Plane position identification method

Abstract

To provide a method for identifying a plane position, that can identify a position set in a forest from the results of laser measurement more easily and quickly than conventional techniques.SOLUTION: The plane position identification method of the present invention is a method for identifying the plane position of a point of interest set within a forest, and is a method comprising a target plate installation process, a measurement process, a ground surface setting process, and a point of interest extraction process. In the target plate installation process, a target plate is installed at the point of interest so that it is at predetermined planned height. In the point of interest extraction process, measurement points around the "planned surface (a surface above the ground surface model by the planned height)" are extracted as specific measurement points from the three-dimensional measurement points obtained in the measurement process.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a technology related to measurements of, for example, forests, and more specifically, to a method for determining planar positions within a forest using a flat plate installed at a predetermined height. [Background technology]

[0002] Wood, such as pillars and planks, is an essential material for wooden buildings, including detached houses. Previously, it was possible to import large quantities of wood from overseas, but since the 1980s, efforts to curb deforestation have become more active in various countries, and domestic production has recently been attracting attention. Currently, the self-sufficiency rate for wood is 35% (27 million m 3 ), but it is expected that domestic timber will become even more mature in the future, and forestry is expected to become a growth industry in Japan.

[0003] For example, when forestry workers seek new trees for lumber or carry out forest management, they must naturally negotiate with the land owner. However, according to the Forestry Agency (2023), the progress rate for cadastral surveys nationwide is 52%, but when limited to forest land, the progress rate is only 46%, making it extremely difficult to find the owner of the forest land.

[0004] On the other hand, mountain villages promoted under the "Mountain Village Promotion Law" are said to account for 60% of the total forest land area, but as a result of depopulation and aging, the degradation of forests in these mountain villages is seen as a problem. As forest owners age and the number of local people familiar with the area decreases, it is becoming more difficult to grasp land boundary information, and there is an urgent need to clarify the boundaries before the information is lost.

[0005] When forest management is carried out in a forest where a cadastral survey has not been conducted, the preparatory work is to "clarify the forest boundary." This forest boundary clarification involves surveying the boundary (ownership boundary) in the presence of the forest owner, creating a map, and obtaining the forest owner's consent. Specifically, the work is carried out through the following steps: "planning and preparation," "notifying the forest owner," "on-site attendance," "surveying," "creating a map," "confirming with the forest owner," and "establishing the forest boundary."

[0006] Previously, when surveying boundaries within forests, plane coordinates (X,Y) were determined using handheld GPS (Global Positioning System) or compass surveying. However, because the work was done within forests, handheld GPS surveying had accuracy issues due to satellite placement, while compass surveying had issues such as excessive man-hours and difficulty in securing personnel.

[0007] In recent years, airborne laser scanning and aerial photogrammetry have become mainstream methods for measuring terrain over a wide area, such as for creating topographical maps. Therefore, it is conceivable to adopt airborne laser scanning for boundary surveys within forests as well. In other words, the coordinates of locations recognized as boundary points as a result of on-site inspections are obtained using airborne laser scanning. However, it is not easy to identify, for example, ordinary wooden stakes within a forest using airborne laser scanning. In such cases, signs that are easy to identify using airborne laser scanning are sometimes installed. For example, the "survey sign" disclosed in Patent Document 1 can be relatively easily identified using airborne laser scanning, even within a forest. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Patent Publication No. 2021-124448 Summary of the Invention [Problem to be solved by the invention]

[0009] When the survey marker described in Patent Document 1 was installed in a forest and laser measurements were performed, it was confirmed that the survey marker could be recognized. However, there are various features, including vegetation, in a forest, and measurement data for all of these features is basically obtained by laser measurements. Therefore, it was found that it takes a considerable amount of time and effort to detect the survey marker from the large amount of measurement data.

[0010] The object of the present invention is to solve the conventional problems, i.e., to provide a planar position determination method that can determine a set position within a forest from the results of laser measurement more easily and quickly than conventional technology. [Means for solving the problem]

[0011] The present invention focuses on the fact that by using a flat plate installed at a specified height, it is possible to easily and quickly identify a desired location within a forest from a large amount of measurement data, and is an invention based on an idea that has not been seen before.

[0012] The planar position identification method of the present invention is a method for identifying the planar position of a "point of interest" set within a forest, and includes a target reflector installation process, a measurement process, a ground surface setting process, and a point of interest extraction process. In the target reflector installation process, a "target reflector" is installed at the point of interest at a predetermined planned height. In the measurement process, laser measurements are performed on the target area including the target reflector. In the ground surface setting process, a "ground surface model" of the target area is set based on the results obtained in the measurement process. In the point of interest extraction process, measurement points located around the "planned surface (a surface above the ground surface model by the planned height)" are extracted as "specific measurement points" from the three-dimensional measurement points obtained in the measurement process. The planned height is set as the height from the ground surface. The planar position of the point of interest can then be identified based on the plan coordinates of the specific measurement points.

