JP6745169B2 - Laser measuring system and laser measuring method - Google Patents

Description

The present invention relates to a laser measuring system using a moving body such as an aircraft, and a laser measuring method in the system.

Conventionally, three-dimensional position coordinates (horizontal coordinates (x, y)) of the footprint of the laser light (the irradiation point or the reflection point of the laser light on the ground) of the laser light reflected from the ground by radiating the laser light from the aircraft to the ground And aerial laser measurement for measuring the coordinate (z) in the height direction. In aviation laser measurement, the round-trip time until the pulsed laser light emitted toward the ground is reflected by the ground surface (including features existing on the ground surface) and returns is measured. Then, the distance from the three-dimensional position and attitude of the aircraft, the round-trip time of the laser light, the rotation angle of the mirror (the irradiation angle of the laser light) to the ground surface or the feature is obtained, and the height of the ground surface or the feature is calculated.

In recent years, an aerial measurement system called Geiger-mode LiDAR, which can detect a single photon using a focal plane array, has been developed. With this system, it is now possible to measure at a high density of at least several hundred times the footprint that could only measure a few points around the square meter when irradiated with laser light from an altitude of about 1,000 m. There is.

By the way, in this aviation laser measurement, strict control is not performed particularly on the accuracy of the coordinates in the horizontal direction. This is because the laser light in a laser measurement system that uses a moving body such as an aircraft is not controlled so as to hit a predetermined position. The laser beam used for aerial laser measurement is generally invisible (for example, near-infrared wavelength) because the position of the footprint of the laser beam is incidental because it is irradiated intermittently and intermittently. Therefore, the position of the footprint cannot be directly specified, and it is based on indirect information such as the three-dimensional position and attitude of the aircraft, the round-trip time of laser light, and the rotation angle of the mirror (irradiation angle of laser light). This is due to reasons such as the fact that it is unavoidable to make an estimation by post hoc analysis.

As a result, in the rules for public surveying work rules established by the Geographical Survey Institute of Japan (all revised on March 31, 2008, partially revised on March 29, 2013), there are only regulations regarding altitude, There are no rules regarding horizontal position.

Although aviation laser measurement is positioned as a surveying technology that directly acquires altitude (terrain), if the horizontal position is not managed, the result can be used as a digital topographic map such as DM (Digital Mapping). When used as an electronic map on the GIS (Geographic Information System), different maps cannot be positionally matched, and the reliability of the information obtained by superimposing the maps fluctuates. In addition, in order to obtain the topographical changes on a steep slope from the difference between the measurement results at different times (for example, before and after the occurrence of a landslide), horizontal position error has a large effect on the result. Management must be done.

Examples of the method for managing the horizontal position include the methods shown in the following (1) to (4) (see Non-Patent Documents 1 to 4 below).

(1) This method pays attention to the outline of a structure such as a building or a place with a clear edge in a gable roof ridge, or is determined from a step chart or a contour map generated from a point cloud of laser light. This is a method of adjusting the horizontal position using the edge so that the laser measurement results measured at the two time points overlap. That is, the method is relative alignment.

(2) This method is a method of evaluating an error in horizontal position by using an edge such as a contour of a building generated from a point group of laser light and comparing it with an existing drawing.

(3) This method is a method that uses edges such as the outline of a building or the like and utility poles, determines the position coordinates by an independent surveying method different from the aviation laser measurement, and evaluates the horizontal position error. This method is adopted in the guideline for evaluating the error in the horizontal position of an aeronautical laser in the United States (see Patent Document 5 below).

(4) In this method, the terrain shape is expressed by contour lines and the like, and the horizontal position is adjusted so that the laser measurement results measured at the two points of time overlap using characteristic points such as curved points of the contour lines. It is a technique. That is, the method is relative alignment.

However, in the place where there is no building and only the natural terrain is present, and there is no feature with a clear edge, the above methods (1) to (3) are not applicable.

