CN111854616A - A laser-assisted visual measurement method and system for tree diameter at breast height - Google Patents

Abstract

A tree breast height diameter visual measurement method and system under the assistance of laser, the hardware device includes: the tree diameter measuring method comprises the steps that a smart phone, laser emitting equipment, RFID read-write equipment and handheld equipment are used, two beams of parallel laser are emitted to a tree to be measured to mark the tree during measurement, a tree photo with laser points is collected, two laser points in the photo are located at the position of the breast diameter of the tree to be measured, the connecting line of the two laser points is parallel to the growth extension direction of the tree, the photo is subjected to image processing, the breast diameter of the tree to be measured is obtained, meanwhile, the RFID read-write equipment identifies the RFDI label of the tree, and the measured breast diameter is stored corresponding to the corresponding tree label. The device is simple and convenient to carry, and can improve the tree breast-height diameter measurement rate.

Description

A laser-assisted visual measurement method and system for tree diameter at breast height

technical field

The invention relates to the technical field of forestry measurement, and relates to a method and system for visual measurement of tree diameter at breast height assisted by laser.

Background technique

Diameter at breast height is an important basis for measuring the price of seedlings. In the inventory of tree diameter at breast height in nurseries, the measurement of tree diameter at breast height is extremely important.

Existing measurement technologies can be divided into two categories: contact measurement and non-contact measurement. The contact measurement is mainly through the diameter at breast height, which surrounds the trunk, and the measurer must be close to the trunk, and the measurement efficiency is very low. In the non-contact measurement device, the measurement system using the principles of triangulation and laser ranging requires a relatively stable platform to measure. In addition, the current measurement devices using image acquisition and processing cannot avoid using a distance ruler to measure the distance between the image acquisition point and the tree to be measured, and the measurement speed is relatively slow, which cannot be applied to a measurement environment with a large number of seedlings.

SUMMARY OF THE INVENTION

The problem to be solved by the present invention is: aiming at the defects of the prior art, it provides a non-contact measurement method of tree diameter at breast height, and at the same time, it meets the requirements of speed and accuracy.

The technical scheme of the present invention is as follows: a laser-assisted visual measurement method for tree diameter at breast height. Trees are provided with RFID tags, the trees are marked by emitting two parallel laser beams to the trees to be measured, and photos of trees with laser points are collected, so that the photos can be displayed in the photos. Two laser points are located at the DBH position of the tree to be measured, and the line connecting the two laser points is parallel to the direction of tree growth. The image is processed to obtain the DBH of the tree to be tested. At the same time, the RFID reading and writing equipment identifies the tree's RFDI tag. , and store the measured DBH corresponding to the corresponding tree label; wherein, the image processing is: determining the position of the laser point in the photo through feature point search, according to the pixel distance in the two laser point images and the laser transmitter of the two laser beams. The actual distance is calculated to obtain the shooting distance of the tree diameter at breast height to be measured, and the geometric relationship between the pixel and the actual is obtained; then the tree outline is obtained by the image segmentation algorithm, and the actual tree diameter at breast height is further obtained.

Further, the inclination verification is performed before the photos are collected, the photos are collected by the smart phone, and the current inclination of the smart phone is obtained by the gyroscope inside the smart phone. When the inclination is within the allowable range, photo collection is allowed.

As a preferred way, the feature point search is specifically: converting the image from RGB color space to HSV color space, filtering out the laser color area in the image using a threshold set based on experience and expanding; then converting the image into a grayscale image, Filter out the high-brightness area according to the set threshold; calculate the connected area and the centroid of each connected area for the intersection of the expansion area and the high-brightness area, and obtain the position of the high-brightness laser point pair; if the high-brightness laser point cannot be detected, then Follow the steps directly after closing the laser color area.