[0013] The planar position specifying method of the present invention may further include a planned height setting step of setting a planned height according to the height of surrounding features. In this case, in the target reflector installation step, a target reflector is installed so as to achieve the planned height set in the planned height setting step. Furthermore, in the target reflector installation step, a plurality of divided regions may be set in the target region, and different planned heights may be set for each divided region.

[0014] The plane position identification method of the present invention can also be a method in which a support post is installed at the boundary point as the point of interest and a target reflector is installed on the top end of the support post. In this case, the support post from which the target reflector has been removed can be used as a boundary post. [Effects of the Invention]

[0015] The plane position specifying method of the present invention has the following effects. (1) By using a flat plate installed at a predetermined height, it is possible to easily and quickly identify a desired location within a forest from a large amount of measurement data. (2) It can be used to identify the location of boundary posts within forests, which means that boundaries can be clarified before forest owners age or become absentee villages. (3) If a target reflector is attached to a support pile installed at a boundary point, the target reflector can be removed after the surveying work and used as a boundary pile. [Brief explanation of the drawings]

[0016] [Figure 1] A model diagram showing the process of installing a target reflector at a target point in advance and then performing airborne laser measurement using an aircraft. [Figure 2] 1 is a flowchart showing the flow of main steps of a plane position specifying method according to the present invention. [Figure 3] FIG. 2 is a front view showing a schematic diagram of a target reflector attached to a support pile. [Figure 4] FIG. 2 is a front view schematically showing a target reflector attached to a surveying tripod. [Figure 5] FIG. 10 is a photograph showing a sheet-shaped target reflector attached to a reinforcing plate. [Figure 6] A model diagram showing a ground surface model and a line located above the ground surface model by the planned height. DETAILED DESCRIPTION OF THE INVENTION

[0017] An example of an embodiment of the planar position specifying method of the present invention will be described with reference to the drawings. One technical feature of the planar position specifying method of the present invention is that it performs laser measurement on an area to be measured (hereinafter referred to as the "target area") and extracts a measurement point (hereinafter referred to as the "specific measurement point") related to a position set within the forest (hereinafter referred to as the "point of interest") from among the multiple measurement points obtained as a result. Because the measurement points obtained by laser measurement have three-dimensional coordinates, the planar position of the point of interest can be specified based on the planar coordinates of the specific measurement point.

[0018] The laser measurement in the present invention can be an aerial laser measurement using a flying object SQ such as a drone or an aircraft, as shown in Figure 1. Before performing the laser measurement, a target sign (hereinafter referred to as "target reflector 101") is installed at the point of interest. At this time, the target reflector 101 is installed so as to be located at a predetermined height from the ground (hereinafter referred to as "planned height"). It is desirable to select a material for the target reflector 101 that strongly reflects the laser used in the laser measurement.

[0019] The planar position specifying method of the present invention will be described in detail below with reference to FIG. 2. FIG. 2 is a flow chart showing the flow of the main steps of the planar position specifying method of the present invention. To specify the planar position of a point of interest using the planar position specifying method of the present invention, as shown in this figure, first, one or more points of interest (three locations in FIG. 1) are set within the forest (Step 10 in FIG. 2). For example, a point of interest can be a "boundary point" set by on-site witnesses. Of course, the planar position specifying method of the present invention can set various positions within the forest as points of interest, not just boundary points.

[0020] Meanwhile, the planned height of the target reflector 101 is set in advance (Step 20 in FIG. 2). This planned height should be set in accordance with the features such as trees and herbs around the point of interest (hereinafter referred to as "surrounding features"). More specifically, the planned height is set so that it is clearly different in height from the height of the surrounding features. For example, if the height of the surrounding features is approximately 50 cm, the planned height is set to 1 m. Therefore, when multiple points of interest are set within the target region, multiple areas (hereinafter referred to as "divided regions") can be set within the target region depending on the conditions of the surrounding features, and a different planned height can be set for each divided region.

[0021] Once the focus point and the planned height are set, the target reflector 101 is installed at the focus point so as to achieve the planned height (Step 30 in FIG. 2). To install the target reflector 101 so as to achieve the planned height, for example, a support pile 102 can be used, as shown in FIG. 3. The support pile 102 is installed at the focus point, and the target reflector 101 is attached to the upper end of this support pile 102. Of course, the support pile 102 to which the target reflector 101 has been previously attached can also be installed at the focus point. In this case, it is preferable if the support pile 102 is marked with a scale, so that the support pile 102 can be installed while checking the planned height. It is advisable to determine in advance the position of the support pile 102 on the target reflector 101, for example, to make it the center (centroid) of the target reflector 101.

