Method for Measuring Stand Canopy Density

Abstract

The present invention relates to a method for measuring forest stand density, which includes the steps of: (1) determining a measurement area, and taking the flight route passing through the measurement area as the density measurement sampling line; (2) mounting an active distance measurement module on an airplane, starting the active distance measurement module, and the airplane performs flight and measurement according to the flight route, measuring the laser measurement distance at each sampling point, and simultaneously storing the sampling point coordinates of the active distance measurement module; and (3) comparing the sampling point coordinates of the active distance measurement module with the takeoff point coordinates, obtaining the height value of the airplane, calculating the difference between the laser distance measurement distance at each sampling point and the height of the airplane, judging whether the difference is greater than the set threshold, if it is, determining this sampling point as not dense, if it is not, determining this sampling point as dense, summarizing the results of all sampling points, and calculating the forest stand density. The measurement accuracy of the present invention is reliable, the measurement speed is fast, and the measurement process is simple, and the forest stand density measurement work can be completed quickly in large quantities.

Description

Technical Field

[0001] The present invention belongs to the field of measuring machines and instrument technology, and specifically relates to a method for measuring forest canopy density.

Background Art

[0002] Forest canopy density is the ratio of the crown projection area to the forest land area in a forest stand, which reflects the degree to which the forest stand utilizes the growth space and is an important factor in forest resource survey activities. In actual surveys, the visual method is mainly used. The actual measurement methods include the crown projection method, the measurement line method, and the statistical method. Due to the large amount of work, the measurement speed is slow. In actual work, the visual method is generally used as an alternative. This method is fast, but the measurement accuracy is low. The new methods of new technologies mainly focus on aspects such as remote sensing image classification, fisheye cameras, and lidar. All of the above methods have problems such as high requirements for measurement operation technology, long processing time in the later stage of measurement, and complex algorithms.

[0003] From the above, it is urgent to provide a method for measuring forest canopy density that can have reliable measurement accuracy, high measurement speed, simple measurement process, and can complete the measurement work of forest canopy density quickly in large quantities.

Summary of the Invention

Problems to be Solved by the Invention

[0004] The purpose of the present invention is to provide a method for measuring forest canopy density that can have reliable measurement accuracy, high measurement speed, simple measurement process, and can complete the measurement work of forest canopy density quickly in large quantities.

[0005] The above object is achieved by the following technical solution. A method for measuring forest canopy density, which includes the following: (1) Determining the measurement area, determining the flight route of the airplane, and using the flight route passing through the measurement area as the canopy density measurement sampling line, the step of (2) Install an active distance measurement module on the aircraft, activate the active distance measurement module, and the aircraft performs flight and measurement according to the flight route. Vertically measure the distance from the active distance measurement module to the ground obstacle at multiple sampling points, that is, the distance of laser distance measurement, and at the same time, the sampling point coordinates of the active distance measurement module Step of storing TIFF0007692536000001.tif5170, and (3) Obtain the measurement data of the aircraft and solve the canopy density of the measured area, step, and (3.1) Sampling point coordinates of the active distance measurement module Compare TIFF0007692536000002.tif5170 with the takeoff point coordinates TIFF0007692536000003.tif5170 to obtain the height value of the aircraft and define it as follows: In the formula of TIFF0007692536000004.tif4170, TIFF0007692536000005.tif4170 is the height of the aircraft, TIFF0007692536000006.tif4170 is the elevation value of the sampling point position, TIFF0007692536000007.tif4170 is the elevation value of the takeoff point position, step, and (3.2) Calculate the difference between the distance of laser distance measurement at each sampling point and the height of the aircraft, and determine whether the difference is greater than the set threshold. If it exceeds, this sampling point is recognized as unclosed; if it does not exceed, this sampling point is recognized as closed, step, and (3.3) Summarize the results of all sampling points, count the number of closed sampling points and the total number of sampling points, and divide the number of closed sampling points by the total number of sampling points to obtain the canopy density of the measured area, including steps.

[0006] By equipping an airplane with an on-board active distance measurement module, the flight route of the airplane with respect to the sample plot or area to be measured is used as the measurement sampling line. By calculating and measuring the height from the active distance measurement module of the airplane to the ground obstacle, and comparing the difference with the height of the airplane itself, the forest canopy closure status of the current sampling point is determined. Finally, the values of each sampling point in all the measurement sampling lines are comprehensively statistically analyzed to calculate the forest canopy density. The measurement accuracy of the present invention is reliable, the measurement speed is fast, the measurement process is simple, and a large amount of rapid measurement work of the forest canopy density can be completed.

