JP6910511B2 - Laser measurement method, laser measurement sign, and coordinate calculation program - Google Patents

Description

The present invention is a technique relating to laser measurement, and more specifically, a laser measurement method for imparting position coordinates to a group of measurement points based on a reference point and an azimuth point whose position coordinates are known, a marker for laser measurement, and the like. And the coordinate calculation program.

In the past, when measuring over a wide area to create topographic maps, it was common to use aerial photographs taken from aircraft, but nowadays, aerial laser measurements are also widely used. Furthermore, ground-based laser measurement, in which a laser measuring instrument (hereinafter referred to as "laser scanner") is installed on the ground for measurement, is becoming widespread.

In aerial laser measurement, an aircraft flies over the terrain to be measured and receives the reflected signal of the laser pulse applied to the terrain for measurement. Since an aircraft is usually equipped with a positioning meter such as GPS (Global Positioning System) and an inertial measurement unit such as IMU (Inertial Measurement Unit), the laser pulse irradiation position (x, y, z) and irradiation posture (x, y, z) and irradiation posture ( ω, φ, κ) can be grasped, and as a result, the three-dimensional coordinates of the measurement point (the point where the laser pulse is reflected) can be obtained from the time difference between the irradiation time and the reception time.

On the other hand, in ground-based laser measurement, as with the total station, which has been the mainstream of ground measurement, a laser scanner is installed in a horizontal position on the existing point, and the reflected signal of the laser pulse emitted to the measurement target is received for measurement. do. At this time, since the irradiation is performed while changing the irradiation direction in the vertical plane (that is, shaking the head) and rotating horizontally (rotating around the vertical axis), all the features (measurement targets) around the installation of the laser scanner are once. Can be measured. Further, since it is possible to measure up to a place where the laser pulse can reach and reflect, the measurement range is extremely wide with a radius of about 1 km. In addition, the scan rate of a general laser scanner is 10,000 to 50,000 points per second, and it is possible to acquire a high-density feature measurement point cloud.

Ground-based laser measurement having many features like this tends to be used in various places. For example, in Patent Document 1, ground-based laser measurement is used to remotely monitor a slope where there is a risk of rockfall or debris flow. Proposing technology.

Japanese Unexamined Patent Publication No. 2012-83237

By the way, unlike aerial laser measurement, ground-based laser measurement does not use an inertial measurement unit such as IMU in most cases. This is because the laser scanner can be fixedly installed in a horizontal position, and the irradiation direction can be calculated mechanically. However, although the vertical angle of irradiation (that is, the elevation angle) can be calculated, the direction of irradiation (so to speak, the absolute horizontal angle with respect to the north) cannot be calculated unless some information is given. In other words, of the three-dimensional coordinate axes consisting of the X-axis, the Y-axis, and the Z-axis, the Z-axis can be specified because the horizontal plane can be grasped, but the direction of the X-axis-Y-axis in the horizontal plane cannot be specified.

Therefore, conventionally, the installation position of the laser scanner is acquired in advance, and the orientation of the X-axis-Y-axis is specified by using a reference point as a mark. Specifically, a reference point that can be automatically recognized by laser measurement is set in advance, and this reference point is automatically extracted from the measurement point group obtained by laser measurement. Of course, the position coordinates of the reference points are measured in advance, and the Helmart transformation is performed using the known coordinates of the three or more reference points and the known coordinates of the laser scanner position to specify the horizontal plane coordinate system (X-axis-Y-axis). Is. Note that FIG. 15 is a model diagram showing an example of a reference point that can be automatically recognized by laser measurement. FIG. 15A shows a checkerboard-patterned reference point, and FIG. 15B shows a spherical reference point having a known radius R. The checkered point is based on the fact that the reflection intensity is extremely different between black and white, and the spherical point is based on the fact that a spherical surface, which is a special shape, can be recognized if the radius is known. ..

However, in order to use such a special reference point, it is costly to manufacture and maintain it, and it is necessary to install and survey the reference point, and this time and effort has significantly increased the measurement cost. In particular, regarding the installation of gauge points, it was necessary to consider the selection of installation location and fixing method for each measurement site, which had a great impact on the measurement cost including the preliminary field survey.

On the other hand, the point cloud acquired by laser measurement may be modeled in three dimensions in order to reproduce the shape of each feature. However, as described above, the scan rate of the laser scanner is extremely high, so that a large number of measurement points can be acquired. That is, it is not easy to create a three-dimensional model of a feature from this huge number of measurement points, and under the condition that the measurement points mainly have information on three-dimensional coordinates. The current situation is that it takes a considerable amount of time.