As a preferred method, the image segmentation and DBH calculation are specifically: remove two laser points in the photo, and then cut the image to reduce the complexity of the image background and reduce the image area; The interactive image segmentation algorithm divides the trunk area in the image to obtain the trunk outline with a contour line width of one pixel; the trunk outline is divided into four parts of equal height along the vertical direction of the tree, and the trunk outline is correspondingly divided into 4 groups of approximately parallel Edge, apply the least squares method to the pixels on each set of edges to perform linear regression, estimate the expression of two edge straight lines, and calculate the angle between the two edge straight lines, if the angle is less than the specified threshold and the two straight lines If the mean square error is less than the specified threshold, the approximate distance between the two edge straight lines is measured, and finally the measured approximate distance is averaged to obtain the tree pixel DBH; the tree pixel DBH is converted to the actual DBH according to the geometric relationship.

The present invention also provides a laser-assisted tree diameter at breast height visual measurement system, comprising: a smart phone, a laser emission device, an RFID reading and writing device and a handheld device, the handheld device is used for loading the smart phone, the laser emission device and the RFID reading and writing device, A computer program is configured in the smart phone, and the above-mentioned detection method is realized when the program is executed; the laser emission device includes two point lasers, and the distance between the two point lasers is fixed, which is used to emit two parallel laser beams, and mark two laser beams on the tree to be tested. A red laser point; RFID reading and writing equipment is used to read the RFID tags of trees.

Further, the smartphone supplies power to the laser emitting device and the RFID reading and writing device through the serial port, and receives data from the RFID reading and writing device.

Further, the handheld device is equipped with a mobile phone bracket with adjustable width, which is suitable for loading support of different types of mobile phones; the handheld device is provided with two switches, and the two switches are provided on the serial port line, which are respectively used to control the circuit of the laser emitting device. The power supply of the RFID reading and writing device is connected and disconnected, and the handheld device is also provided with a charging socket, which is connected to the serial port line for external charging.

Most of the existing tree diameter measurement methods need to be in contact with the trees, and the measurement process is cumbersome, which is inconvenient in scenarios where a large number of trees need to be measured and recorded. In order to solve this problem, the present invention can complete the measurement of tree diameter at breast height without touching the tree, and store the measurement result in the server, and display it at the same time. The invention provides a method and system for non-contact measurement of tree diameter at breast height. The ratio of pixel distance to actual distance is calculated by point lasers, and the actual diameter at breast height of trees is obtained without contacting trees, thereby improving the measurement efficiency. Simple and easy to carry.

Description of drawings

FIG. 1 is a schematic diagram of a hardware device for measuring tree diameter at breast height in an embodiment of the present invention.

2 is a schematic flowchart of a method for measuring tree diameter at breast height according to an embodiment of the present invention.

FIG. 3 is a schematic flowchart of image processing in tree diameter at breast height measurement according to an embodiment of the present invention.

FIG. 4 is a schematic diagram of the geometric relationship described in the image processing in the tree diameter at breast height measurement according to the embodiment of the present invention.

Detailed ways

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the protection scope of the present invention.

FIG. 1 is a schematic structural diagram of an apparatus for measuring tree diameter at breast height according to an embodiment of the present invention. The embodiment of the present invention will be described in detail below with reference to FIG. 1 .

As shown in FIG. 1 , the system for non-contact tree diameter measurement provided in this embodiment includes: a smart phone 1 , a laser emitting device 7 , an RFID reading and writing device, and a handheld device 6 . The smart phone 1 and the laser emitting device 7 is arranged on the handheld device 6; the camera 2 of the smartphone 1 faces the same direction as the laser emitting device 7, and the laser emitting device 7 is used for collecting the diameter at breast height photo of the tree to be measured by the smartphone 1. The tree to be measured emits laser light to form two laser spots in the obtained picture of the diameter at breast height of the tree to be measured.

The handheld device 6 is provided with a mobile phone holder 3 with an adjustable width, which is used to place the smartphone 1. After the laser emitting device shoots two laser points on the tree to be measured, the smartphone collects the tree to be measured with the two point lasers. Diameter at breast height picture, the two point lasers are used to calculate the distance between the non-contact tree diameter at breast height measuring device and the tree to be measured. As shown in Figure 1, the laser emitting device is set on the left side of the smartphone camera. As long as the smartphone camera and the laser emitting device do not block each other, it is ensured that the smartphone can capture the two points formed by the laser emitting device on the tree to be measured. A laser may be used, and its specific position is not specifically limited in the embodiment of the present invention.

