipment for collecting laser signals or image information to different measurement heights for measurement. This method has the problems of complex operation, high cost of auxiliary equipment and inconvenience of portability. Especially for the shelter forest belt with a height of about 20-25m, the auxiliary equipment used for measurement needs to have a higher telescopic height and a stronger supporting force, which inevitably leads to the inconvenience of moving the auxiliary equipment. In addition, since the sensor is deeply inserted into the canopy, the measurement personnel cannot judge the quality of the collected signals and images in real time, which will lead to the problem of low efficiency of measurement in the unsuitable measurement environment in the canopy. SUMMARY

[0004] The purpose of the present application is to solve the above-mentioned problems in the prior art. The present application provides a kind of based on unmanned aerial vehicle's shelter forest belt layered leaf area density measuring device and method, can be flexible, efficient, non-destructive measurement of forest belt layered leaf area density, provide important parameters for farmland shelter forest aerodynamics research, and provide the basis for scientific construction and management of farmland shelter forest.

[0005] In order to achieve the above-mentioned purpose, the present application adopts the following technical solutions:

[0006] A kind of based on unmanned aerial vehicle's shelter forest belt layered leaf area density measuring device,

[0007] The device comprises: an unmanned aerial vehicle, a camera holder, a motion camera and a fisheye lens;The camera holder is fixedly connected to the upper surface of the unmanned aerial vehicle, the motion camera is fixedly connected to the camera holder, the fisheye lens is fixedly installed on the motion camera, the camera holder is adjusted so that the fisheye lens is perpendicular to the top, and the wireless control device is wirelessly connected to the control system of the unmanned aerial vehicle and the control system of the motion camera.

[0008] In some embodiments, a two-dimensional adjusting platform is used to replace the camera holder, and the two-dimensional adjusting platform comprises an x-direction adjusting platform and a y-direction adjusting platform; the x-direction adjusting platform comprises an x-direction base and an x-direction moving plate; the x-direction base is provided with four through holes for connecting the upper surface of the unmanned aerial vehicle; the two sides of the x-direction base are respectively extended upwards to form x-direction support plates; the two x-direction support plates are respectively provided with four x-direction slide rods on the inner sides; the x-direction moving plate is suspended and slid by cooperation of the four x-direction slide rod holes on the two sides of the x-direction moving plate and the four x-direction slide rods; an x-direction spring is sleeved on each x-direction slide rod; one end of the x-direction spring is connected with the x-direction support plate, and the other end of the x-direction spring is connected with the x-direction moving plate; an x-direction motor is arranged on the outer side wall of one x-direction support plate; the output shaft of the x-direction motor is connected with an x-direction driving rod; the outer side of the x-direction driving rod is provided with an external thread which is matched with an x-direction internal thread hole arranged on the x-direction moving plate to realize x-direction left and right movement of the x-direction moving plate; the x-direction adjusting platform and the y-direction adjusting platform have the same structure, and the y-direction adjusting platform is smaller than the x-direction adjusting platform; the y-direction base of the y-direction adjusting platform is fixedly installed on the upper surface of the x-direction moving plate.

[0009] In some embodiments, the fisheye lens is a fisheye lens clamp.

[0010] In some embodiments, the fisheye lens is fixedly connected with the action camera through a connecting device; the connecting device comprises an adapter plate and clamping plates formed by extending downwards from the two sides of the adapter plate; the two clamping plates are located on the two sides of the action camera; at least two threaded holes are formed on the clamping plates; a fastening screw is used to fix the connecting device on the action camera by penetrating the threaded holes; a through hole is arranged on the adapter plate to allow the upper housing of the action camera to pass through; a circular ring-shaped protrusion is formed on the upper surface of the adapter plate outside the through hole of the adapter plate; a circular ring-shaped strong magnet is formed on the top of the circular ring-shaped protrusion; a plurality of conical recesses are formed on the outer side of the circular ring-shaped protrusion.

[0011] In some embodiments, a circular ring-shaped groove for accommodating the circular ring-shaped protrusion and the circular ring-shaped strong magnet of the connecting device is formed on the bottom of the cylindrical housing; a plurality of magnetic attraction fixing mechanisms are uniformly distributed on the outer side of the circular ring-shaped groove in the cylindrical housing; the number of the plurality of magnetic attraction fixing mechanisms is the same as the number of the plurality of conical recesses; the circular ring-shaped strong magnet and the circular ring-shaped protrusion are completely inserted into the circular ring-shaped groove; the circular ring-shaped strong magnet attracts the steel block; the steel block is attached to the circular ring-shaped strong magnet; the return spring connected between the rear of the steel block and the cylindrical housing is in a stretched state; the steel block drives the conical positioning block to move towards the circular ring-shaped protrusion through the curved connecting rod; the fisheye lens is rotated until the conical positioning block falls into the conical recess.