An object of the present invention is to solve a conventional problem, that is, to provide laser measurement in which measurement cost is reduced as compared with the conventional one by efficiently measuring, and specifically, a coordinate point is set. It is an object of the present invention to provide a laser measurement method capable of measuring without performing a procedure, and a coordinate calculation program capable of obtaining the position coordinates of a group of measurement points obtained by this method.

In the present invention, an azimuth point whose position coordinates are known is set, various filtering processes are performed from a large number of measurement point groups to extract a "reference point cloud", and "provisional azimuth point coordinates" are extracted from this reference point cloud. This is an invention made based on an idea that has never existed before, focusing on the point that the coordinates are converted after calculating.

The laser measurement method of the present invention is a method of obtaining the position coordinates of a group of measurement points by laser measurement based on a reference point and an azimuth point whose position coordinates are known, and is a machine installation step, a measurement step, and a provisional coordinate calculation step. , A reference point cloud extraction step, a provisional azimuth point coordinate calculation step, and a definite coordinate calculation step are provided. Of these, in the machine installation process, a laser measuring machine is installed at a reference point, and in the measuring process, a measurement point group of a measurement object is obtained by sweeping a laser from the laser measuring machine. In the provisional coordinate calculation step, a provisional coordinate system based on the reference point is set, and provisional coordinates are given to the measurement point cloud based on this provisional coordinate system. In the reference point group extraction step, a reference point group for obtaining an azimuth point is extracted from the measurement point group, and in the provisional azimuth point coordinate calculation step, the position coordinates of the azimuth point in the provisional coordinate system are obtained based on the reference point group. Calculated as provisional azimuth point coordinates. Then, in the definite coordinate calculation step, a definite coordinate system obtained by converting the provisional coordinate system based on the position coordinates of the reference point, the position coordinates of the azimuth point, and the provisional azimuth point coordinates is obtained, and the provisional coordinate system assigned to the measurement point group is obtained. The coordinates are converted to a definite coordinate system. In the reference point group extraction process, "specific height difference filtering" is used to thin out the measurement point group by comparing the relative height difference between the reference point and the azimuth point, and "measurement point group is thinned out by comparing the distance between the reference point and the azimuth point". The reference point group is extracted by "distance filtering" and "direction filtering" in which the measurement point group is thinned out by comparing the reference point and the direction obtained by the direction point.

The laser measurement method of the present invention may be a method further including a direction measurement step of measuring the direction with respect to the reference point. In this case, in the provisional coordinate calculation step, the provisional coordinate system is set based on the orientation and the reference point measured in the orientation measurement step.

The laser measurement method of the present invention can also be a method using an azimuth point provided on a baseline (hereinafter referred to as "observation line") formed by two substantially vertical (including vertical) surfaces. ..

The laser measurement method of the present invention may be a method further including a step of placing a sign (mark setting step). This sign has a bottom plate and two side plates (which serve as a reflecting surface for the laser), and two side plates arranged substantially perpendicular to (including perpendicular to) the bottom plate are fixed to the bottom plate. Is. Further, the two side plates are arranged substantially perpendicular to each other (including vertical), and a baseline (observation line) is formed by these two side plates. In the sign installation step, the sign is installed in a posture in which the two side plates are substantially vertical (including the vertical), and the directional point is provided on the observation line.

The laser measurement method of the present invention may be a method further including a linear setting step. In this straight line setting step, the reference point group is divided into two sets of point groups, and a straight line is set based on each set of point groups. In this case, in the provisional directional point coordinate calculation step, the intersection of the two straight lines set in the straight line setting step is calculated as the provisional directional point coordinates.

The laser measurement marker of the present invention has a bottom plate and two side plates (which serve as a reflection surface of the laser). The two side plates are arranged substantially perpendicular to (including perpendicular to) the bottom plate and are fixed to the bottom plate. Further, the two side plates are arranged substantially perpendicular to each other (including vertical), and a baseline (observation line) is formed by these two side plates.

The laser measurement label of the present invention may also have a small hole provided in the bottom plate. The center of this small hole is located on the extension of the observation line.

