KR100884100B1 - System and method for detecting vegetation canopy using airborne laser surveying - Google Patents

Abstract

A system and a method for detecting vegetation canopy by using airborne laser surveying are provided to create accurate canopy based on a measured laser pointer by scanning a laser pulse at a regular interval according to flight attitude. An aeronautical system drives an aviation laser scanner, a GPS(Global Positioning System) and an INS(Initial Navigation System)(S201), and receives position information of an airplane based on the GPS(S203). A system operating unit irradiates a pulsed laser signal at a regular interval and calculates a real distance as to the interval of the laser pulse by using the GPS and INS(S205). In addition, the system operating unit collects the image information photographed at an image photographing unit and the scan information provided through a laser scanner(S207). An operating system receives the image information and the laser scan information transmitted from a transmitting unit(S209). A tree height measurement unit searches the highest point data as the height of a tree and defines the highest point data as the height of the tree(S211). A canopy calculating unit calculates the canopy as to a corresponding tree(S213).

Description

Tree canopy extraction system and method using aerial laser surveying {SYSTEM AND METHOD FOR DETECTING VEGETATION CANOPY USING AIRBORNE LASER SURVEYING}

The present invention relates to aviation laser surveying, and more particularly to a tree canopy extraction system and method using aviation laser surveying to enable easy acquisition of tree canopy data using aerial laser surveying to enable three-dimensional model analysis. It is about.

Recently, as interest in geographic information system (GIS) has increased and research and development in related fields have been actively conducted, the scope of application and utilization of GIS is rapidly expanding in various fields. GIS is a computer-based system for using and managing geographic data to solve space related problems.

Here, the most basic data in constructing the GIS is a digital map. Numerical maps, unlike classical paper maps, store and index various terrain data obtained by surveying into numerical files. The production of digital maps is usually based on topographical data obtained from aerial photographs and satellite images, and it is necessary to interpret and quantify these data. On the other hand, recently, techniques for acquiring digital terrain data using a global positioning system (GPS) have been actively studied. GPS is a state-of-the-art navigation system using satellites, which is used to determine the exact position of measurement on the ground. Specially designed GPS receivers can measure the absolute position of a stationary or moving object by receiving information from satellites anywhere in the world without time constraints.

Techniques that use GPS to obtain or correct digital terrain data include, for example, Korean Patent Publication No. 10-0404400, Korean Patent Publication No. 10-0456377, Korean Patent Publication No. 10-0496814, and Korean Patent Registration Publication 10-0510834 and the like. Republic of Korea Patent Publication No. 10-0404400 proposes a technique for correcting the position coordinates of the vehicle by setting two or more reference points and obtaining the distance information from the reference point to the vehicle to obtain the movement trajectory of the vehicle equipped with GPS, and have.

Republic of Korea Patent Publication No. 10-0456377 proposes a technology for updating the numerical map in real time by determining whether the road subsidiary facilities displayed on the numerical map is actually matched while moving the GPS-equipped vehicle. Korean Patent Publication No. 10-0496814 discloses a technique for producing a digital map by correcting road coordinate values and survey information obtained in real time from a GPS receiver with a standard correction function.

In addition, the Republic of Korea Patent Publication No. 10-0510834 discloses a technique for producing a digital map reflecting the status of the road facilities by survey date by recording the location and surrounding information of the road facilities obtained from the GPS receiver. As can be seen from the above-described state of the art, the digital map is used not only to include terrain information but also to provide various geographical information by storing additional information such as facilities around roads.

However, although the above-described conventional technologies are constructed geographic information for the purpose of obtaining road information by using a GPS-equipped vehicle, the construction of trees-related information for the purpose of forest management is difficult with current technologies and equipment. In other words, forest information is generated for the trees by using manual methods for direct tree management and remote sensing techniques such as aerial photographs or satellite images. However, the direct measurement method takes enormous time and cost, and the method using aerial photographs or satellite photographs only photographs the surface of the forest, thereby degrading the utility of information. It is difficult to carry out three-dimensional analysis such as canopy analysis of trees and the production of digital surface model (DSM) of the terrain. In addition, there is a problem in that the aerial photograph shows a difference in spatial resolution according to the altitude taken, and the satellite image shows a difference in the spatial resolution of the image according to the type of the satellite photographed.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a tree canopy extraction system and method using aerial laser surveying that can easily obtain canopy data of trees using aerial laser surveying. have.

Another object of the present invention is to measure a tree over a leaf surface of a forest by laser surveying, and thus, tree using aerial laser surveying capable of analyzing three-dimensional models of trees that could not be analyzed by low resolution aerial photographs or satellite images. It provides a canopy extraction system and method.