[0012] In some embodiments, a filling strip is arranged on the lower surface of the adapter plate near the edge of the action camera; the material of the filling strip is a high-molecular synthetic resin with good plasticity.

[0013] In some technical solutions, the fisheye lens comprises: first lens L1, second lens L2, third lens L3, fourth lens L4, fifth lens L5, sixth lens L6, seventh lens L7, eighth lens L8 and ninth lens L9 arranged in sequence from the object plane to the image plane, the first lens L1, the second lens L2 and the ninth lens L9 are meniscus lenses with negative focal length, the fourth lens L4 and the sixth lens L6 are double-concave lenses with negative focal length, the third lens L3, the fifth lens L5, the seventh lens L7 and the eighth lens L8 are double-convex lenses with positive focal length, each lens is a plastic spherical lens, the fifth lens L5 and the sixth lens L6 are a first cemented lens group, and the eighth lens L8 and the ninth lens L9 are a second cemented lens group;

[0014] The fisheye lens also needs to meet the following conditions:

[0015] 11<f<11.35, f is the focal length of the fisheye lens; -11<f1<-10.5, -8.4<f2<-7.9, -7.6<f4<-7.2, 6.0<f8<6.3, -8.2<f9<-8.0, f1, f2, f4, f8, f9 are the focal lengths of the first lens L1, the second lens L2, the fourth lens L4, the eighth lens L8 and the ninth lens L9 respectively; 24.5≤TTL≤25, TTL is the total optical length in air; the full field of view is >180°; the aperture F=2.2; the length unit is mm.

[0016] A method for measuring the leaf area density of a protective forest belt based on a UAV, comprising: (1) determining the lower edge height of the forest canopy layers and converting the actual height of the lower edge of each layer of the forest canopy from bottom to top; (2) using a measuring device to obtain fisheye lens photos at the above heights from bottom to top, and the measuring device flies out of the forest canopy from the top of the forest canopy; (3) using professional software for calculating forest canopy structure information to extract corresponding leaf area index values from the fisheye lens photos; and (4) using the obtained leaf area index of each layer of the forest canopy to calculate the leaf area density of each layer.

[0017] In some technical solutions, the height of the lower edge of each layer is taken as the y-axis variable, and the leaf area density of each layer is taken as the x-axis variable, and a height distribution graph of the leaf area density of the forest belt is drawn.

[0018] The present application has the following advantages:

[0019] (1) The present application uses a wireless control device to connect the control system of the UAV and the control system of the motion camera to realize wireless communication, and fixes the camera on the upper surface of the UAV, so that images can be quickly and efficiently obtained for analysis, and the shooting process is not affected by the UAV;

[0020] (2) In order to further improve the performance of the measuring device, the application creatively proposes a two-dimensional adjustment platform with anti-shaking and automatic balance adjustment. The suspension design of the x-direction moving plate and the y-direction moving plate can effectively prevent shaking, reduce the stiffness of the entire two-dimensional adjustment platform, and the x-direction spring and the y-direction spring can further play a buffering role to absorb vibration energy. The balance of the measuring device can be achieved through the adjustment of the two-dimensional adjustment platform, thereby effectively avoiding shaking caused by imbalance;

[0021] (3) The connecting device of the fisheye lens and the action camera provided by the application can avoid the instability caused by the fisheye lens clamp, provide connection strength, and be convenient to disassemble. The symmetrical form of each component can effectively avoid the imbalance of the unmanned aerial vehicle caused by uneven weight distribution.

[0022] (4) The fisheye lens can realize good imaging effect in the visible light wave band by reasonably setting the shape and focal length of each lens and optimizing the diaphragm position, which helps to reduce image distortion, and the lens is easier to process and has lower cost, which is more conducive to leaf imaging. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 The structure schematic diagram of the protective forest belt layered leaf area density measuring device based on the unmanned aerial vehicle is shown.

[0024] Figure 2 The side view cross-sectional view of the x-direction adjustment table in the two-dimensional adjustment platform is shown.