[0007] As a further technical solution, in the step (3.2), the value of the threshold is determined based on the measurement target. When only measuring the canopy density of tall tree forests, the threshold is the height of the tallest shrub. When measuring the coverage of tall tree forests and shrub forests, the threshold is the height of the tallest ground cover.

[0008] As a further technical solution, the specific steps of the step (2) are as follows: (2.1) Recording the measurement takeoff point coordinates of the active distance measurement module; (2.2) Starting and flying the airplane, measuring the current coordinates of the active distance measurement module, comparing the range of the area to be measured, and determining whether to enter the measurement area; (2.3) After entering the measurement area, at a set fixed time interval, vertically measuring the distance from the on-board active distance measurement module to the ground obstacle. The measurement point is the sampling point, and at the same time, storing the sampling point coordinates of the active distance measurement module.

[0009] As a further technical solution, the calculation formula for the forest canopy density of the measurement area in the step (3) is as follows: TIFF0007692536000008.tif30170

[0010] In the formula, TIFF0007692536000009.tif4170 is the stand canopy density, TIFF0007692536000010.tif3170 is the number of sampling points to be closed, TIFF0007692536000011.tif4170 is the total number of sampling points, TIFF0007692536000012.tif4170 is the TIFF0007692536000013.tif4170 is the canopy condition of the sampling points. The case of 1 represents canopy, and the case of 0 represents non-canopy, TIFF0007692536000014.tif4170 is the TIFF0007692536000015.tif4170 is the distance of laser distance measurement of the sampling points, TIFF0007692536000016.tif4170 is the threshold determined based on the measurement target.

[0011] As a further technical solution, the PCB circuit board of the active distance measurement module includes a microprocessor, a power module, an RTK module, a memory module, a data interface, a timer, a laser distance measurement module, and a lamp. The microprocessor is used to complete the calculation, storage, and control of data measurement. The power module is used to provide power to the microprocessor. The RTK module is used to obtain the real-time spatial position coordinates of the active distance measurement module. The memory module is used to store the microprocessor recording data. The data interface is used for development, testing, or on-site problem handling. The timer is used to provide high-precision timing. The laser distance measurement module is used to measure the distance to obstacles.

[0012] As a further technical solution, the aircraft is a drone.

Advantages of the Invention

[0013] Compared with the prior art, the technical solution of the present invention has the following advantages: High measurement accuracy of canopy density: In the present invention, it is the actual measurement for each sampling line and sampling point. By using the method of laser distance measurement and altitude comparison, the reliability of the measurement results is guaranteed. Since the sampling points and sampling lines to be sampled cover the entire sample plot or the area to be measured, the canopy closure situation of the forest stand is truly reflected. In particular, it can also measure the void points in the crown width of tall trees, and the measurement accuracy is high.

[0014] The measurement process is simple and can achieve rapid measurement: The present invention only needs to fly a drone equipped with an active distance measurement module to obtain measurement data, without the need for other measurement processes, and the measurement process is simple. Since the measurement frequency of each sampling point depends on the emission time interval of the active distance measurement module, the single measurement time interval of the laser distance measurement module is extremely short (it can reach the millisecond level), and rapid measurement can be achieved.

Brief Description of the Drawings

[0015] The accompanying drawings constituting a part of the present invention are used to provide a further understanding of the present invention. The exemplary embodiments and their descriptions of the present invention do not constitute an undue limitation on the present invention and are used to explain the present invention.

Figure 1

Modes for Carrying Out the Invention

[0016] Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. However, the description of this part is only exemplary and interpretive and does not limit the protection scope of the present invention. Furthermore, those skilled in the art can combine the features in the examples and different examples in this specification based on the description of this specification.