The coordinate calculation program of the present invention is a program for obtaining the position coordinates of a measurement point group by laser measurement based on a reference point and an azimuth point whose position coordinates are known, and is a known point coordinate reading process and a measuring point group reading process. , The provisional coordinate calculation process, the provisional azimuth point coordinate calculation process, and the definite coordinate calculation process are provided. Of these, the known point coordinate reading process is a process for reading the position coordinates of the reference point and the azimuth point, and the measurement point cloud reading process is a measurement object obtained by laser sweeping of a laser measuring machine installed at the reference point. This is a process of reading out a group of measurement points. The provisional coordinate calculation process is a process of setting a provisional coordinate system based on a reference point and assigning provisional coordinates to a group of measurement points based on this provisional coordinate system. The reference point group extraction process is a process of extracting a reference point group for obtaining an azimuth point from a measurement point group, and a provisional azimuth point coordinate calculation process is a process of extracting an azimuth point in a provisional coordinate system based on the reference point group. This is a process of calculating the position coordinates of the above as provisional azimuth point coordinates. Then, in the definite coordinate calculation process, the provisional coordinate system is converted to obtain the definite coordinate system based on the position coordinates of the reference point, the position coordinates of the azimuth point, and the provisional azimuth point coordinates, and the provisional coordinate system given to the measurement point group is obtained. This is a process of converting coordinates into a definite coordinate system. In the reference point group extraction process, the measurement point group is thinned out by comparing the relative height difference between the reference point and the azimuth point, and the measurement point group is thinned out by comparing the distance between the reference point and the azimuth point. The reference point group is extracted by "distance filtering" and "direction filtering" in which the measurement point group is thinned out by comparing the reference point and the direction obtained by the direction point.

The laser measurement method, the laser measurement marker, and the coordinate calculation program of the present invention have the following effects.
(1) Since no special checkered point such as a checkered point or a spherical point, which has been used in the past, is required, the cost for manufacturing, maintenance, and installation can be significantly reduced.
(2) Since the directional point required for the present invention can be set on a straight line where two vertical faces intersect, various existing objects can be used as the directional point. As a result, measurement can be easily performed without making special preparations.

The flow chart which shows the flow of the main processing of the measurement stage in this invention. A model diagram showing directional points set at the corners of a building. (A) is a plan view of a sign whose two surfaces are orthogonal to each other in a corner shape, (b) is a front view of this sign, and (c) is a perspective view of this sign. (A) is a side view showing a sign installed on a tripod, and (b) is a plan view of the sign installed on a tripod as viewed from above. A perspective view of the sign installed on the tripod as viewed from the front. (A) is a cross-sectional view of a sign installed on a tripod, and (b) is a plan view of the sign installed on a tripod as viewed from above. A plan view showing a group of reference points scattered near two straight lines. A model diagram showing calculated azimuth points and conversion azimuth points arranged in XY of a provisional coordinate system having a reference point (or a laser scanner measurement center) as a coordinate origin. The flow chart which shows the main processing flow of the modeling stage in this invention. A model diagram showing a group of measurement points arranged in a definite coordinate system consisting of three axes and a constituent cross section. A model diagram showing a group of segment points arranged in a definite coordinate system consisting of three axes and a constituent cross section. A model diagram showing line data generated based on a segment point cloud. (A) is a model diagram showing line data generated based on the Z-axis structural cross section, and (b) is a model diagram showing a three-dimensional model created from the line data. (A) is a model diagram showing line data generated based on the Y-axis structural cross section, and (b) is a model diagram showing a three-dimensional model created from the line data. (A) is a model diagram showing a checkered pattern point that can be automatically recognized by laser measurement, and (b) is a model diagram showing a spherical point with a known radius that can be automatically recognized by laser measurement.

An example of the laser measurement method, the laser measurement sign, and the embodiment of the coordinate calculation program of the present invention will be described with reference to the drawings. The invention of the present application can be roughly divided into two stages. One is the "measurement stage" where measurements are taken on-site and coordinates are calculated based on the data, and the other is the "modeling stage" where a three-dimensional model of the feature is created based on the coordinates obtained in the measurement stage. ". Hereinafter, the measurement stage and the modeling stage will be described step by step.

1. 1. Measurement stage FIG. 1 is a flow chart showing the main processing flow of the measurement stage in the present invention. The processing to be performed is shown in the center column, and the input information required for the processing is shown in the left column on the right. The columns show the output information that results from that process. The measurement stage of the present invention will be described with reference to this flow chart.