[0025] Figure 3 The top view of the x-direction adjustment table in the two-dimensional adjustment platform is shown.

[0026] Figure 4 Another side view cross-sectional view of the x-direction adjustment table in the two-dimensional adjustment platform is shown.

[0027] Figure 5 The top view of the two-dimensional adjustment platform is shown.

[0028] Figure 6 The side view cross-sectional view of the connecting device of the fisheye lens and the action camera is shown.

[0029] Figure 7 The structure schematic diagram of the connecting device of the fisheye lens and the action camera is shown.

[0030] Figure 8 The shell structure schematic diagram of the fisheye lens is shown.

[0031] Figure 9 The enlarged schematic diagram of the magnetic attraction fixing mechanism connected with the fisheye lens shell and the connecting device is shown.

[0032] Figure 10 The diagram shown is a structural schematic of a fisheye lens;

[0033] Figure 11 The diagram shown illustrates the process of dividing forest belts into layers and collecting photographs.

[0034] Figure 12 The image shows fisheye lens photos taken at the 1st, 5th, and 9th levels of the forest belt, as well as a schematic diagram of fisheye lens photos taken at the 1st, 5th, and 9th levels of the forest belt processed using software.

[0035] Figure 13 Distribution of leaf area density with altitude in stratified forest belts. Detailed Implementation

[0036] The present application will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the application and not intended to limit it. Furthermore, it should be noted that, for ease of description, only the parts relevant to the present application are shown in the accompanying drawings, not all of them.

[0037] This application was conducted in a farmland shelterbelt in Shenbei District, Shenyang City, Liaoning Province. The shelterbelt is a poplar shelterbelt, about 200m long and 12m wide, with 4 rows and a plant spacing of 2.0m × 3.5m.

[0038] like Figure 1 As shown, a device for measuring the layered area density of shelterbelts based on unmanned aerial vehicles (UAVs) includes: an unmanned aerial vehicle (UAV) 4, a camera gimbal 3, an action camera 2, and a fisheye lens 1; the camera gimbal 3 is fixedly connected to the upper surface of the UAV 4, the action camera 2 is fixedly connected to the camera gimbal 3, the fisheye lens 1 is fixedly mounted on the action camera 2, the camera gimbal 3 is adjusted so that the fisheye lens 1 is vertically upward, and a wireless control device is connected to the control system of the UAV 4 and the control system of the action camera.

[0039] The specific equipment information for the measuring apparatus is shown in the table below:

[0040]

[0041] The fisheye lens 1 uses a fisheye lens clip, and the wireless control device can be a mobile phone, PAD, PDA or laptop computer, etc.; use the wireless control device to remotely control the action camera 2 to start the shooting mode, use the wireless control device to remotely control the drone 4 to take off from the take-off platform; use the wireless control device to control the drone 4 to hover at different predetermined heights from bottom to top, and take pictures through the fisheye lens until it flies out of the forest belt from the top of the forest canopy.

[0042] Use such as Figure 1Although the camera holder 3 shown in the figure can achieve flexible adjustment of the motion camera 2, the adjustment mode of such design is easy to cause imbalance of the unmanned aerial vehicle 4 and affect the picture acquisition, therefore the present application proposes a two-dimensional adjustment platform capable of automatic adjustment of balance and anti-shake as shown in the figure.

