Method for measuring canopy density and electronic device

Abstract

The invention relates to the field of forestry, and discloses a method for measuring canopy density and an electronic device. According to the method, a scheme for measuring the canopy density is provided according to the change rule of illumination values in forests at different latitudes in a crown shielding area and a crown-free shielding area in the forest. The electronic device comprises a plurality of supports, a plurality of photoelectric detector units are assembled on each support, every two adjacent supports are movably connected through a connecting piece, and the supports connected together can be folded, detached and replaced. The photoelectric detector units are arranged in each support in parallel at equal intervals, the plurality of photoelectric detector units are electrically connected in parallel to form a photoelectric detector array, one side of each support is movably connected with a controller through the connecting piece, and the photoelectric detector array is electrically connected with the controller. The method has the advantages of accurate measurement, quick response, flexibility, portability, user friendliness, low maintenance cost and the like, and is suitable for carrying out forest canopy density survey work.

Description

Technical Field

[0001] The invention relates to the field of forestry, and in particular to a method and an electronic device for measuring canopy density. Background Art

[0002] Canopy closure refers to the ratio of the projection area of ​​the tree canopy on the ground under light to the total forest area. Canopy closure is an important factor reflecting the overall structure and environment of the forest. It has important applications in forest farm and forestry division, forest cultivation, forest management, forest protection, and water and soil conservation. The determination of canopy closure includes visual inspection, sample line method, sample point method, fisheye camera measurement method, and drone remote sensing measurement. Visual inspection is the simplest measurement method, but it is limited by the subjective consciousness of the person measuring, and the measurement results are often inaccurate. The sample line method calculates by dividing the total length of the canopy by the total length of the two diagonals of the sample plot. This method ignores the effect of the gaps in the canopy on the canopy closure and causes deviations in the results. The sample point method is to set sample points in the experimental sample plot, determine whether the set sample points are covered by the canopy, and divide the number of covered sample points by the total number of set sample points, but it often requires setting hundreds of sample points, which is time-consuming and labor-intensive. Fisheye camera measurement method uses fisheye camera to estimate canopy density from all-sky photos, but it is only suitable for forest areas with flat terrain. Drone remote sensing measurement in the forest requires a lot of work such as charging, landing and sampling, and further analysis of the photos obtained, which is slow to produce results. In addition, too much image information and too many gaps between trees will also affect the measurement results.

[0003] This method is a new method for measuring canopy closure based on the measurement of illuminance in areas without canopy shading and areas with canopy shading in forest areas of Shandong, Zhejiang and Guangdong provinces. The principle of the method is that the illuminance in areas without canopy shading is 4.96-51.74 times that in areas with canopy shading, and there is no overlapping range between the distribution range of illuminance values ​​in areas without shading and areas with canopy shading. This method avoids the operational complexity of existing canopy closure measurements and improves the accuracy of the measurements. Compared with other canopy closure measurement methods, it has the following advantages: This method is a direct measurement on the ground, which is more accurate and intuitive, can effectively avoid the influence of terrain on the measurement results, can directly obtain the results, does not require complex analysis and calculation, is simple to operate, and is easy to carry. Summary of the invention

[0004] The object of the present invention is to provide a method and an electronic device for measuring canopy density to solve the above technical problems.

[0005] The purpose of the present invention can be achieved through the following technical solutions:

[0006] A method for measuring canopy closure comprises the following steps:

[0007] S1. Predefine multiple testing plots in the target forest;

[0008] S2. Place the electronic device in one of the sample plots pre-demarcated in the target forest, turn on the electronic device, and all the photoelectric detector units (1) on the electronic device measure the current illuminance value; and make the following determinations based on the illuminance value:

[0009] If the measured illuminance value is lower than the preset value , it is determined to be a tree canopy shading area; if the measured illumination value is higher than the preset value , it is determined as an area without tree canopy shading;

[0010] Count all values ​​below the preset value The number of values ​​is n, the number of illumination values ​​obtained by all photoelectric detector units is N, and the canopy density value of the current detection plot is ;

[0011] By formula Calculate the canopy density of the current plot , The current plot The canopy density values ​​measured are: , The total number of measurements for the current test plot;

[0012] S3, repeating step S2 for each sample plot to obtain the canopy density of multiple sample plots;

[0013] S4. Substitute the canopy density of multiple plots into the formula Obtain the canopy density value of the target forest , where is the total number of sample plots, is the weight coefficient corresponding to each sample plot.