Regarding (4), the shape of the contour line depends on the arrangement and the interval of the point cloud of the original data that generates the contour line, while the arrangement and the interval of the point cloud cannot be matched in the laser measurement at two time points. Moreover, it is not possible to obtain many clear feature points everywhere only from contour lines. Further, even if the alignment can be performed from the contour line shape, it is only relative alignment.

By the way, if you can directly grasp where on the ground the laser light hits, that is, the position of the footprint of the laser light, measure the coordinates of that place by another independent method such as GNSS (Global Navigation Satellite System). Then, by using the verification point, the horizontal position accuracy of laser measurement can be verified.

As a method to capture the footprint of the laser light, spread the photodiode on the ground and determine the position and size of the footprint of the laser light that is instantaneously irradiated from the aircraft on the photodiode at the timing of the laser light irradiation. A method of knowing from the fluctuation of the excited voltage can be considered. However, this is an expensive mechanism, and as a means for evaluating the accuracy of the horizontal position in the actual measurement work, it is possible to place a plurality (for example, about 20) at locations (hereinafter, verification points) where the accuracy of the horizontal position is evaluated. Because it is necessary, it is economically unrealizable.

An infrared camera that can detect light in the wavelength range (generally the infrared range) used for laser measurement captures a video of the ground, monitors the footprint occurrence status during the laser measurement time, and records the footprint from the captured video. A method of determining a point and deciding the position of the point is also conceivable. However, the infrared camera is expensive as in the case of the photodiode, and is economically impractical as a means for evaluating the accuracy of the horizontal position in the actual measurement work.

Furthermore, instead of a photodiode or an infrared camera, an artifact that can extract edges and contours is placed on the surface of the earth, the footprint of the laser beam that hits the artifact is determined, and the XYZ measurement values are used in the same way as the previous method. There may be a method of evaluating the horizontal position. However, this requires the preparation of pyramid-shaped artifacts of a considerable size depending on the laser beam footprint spacing (for example, if the footprint spacing is about 50 cm, identify one surface). In order to achieve this, it is necessary to obtain a minimum footprint of 3. Pyramid-shaped artifacts must be constructed with 3 to 4 such planes, and the area and height that occupy space will be large. ), it is not feasible if it is assumed that a plurality of them are placed at the verification points.

In relation to such problems of the existing technology, in Patent Document 1 below, a laser measuring device that irradiates a laser beam and measures the position of a reflecting object by the reflected light, and the laser measuring device irradiates A calibration system is described that includes a calibration device having a marker that reflects laser light, and a computer that performs calculations for calibrating the laser measurement device. The calibration device has at least three markers including a first marker, a second marker, and a third marker, and the at least three markers are arranged in a predetermined relative positional relationship. There is. The laser measurement device measures the position of each of the markers, and the computer calculates the position from the position of the second marker measured by the laser measurement device and the position of the third marker measured by the laser measurement device. A reference position, which is the position of the first marker, is calculated, and a measurement error of the laser measuring device is calculated based on the difference between the position of the first marker measured by the laser measuring device and the reference position. A function of the distance to the reflecting object is generated from the calculated measurement error.

JP, 2013-250110, A

Japan Surveying Technology Association, "Illustrated Laser Measurement", Chapter 5: Data Analysis, <URL:http://www.sokugikyo.or.jp/publication/book/11.html> Geospatial Information Authority of Japan, “Survey research on construction method and utilization of GIS next-generation information infrastructure”, <URL: http://www.gsi.go.jp/GIS/what-gis_gisedai6.html#5> Geospatial Information Authority of Japan, "Research on technology for using aerial laser surveying", <URL:http://www.gsi.go.jp/common/000022304.pdf> Asahi Yoko, "Aerial Laser Survey Quality Evaluation", Photogrammetry and Remote Sensing Vol.41, No.1, 2002, <URL:https://www.jstage.jst.go.jp/article/jsprs1975/41 /1/41_1_21/_pdf> ASPRS LIDAR GUIDELINES: Horizontal Accuracy Reporting, <URL:http://www.asprs.org/a/society/committees/standards/Horizontal_Accuracy_Reporting_for_Lidar_Data.pdf>

However, in the technique described in Patent Document 1, at least three markers are required to calculate the measurement error, and the equipment becomes large in scale and the processing becomes complicated.