(Installation of known points)
First, a reference point is set (Step 10), and an azimuth point is set (Step 20). The reference point is a point where the laser scanner is installed, and is installed at a convenient point for laser measurement of the target object. On the other hand, the directional point is for determining the coordinate system as described later, and can be newly installed for the present invention, or can be set by using an existing structure or the like. It is necessary to know the position coordinates of the reference point and the azimuth point, respectively, and the reference point and the azimuth point are surveyed in advance by a conventional method such as a total station or a satellite observation system (GNSS: Global Navigation Satellite System). The position coordinates of the reference point and the azimuth point obtained here are three-dimensional coordinates consisting of the plane coordinate value and the height, and the plane coordinate value is the latitude and longitude or the Cartesian coordinate system (X coordinate, Y coordinate). It is represented, and the height means the distance in the vertical direction from a predetermined reference horizontal plane such as an altitude.

FIG. 2 is a model diagram showing directional points set at the corners of the building. As shown in this figure, the directional point can be set by using the existing structure. In particular, it is preferable to set the directional point on a line segment (that is, the vertical line at the corner where the two surfaces intersect) formed by two substantially orthogonal (including orthogonal) surfaces (wall surface in FIG. 2). Here, this line segment (a part of a straight line) is referred to as an "observation line" for convenience. In FIG. 2, the directional point is set at the uppermost end of the observation line, but of course, it may be set at the lowermost end or at the middle portion.

Further, the directional point can be set on the observation line of the two-sided intersection having the inside corner, as well as the two-sided intersection having the outside corner as shown in FIG. 3A and 3B are signs 10 having two surfaces orthogonal to each other in a corner shape, where FIG. 3A is a plan view, FIG. 3B is a front view, and FIG. 3C is a perspective view. The sign 10 shown in this figure is installed at an appropriate position, and the directional point is set on the observation line of the two-sided intersection.

Further, the directional point can be set on the sign 10 (hereinafter, particularly referred to as "three-sided sign 10S") that can be installed on the tripod 20. 4A and 4B are views showing a three-sided sign 10S installed on the tripod 20, where FIG. 4A is a side view thereof and FIG. 4B is a plan view seen from above. As shown in this figure, the three-sided label 10S can be installed on the tripod 20 by using a leveling table 30 provided with a circular bubble tube and a leveling screw.

Here, the structure of the three-sided sign 10S will be described in detail with reference to FIGS. 5 and 6. 5A and 5B are perspective views of the three-sided sign 10S as viewed from the front, FIG. 6A is a cross-sectional view of the three-sided sign 10S, and FIG. 6B is a plan view of the three-sided sign 10S as viewed from above. As shown in FIG. 5, the three-sided sign 10S has a structure in which two side plates 12S are fixed on the bottom plate 11S. Specifically, as shown in FIG. 6A, the two side plates 12S are arranged in a substantially vertical (including vertical) posture with respect to the bottom plate 11S, and further, as shown in FIG. 6B, the two side plates 12S are arranged. They are arranged so as to be substantially perpendicular to each other (including vertical), and are fixed to the bottom plate 11S by welding or the like. The bottom plate 11S shown in the drawing has an L-shape that matches the arrangement of the two side plates 12S, but the shape is not limited to this and can be designed in various shapes such as a rectangle and a circle.

Further, as can be seen from FIG. 5, an observation line is formed on the three-sided sign 10S by the two side plates 12S. More specifically, the two side plates 12S are in contact (intersection), and a boundary line (line segment), that is, an observation line is formed at the contact portion. Further, the bottom plate 11S is provided with a small hole 13S for attaching to the leveling table 30, and a line extending the observation line (arrow shown in FIG. 5) penetrates the center point of the small hole 13S. The two side plates 12S may be a combination of two independent plates, or one plate may be bent. Further, the shape of the small hole 13S can be a circle shown in FIG. 5, or an arbitrary shape such as a hexagon or an ellipse can be selected.

The three-sided sign 10S may be provided with the notch portion 14S shown in FIGS. 5 and 6A. When the three-sided sign 10S is attached to the leveling table 30, it is the cutout portion 14S that provides a space that can accommodate a part (screws, nuts, etc.) of the leveling table 30. Therefore, the notch portion 14S may be provided directly above the small hole 13S.