In addition, in the device described in the embodiment of the present invention, the smart phone 1 supplies power to the entire hardware circuit through the serial port. The hand-held device is provided with a master switch 4 and a laser emission device switch 5, which are used to control the startup of the device and the emission of laser light respectively. The serial port can also complete the function of data transmission while supplying power.

In the embodiment of the present invention, the laser emitting device includes two point lasers. Because the color of the red laser is more obvious than that of the trees, two red point lasers can be used in the embodiment of the present invention. Of course, other laser emitting devices, such as two blue dot lasers, etc., may also be used as required, which is not specifically limited in the embodiment of the present invention.

The present invention provides a method for measuring tree diameter at breast height, which is realized by means of a computer program in combination with the above-mentioned device. As shown in Figure 2, the measurement method is as follows: the trees are equipped with RFID tags, and the trees are marked by sending two parallel laser beams to the trees to be measured, and a photo of the trees with laser points is collected, so that the two laser points in the photo are located in the trees to be measured. At the DBH position, the line connecting the two laser points is parallel to the tree growth and extension direction, and image processing is performed on the photo to obtain the DBH of the tree to be tested. The tree labels are stored correspondingly; wherein, the image processing is: determining the position of the laser point in the photo through feature point search, and calculating the distance between the pixels in the two laser point images and the actual distance of the laser emitters of the two laser beams and the tree to be measured. The shooting distance of DBH is used to obtain the actual geometric relationship between pixels and the actual tree diameter. Then, the tree outline is obtained according to the image segmentation algorithm, and the actual tree DBH is further obtained. Preferably, the inclination verification is performed before capturing the photo, the photo is captured by the smartphone, and the current inclination of the smartphone is obtained by the gyroscope inside the smartphone. When the inclination is within the allowable range, the photo capture is allowed.

As shown in Figure 3, the feature point search is used to narrow the search range of laser points and reduce the error rate of laser point detection: convert the image from the RGB color space to the HSV color space, and use an experience-based threshold to filter out the The red area is expanded; then the image is converted into a grayscale image, and the high-brightness area is filtered out using an experience-based threshold; the connected area and the centroid of each connected area are calculated for the intersection of the two parts to accurately obtain the high-brightness laser point pair. position; when obtaining a high-brightness laser spot fails, the intersection of the red area and the high-brightness area is no longer used, but the red area is closed and the subsequent steps are executed directly; the stability of the laser spot detection is effectively improved.

The image segmentation and DBH calculation are as follows: remove the two laser points in the photo, and then cut the image to reduce the complexity of the image background and reduce the image area; using the existing interactive image based on deep convolutional neural network Segmentation algorithm (Interactive Image Segmentation with Latent diversity (CVPR2018, MIT license is available for commercial use), segment the trunk area in the image, and obtain the trunk outline with a contour line width of one pixel; divide the trunk outline into equal heights along the vertical direction of the tree The four parts of , the trunk outline is correspondingly divided into 4 groups of approximately parallel edges, the least squares method is applied to the pixels on each group of edges to perform linear regression, 2 edge line expressions are estimated, and the distance between the 2 edge lines is calculated. If the angle is less than the specified threshold and the mean square error of the two straight lines is less than the specified threshold, measure the approximate distance between the two edge straight lines, and finally average the measured approximate distances to obtain the tree pixel diameter at breast height; Convert the tree pixel DBH to actual DBH according to the geometric relationship (shown in Figure 4).

The method, device and system for measuring tree diameter at breast height provided by the embodiments of the present invention have a simple structure and are easy to carry. By using two point lasers, the diameter at breast height of the tree to be measured can be quickly and accurately obtained after the smartphone collects the DBH picture of the tree to be measured , which improves the measurement efficiency and accuracy of tree diameter at breast height.