[0022] Also, instead of the support stake 102, a tripod 103 can be used as shown in Figure 4. This tripod 103 is used to install surveying equipment such as a transit, level, or total station, and in this case too, it is installed so that the center of the target reflector 101 coincides with the planar position of the point of interest, and so that the target reflector 101 is located at the planned height. Alternatively, the support stake 102 can be installed at the point of interest by using, for example, a tree branch, without using any special tools such as the support stake 102 or tripod 103. Note that if the support stake 102 is installed at a boundary point as the point of interest, it can be used as a "boundary stake" by removing the target reflector 101 after the series of operations.

[0023] The target reflector 101 can be a thin plate-like member, and can have various shapes such as a square or circle in a plan view. As described above, it is preferable to select a material for the target reflector 101 that is highly reflective to the laser used for laser measurement. The target reflector 101 can also be formed in a sheet shape as shown in FIG. 5. In this case, it is preferable to use the target reflector 101 after attaching it to a reinforcing plate 104, and to form the target reflector 101 from a "reflective sheet" that is highly reflective to the laser used for laser measurement.

[0024] Once the target reflector 101 is placed at the point of interest, laser measurement is performed using the flying object SQ to obtain measurement points in the target area including the point of interest (Step 40 in Fig. 2). Once the measurement points in the target area are obtained by laser measurement, a spatial model (hereinafter referred to as the "ground surface model") representing the shape of the ground surface is set (Step 50 in Fig. 2), as shown in Fig. 6. Note that various conventional techniques, including TIN (Triangulated Irregular Network), can be used to set the ground surface model.

[0025] Once the ground surface model is set, "specific measurement points" are extracted based on a surface (hereinafter referred to as the "plan surface") located above the ground surface model by the planned height, as shown by the dashed line in Figure 6 (Step 60 in Figure 2). Specifically, a "buffer zone" is set by expanding the plan surface by a predetermined width vertically, and measurement points within the buffer zone are extracted as specific measurement points. Then, based on the plan coordinates (X, Y) of the extracted specific measurement points, the plan coordinates of the target point are calculated (Step 70 in Figure 2). If two or more specific measurement points are extracted as a group within a predetermined range (e.g., the area of ​​the target reflector 101), the plan coordinates of the multiple specific measurement points can be statistically processed, such as by calculating their average or median, and set as the plan coordinates of the target point. On the other hand, if only one specific measurement point is independently extracted within the predetermined range, the plan coordinates of the specific measurement point are directly set as the plan coordinates of the target point. [Industrial Applicability]

[0026] The planar position specifying method of the present invention can be used to specify various positions within a forest, and is particularly suitable for boundary surveying in "clarifying forest boundaries." The present invention can clarify boundaries before forest owners age and become absentee villages, which can be expected to revitalize Japan's forestry industry. Considering this, the present invention can be said to be an invention that can be expected to not only be used industrially but also to make a significant contribution to society. [Explanation of symbols]

[0027] 101 Target reflector 102 Support pile 103 Tripod 104 Reinforcement plate SQ Aircraft

Claims

1. A method for identifying a planar position of a point of interest set in a forest, comprising: a target reflector installation step of installing a target reflector at the point of interest so as to have a predetermined planned height; a measurement step of performing laser measurement on a target area including the target reflector; a ground surface setting step of setting a ground surface model of the target area based on the results obtained in the measurement step; and a focus point extraction step of extracting, from the three-dimensional measurement points obtained in the measurement step, measurement points located around a surface above the ground surface model by the planned height as specific measurement points, The planned height is set as a height from the ground surface, The planar position of the point of interest can be identified based on the planar coordinates of the specific measurement point. A plane position specifying method characterized by:

2. The method further includes a planned height setting step of setting the planned height according to the height of surrounding features, In the target reflector installation step, the target reflector is installed so as to have the planned height set in the planned height setting step.

2. The method of claim 1, wherein the plane position is determined by the plane position determining method.

3. In the planned height setting step, a plurality of divided regions are set in the target region, and different planned heights are set for the respective divided regions.

3. The method for specifying a plane position according to claim 2.

4. In the target reflector installation step, a support pile is installed at the boundary point that is the point of interest, and the target reflector is installed at the upper end of the support pile. The support pile from which the target reflector has been removed can be used as a boundary pile.

2. The method of claim 1, wherein the plane position is determined by the plane position determining method.

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