Next, the setting of the directional point (Step 20) when the three-sided sign 10S is used will be described in detail with reference to FIG. First, the leveling table 30 is set at a point whose three-dimensional coordinates are known (here, a surveying stud fixed on the ground) while maintaining a horizontal posture using a tripod 20 as in the transit or total station. Then, the three-sided sign 10S is attached to the leveling table 30 by using a part (for example, a screw) of the leveling table 30 inserted through the small hole 13S (mark installation step). At this time, it is advisable to attach the three-sided marker 10S so that the center point of the small hole 13S and the plane position of the surveying stud (known coordinate point) coincide with each other. In other words, the three-sided marker 10S is installed so that the surveying stud is located vertically below the center point of the small hole 13S. Further, the three-sided sign 10S is installed in a posture in which the bottom plate 11S is substantially horizontal (including horizontal), that is, a posture in which the two side plates 12S are substantially vertical (including vertical).

When the three-sided sign 10S can be installed, an azimuth point is set at an arbitrary position (the uppermost end in FIG. 4A) on the observation line formed on the three-sided sign 10S, and three-dimensional coordinates are given to this directional point. As described above, and as can be seen from FIG. 4 (b) (in this figure, the bottom plate 11S is shown by a broken line for convenience), the observation line of the three-sided sign 10S attached to the leveling table 30 (the plane position thereof). ) Coincides with the center point of the small hole 13S. Therefore, the plane coordinates (X coordinate and Y coordinate, or latitude and longitude) of the three-dimensional coordinates of the azimuth point can be obtained from the coordinates of the survey stud. On the other hand, the height of the three-dimensional coordinates can be obtained by measuring the height H from the surveying stud to the directional point and adding this value to the coordinates of the surveying stud, as shown in FIG. 4A. can.

Up to this point, the case where the three-dimensional marker 10S is installed at the position of the surveying stud, which is a known coordinate point, has been described, but the tripod 20 and the leveling table 30 are used without using the known coordinate point (surveying stud, etc.). The three-sided marker 10S can be installed at an arbitrary position, and then the orientation point can be directly measured and three-dimensional coordinates can be given. However, also in this case, it is preferable to install the three-sided sign 10S in a posture in which the two side plates 12S are substantially vertical (including vertical).

(measurement)
When the preparations such as setting the reference point (Step 10) and setting the directional point (Step 20) are completed, the actual measurement is performed. First, as with the transit and total stations, a laser scanner for ground-based laser measurement (hereinafter referred to as "ground-based laser scanner") is installed at a reference point while maintaining a horizontal posture using a tripod (Step 30). At this time, the height from the reference point to the measurement center of the laser scanner (hereinafter referred to as "mechanical height") is measured. Then, the laser measurement is started by the ground-based laser scanner (Step 40). As described above, the ground-based laser scanner irradiates the laser pulse while rotating in the vertical plane (that is, around the horizontal axis) to change the irradiation direction and also rotating in the horizontal plane (that is, around the vertical axis). When the three-sided marker 10S is irradiated with a laser pulse, the two side plates 12S mainly serve as the reflecting surface of the laser.

On the other hand, the direction around the reference point (for example, north) is measured using a compass or the like (Step 50). The direction at this time does not need to be measured accurately, and it is sufficient if the approximate direction can be grasped. Therefore, it is also possible to use the approximate orientation obtained by a sensor (electronic compass or the like) built in the ground-based laser scanner.

(Temporary coordinate system and provisional coordinates)
Once the orientation centered on the reference point can be grasped, a three-dimensional coordinate system based on the reference point is set (Step 60). For example, a coordinate system is set in which the reference point is the coordinate origin and the north-south direction, the east-west direction, and the vertical direction are the three axes. Alternatively, a coordinate system may be set with the measurement center of the laser scanner as the coordinate origin. This provisional coordinate system setting can also be processed by the computer built in the ground-based laser scanner. Since the obtained orientation is an approximate value, the coordinate system set here is referred to as a "provisional coordinate system".

The ground-based laser scanner that receives the reflected signal of the laser pulse calculates the position coordinates of the irradiation point (reflection point) of the laser pulse based on the set provisional coordinate system (Step 70). Since the position coordinates obtained here are on the provisional coordinate system, they are referred to as "provisional coordinates".

The processes up to this point (Steps 10 to Step 70) are those in the field where laser measurement is performed, and the processes described here can be performed indoors such as in an office because a computer is mainly used. Of course, it may continue to be processed locally.

(Filtering and reference point cloud)
In order to calculate the directional point based on the provisional coordinates of the measurement point group, first, the reference point group is extracted (Step 80). If the azimuth points are obtained by using all the many measurement points obtained by the laser measurement, a considerable calculation time is required. Therefore, among a large number of measurement points, those that are useful for calculating the directional points, that is, the measurement points around the directional points are selected as a "reference point group", and the directional points are obtained from a limited number of measurement points to obtain the calculation time. This is to shorten the time.