[0043] The two-dimensional adjustment platform comprises an x-direction adjustment table 5 and a y-direction adjustment table. Figure 2 and 3 As shown in the figure, the x-direction adjustment table 5 comprises an x-direction base 51 and an x-direction moving plate 53, the x-direction base 51 is provided with four through holes 60 for connecting the upper surface of the unmanned aerial vehicle 4, the two sides of the x-direction base 51 are respectively extended upward to form x-direction support plates 52, the two x-direction support plates 52 are respectively formed with four x-direction slide rods 58 on the inner side, the x-direction moving plate 53 is suspended and slid by cooperation of the four x-direction slide rod holes 57 formed on the two sides thereof with the four x-direction slide rods 58; the x-direction slide rods 58 are respectively sleeved with x-direction springs 59, one end of the x-direction spring 59 is connected with the x-direction support plate 52, and the other end of the x-direction spring 59 is connected with the x-direction moving plate 53; an x-direction motor 54 is arranged on the outer side wall of one x-direction support plate 52, the output shaft of the x-direction motor 54 is connected with an x-direction driving rod 55, and the outer side of the x-direction driving rod 55 is provided with an external thread which is matched with an x-direction internal thread hole 56 arranged on the x-direction moving plate 53 to realize x-direction left and right movement of the x-direction moving plate 53. Figure 5 As shown in the figure, the x-direction adjustment table 5 and the y-direction adjustment table have the same structure, the y-direction adjustment table is smaller in size than the x-direction adjustment table 5, and the y-direction base of the y-direction adjustment table is fixedly installed on the upper surface of the x-direction moving plate 53; the motion camera 2 is installed on the y-direction moving plate of the y-direction adjustment table. The suspended design of the x-direction moving plate 53 and the y-direction moving plate can play a good anti-shake role, reduce the rigidity of the whole two-dimensional adjustment platform, and the x-direction spring 59 and the y-direction spring can further play a buffering role, absorb part of the vibration energy, and avoid transmission of the vibration from the unmanned aerial vehicle 4 to the motion camera 2 and the fisheye lens 1 through the two-dimensional adjustment platform. Through finite element analysis, it is known that the vibration isolation effect can be achieved by reasonably selecting the size and proportional relationship of the base and the support plate. Meanwhile, the operator or the wireless control device can also determine whether there is imbalance through the flight attitude analysis of the unmanned aerial vehicle 4, if there is imbalance, the wireless control device sends a command to the x-direction motor 54 and the y-direction motor of the two-dimensional adjustment platform to adjust the position of the motion camera 2 and the fisheye lens 1 arranged on the two-dimensional adjustment platform, so as to realize the balance of the determination device, which can effectively avoid the shaking caused by the imbalance and improve the quality of the acquired pictures. Figure 2 The x-direction slide rod hole 57 and the x-direction internal thread hole 56 are not located in one section, and they are shown in one section in the figure for convenience.

[0044] As shown in the figure, Figure 4As shown, the x-axis adjustment platform 5 is shown with Figure 2 The x-axis adjustment platform 5 shown is basically the same, except that the lower surface of the x-axis base 51 is provided with a trapezoidal groove 61. The groove can reduce the weight of the two-dimensional adjustment platform. If necessary, a vibration-absorbing material layer can be filled in the trapezoidal groove 61.

[0045] In the above technical solution, the connection between the fisheye lens clip and the action camera 2 is also unstable, which will affect the quality of the captured images. Therefore, this application also proposes a connection device 7 between the fisheye lens 1 and the action camera 2 as shown in 6-9.

[0046] like Figure 6 and 7 As shown, the connecting device 7 includes: an adapter plate 74 and clamping plates 71 extending downward from both sides of the adapter plate 74; the two clamping plates 71 are located on both sides of the action camera 2, and at least two threaded holes 72 are formed on the clamping plates 71. Fastening screws pass through the threaded holes 72 to fix the connecting device 7 to the action camera 2. The adapter plate 74 has a through hole for the upper housing of the action camera 2 to pass through. An annular protrusion 75 is formed on the upper surface of the adapter plate 74 outside the through hole. An annular strong magnet 76 is formed on the top of the annular protrusion 75, and several conical recesses 77 are formed on the outer side of the annular protrusion 75. When the upper surface of the action camera 2 in contact with the connecting device 7 has a smooth curved surface instead of a flat surface, a filling strip 73 can be provided on the lower surface of the adapter plate 74 near the edge of the action camera 2. The material of the filling strip 73 is a polymer synthetic resin with good plasticity. This can improve the stability of the connection between the connecting device 7 and the action camera 2.