In order to achieve the above object, the tree canopy extraction system using aerial laser surveying according to the first aspect of the present invention includes an image capturing unit for capturing aerial images of a corresponding area; An aviation system comprising a system operator for generating laser scan information on trees using the image information captured by the image capturing unit and the LiDAR system; After receiving the canopy information for the tree based on the aerial image information and the laser scan information, the operation control unit for matching the aerial image information and canopy information, and a display unit for displaying the operation results of the operation control unit as an image And a tree identification unit for determining whether the object is vegetation based on the laser scan information provided from the calculation control unit, and each tree in the vegetation based on the pulse arrival time of the laser scan information when the object is a vegetation. Based on the measurement result of the tree height measuring unit for measuring the height of the tree, and the tree height measuring unit detects the position where the maximum amount of change in the tree height based on the highest point for each tree and assumes the circumference of the corresponding tree, Canopy information for each tree based on the peak and tree circumference Characterized in that consisting of; arithmetic system consisting of a canopy calculation unit for generating a.

Meanwhile, a tree canopy extraction method using aerial laser surveying according to a second aspect of the present invention for achieving the above object comprises the steps of: a) extracting peak data for each tree in a vegetation based on an aerial laser scan; b) calculating distance information from the closest peak data based on the peak data for any one tree; And c) calculating the distance information as a canopy for the tree.

Specifically, the method may further include providing three-dimensional graphic information about the tree by including the height of the tree corresponding to the highest point data.

The tree canopy extraction system and method using aviation laser surveying according to the present invention obtains the effect of generating an accurate canopy based on the measured laser pointer by scanning and irradiating a laser pulse at a predetermined interval according to the flight altitude. . In addition, the accurate tree canopy is implemented as a three-dimensional model based on laser surveying, so that the forest information can be accurately constructed.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a system configuration for the tree canopy measurement according to the present invention. As shown, a Light Detection And Ranging (LiDAR) system, which consists of a Global Positioning System (GPS) 111, an Inertial Navigation System (INS) 109, and an Airborne Laser Scanner (103) for aviation laser surveying, Including, the image capture unit 107 for capturing the aerial image for the area, the image information captured by the image capture unit 107 and the system for generating laser scan information for the tree using the LiDAR system An aviation system (100) comprising an operator (101) and a transmitter (105) for transmitting the aerial image information and the laser scan information generated by the system operator (101); The receiver 125 demodulates the aerial image information and the laser scan information provided from the transmitter 105, and extracts the aerial image information and the laser scan information based on the demodulated information from the receiver 125. After receiving the canopy information for the tree, the operation control unit 121 for matching the aerial image information and the canopy information, the display unit 123 for displaying the operation results of the operation control unit 121 as an image, The tree identification unit 127 determines whether the object is vegetation based on the laser scan information provided from the calculation control unit 121, and when the object is a vegetation, based on the pulse arrival time of the laser scan information. Based on the measurement results of the tree height measuring unit 129 and the tree height measuring unit 129 for measuring the height for each vegetation, The canopy calculation unit 131 detects a position where the change amount of tree height is maximized and assumes it as the circumference of the corresponding tree, and generates canopy information for each tree based on the highest point and the circumference of the tree. Computation system 120.

The aviation system 100 and the arithmetic system 120 transmit and receive the image information and the laser scan information using the transmitter 105 and the receiver 125, but this is a wired communication or a wireless communication. Could be based on That is, the aeronautical system 100 and the arithmetic system 120 may be operated in separate spaces as separate devices from each other, and the aeronautical system 100 and the arithmetic system 120 may be one unified system as necessary. Could be. For example, if the aeronautical system 100 and the arithmetic system 120 are separate devices, the aeronautical system 100 is mounted as an aircraft, the arithmetic system 120 is operated on the ground, and photographed in the aeronautical system 100. Tree canopy information for any area may be provided on the ground.

Meanwhile, in the present invention, the canopy of the tree is calculated, but the canopy calculation for each tree in the vegetation composed of a plurality of trees is defined as the canopy of the tree as the distance between the highest points of the plurality of laser points for the vegetation. Can be. In other words, a number of laser points corresponding to the highest point among the vegetation points for vegetation are formed, and this peak will correspond to the peak of one tree. Thus, the canopy of each tree will correspond to the canopy radius of that tree with the median distance between the other peaks closest to that tree's peak.

2 is a flowchart for explaining the main operation of the present invention.

As shown, in step S201 the aviation system 100 starts the LiDAR system, that is, the aviation laser scanner 103, GPS 111 and INS 109. This is for the aerial LiDAR survey, the aviation system 100 receives the position of the aircraft, that is, the location information to be photographed based on the GPS 111 and a plurality of satellites in step S203. In addition, the acceleration of the aircraft is measured using the INS 109, that is, an inertial navigation system.