In view of the above circumstances, an object of the present invention is to provide a laser measurement system and a laser measurement method capable of calculating a measurement error in laser measurement simply and with high accuracy.

In order to achieve the above object, a laser measurement system according to one aspect of the present invention includes a laser measurement device, a reflection target body, and a calculation device. The laser measuring device is capable of irradiating the ground with laser light and measuring the position of the footprint of the laser light by the reflected light from the ground. The reflection target body is a surveying tripod installed on a reference point having known coordinates on the ground, or a GNSS surveying instrument having the known coordinates installed on the ground or an electronic reference point, and a sphere having a predetermined radius. It has a hemispherical shape obtained by halving, and can reflect the laser light. The calculation device calculates the center position coordinate of the sphere based on each three-dimensional position coordinate calculated from at least four reflected lights that are estimated to be emitted from the laser measurement device and reflected by the reflection target body. An error can be calculated from the difference between the calculated center position coordinate and the known coordinate.

Accordingly, the laser measurement system uses a surveying tripod having known coordinates, a GNSS surveying instrument, or a hemispherical reflective target attached to an electronic reference point to easily and accurately calculate a measurement error in laser measurement. be able to.

The calculating device may calculate the center position coordinate of the sphere by using the least squares method based on each three-dimensional position coordinate calculated from the at least four reflected lights.

Thereby, the laser measurement system can calculate the center position coordinates of the sphere having the predetermined radius, which is the basis of the reflection target body, based on each reflection position of at least four reflected lights.

The reflective target body may have an internal thread that can be screwed into a constant-length rod provided at the head of the survey tripod.

Accordingly, the laser measurement system can easily install the reflection target body on the surveying tripod by effectively utilizing the fixed core rod of the surveying tripod. In this case, a tubular member is provided inside the reflective target body, for example, hanging from the apex and having the internal thread formed on the inner circumference.

The reflective target body may be attached as a cover body at the tip of the GNSS surveying instrument or the electronic reference point.

This allows the laser measurement system to easily attach the reflective target body by using the reflective target body as a cover for the GNSS surveying instrument or the electronic reference point, without providing a dedicated mechanism for installing the reflective target body. Can be completed.

The calculation device calculates the center position coordinates and radius of the sphere based on each of the three-dimensional position coordinates, and determines whether the calculated radius matches the predetermined radius of the sphere. Good.

Thereby, the laser measurement system can determine the accuracy of the error of the calculated center position coordinates of the sphere by determining whether or not the calculated radius matches the known radius of the reflection target body. it can.

The reflection target body may be attached to each of the plurality of surveying tripods, the GNSS surveying instrument, or the electronic reference point existing in a predetermined area. In this case, the calculation device may calculate each of the plurality of errors regarding the plurality of reflection target bodies and calculate an average error of the plurality of calculated errors.

As a result, the laser measurement system calculates the average error using a plurality of reflection target bodies installed in a predetermined area (for example, within a few km from a certain point), and the laser measurement result in the predetermined area is calculated as a whole. It is possible to understand how much the value deviates from the true value.

The calculation device may correct the measurement result by the laser measurement device based on the calculated average error.

With this, the laser measurement system can correct each measurement value in a predetermined area so as to approach a true value as a whole by using the average error.