Extracting the reference point group from the measurement point group is, in other words, sifting (thinning out) unnecessary measurement points from the measurement point group, and here, this process is referred to as filtering. In the present invention, three types of filtering are prepared: relative height difference filtering, distance filtering, and directional filtering. Each will be described in detail below.

The relative height difference filtering is a process of extracting only the measurement points whose provisional coordinates are at a predetermined height. Since the coordinates of the reference point and the directional point are known and the mechanical height is also obtained, the height of the directional point (Z-axis coordinate) in the provisional coordinate system can be calculated. For example, when the measurement center of the laser scanner is set as the coordinate origin of the provisional coordinate system, the value obtained by subtracting the mechanical height from the relative height difference between the reference point and the orientation point obtained based on the known coordinates is the value of the orientation point in the provisional coordinate system. It becomes the height. Therefore, it is possible to extract measurement points around the height of the azimuth point in the provisional coordinate system, for example, measurement points within the altitude threshold (between the highest altitude and the lowest altitude).

Distance filtering is a process of extracting only measurement points at a predetermined distance from a reference point. Since the coordinates of the reference point and the directional point are known, the distance between the reference point and the directional point can be obtained. Therefore, it is possible to extract a measurement point at a predetermined distance from a reference point (for example, a coordinate origin) in the provisional coordinate system. This predetermined distance may be set with a certain range (buffer) such as determining the minimum value and the maximum value.

Direction filtering is a process of extracting only measurement points in a predetermined direction from a reference point. Since the coordinates of the reference point and the directional point are known, the direction (vector) connecting the reference point and the directional point can be obtained. Therefore, it is possible to extract a measurement point in a predetermined direction from a reference point (for example, a coordinate origin) in the provisional coordinate system. This predetermined direction may also be set with a certain range (buffer) such as determining the minimum value and the maximum value.

Any order may be selected when performing the three types of filtering, but the next filtering process is performed on the measurement points left by the filtering, and the measurement points are gradually narrowed down. For example, the relative height difference filtering is performed on the measurement point group to narrow down the measurement points, the distance filtering is performed on the narrowed down measurement points, and the direction filtering is further performed on the measurement points extracted here. The reference point cloud is extracted.

(Calculation of provisional directional point coordinates)
The reference point groups extracted through the three types of filtering are generally scattered on the plane because they have undergone the relative height difference filtering. In particular, when the azimuth point is set on the observation line (straight line intersecting two surfaces), the measurement point group (that is, the reference point group) is reflected on one of the two surfaces (two side plates 12S in the case of the three-sided marker 10S). Therefore, the reference point groups are scattered around the two straight lines. FIG. 7 is a plan view showing a group of reference points scattered around two straight lines. The intersection of these two straight lines is considered to be the position of the directional point.

Therefore, these two straight lines are set (Step 90), and the coordinates of the intersection are obtained as the directional points (Step 100). Specifically, the reference point group is first divided into two groups, then the regression line is obtained in each group, and the reference point group is calculated as a linear expression in the provisional coordinate system. If the two straight lines on the provisional coordinate system can be specified, the coordinates of the intersection of these two straight lines are calculated and obtained as the coordinates of the azimuth points on the provisional coordinate system (hereinafter, referred to as "provisional azimuth point coordinates"). Since the two straight lines set here are straight lines in a three-dimensional space, they do not always intersect. Therefore, the position where the two straight lines are closest to each other should be regarded as the intersection. Alternatively, the regression line may be set on a predetermined plane (for example, a horizontal plane).

(Definite coordinate system and definite coordinates)
By the way, the azimuth point is actually a known point in the absolute coordinate system (for example, the world geodetic system), and the azimuth point can be arranged in the provisional coordinate system because of the relationship with the reference point which is also the known point in the absolute coordinate system. can. That is, in the provisional coordinate system, the directional point obtained from the intersection of the two straight lines described above (hereinafter, referred to as "calculated directional point" for convenience) and the directional point arranged from the relationship with the reference point (hereinafter, "converted directional point" for convenience). The directional point can be represented by two types of.). Originally, the calculated directional point and the converted directional point should match, but the two may not match because the directional values are approximate values or due to a measurement error.