[0014] A further solution is to obtain the target forest illumination threshold T0 as follows:

[0015] The electronic device is placed in an area of ​​the target forest without any tree canopy obstruction for calibration. Multiple measurements are taken to obtain the average value to obtain the signal strength value T1.

[0016] Place the electronic device in an area completely blocked by tree canopies in the target forest, measure multiple times and calculate the average value to obtain the signal strength value T2;

[0017] Set the canopy density threshold in the canopy density detector to , where is the preset coefficient.

[0018] A further solution is to obtain the preset coefficient The method is:

[0019] Measure the illumination value of the area without tree canopy shade n times in each plot and calculate the average value and minimum value and the average illumination of the area blocked by the tree canopy and maximum value ;

[0020] By formula Calculate the upper limit of the preset interval for each plot ;

[0021] Then through the formula Calculate the lower limit of the preset interval for each plot ;

[0022] Get the preset interval for each plot The public interval of the target forest is obtained ;

[0023] exist All values ​​in the table can be used as preset coefficients for the target forest. .

[0024] In a further embodiment, the preset coefficient The available value range is 0.279-0.419.

[0025] A further solution is to obtain the weight coefficient The method is:

[0026] The time from the first measurement of the sample plot is recorded as , the time when the last measurement of the plot is completed is recorded as , record this period as the measurement period of the sample plot;

[0027] The measurement period of the sample plot is divided into Time-sharing period ~ , fitting to obtain the curve of the canopy density change over time in each time period And the curve of the change of canopy closure threshold over time ;

[0028] By formula group: Calculate the weight coefficient of the current plot ;in, ;

[0029] In the formula, The coefficient of variation Deviation from preset threshold The judgment function of is the average value of the weight coefficient, is the preset scale factor, It is a preset fixed coefficient.

[0030] In a further embodiment, the coefficient of deviation .

[0031] An electronic device for measuring canopy density comprises a plurality of brackets, each of which is equipped with a plurality of photoelectric detector units, two adjacent brackets are movably connected by a connecting piece, the connected brackets are foldable and each independent bracket is detachable and replaceable;

[0032] The photodetector units are arranged in parallel at equal intervals in each bracket, and a plurality of the photodetector units are electrically connected in parallel to form a photodetector array. One side of the bracket is movably connected to a controller via the connecting piece, and the photodetector array is electrically connected to the controller.

[0033] In a further solution, the controller housing is provided with a display screen, operation buttons and a charging interface; the controller is internally provided with an amplification circuit, a data acquisition module, a microprocessor, a power supply module and a drive circuit module;

[0034] The photodetector unit comprises a housing, a light-illuminating surface is arranged on one side of the housing, a focusing lens is mounted on the light-illuminating surface, and the focusing lens is used to converge incident light, and the incident light is converged on a photosensitive surface inside the housing corresponding to the light-illuminating surface;

[0035] The photosensitive surface is fixed on a concave base provided inside the housing, and a window piece is also provided at the notch of the concave base, and the window piece is used to encapsulate and protect the photosensitive surface;

[0036] A pin is provided on one side of the housing, and the pin is used for electrically connecting with the controller.

[0037] Beneficial effects of the present invention:

[0038] (1) The present invention first divides a target forest into multiple sample plots, then continuously measures the canopy density values ​​of one of the sample plots for multiple times, calculates the average value as the canopy density of the sample plot, and then measures the canopy density of each sample plot and then calculates the average value to obtain the canopy density of the entire target forest. The canopy density of multiple random sample plots can accurately represent the canopy density of the entire forest by averaging, thereby improving the accuracy of measurement;

[0039] (2) The measurement method of the present invention is a direct measurement on the ground, which is more accurate and intuitive, and is easier to operate. It can effectively avoid the influence of terrain on the measurement results, and can directly obtain the results in the forest canopy density measurement without the need for complex analysis and calculation. The electronic device has a simple structure and is easy to carry. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] The present invention will be further described below in conjunction with the accompanying drawings.