Claims (7)

1. A method for visual measurement of tree diameter at breast height under laser assistance, characterized in that the tree is provided with an RFID tag, and the tree is marked by sending two parallel laser beams to the tree to be tested, and a photo of the tree with the laser point is collected, so that two in the photo are marked. The point laser is located at the DBH position of the tree to be measured, and the line connecting the two laser points is parallel to the direction of tree growth. The image is processed to obtain the DBH of the tree to be tested. The measured diameter at breast height and the corresponding tree label are stored correspondingly; wherein, the image processing is: determining the position of the laser point in the photo through feature point search, according to the pixel distance in the two laser point images and the actual distance of the laser emitters of the two laser beams Calculate the shooting distance from the DBH of the tree to be measured, and obtain the actual geometric relationship between the pixels and the actual tree; then obtain the tree outline according to the image segmentation algorithm, and further obtain the actual tree DBH. 2. the visual measurement method of tree diameter at breast height under a kind of laser aid according to claim 1, it is characterized in that carrying out inclination verification before collecting photo, collecting photo by smart phone, obtain current intelligence by the gyroscope inside smart phone. The inclination of the mobile phone, when the inclination is within the allowable interval, photo collection is allowed. 3. the visual measurement method of tree diameter at breast height under a kind of laser aid according to claim 1, it is characterized in that described feature point search is specifically: image is converted into HSV color space by RGB color space, use the threshold value that is set based on experience Filter out the laser color area in the image and expand it; then convert the image to a grayscale image, and filter out the high-brightness area according to the set threshold; calculate the connected area and the centroid of each connected area for the intersection of the expanded area and the high-brightness area , obtain the position of the high-brightness laser point pair; if the high-brightness laser point cannot be detected, perform the subsequent steps directly after closing the laser color area. 4. the visual measurement method of tree diameter at breast height under a kind of laser aid according to claim 1, it is characterized in that described image segmentation and DBH calculation are specifically: remove two laser points in the photo, then the image is cut, Reduce the complexity of the image background and reduce the image area; use the interactive image segmentation algorithm based on the deep convolutional neural network to segment the trunk area in the image, and obtain the trunk outline with a contour line width of one pixel; The vertical direction is divided into four parts of equal height, and the trunk outline is correspondingly divided into 4 groups of approximately parallel edges. The pixels on each group of edges are subjected to linear regression by applying the least squares method to estimate 2 edge straight line expressions, and calculate The angle between the two edge lines, if the angle is less than the specified threshold and the mean square error of the two lines is less than the specified threshold, then measure the approximate distance between the two edge lines, and finally take the average of the measured approximate distances , get the tree pixel DBH; convert the tree pixel DBH to the actual DBH according to the geometric relationship. 5. A visual measurement system for tree diameter at breast height under a laser aid, which is characterized in that it comprises: a smart phone, a laser emission device, an RFID reading and writing device and a handheld device, and the handheld device is used to load a smart phone, a laser emission device and an RFID reading and writing device. , a computer program is configured in the smart phone, and when the program is executed, the method described in any one of claims 1-3 is realized; the laser emitting device includes two point lasers, and the distance between the two point lasers is fixed, for emitting two beams The parallel laser marks two red laser points on the trees to be tested; the RFID reading and writing equipment is used to read the RFID tags of the trees. 6. The visual measurement system of tree diameter at breast height under a kind of laser aid according to claim 5, wherein the smart phone supplies power for the laser emission device and the RFID reading and writing device through the serial port, and receives data from the RFID reading and writing device. 7. The visual measurement system of tree diameter at breast height under a kind of laser aid according to claim 6, it is characterized in that described handheld device is equipped with the mobile phone bracket with adjustable width, for being applicable to different model mobile phone loading support; Two switches, two switches are arranged on the serial port line, which are used to control the power supply of the laser emitting device circuit and the RFID reading and writing device respectively. The handheld device also has a charging socket, which is connected to the serial port line for external charging.

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