A laser measuring method according to another embodiment of the present invention,
Irradiate a laser beam on the ground and irradiate a laser from a laser measuring device capable of measuring the position of the footprint of the laser beam by the reflected light from the ground,
A surveying tripod installed on a reference point having known coordinates on the ground, or a GNSS surveying instrument installed on the ground having the known coordinates or attached to an electronic reference point, and a hemisphere that divides a sphere with a predetermined radius into two equal parts. A three-dimensional position coordinate is calculated from each of at least four reflected lights that have a body shape and are estimated to be reflected by a reflection target that can reflect the laser light,
Calculate the center position coordinates of the sphere based on the calculated three-dimensional coordinates,
The method includes calculating an error from the difference between the calculated center position coordinate and the known coordinate.

As described above, according to the present invention, the measurement error in laser surveying can be calculated easily and with high accuracy. However, this effect does not limit the present invention.

It is a figure showing the outline of the laser measurement system concerning one embodiment of the present invention. It is the figure which showed the hardware constitutions of the data analysis device in the said laser measurement system. It is the figure which showed the detail of the reflective target body in the said laser measurement system. 6 is a flowchart showing a flow of operations of the laser measurement system. It is the figure which showed notionally the footprint reflected by the reflective target body by laser measurement. It is the figure which showed the determinant for calculating the center coordinate of the sphere from which the reflection target body was cut out by the least squares method based on the three-dimensional position coordinates of the footprint of four points reflected by the reflection target body. It is the figure which showed the reflective target body installed in the electronic reference point in the laser measurement system which concerns on other embodiment of this invention. 6 is a flowchart showing a flow of operations of a laser measurement system according to another embodiment of the present invention. It is the figure which showed the reflective target body installed in the GNSS surveying instrument in the laser measuring system which concerns on other embodiment of this invention. 6 is a flowchart showing a flow of operations of a laser measurement system according to another embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[Configuration of laser measurement system]
FIG. 1 is a diagram showing an outline of a laser measurement system according to an embodiment of the present invention.

As shown in the figure, the system includes an aircraft 10, a reflection target body 1, and a data analysis device 100.

The aircraft 10 flies along a flight course planned in advance and collects various data. The aircraft 10 is equipped with a laser range finder 11, a GNSS receiver 12, an IMU (Inertial Measurement Unit) 13, and other related equipment (not shown). In the present embodiment, the laser distance measuring device 11, the GNSS receiver 12 and the IMU 13 may be collectively referred to as a laser measuring device.

The laser range finder 11 emits laser light toward the ground so as to scan laterally with respect to the traveling direction of the aircraft 10 shown in the figure during flight of the aircraft 10, and reflects the laser light from the ground. It receives light and measures the distance to the ground by the round-trip time of the reflected light to the ground.

As the laser distance measuring device 11, for example, a distance measuring device called Geiger-mode LiDAR capable of high-density measurement is used.

The GNSS receiver 12 measures the three-dimensional position of the aircraft 10. The position of the aircraft 10 is calculated from this measurement data and the data observed by a GNSS reference station (not shown) on the ground.

The IMU 13 measures the attitude angle (ω, φ, κ) of the aircraft 10. The direction of the laser beam emitted from the laser range finder 11 is corrected (calibrated) based on this measurement value, and detailed position coordinates of the aircraft 10 are calculated.

The data analysis device 100 is based on distance measurement data, GNSS data, and IMU data (hereinafter collectively referred to as laser measurement data) measured by the laser measurement device on the aircraft 10 for each laser light point. Horizontal coordinate values (x, y) and elevation values (z) are calculated to generate point cloud data.

Further, the data analysis device 100 performs various inspection processes and noise removal processes on the point cloud data to generate three-dimensional measurement data. Further, the three-dimensional measurement data is subjected to processing such as mesh processing to generate mesh data such as DSM (Digital Surface Model) and DEM (Digital Elevation Model).

The reflective target body 1 is attached to a surveying tripod 2 installed at a triangular point 3 having known coordinates on the ground under the flight course of the aircraft 10 in order to reflect the laser light. Details of the reflective target body 1 will be described later.