[0017] Examples of the present invention are as follows. Referring to FIG. 1, it is a method for measuring forest canopy density. Specifically, (1) Determine the measurement area, determine the flight route of the aircraft, and use the flight route passing through the measurement area as the canopy density measurement sampling line. (2) Install an active distance measurement module on the aircraft, activate the active distance measurement module, and the aircraft performs flight and measurement according to the flight route. Vertically measure the distance from the active distance measurement module to the ground obstacle, that is, the distance of laser distance measurement, at multiple sampling points, and simultaneously record the sampling point coordinates of the active distance measurement module, TIFF0007692536000017.tif5170. (3) Obtain the measurement data of the aircraft and solve the forest canopy density of the measured area. (3.1) Compare the sampling point coordinates TIFF0007692536000018.tif5170 of the active distance measurement module with the takeoff point coordinates TIFF0007692536000019.tif5170 to obtain the height value of the aircraft, and define it as follows: TIFF0007692536000020.tif4170 where, TIFF0007692536000021.tif4170 is the height of the aircraft, TIFF0007692536000022.tif4170 is the elevation value of the sampling point position, TIFF0007692536000023.tif7170 is the elevation value of the takeoff point position. (3.2) Calculate the difference between the laser distance measurement distance of each sampling point and the height of the aircraft, and determine whether the difference is greater than the set threshold. If it exceeds, this sampling point is recognized as unclosed; if it does not exceed, this sampling point is recognized as closed. (3.3) Summarize the results of all sampling points, count the number of closed sampling points and the total number of sampling points, and divide the number of closed sampling points by the total number of sampling points to obtain the forest canopy density of the measurement area. This step is included.

[0018] By equipping an aircraft with an on-board active distance measurement module, the flight route of the aircraft with respect to the sampling area or the area to be measured is used as a measurement sampling line. By calculating and measuring the height from the on-board active distance measurement module to the ground obstacle, and comparing the difference with the height of the aircraft itself, the forest canopy closure status of the current sampling point is judged. Finally, the values of each sampling point in all measurement sampling lines are comprehensively counted to calculate the forest canopy density. The measurement accuracy of the present invention is reliable, the measurement speed is fast, the measurement process is simple, and a large amount of rapid measurement work of forest canopy density can be completed.

[0019] In addition to the above embodiments, in other embodiments of the present invention, in step (3.2), the value of the threshold is determined based on the measurement target. When only measuring the canopy density of a tall tree forest, the threshold is the height of the tallest understory tree. When measuring the coverage of a tall tree forest and an understory forest, the threshold is the height of the tallest ground cover.

[0020] In addition to the above embodiments, in other embodiments of the present invention, the specific steps of step (2) are as follows: (2.1) Record the measurement takeoff point coordinates of the active distance measurement module. (2.2) Start and fly the aircraft, measure the current coordinates of the active distance measurement module, compare the range of the area to be measured, and judge whether to enter the measurement area. (2.3) After entering the measurement area, at a set fixed time interval, vertically measure the distance from the on-board active distance measurement module to the ground obstacle. The measurement point is the sampling point, and at the same time, store the sampling point coordinates of the active distance measurement module.

[0021] A further technical solution is that the calculation formula for the canopy density of the measurement area in step (3) is as follows: TIFF0007692536000024.tif29170

[0022] In the formula, TIFF0007692536000025.tif4170 is the canopy density, TIFF0007692536000026.tif3170 is the number of sampled points to be closed, TIFF0007692536000027.tif4170 is the total number of sampled points, TIFF0007692536000028.tif4170 is the TIFF0007692536000029.tif4170 is the closure situation of the sampled points of TIFF0007692536000030.tif4170 is the TIFF0007692536000031.tif4170 is the distance of the laser distance measurement of the sampled points of TIFF0007692536000032.tif4170 is the threshold value determined based on the measurement target.

[0023] In addition to the above embodiments, in other embodiments of the present invention, the PCB circuit board of the active distance measurement module includes a microprocessor, a power supply module, an RTK module, a memory module, a data interface, a timer, a laser distance measurement module, and an indicator lamp. Among them, the microprocessor is used to complete the calculation, storage, and control of data measurement, the power supply module is used to supply power to the microprocessor, the RTK module is used to obtain the real-time spatial position coordinates of the active distance measurement module, the memory module is used to store the recorded data of the microprocessor, the data interface is used for development, testing, or on-site problem handling, the timer is used to provide high-precision timing, and the laser distance measurement module is used to measure the distance to an obstacle.