[0047] like Figure 8 The diagram shows the structure of the fisheye lens housing 8. The fisheye lens housing 8 includes a cylindrical housing 81 and a cavity 82 formed inside the housing 81. The cavity 82 is used to accommodate the lens assembly (the lens in the figure is only for illustration). The lower part of the housing 81 is provided with a magnetic fixing mechanism for cooperating with the annular protrusion 75 and the annular strong magnet 76 of the connecting device 7 to lock and fix the fisheye lens 1. Figure 9 The diagram shown is an enlarged schematic of the magnetic fixing mechanism connecting the fisheye lens housing and the connecting device. Figure 8The bottom of the cylindrical shell 81 is formed with an annular groove 83 for accommodating the annular protrusion 75 of the connecting device 7 and the annular strong magnet 76, and the outer side of the annular groove 83 in the cylindrical shell 81 is uniformly distributed with a plurality of magnetic attraction fixing mechanisms, the number of the plurality of magnetic attraction fixing mechanisms being the same as the number of the plurality of tapered recesses 77, the annular protrusion 75 of the annular strong magnet 76 is completely inserted into the annular groove 83, the annular strong magnet 76 attracts the steel block 86, the steel block 86 is attached to the annular strong magnet 76, at this time, the return spring 87 connected between the back of the steel block 86 and the cylindrical shell 81 is in a stretched state, the steel block drives the tapered positioning block 85 to move towards the annular protrusion 75 through the curved connecting rod 84, and the fisheye lens 1 is rotated until the tapered positioning block 85 falls into the tapered recess 77. Such a connection design can avoid the unstable factors caused by the fisheye lens clamping piece, provide the strength of the connection, and facilitate disassembly; and the symmetrical form of each component can effectively avoid the imbalance of the unmanned aerial vehicle 4 caused by uneven weight distribution, so that the unmanned aerial vehicle 4 can fly smoothly and improve the quality of the collected pictures.

[0048] Figure 10 The fisheye lens includes: first lens L1, second lens L2, third lens L3, fourth lens L4, fifth lens L5, sixth lens L6, seventh lens L7, eighth lens L8 and ninth lens L9 arranged in sequence from object plane to image plane, the first lens L1, the second lens L2 and the ninth lens L9 are meniscus lenses with negative focal length, the fourth lens L4 and the sixth lens L6 are double concave lenses with negative focal length, the third lens L3, the fifth lens L5, the seventh lens L7 and the eighth lens L8 are double convex lenses with positive focal length, each lens is a plastic spherical lens, the fifth lens L5 and the sixth lens L6 are a first cemented lens group, and the eighth lens L8 and the ninth lens L9 are a second cemented lens group; the IRF is a narrowband infrared filter located on the image side of the ninth lens L9, can filter out stray light, and ensures imaging quality.

[0049] The high-resolution fisheye lens also needs to meet the following conditions:

[0050] 11<f<11.35, f is the focal length of the fisheye lens; -11<f1<-10.5, -8.4<f2<-7.9, -7.6<f4<-7.2, 6.0<f8<6.3, -8.2<f9<-8.0, f1, f2, f4, f8, f9 are the focal lengths of the first lens L1, the second lens L2, the fourth lens L4, the eighth lens L8 and the ninth lens L9 respectively; 24.5≤TTL≤25, TTL is the total optical length in air; the full field of view is >180°; the aperture F=2.2; the length unit is mm.

[0051] The fisheye lens can further include an aperture stop STO located between the fourth lens L4 and the fifth lens L5.

[0052] By reasonably setting the shape and focal length of each lens, optimizing the position of the stop, and achieving good imaging effect in the visible light wave band, it is helpful to reduce image distortion, and the lens is easier to process, the cost is lower, and it is more conducive to leaf imaging.

[0053] In a specific embodiment, the fisheye lens is described, and the optical parameters of each lens are shown in the following table.

[0054] lens focal length / mm L1 -10.82 L2 -8.03 L3 11.08 L4 -7.37 L5 4.67 L6 -10.75 L7 7.66 L8 6.21 L9 -8.13

[0055]

[0056]

[0057] In the table, surface numbers 1 to 8 correspond to the respective lens surfaces of the first lens L1 to the fourth lens L4 distributed in order from the object surface to the image surface, surface numbers 9 to 16 correspond to the respective lens surfaces of the fifth lens L5 to the ninth lens L9 distributed in order from the object surface to the image surface, and the cemented surfaces of the double cemented lens are marked with the same surface number, IRF is an infrared filter, and STO is an aperture stop.

[0058] Figure 11 The figure shows the division of the forest belt into layers and the collection of photos; the method for measuring the leaf area density of the protective forest belt based on the unmanned aerial vehicle includes: (1) determining the lower edge height of the canopy layer; the average tree height H of the forest belt is measured to be 22.0 m, the average branch height h is 1.8 m, and the canopy length H-h is 20.2 m. The canopy of the forest belt is evenly divided into 10 layers in the vertical direction (i.e. n=1, 2, 3…, N, N=10), and the height of each layer is 2.02 m. For convenience of calculation, 2.0 m is taken as the height of a single layer.

[0059]

[0060] The actual height of the lower edge of each layer of the canopy from bottom to top is converted according to formula 1, and the results are shown in the following table.