FIG. 8 is a model diagram showing calculated directional points and conversion directional points arranged in XY of the provisional coordinate system having the reference point (or the measurement center of the laser scanner) as the coordinate origin. The direction (vector) from the reference point to the directional point should be a vector from the reference point to the conversion directional point, but the vector from the reference point to the calculated directional point is in a different direction. That is, the rotation angle φ caused by the difference between the two directions is the deviation between the correct coordinate system and the provisional coordinate system. In other words, when the provisional coordinate system is rotated by the rotation angle φ, the correct coordinate system is obtained. Therefore, the provisional coordinate system is rotationally transformed to obtain the correct coordinate system (hereinafter referred to as "fixed coordinate system") (Step110), and the coordinates of the provisional coordinates of the measurement point group obtained by laser measurement based on the fixed coordinates. The conversion is performed, and the converted coordinates are acquired as "determined coordinates" (Step 120).

As described above, in the ground-based laser measurement, the Z-axis can be specified because the horizontal plane can be grasped among the three-dimensional coordinate axes consisting of the X-axis-Y-axis-Z-axis, but the direction of the X-axis-Y-axis in the horizontal plane is It can not be identified. Therefore, the transformation of the coordinate system performed here rotates only the two axes (for example, the X-axis and the Y-axis) arranged on the horizontal plane. That is, the rotation angle φ obtained in FIG. 8 uses only the X coordinate and the Y coordinate, and does not use the Z coordinate.

Further, as can be seen from FIG. 8, the calculated directional point and the converted directional point may differ not only in the direction from the reference point but also in the distance from the reference point. In other words, when transforming the coordinate system, not only the rotational transformation of the coordinate system but also the transformation method of transforming the plane such as the Helmart transformation and the affine transformation can be considered. Of course, such a conversion method can be used, but due to the nature of ground-based laser measurement, it is better to use a simple rotational conversion that does not deform the plane.

2. Modeling stage FIG. 9 is a flow chart showing the main processing flow of the modeling stage in the present invention. The processing to be performed is shown in the center column, and the input information required for the processing is shown in the left column. , The right column shows the output information generated from the processing. The modeling stage of the present invention will be described with reference to this flow chart. Each process in the modeling stage is executed using a computer, and the process described here is specifically a function of configuring a program to be executed by the computer.

(Setting of constituent cross section)
First, the measurement point cloud stored here and its definite coordinates are read out from the measurement point cloud storage means (Step 130). As a matter of course, the measurement point cloud read out here can be arranged in a definite coordinate system consisting of three axes. Here, for convenience, the three axes of the definite coordinate system will be described in the case of the X-axis-Y-axis-Z-axis.

One of the features of the present invention is that a "constituent cross section" is set (Step 140) when modeling. FIG. 10 is a model diagram showing a group of measurement points arranged in a definite coordinate system composed of three axes and a constituent cross section. The measurement point group shown in this figure is obtained by laser measurement of an office building as shown in FIG. 2, for example. As shown in FIG. 10, the constituent cross section is a plane orthogonal to the coordinate axis (Z axis in this figure). That is, the structural cross section can be set in three directions. For convenience, the structural cross section orthogonal to the X axis is the "X-axis structural cross section", the structural cross section orthogonal to the Y axis is the "Y-axis structural cross section", and the Z axis. The structural cross section orthogonal to is referred to as a "Z-axis structural cross section".

Two or more constituent cross sections are set for one axis. For example, in FIG. 10, four Z-axis structural cross sections are set. It is preferable to set a plurality of two or more constituent cross sections at regular intervals, but it is also possible to set two or more constituent cross sections at unequal intervals depending on the object to be modeled. Further, in modeling, one type (for example, only the Z-axis structural cross section) can be set, but two types (for example, the Y-axis structural cross section and the Z-axis structural cross section) can be set. It is also possible to set all three types of constituent cross sections.

(Segment point cloud)
After the constituent cross section can be set, the segment point cloud is set next (Step150). FIG. 11 is a model diagram showing a segment point cloud and a constituent cross section arranged in a definite coordinate system composed of three axes. As shown in this figure, the segment point cloud is set by extracting the measurement point cloud arranged in the definite coordinate system around the constituent cross section. Specifically, a segment point cloud is set by extracting measurement points within a threshold distance from the constituent cross section. Therefore, the segment point group is set for each constituent cross section, in other words, the segment point group and the constituent cross section are associated with each other.