The INS 109 starts up the aircraft engine and at the same time the current coordinates are input, the INS 109 reads the acceleration whenever the aircraft moves. Then, the acceleration is integrated to find the velocity, and the position change is calculated based on the velocity to accurately detect the current position. Thereafter, the system operator 101 photographs a geographic image of a corresponding region using the image capturing unit 107 and scans a forest region using the laser scanner 103.

The laser scan irradiates a laser beam to a ground tree at a predetermined distance, for example, 10 cm to 30 cm, and the system operator 101 detects the irradiation time of the laser and the received reflection time. That is, as in step S205, the system operating unit 101 irradiates the pulsed laser signal at regular intervals, but calculates a substantial distance with respect to the laser pulse interval using the GPS 111 and the INS 109. As such, the system operating unit 101 collects scan information provided through the laser scanner 103 including the image information captured by the image capturing unit 107 in operation S207. The scan information is laser scan information of a region corresponding to the image information.

The system operator 101 transmits the above-described image information and scan information to the calculation system 120 through the transmitter 105. This may be transmitted through a wired or wireless network as described above, but of course, the calculation system 120 may be installed into the aviation system 100 as necessary. That is, the aviation system 100 and the arithmetic system 120 can be started simultaneously inside the aircraft. Therefore, the operation system 120 receives the image information and the laser scan information transmitted from the transmitter 105 in step S209. When the transceivers 105 and 125 are configured in a wireless network, the receiver 125 will include a demodulation circuit, and thus the calculation controller 121 extracts image information and laser scan information from the demodulated signal. .

The calculation control unit 121 first provides laser scan information to the tree identification unit 127. In step S209, the tree identification unit 127 receives the laser point information according to the laser scan currently received, and calculates correlation with the laser point information. The point information may be assumed as return time information for each laser pulse, and the type of the object, for example, a tree, a terrain, a building, or the like is determined based on the time information. If the return time for the laser pulse is detected constantly with a certain area, it is determined as the terrain, and if the variation of the return time is detected linearly within a certain range, it is determined as the ground, and the return time of the laser pulse is If it is not constant, it is judged as tree or vegetation.

The terrain is data excluding vegetation and buildings that are artificial features, and the vegetation is determined based on the data. The terrain data represents only the terrain of all data acquired by the aviation laser scanner, and an initial point is required. The initial points are low points that are lower than the terrain, and mean data defined as error points. These initial points are used to classify the next highest terrain data, and the actual terrain data is searched for by a triangular network constructed internally by the initial points. The planting identification unit 127 classifies the one having a height higher than the terrain using the terrain data classified using the raw LiDAR data.

The taller than the terrain is classified as a vegetation and artificial buildings, and the classification of vegetation is classified into a certain height range based on the value using the data classified as the topography. For example, from the topographical data, it may be classified as low vegetation up to 0.25m, medium vegetation up to 2m and high vegetation up to 2m. Since most buildings exist in vegetation higher than 2 m, it is possible to classify high vegetation based on the above-described building classification algorithm. 3A and 3B show image information classifying vegetation and terrain, with green parts representing vegetation and gray being terrain. Black is the absence of laser scan information and indicates sea, lake, etc.

Meanwhile, the tree identification unit 127 classifies the terrain and the vegetation according to the above description, and then provides the classified vegetation information to the tree height measurement unit 129. In general, the vegetation is because the radially spread laser points are clustered, the tree height measuring unit 129, as in step S211, retrieves the highest point data corresponding to the highest height among the data determined as vegetation of the tree Defined by height. For example, as shown in FIG. 4, the peak data of the vegetation, that is, the height of the tree, is extracted based on the pulse return time for the laser point scanned into the vegetation. In calculating the height of the vegetation, the tree height measuring unit 129 may calculate the height of the tree based on previously detected terrain data, but if necessary, calculate the maximum height of the plurality of laser points as the height of the tree. Could be.

Thereafter, the process proceeds to step S213 and the canopy calculator 131 calculates a canopy for the corresponding vegetation or tree, and calculates a width value of the tree for this purpose. That is, the maximum value in the left and right directions is extracted based on the tree height data corresponding to the highest point of the tree. When the height of the tree is referred to as a Z value, the maximum value in the left and right directions of the tree may correspond to a Y or X value. The X and Y values indicate the direction of the width of the tree detected in the same manner, and may be used as data for generating 3D information later. 5 is a photograph illustrating a method of calculating the width of vegetation.

The canopy calculating unit 131 transmits the height information of the tree (vegetation) detected by the tree height measuring unit 129 to the calculation control unit 121 including the tree or vegetation width information. The operation control unit 121 provides the canopy information and the image information according to the topographical photograph to the display unit 123, so that the display unit 123 provides a canopy of a vegetation or a tree in a corresponding region as shown in FIG. As shown, the canopy of the tree is displayed in a circular structure corresponding to the width of the tree, in the case of vegetation can be implemented as an oval.