[0061]

[0062] (2) Use the wireless control device to remotely control the motion camera 2 to start the photo mode, and use the wireless control device to remotely control the unmanned aerial vehicle 4 to take off from the take-off platform; collect fisheye lens photos; hover at the lower edge height L1=1.8 m of the first layer (such as Figure 2As shown in the image, the image quality within the lens of the action camera 2 was observed using a wireless control device. Under suitable conditions with no nearby obstacles and appropriate exposure, the action camera 2 was remotely controlled using the wireless control device to take pictures, obtaining a fisheye lens image of the canopy vertically upwards at this height. The aerial drone was controlled using the wireless control device to hover sequentially from bottom to top at 3.8m, 5.8m, 7.8m, 9.8m, 11.8m, 13.8m, 15.8m, 17.8m, and 19.8m, acquiring fisheye lens images until it flew out of the canopy from the top of the forest belt. High-quality fisheye lens images of the forest belt are shown below. Figure 12 As shown in (A)-(C).

[0063] Figure 12 The image shows fisheye lens photos taken at the 1st, 5th, and 9th heights of the forest belt, and a schematic diagram of the fisheye lens photos taken at the 1st, 5th, and 9th heights of the forest belt processed using GapLight Analyzer 2.0 software; (3) Extracting leaf area index; Using a wireless control device, the fisheye lens photos stored in the action camera 2 are exported as jpg format and saved to the mobile phone memory, and then transferred to the computer memory. Using the professional software Gap Light Analyzer 2.0, which is pre-installed on the computer and is based on the hemispherical photography principle to calculate canopy structure information, after appropriate parameter adjustment and matching, the corresponding leaf area index value is extracted from the fisheye lens photos. The process is as follows. Figure 12 As shown in (D)-(F).

[0064] Calculate the leaf area density of each canopy layer. Using the obtained leaf area index of each canopy layer in the forest belt, through...

[0065] Equation 2 calculates the leaf area density (LAD) for each canopy layer. n The canopy stratification of each forest belt is shown in Table 3.

[0066]

[0067] Leaf Area Index (LAI) values ​​of different canopy layers in the forest belt 4Ring_n Leaf area index (LAD) n As shown in the table below.

[0068]

[0069] Using the height of the lower edge of the layer as the y-axis variable and the layer leaf area density LAD as the variable... n As the x-axis variable, plot the results. Figure 13 Distribution of leaf area density with altitude in stratified forest belts.

[0070] The above merely describes the preferred embodiments of the present application and is not intended to limit the present application. Although the present application is described in detail with reference to the foregoing embodiments, those skilled in the art can make modifications to the technical solutions described in the foregoing embodiments or make equivalent replacements to some of the technical features, without departing from the spirit and principle of the present application. Any modifications or equivalent replacements made in the spirit and principle of the present application shall be included in the scope of protection of the present application.