(Line data)
When the segment point cloud can be set, line data is generated (Step 160). FIG. 12 is a model diagram showing line data generated based on the segment point cloud. The present invention is characterized in that the outer peripheral line of the measurement object is obtained as "line data", and a three-dimensional shape composed of a plurality of line data is used as a three-dimensional model of the measurement object. The segment point cloud shown in FIG. 11 is not sharp enough to create a cubic model, although the contour of the object to be measured can be assumed to some extent. Therefore, line data based on the segment point cloud is generated.

Line data is data formed by a plurality of line segments arranged on a plane (for example, a constituent cross section), and is generated based on a group of segment points. Therefore, line data is generated for each segment point group, that is, the line data is also associated with the constituent cross sections. Line data can be generated by several methods. For example, any one point in the segment point group is designated as the "starting point", points around it (for example, the closest point) are extracted and connected as "line constituent points", and this is repeated to generate line data. Can be generated. At this time, the direction of connection from the starting point can be determined in advance. Further, the starting point can be specified by an operator operation, or can be automatically specified according to a predetermined rule (for example, the minimum value of the X coordinate).

Further, the line data can be generated after projecting the segment point cloud on the constituent cross section in advance. Specifically, any one of the measurement points projected on the constituent cross section (hereinafter, simply referred to as “projected point”) is designated as the “starting point”, and the points around it are designated as the line constituent points. .. In this case, the projection point selected as the line constituent point may be excluded from the projection point for selecting the next line constituent point. That is, the line constituent points are sequentially reduced, and the selection time of the line constituent points is gradually shortened.

It is also possible to generate line data by estimating a predetermined line from the arrangement shape of the segment point group, instead of the method of generating line data while sequentially connecting from the starting point. In this case, a conversion processing technique such as the Hough transform that has been conventionally used can be adopted. Also in this case, line data can be generated from the arrangement shape of the projection points on which the measurement point group is projected on the constituent cross section.

(3D model)
When the line data can be generated, a three-dimensional model of the measurement target is created. First, a plurality of line data are arranged so as to be overlapped (Step 170), a plurality of outer surfaces are estimated from the outer surface (Step 180), and a three-dimensional model is created based on the outer surfaces (Step 190).

By the way, as described above, the segment point group is set for each constituent cross section, and the line data beam segment point group is generated for each segment point group. That is, line data is generated as many as the number of constituent cross sections. He also stated that all three types of cross sections (that is, for three axes) can be set, and only one type can be set. Therefore, only line data orthogonal to the Z axis may be generated, or line data orthogonal to all three axes (that is, line data in the three axis directions) may be generated. FIG. 13A is a model diagram showing line data generated based on the Z-axis configuration cross section, and FIG. 13B is a model diagram showing a three-dimensional model created from the line data. On the other hand, FIG. 14A is a model diagram showing line data generated based on the Y-axis configuration cross section, and FIG. 14B is a model diagram showing a three-dimensional model created from the line data. be.

As shown in FIGS. 13 (b) and 14 (b), a plurality of line data are arranged at predetermined positions (for example, positions of a constituent cross section), and some "faces" are set by the plurality of line data. A three-dimensional model of the object to be measured is created based on this surface. Of course, as shown in FIGS. 13 and 14, a three-dimensional model can be created with line data consisting of one type of structural cross section, or can be created from line data consisting of two types of structural cross sections. It can also be created from line data consisting of different types of structural cross sections.

The laser measurement method, the laser measurement marker, and the coordinate calculation program of the present invention can be used for ground-based laser measurement for ground measurement and aerial laser measurement from the sky. It can also be used to measure indoor objects as well as outdoor objects.

10 Marker 10S Three-sided sign 11S (Three-sided sign) Bottom plate 12S (Three-sided sign) Side plate 13S (Three-sided sign) Small hole 14S (Three-sided sign) Notch 20 Tripod 30 Leveling table

Claims (2)

A marker for setting the directional point, which is used in a laser measurement method for obtaining the position coordinates of a group of measurement points obtained by performing laser measurement based on a reference point and an azimuth point whose position coordinates are known.
It has a bottom plate and two side plates that serve as a reflecting surface for the laser.
The two side plates are arranged vertically or substantially perpendicular to the bottom plate and fixed to the bottom plate.
Further, a laser measurement marker characterized in that the two side plates are arranged perpendicularly or substantially vertically to each other, and an observation line is formed by the two side plates. A small hole is provided in the bottom plate.
The laser measurement marker according to claim 1, wherein the center of the small hole is on an extension of the observation line.

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