Although not shown, the surveying tripod 2 may be installed at another triangular point 3 under the flight course of the aircraft 10, and the reflection target body 1 may be attached to the surveying tripod 2. That is, the reflection target body 1 can be installed on each of a plurality of surveying tripods 2 installed in a predetermined area on the ground.

The data analysis device 100 calculates the error of the position coordinates (x, y, z) in the laser measurement processing based on the three-dimensional position coordinate data of the laser light reflected by the reflection target bodies 1.

[Configuration of data analysis device]
FIG. 2 is a diagram showing a hardware configuration of the data analysis device 100. The data analysis device 100 may be configured as dedicated hardware for executing various arithmetic processes in the present system, but in the present embodiment, it is configured by a general-purpose computer and a program executed on the computer.

As shown in FIG. 1, the data analysis device 100 includes a CPU (Central Processing Unit) 110, a ROM (Read Only Memory) 120, a RAM (Random Access Memory) 130, an input/output interface 150, and a bus connecting these components to each other. And 140.

The CPU 110 appropriately accesses the RAM 130 and the like as needed, and performs overall control of each block of the data analysis device 100 while performing various arithmetic processes. The ROM 120 is a non-volatile memory in which an OS to be executed by the CPU 110 and firmware such as programs and various parameters are fixedly stored. The RAM 130 is used as a work area of the CPU 110 and the like, and temporarily holds the OS, various applications being executed, and various data being processed.

A display unit 160, an operation receiving unit 170, a storage unit 180, a communication unit 190, etc. are connected to the input/output interface 150.

The display unit 160 is a display device using, for example, an LCD (Liquid Crystal Display), an OELD (Organic ElectroLuminescence Display), a CRT (Cathode Ray Tube), or the like.

The operation reception unit 170 is, for example, a pointing device such as a mouse, a keyboard, a touch panel, and other input devices. When the operation reception unit 170 is a touch panel, the touch panel can be integrated with the display unit 160.

The storage unit 180 is a non-volatile memory such as an HDD (Hard Disk Drive), a flash memory (SSD; SolID State Drive), or other solid-state memory. The storage unit 180 stores the OS, various applications, and various data.

Particularly, in the present embodiment, the storage unit 180 stores the laser measurement data (ranging data, GNSS data, and IMU data) collected by using the aircraft 10, and the three-dimensional measurement data generated from those data. Alternatively, error data of position coordinates calculated using the reflection target body 1 and the like are also stored. The laser measurement data may be loaded from the storage device installed in the aircraft 10 into the storage unit 180 of the data analysis device 100 via a portable storage medium, or may be transmitted from the aircraft 10 to the data analysis device 100. It may be received via the communication unit 190 and stored in the storage unit 180.

The communication unit 190 is, for example, a NIC (Network Interface Card) for Ethernet, and is responsible for communication processing with devices in the aircraft 100 and other devices.

[Structure of reflective target]
Next, details of the reflective target body 1 will be described. FIG. 3 is a sectional view of the reflection target body 1 attached to the survey tripod 2.

As shown in the figure, the reflection target body 1 has a semi-spherical shape without distortion which is obtained by dividing a sphere B having a predetermined radius r into two equal parts. An undistorted hemisphere has a spherical surface that is equidistant from the center coordinates of a precise sphere within a certain range, and the center coordinates of the sphere can be installed at the center of the survey tripod 2 as a known point.

Inside the reflection target body 1, a tubular member 1b that can be screwed into a fixed rod 2a provided at the center of the top of the survey tripod 2 is provided so as to hang from the apex.

The constant core rod 2a is a male screw defined by Japanese Industrial Standard (JIS) to be 5/8 inch, and the inner circumference of the tubular member 1b is 5/8 that can be screwed into the constant core rod 2a. Inch female thread is formed. Thereby, the reflection target body 1 can be installed at the center of the surveying tripod 2 and can be used as a precise ground reference point.