[0041] Figure 1 It is a schematic diagram of the three-dimensional structure of the canopy density detector in the present invention.

[0042] Figure 2 It is a two-dimensional structural schematic diagram of the canopy density detector in the present invention.

[0043] Figure 3 It is a schematic diagram of the light collection structure of the photoelectric detector unit in the present invention.

[0044] Figure 4 It is a circuit system block diagram of the canopy density detector in an embodiment of the present invention.

[0045] Figure 5 It is a circuit diagram of the photoelectric detector unit in the present invention for collecting light signals and realizing amplification.

[0046] Figure 6 It is a circuit diagram for processing the photodetector array signal in the present invention.

[0047] Figure 7 Schematic diagram of a photoelectric conversion curve of a photoelectric detector unit in an embodiment of the present invention.

[0048] Figure 8 Schematic diagram of the canopy density threshold in an embodiment of the present invention.

[0049] Description of the drawings: 1. Photodetector unit; 1-1. Focusing lens; 1-2. Window; 1-3. Photosensitive surface; 1-4. Housing; 1-5. Base; 1-6. Pin; 2. Bracket; 3. Connector; 4. Controller; 5. Display; 6. Operation button; 7. Amplifier circuit; 8. Data acquisition module; 9. Microprocessor; 10. Power module; 11. Drive circuit module; 12. Charging interface; 13. Photodetector array. DETAILED DESCRIPTION

[0050] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0051] Specifically, a method and an electronic device for measuring canopy density work as follows:

[0052] S1. Predefine multiple testing plots in the target forest;

[0053] S2. Place the electronic device in one of the sample plots pre-demarcated in the target forest, turn on the electronic device, and all the photoelectric detector units (1) on the electronic device measure the current illuminance value; and make the following determinations based on the illuminance value:

[0054] If the measured illuminance value is lower than the preset value , it is determined to be a tree canopy shading area; if the measured illumination value is higher than the preset value , it is determined as an area without tree canopy shading;

[0055] Count all values ​​below the preset value The number of values ​​is n, the number of illumination values ​​obtained by all photoelectric detector units is N, and the canopy density value of the current detection plot is ;

[0056] By formula Calculate the canopy density of the current plot , The current plot The canopy density values ​​measured are: , The total number of measurements for the current test plot;

[0057] S3, repeating step S2 for each sample plot to obtain the canopy density of multiple sample plots;

[0058] S4. Substitute the canopy density of multiple plots into the formula Obtain the canopy density value of the target forest , where is the total number of sample plots, is the weight coefficient corresponding to each sample plot.

[0059] A further solution is to obtain the target forest illumination threshold T0 as follows:

[0060] The electronic device is placed in an area in the forest without any tree canopy obstruction for calibration. Multiple measurements are taken to obtain the average value to obtain the signal strength value T1.

[0061] Place the electronic device in an area completely blocked by tree canopies in the forest, measure multiple times and calculate the average value to obtain the signal strength value T2;

[0062] Set the canopy density threshold in the canopy density detector to , where is the preset coefficient, The available value range is 0.279-0.419.

[0063] A further solution is to obtain the preset coefficient The method is:

[0064] Measure the illumination value of the area without tree canopy shade n times in each plot and calculate the average value and minimum value and the average illumination of the area blocked by the tree canopy and maximum value ;

[0065] By formula Calculate the upper limit of the preset interval for each plot ;

[0066] Then through the formula Calculate the lower limit of the preset interval for each plot ;

[0067] Get the preset interval for each plot The public interval of the target forest is obtained ;

[0068] exist All values ​​in the table can be used as preset coefficients for the target forest. .

[0069] A further solution is to obtain the preset coefficient The basis for the selectable value range of 0.279-0.419 is:

[0070] The data comes from field measurements of 30 forest plots in Huzhou, Jinan and Guangzhou.

[0071] Each sample plot in the forest was 20 m × 20 m, and different light spots and shielded area points in each sample plot were measured 100 times.