[0024] When the active distance measurement module is working, the microprocessor obtains the current spatial position coordinates from the RTK module, the current time from the timer, and the current distance of the active distance measurement module from an obstacle from the laser distance measurement module according to the requirements of the user's set time interval.

[0025] In addition to the above embodiments, in other embodiments of the present invention, the aircraft is a drone.

[0026] The above are only preferred embodiments of the present invention. Those skilled in the art should note that various improvements and modifications can be made without departing from the spirit of the present invention, and these improvements and modifications should also be regarded as within the protection scope of the present invention.

Claims

1. The method for measuring forest canopy density includes the following steps: (1) Determining the measurement area, determining the flight route of the aircraft, and using the flight route passing through the measurement area as the sampling line for canopy density measurement; (2) Installing an active distance measurement module on the aircraft, activating the active distance measurement module, the aircraft flying and measuring according to the flight route, and vertically measuring the distance from the active distance measurement module to the ground obstacle, i.e., the laser measurement distance, at multiple sampling points, and simultaneously recording the sampling point coordinates of the active distance measurement module ; (3) Obtaining the measurement data of the aircraft and solving the forest canopy density of the measured area; (3.1) Comparing the sampling point coordinates of the active distance measurement module with the take-off point coordinates to obtain the height value of the aircraft, and defining it as follows: Wherein, is the height of the aircraft, is the elevation value of the sampling point position, is the elevation value of the take-off point position; (3.2) Calculating the difference between the laser distance measurement distance of each sampling point and the height of the aircraft, and determining whether the difference is greater than the set threshold. If the difference is greater than the set threshold, this sampling point is recognized as unclosed; if the difference is less than the set threshold, this sampling point is recognized as closed; (3.3) Summarizing the results of all sampling points, counting the number of closed sampling points and the total number of sampling points, and calculating the forest canopy density of the measurement area by dividing the number of closed sampling points by the total number of sampling points. A method for measuring forest canopy density, characterized by the above.

2. In step (3.2), the threshold is determined based on the measurement target. When the measurement target is the canopy density of a tall tree forest, the threshold is the height of the tallest shrub. When the measurement target is the coverage of tall tree forests and shrub forests, the threshold is the height of the tallest ground cover. The method for measuring forest canopy density according to claim 1, characterized by the above.

3. The specific steps of step (2) are: (2.1) Recording the measurement take-off point coordinates of the active distance measurement module; (2.2) Starting and flying the aircraft, measuring the current coordinates of the active distance measurement module, comparing the range of the measured area, and determining whether to enter the measurement area. After entering the measurement area, at the set fixed time intervals, the distance from the on-board active distance measurement module to the ground obstacles is measured vertically. The measurement points are sampling points, and at the same time, the sampling point coordinates of the active distance measurement module are memorized. This is a step. The method for measuring the forest canopy density according to claim 1 or 2, characterized in that.

4. The calculation formula for the forest canopy density of the measurement area in the step (3) is as follows. In the formula, is the forest canopy density. is the number of sampling points that are closed. is the total number of sampling points. is the closed condition of the sampling point, where the case of 1 represents closed and the case of 0 represents unclosed. is the distance of the laser distance measurement of the sampling point. is the threshold value determined based on the measurement target. The method for measuring the forest canopy density according to claim 3, characterized in that.

5. The PCB circuit board of the active distance measurement module includes a microprocessor, a power supply module, an RTK module, a memory module, a data interface, a timer, a laser distance measurement module, and a lamp. The microprocessor is used to complete the calculation, storage, and control of data measurement. The power supply module is used to provide power to the microprocessor. The RTK module is used to obtain the real-time spatial position coordinates of the active distance measurement module. The memory module is used to store the data recorded by the microprocessor. The data interface is used for development, testing, or on-site problem handling. The timer is used to provide high-precision timing. The laser distance measurement module is used to measure the distance to the obstacle. The method for measuring the forest canopy density according to claim 4, characterized in that.

6. The aircraft is a drone. The method for measuring the forest canopy density according to claim 5, characterized in that.

7. When the active distance measurement module is working, the microprocessor obtains the current spatial position coordinates from the RTK module, obtains the current time from the timer, and obtains the distance of the current active distance measurement module from the obstacle from the laser distance measurement module according to the requirement of the user's set time interval. The method for measuring the forest canopy density according to claim 5, characterized in that.

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