A color or a coating material that well reflects the laser light (near infrared light) emitted from the laser distance measuring device 11 is used for the reflecting surface 1 a of the reflecting target 1.

However, if the reflection intensity of the reflection surface 1a is too high, it may affect the measurement result of the laser range finder 11. Therefore, the reflection intensity is preferably a value that does not have such an influence. ..

On the other hand, on the surface of the surveying tripod 2 to which the reflective target body 1 is attached, it is preferable to use a color or a coating material that absorbs near infrared light well.

Since the reflective surface 1a of the reflective target body 1 is formed as a hemispherical surface, if there are at least four footprint measurement values on the reflective surface 1a in aeronautical laser measurement, the formula of the center coordinates and radius of the sphere is obtained. Thus, the center position coordinates of the virtual sphere B can be calculated using the least squares method.

In the present embodiment, the difference between the center position coordinate of the virtual sphere B calculated from the value acquired by the aerial laser measurement and the known position coordinate of the triangular point 3 on which the reflection target body 1 is installed is determined by the aerial laser measurement. It can be verified as an error in the position coordinates.

[Operation of laser measurement system]
Next, the operation of the laser measurement system configured as above will be described. The operation after the laser measurement data acquisition by the aircraft 10 is executed by the cooperation of the hardware such as the CPU 110 of the data analysis device 100 and the software stored in the storage unit 180.

FIG. 4 is a flowchart showing a flow of operations of the laser measurement system.

As shown in the figure, first, an operator attaches the reflective target body 1 to the fixed rod 2a of the survey tripod 2 (step 41).

Subsequently, the worker installs the surveying tripod 2 in accordance with the triangular point 3 having known position coordinates existing in a predetermined area under the flight route of the aircraft 10 (step 42). Of course, the reflection target body 1 may be attached to the surveying tripod 2 after the surveying tripod 2 is installed at the triangular point 3.

Then, laser measurement is carried out by the aircraft 10 on the flight route (step 43). As a result, laser measurement data such as round-trip time data of laser light, GNSS data, and IMU data is acquired.

Then, the data analysis process by the data analysis device 100 is executed.

First, the CPU 110 of the data analysis apparatus 100 extracts four or more footprints detected in the vicinity of the reflection target 1 that have a reflection intensity of a predetermined threshold value or more (step 44). This process may be omitted when the reflection intensity above a certain level can be guaranteed from any footprint.

Subsequently, the CPU 110 calculates the center position coordinates of the virtual sphere B forming the reflection target body by the least square method based on the extracted three-dimensional coordinates of the footprint (step 45).

FIG. 5 is a diagram conceptually showing the calculation processing of the center position coordinates of the virtual sphere B that constitutes the reflection target body 1.

The CPU 110 fits the extracted three-dimensional coordinates of the footprints F of four or more points to the spherical surface by the least-squares method, so that the center position coordinates of the sphere B from which the reflection target body 1 is generated and the sphere B are calculated. Calculate the radius. The calculation method will be described below.

First, the formulas of the center coordinates of the sphere and the radius of the sphere are as follows.
(X-a) ² + (Y-b) ² + (Z-c) ² = r ²
Where the center coordinates of the sphere: (a, b, c)
Sphere radius: r

Further, the three-dimensional position coordinates on the extracted reflective target body 1 are defined as (Xi, Yi, Zi). i is the point number (i = 1, 2, ..., n).