The tree described above calculates the tree's width and canopy by calculating the tree's width based on the peak of the laser point, but the vegetation in which a large number of trees are combined is based on the peaks of the laser point, Calculate the canopy. For example, as shown in Figure 7, in the presence of a myriad of laser points, a plurality of laser points corresponding to the highest point is detected, and based on this, the trees in the vegetation are determined.

In addition, the canopy for each tree may be set to a radius of the canopy by separating the distance to the nearest peak by 1/2, from which the canopy of vegetation has a structure in which a plurality of canopies are overlapped. The tree shape of each tree shown in FIG. 7 is represented by the canopy of the corresponding tree, that is, the horizontal length of the square shape, with the height of the tree based on the highest point, and the diameter corresponding to the circle of the canopy shown in FIG. It is the horizontal length of the square shape mentioned above. As described above, the present invention calculates the height and canopy of the tree based on the information on the laser point to provide the distribution of vegetation, the size of the vegetation, and the like.

As described above, the tree canopy extraction method according to the present invention makes it possible to easily obtain tree canopy data based on aerial laser surveying, so that information can be efficiently constructed by the Korea Forest Service and not analyzed by general aerial photographs or satellite images. As the three-dimensional model of the tree can be provided, it is considered that industrial availability is sufficient because the information utilization for forest management and operation is extremely high.

1 is a block diagram showing a tree canopy extraction system according to the present invention.

2 is a flowchart illustrating a tree canopy extraction method according to the present invention.

3A and 3B are photographs classifying vegetation and terrain.

4 is a photograph of detecting the height of the vegetation.

5 is a photograph of the width of the vegetation.

6 is a graphic depicting a canopy of vegetation.

7 is a graphic illustrating canopy detection of trees in vegetation.

<Explanation of symbols for main drawings>

100: aviation system 101: system operation unit

103: laser scanner 105: transmitter

107: video recording unit 109: INS

111 GPS 120 Computation System

121: operation control unit 123: display unit

125: receiving unit 127: tree identification unit

129: tree height measuring unit 131: canopy calculating unit

Claims (7)

Measure the canopy of trees or vegetation using the Light Detection And Ranging (LIDAR) system, which consists of a Global Positioning System (GPS), an Inertial Navigation System (INS) for Airborne Laser Surveying, and an Airborne Laser Scanner. In the system for An image capturing unit for capturing aerial images of the region; An aviation system comprising a system operator for generating laser scan information on trees using the image information captured by the image capturing unit and the LiDAR system; After receiving the canopy information for the tree based on the aerial image information and the laser scan information, the operation control unit for matching the aerial image information and canopy information, and a display unit for displaying the operation results of the operation control unit as an image And a tree identification unit determining whether the vegetation of the object is based on the laser scan information provided from the operation control unit, but whether the vegetation exists in a predetermined height based on the terrain data, and determining the vegetation based on a preset building classification algorithm. And, if the object is a vegetation, the tree height measuring unit for measuring the height for each tree in the vegetation based on the pulse arrival time of the laser scan information, and for each tree based on the measurement results of the tree height measuring unit Detect the position where the maximum amount of change in tree height is based on the highest point A tree canopy extraction using aerial laser surveying, comprising: an arithmetic system composed of a canopy calculation unit for assuming the circumference of a corresponding tree and generating canopy information for each tree based on the highest point and the circumference of the tree. system. The method of claim 1, The aviation system includes a transmitter for transmitting aerial image information and laser scan information generated by the system operator, and the calculation system includes a receiver for demodulating aerial image information and laser scan information provided from the transmitter. Tree canopy extraction system using aerial laser surveying. The method of claim 2, The tree canopy extraction system using aerial laser survey, characterized in that the data communication between the aviation system and the computing system is based on a wired or wireless communication system. The method of claim 1, When the tree is a complex vegetation, the canopy calculation unit assumes the distance between the highest point of the plurality of laser points for the vegetation as canopy information for the tree, tree canopy extraction system using aerial laser surveying . In the tree canopy extraction method using the tree canopy extraction system according to claim 1, a) determining whether or not the laser scan information exists in a range of a predetermined height based on the terrain data, and whether or not the vegetation of the object is based on a preset building classification algorithm; b) extracting peak data for each tree in the vegetation; c) calculating distance information with closest peak data based on the peak data for any one tree; And d) calculating tree canopy using aerial laser survey, characterized in that the step of calculating the distance information to the canopy for the tree. The method of claim 5, wherein and e) providing the three-dimensional graphic information for the tree by including the height of the tree corresponding to the peak data. The method according to claim 5 or 6, Canopy information according to the canopy calculation is a tree canopy extraction method using aerial laser survey, characterized in that is provided with terrain information.

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