Claims

1. A drone-based device for measuring the leaf area density of shelterbelt layers, characterized in that, The device comprises: The unmanned aerial vehicle, the two-dimensional adjusting platform, the motion camera and the fisheye lens; the camera holder is fixedly connected to the upper surface of the unmanned aerial vehicle, the motion camera is fixedly connected to the camera holder, the fisheye lens is fixedly installed on the motion camera, the camera holder is adjusted so that the fisheye lens is vertically upward, and the wireless control device is wirelessly connected to the control system of the unmanned aerial vehicle and the control system of the motion camera; The two-dimensional adjusting platform comprises: an x-direction adjusting table and a y-direction adjusting table; the x-direction adjusting table comprises: an x-direction base and an x-direction moving plate, the x-direction base is provided with four through holes for connecting the upper surface of the unmanned aerial vehicle, the two sides of the x-direction base are respectively upwardly extended to form x-direction support plates, the two x-direction support plates are respectively inwardly formed with four x-direction slide rods, the x-direction moving plate is suspended and slid by cooperation of the four x-direction slide rod holes and the four x-direction slide rods; the x-direction slide rods are all sleeved with x-direction springs, one end of the x-direction spring is connected to the x-direction support plate, and the other end of the x-direction spring is connected to the x-direction moving plate; the outer side wall of one x-direction support plate is provided with an x-direction motor, the output shaft of the x-direction motor is connected to an x-direction driving rod, the outer side of the x-direction driving rod is provided with an external thread which is matched with an x-direction internal thread hole arranged on the x-direction moving plate to realize x-direction left and right movement of the x-direction moving plate; the x-direction adjusting table and the y-direction adjusting table are the same in structure, the y-direction adjusting table is smaller in size than the x-direction adjusting table, and the y-direction base of the y-direction adjusting table is fixedly installed on the upper surface of the x-direction moving plate; The fisheye lens and the motion camera are fixedly connected through the connecting device, the connecting device comprises: an adapter plate and clamping plates downwardly extended from the two sides of the adapter plate; the two clamping plates are located on the two sides of the motion camera, the clamping plates are formed with at least two threaded holes, a fastening screw passes through the threaded holes to fix the connecting device on the motion camera, the adapter plate is provided with a through hole for the upper housing of the motion camera to pass through, a circular convex is formed on the outer portion of the adapter plate through hole and the upper surface of the adapter plate, a circular strong magnet is formed on the top of the circular convex, and a plurality of conical depressions are formed on the outer side of the circular convex; The shell of the fisheye lens comprises: a cylindrical shell and a cavity formed in the shell, the cavity is used for accommodating a lens group, and the lower portion of the shell is provided with a magnetic attraction fixing mechanism for matching with the circular convex and the circular strong magnet of the connecting device to realize locking and fixing of the fisheye lens; The bottom of the cylindrical shell is formed with an annular groove for accommodating the circular convex and the circular strong magnet of the connecting device, a plurality of magnetic attraction fixing mechanisms are uniformly distributed on the outer side of the annular groove in the cylindrical shell, the number of the plurality of magnetic attraction fixing mechanisms is the same as the number of the plurality of conical depressions, the circular strong magnet and the circular convex are completely inserted into the annular groove, the circular strong magnet attracts a steel block, the steel block is attached to the circular strong magnet, a reset spring connected between the rear of the steel block and the cylindrical shell is in a stretched state, the steel block drives the conical positioning block to move towards the circular convex through the curved connecting rod, and the fisheye lens is rotated until the conical positioning block falls into the conical depression.

2. The assay device of claim 1, wherein The fisheye lens is a fisheye lens clamping piece.

3. The assay device of claim 1, wherein A filling belt is arranged on the lower surface of the adapter plate close to the edge of the motion camera, and the material of the filling belt is a high-molecular synthetic resin with good plasticity.

4. The assay device of claim 1, wherein The fisheye lens comprises: first lens L1, second lens L2, third lens L3, fourth lens L4, fifth lens L5, sixth lens L6, seventh lens L7, eighth lens L8 and ninth lens L9 arranged in sequence from an object plane to an image plane, the first lens L1, the second lens L2 and the ninth lens L9 are meniscus lenses with negative focal length, the fourth lens L4 and the sixth lens L6 are double-concave lenses with negative focal length, the third lens L3, the fifth lens L5, the seventh lens L7 and the eighth lens L8 are double-convex lenses with positive focal length, each lens is a plastic spherical lens, the fifth lens L5 and the sixth lens L6 are a first cemented lens group, and the eighth lens L8 and the ninth lens L9 are a second cemented lens group; The fisheye lens also needs to meet the following conditions: 11<f<11.35, f is the focal length of the fisheye lens; -11<f1<-10.5, -8.4<f2<-7.9, -7.6<f4<-7.2, 6.0<f8<6.3, -8.2<f9<-8.0, f1, f2, f4, f8 and f9 are the focal lengths of the first lens L1, the second lens L2, the fourth lens L4, the eighth lens L8 and the ninth lens L9 respectively; 24.5≤TTL≤25, TTL is the total optical length in air; the full field of view is >180°; the aperture F=2.2; the length units are all mm.

5. A method for measuring the leaf area density of a UAV-based shelterbelt in layers, using the measuring device according to any one of claims 1 to 4, characterized in that, It comprises: (1) determining the lower edge height of the canopy layering, and converting the actual height of the lower edge of each layering canopy from bottom to top; (2) using a measuring device to obtain fisheye lens photos at the above heights from bottom to top, the measuring device flying out of the forest belt from the top of the forest canopy; (3) based on professional software for calculating canopy structure information, corresponding leaf area index values are extracted from the fisheye lens photos; (4) using the obtained leaf area index of each canopy layering of the forest belt to calculate the leaf area density of the layering.

6. The method of claim 5, wherein, Taking the height of the layering lower edge as the y-axis variable and the leaf area density of the layering as the x-axis variable, a distribution diagram of the leaf area density of the forest belt with height is drawn.

Images