[0072] After measurements at all the above locations, it was found that the illuminance in the area without tree canopy obstruction was 4.96-51.74 times that of the area blocked by tree canopy. In addition, in all measurements of a total of 90 forest blocks at different locations and times, within the same time period at the same location (the time interval between the first measurement and the last measurement is defined as no more than 2 hours, and this time period is between 9:00 and 15:00), there is no overlapping interval between the distribution range of illuminance values ​​in the unobstructed area and the distribution range of illuminance values ​​in the area blocked by tree canopy.

[0073] The data collected from the field measurements of 30 forest plots in Huzhou City, Jinan City and Guangzhou City are calculated according to the above method to obtain the preset coefficients. The available value range is 0.279-0.419.

[0074] A further solution is to obtain the weight coefficient The method is:

[0075] The time from the first measurement of the sample plot is recorded as , the time when the last measurement of the plot is completed is recorded as , record this period as the measurement period of the sample plot;

[0076] The measurement period of the sample plot is divided into Time-sharing period ~ , fitting to obtain the curve of the canopy density change over time in each time period And the curve of the change of canopy closure threshold over time ;

[0077] By formula group: Calculate the weight coefficient of the current plot ;in, ;

[0078] In the formula, The coefficient of variation Deviation from preset threshold The judgment function of is the average value of the weight coefficient, is the preset scale factor, It is a preset fixed coefficient.

[0079] In a further embodiment, the coefficient of deviation .

[0080] See also Figure 1-Figure 8As shown, the present invention is an electronic device for measuring canopy density, comprising a plurality of brackets 2, each of which is equipped with a plurality of photoelectric detector units 1, two adjacent brackets 2 are movably connected by a connecting member 3, the plurality of brackets 2 connected together are foldable and each independent bracket is detachable and replaceable;

[0081] The photodetector units 1 are arranged in parallel at equal intervals in each of the brackets 2, and a plurality of the photodetector units 1 are electrically connected in parallel to form a photodetector array 13. A controller 4 is movably connected to one side of the bracket 2 through the connector 3, and the photodetector array 13 is electrically connected to the controller 4. In the present invention, a plurality of brackets 2 are movably connected, and a plurality of photodetector units are arranged on the brackets 2, so that the electronic device can be folded for easy storage.

[0082] In a further solution, the controller 4 housing 1-4 is provided with a display screen 5, an operation button 6 and a charging interface 12; the controller 4 is internally provided with an amplifier circuit 7, a data acquisition module 8, a microprocessor 9, a power supply module 10, and a drive circuit module 11;

[0083] The photodetector unit 1 includes a housing 1-4, a light-illuminating surface is provided on one side of the housing 1-4, a focusing lens 1-1 is mounted on the light-illuminating surface, and the focusing lens 1-1 is used to converge incident light, and the incident light is converged on a photosensitive surface 1-3 inside the housing 1-4 corresponding to the light-illuminating surface, so as to improve the light collection efficiency and signal-to-noise ratio of the photodetector unit 1;

[0084] The photosensitive surface 1-3 is fixed on a concave base 1-5 provided inside the housing 1-4, and a window sheet 1-2 is also provided at the notch of the concave base 1-5, and the window sheet 1-2 is used to encapsulate and protect the photosensitive surface 1-3;

[0085] A pin 1 - 6 is provided on one side of the housing 1 - 4 , and the pin 1 - 6 is used for electrically connecting to the controller 4 .

[0086] The photodetector units 1 are electrically connected in parallel to form a photodetector array 13. The photodetector array 13 generates an electrical signal after receiving light, which is amplified and converted into a voltage signal by the amplifier circuit 7 and transmitted to the data acquisition module 8. The data acquisition module further transmits the signal to the microprocessor 9 for processing through A / D conversion. The power supply module 10 simultaneously supplies power to the drive circuit module 11 and the microprocessor 9 of the photodetector array 13. The microprocessor 9 is connected to the display module, and the display screen 5 of the display module displays the plot related to the measurement data and the final canopy density result.

[0087] Figure 5The circuit diagram of the photodetector unit 1 in the present invention for collecting light signals and amplifying them is shown. The circuit consists of a photodiode (PD) equivalent circuit and a photodiode amplifier circuit 7 in photovoltaic mode. Among them, I is the photocurrent source caused by the incident light, and its intensity is proportional to the incident light intensity. ID is the dark current, that is, the leakage current flowing through the photodiode under reverse bias voltage conditions, which is in the order of pA at room temperature. C D is the junction capacitance, which is proportional to the photosensitive area of ​​the PD and inversely proportional to the reverse bias voltage. D Node shunt resistance represents the parallel resistance of the photodiode node under zero bias, which is usually in the order of kMΩ. Under ideal conditions, the resistance is infinite.

[0088] In addition, the voltage across the photodiode is zero in photovoltaic mode. Ideally, no dark current will flow through the photodiode, and the linearity and sensitivity are at their highest, with the lowest noise level. It is very suitable for high-precision applications such as forest canopy density detection. The circuit design uses the MCP6491 operational amplifier to form a transimpedance amplifier circuit 7, and the output signal Vout = I·RF.

[0089] Figure 6 The circuit diagram of the present invention for processing the signal of the photodetector array 13 is shown. The data reading and processing of the photodetector array 13 is composed of an analog-to-digital conversion module and a host computer. The analog signal of the amplifier circuit 7 is processed by the AD conversion chip PCF8591 and then input into the host computer for statistical and analytical processing.

[0090] The multiple photodetector units 1 in the canopy density detector of the present invention are arranged at equal intervals to form a one-dimensional photodetector array 13. When the photosensitive surfaces 1-3 of the photodetector units receive light signals, the light energy is converted into electrical energy, and the intensity of the generated photocurrent is proportional to the intensity of the incident light, such as Figure 7 As shown; however, since the photocurrent generated by the photodetector unit 1 is very weak, it needs to be amplified by the amplifier circuit 7. The amplifier circuit 7 receives the photocurrent signal from the photodetection unit, amplifies it, and converts it into a corresponding voltage signal. The amplified voltage signal is easier for subsequent data processing and transmission. The data acquisition module 8 is responsible for A / D conversion (analog-to-digital conversion) of the amplified analog voltage signal, that is, converting the analog signal into a digital signal and passing it to the microprocessor 9 for processing. The microprocessor 9 performs comprehensive processing on the signals of each photodetection unit according to a preset algorithm, calculates the intensity and distribution of the light, and the microprocessor 9 displays the drawing and the final measurement results on the display screen 5.

[0091] Specifically, a method and an electronic device for measuring canopy density include the following steps:

[0092] 1. Arrive at the target forest, turn on the electronic device, click the T1 button on the display screen to enter the T1 measurement mode, enter the area in the forest that is completely unobstructed by the tree canopy, place the electronic device on the ground, and measure 3 times; click the T2 button on the display screen to enter the T2 measurement mode, enter the area in the forest that is completely obstructed by the tree canopy, place the electronic device on the ground, and measure 3 times.

[0093] 2. Setting of canopy closure threshold coefficient and weight coefficient for each measurement. Enter the canopy closure threshold coefficient, the recommended range is 0.279-0.419. After the input is completed, the electronic device automatically generates the T0 value. When the number of measurements in the forest is greater than 10 times, the weight coefficient for each measurement can be set to 1, that is, the weight of each measurement is the same. You can also measure the canopy closure threshold coefficient of the target location according to the working principle section and calculate the weight coefficient according to the working principle section.

[0094] 3. Enter the multiple sample plots designated in the forest, place the electronic device, and click the measurement button. For example, if the forest is set to have 5 sample plots and each sample plot is measured 3 times, then measure 15 times in sequence. After 15 measurements are completed, click the Finish button. The electronic device will automatically calculate and display the forest canopy density value, and the entire forest canopy density measurement can be completed.

[0095] In the following three embodiments, the closure threshold coefficient is 0.35 within the recommended range of 0.279-0.419, and the weight coefficient is 1; the electronic device is used from 9:00 to 15:00; the weather is clear and there is no obvious cloud cover to block the sun when in use; the measurement time of data T1 and T2 in the closure threshold and the closure measurement time shall not be greater than 2 hours.

[0096] Embodiment 1:

[0097] Number of illumination measurements: 200, including 100 in areas without tree canopy shading and 100 in areas with tree canopy shading;

[0098] Experimental location, Huzhou City, Zhejiang Province (120.143063, 30.880411)

[0099] Measurement time: May 24, sunny, measurement time period 12-14 o'clock;

[0100] The average illumination of the part blocked by the tree canopy is 16766.3 ( ), the maximum value is 32770, the minimum value is 4152;

[0101] The average illumination of the part without tree canopy shading is 125767.7 ( ), the maximum value is 147492, the minimum value is 106323;

[0102] The canopy closure threshold is ×0.35=49886.9;

[0103] The maximum value of the canopy-blocked part, 32770, is less than the canopy closure threshold of 49886.9, and the minimum illumination value of the non-canopy-blocked part, 106323, is greater than the canopy closure threshold of 49886.9. Therefore, the canopy closure threshold of 49886.9 is used for division, and all 200 measured values ​​can be correctly divided. In summary, according to the experimental principle of the present invention, the canopy closure is measured in the target forest, and the accuracy of this measurement is 100%.

[0104] Embodiment 2:

[0105] Number of illumination measurements: 200, including 100 in areas without tree canopy shading and 100 in areas with tree canopy shading;

[0106] Experimental location: Jinan City, Shandong Province (116.948265, 36.672269);

[0107] Measurement time: June 17, sunny, measurement time period 12-14 o'clock;

[0108] The average illumination of the canopy-blocked part is 10263.9 ( ), the maximum value is 20429, the minimum value is 1444;

[0109] The average illumination of the part without tree canopy shading is 75113.4 ( ), the maximum value is 94318 and the minimum value is 38900;

[0110] The canopy closure threshold is ×0.35=29882.1;

[0111] The maximum value 20429 of the part blocked by the crown is less than the canopy density threshold of 29882.1, and the minimum value 38900 of the illumination value of the part not blocked by the crown is greater than the canopy density threshold of 29882.1. Therefore, the canopy density threshold of 29882.1 is used for division, and all 200 values ​​can be correctly divided. In summary, according to the experimental principle of the present invention, the canopy density is measured in the target forest, and the accuracy of this measurement is 100%.

[0112] Embodiment 3:

[0113] Number of illumination measurements: 200, including 100 in areas without tree canopy shading and 100 in areas with tree canopy shading;

[0114] Experimental location: Guangzhou, Guangdong Province (113.315544, 23.198085);

[0115] Measurement time: June 21, sunny, measurement time period 12-14 o'clock;

[0116] The average illumination of the part blocked by the tree canopy is 16546 ( ), maximum value 21718, minimum value 13247

[0117] The average illumination of the part without tree canopy is 123095 ( ), the maximum value is 140142, the minimum value is 94498

[0118] The canopy closure threshold is ×0.35=48874.4;

[0119] The maximum value 21718 of the part blocked by the crown is less than the canopy density threshold of 48874.4, and the minimum value 94498 of the illumination value of the part not blocked by the crown is greater than the canopy density threshold of 48874.4. Therefore, the canopy density threshold of 48874.4 is used for division, and all 200 values ​​can be correctly divided. In summary, according to the experimental principle of the present invention, the canopy density is measured in the target forest, and the accuracy of this measurement is 100%.

[0120] The above is a detailed description of an embodiment of the present invention, but the content is only a preferred embodiment of the present invention and cannot be considered to limit the scope of implementation of the present invention. All equivalent changes and improvements made within the scope of the present invention should still fall within the scope of the patent coverage of the present invention.

Claims

1. A method for measuring canopy closure, characterized in that: The steps include: S1. Predefine multiple testing plots in the target forest; S2. Place the electronic device in one of the sample plots pre-demarcated in the target forest, turn on the electronic device, and all the photoelectric detector units (1) on the electronic device measure the current illuminance value; and make the following determinations based on the illuminance value: If the measured illuminance value is lower than the preset value , it is determined to be a tree canopy shading area; if the measured illumination value is higher than the preset value , it is determined as an area without tree canopy shading; Count all values ​​below the preset value The number of values ​​is n, the number of illumination values ​​obtained by all photoelectric detector units is N, and the canopy density value of the current detection plot is ; By formula Calculate the canopy density of the current plot , For the current plot The canopy density values ​​measured are: , The total number of measurements for the current test plot; S3, repeating step S2 for each sample plot to obtain the canopy density of multiple sample plots; S4. Substitute the canopy density of multiple plots into the formula Obtain the canopy density value of the target forest , where is the total number of sample plots, is the weight coefficient corresponding to each sample plot.

2. The method for measuring canopy density according to claim 1, characterized in that: The method to obtain the target forest illumination threshold T0 is: The electronic device is placed in an area of ​​the target forest without any tree canopy obstruction for calibration. Multiple measurements are taken to obtain the average signal strength value T1. Place the electronic device in an area completely blocked by tree canopies in the target forest, measure multiple times and calculate the average value to obtain the signal strength value T2; Set the canopy density threshold in the canopy density detector to , where is the preset coefficient.

3. The method for measuring canopy density according to claim 2, characterized in that: Get the preset coefficient The method is: Measure the illumination value of the area without tree canopy shade n times in each plot and calculate the average value and minimum value and the average illumination of the area blocked by the tree canopy and maximum value ; By formula Calculate the upper limit of the preset interval for each plot ; Then through the formula Calculate the lower limit of the preset interval for each plot ; Get the preset interval for each plot The public interval of the target forest is obtained ; exist All values ​​in the table can be used as preset coefficients for the target forest. .

4. The method for measuring canopy density according to claim 2, characterized in that: The preset coefficient The available value range is 0.279-0.

419.

5. The method for measuring canopy density according to claim 1, characterized in that: Get the weight coefficient The method is: The time from the first measurement of the sample plot is recorded as The time when the last measurement of the plot is completed is recorded as , record this period as the measurement period of the sample plot; The measurement period of the sample plot is divided into Time-sharing period ~ , fitting to obtain the curve of the canopy density change over time in each time period And the curve of canopy closure threshold changing over time ; By formula group: Calculate the weight coefficient of the current plot ;in, ; In the formula, The coefficient of variation Deviation from preset threshold The judgment function of is the average value of the weight coefficient, is the preset scale factor, It is a preset fixed coefficient.

6. The method for measuring canopy density according to claim 4, characterized in that: The coefficient of variation .

7. An electronic device for measuring canopy density, characterized in that: It comprises a plurality of brackets (2), each of the brackets (2) being equipped with a plurality of photoelectric detector units (1), two adjacent brackets (2) being movably connected by a connecting piece (3), the plurality of brackets (2) connected together being foldable and each independent bracket being detachable and replaceable; The photodetector units (1) are arranged in parallel at equal intervals in each of the brackets (2), and a plurality of the photodetector units (1) are electrically connected in parallel to form a photodetector array (13); one side of the bracket (2) is movably connected to a controller (4) via the connecting piece (3); and the photodetector array (13) is electrically connected to the controller (4).

8. The electronic device for measuring canopy density according to claim 7, characterized in that: The controller (4) is provided with a display screen (5), operation buttons (6) and a charging interface (12) on its housing (1-4); the controller (4) is provided with an amplification circuit (7), a data acquisition module (8), a microprocessor (9), a power supply module (10) and a drive circuit module (11) inside. The photodetector unit (1) comprises a housing (1-4), a lighting surface being provided on one side of the housing (1-4), a focusing lens (1-1) being mounted on the lighting surface, the focusing lens (1-1) being used to converge incident light, the incident light being converged on a photosensitive surface (1-3) inside the housing (1-4) corresponding to the lighting surface; The photosensitive surface (1-3) is fixed on a concave base (1-5) provided inside the housing (1-4); a window sheet (1-2) is also provided at the notch of the concave base (1-5); the window sheet (1-2) is used to encapsulate and protect the photosensitive surface (1-3); A pin (1-6) is provided on one side of the housing (1-4), and the pin (1-6) is used to be electrically connected to the controller (4).

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