Here, the residual Vi is defined as follows.
Vi = {(Xi - a) 2 + (Yi - b) 2 + (Zi - c) 2} -r 2

Next, a condition for minimizing the sum of squares of the residual Vi (S below) will be obtained using the least squares method.
S = ΣVi ²
= Σ{Xi ² + Yi ² + Zi ² + AXi + BYi + CYi +D} ²
Where A = -2a..................Equation (1)
B = -2b・・・・・・・・・・(2)
C = -2c...Equation (3)
D = a ² + b ² + c ² -r ² ...Equation (4)

The condition that minimizes S can be expressed as follows.
∂S/∂A = AΣXi ² + BΣXiYi + CΣXiZi + DΣXi + ΣXi ³ + ΣXiYi ² + ΣXiZi ² = 0
∂S/∂B = AΣXiYi + BΣYi ² + CΣYiZi + DΣYi + ΣXi ² Yi + ΣYi ³ + ΣYiZi ² = 0
∂S/∂C = AΣXiZi + BΣYiZi + CΣZi ² + DΣZi + ΣXi ² Zi + ΣYi ² Zi + ΣZi ³ = 0
∂S/∂D = AΣXi + BΣYi + CΣZi + DΣ1 + ΣXi ² + ΣYi ² + ΣZi ² = 0

When this is expressed in a matrix, it becomes as shown in FIG. The matrix equation is solved to obtain A, B, C, D, and the center position coordinates (a, b, c) of the sphere B and the radius r are obtained from the above equations (1) to (4).

Here, when three points are selected from the extracted i three-dimensional position coordinates and used in the above calculation, only _i C ₃ center position coordinates of the sphere B can be obtained. The accuracy of the reflection data differs depending on the time resolution of the laser, and in order to smooth this error, the CPU 11 performs the above calculation for _i C ₃ pieces and calculates the sum of squares of the residual Vi by the least square method. The minimum center position coordinates (a, b, c) of one point may be obtained.

Returning to FIG. 4, the CPU 110 calculates an error between the center position coordinates (a, b, c) of the sphere B thus obtained and the known position coordinates of the triangular point 3 (step 46).

Then, the CPU 110 executes this error calculation process for each of the plurality of reflection target bodies 1 attached to the plurality of surveying tripods 2 installed in the predetermined area, and calculates an average error from those errors (step 47). ..

The data analysis apparatus 100 may correct the position coordinates in the aviation laser measurement data using this average error. As a result, each measurement value in the measurement area can be brought closer to the true value as a whole.

Of course, if there is a value (maximum value, minimum value) that is more prominent than other values, the average value may be recalculated excluding that value, if necessary.

As described above, according to the present embodiment, the laser measurement system uses the hemispherical reflection target body 1 that can be attached to the surveying tripod 2 installed at the triangular point 3 having the known coordinates, and thus the existing laser measurement system can be used. The measurement error in laser measurement can be calculated easily and highly accurately by effectively utilizing the reference point of. This allows the aircraft rider to be used in surveying methods to create high precision maps or 3D map data.

[Modification]
The present invention is not limited to the above-described embodiments, but can be variously modified without departing from the scope of the present invention.

In the embodiment described above, the reflective target body 1 was attached to the surveying tripod 2. However, the reflective target body 1 can also be attached to other reference points having known coordinates.

Specifically, the reflective target body 1 may be installed at an electronic reference point. As shown in FIG. 7, the reflective target body 1 may be attached to the tip of the electronic reference point 70 as a cover body.

The electronic reference point 70 is a GPS continuous observation point installed at about 1300 locations nationwide in Japan. The appearance is a stainless steel pillar with a height of 5 m, and an antenna for receiving radio waves from GPS satellites is provided at the upper end, The receiver and the communication device are stored in. As shown in FIG. 7, the reflection target body 1 can be attached as a cover body of the antenna at the upper end of the electronic reference point 70.

FIG. 8 is a flowchart showing the operation flow of the laser measurement system when the reflective target body 1 is attached to the electronic reference point 70.

As shown in the figure, first, the worker attaches the reflection target body 1 as an antenna cover of the electronic reference point 70, and aligns the center of the antenna with the center of the reflection target body 1 (step 81). Similar to the above-described embodiment, the reflective surface 1a of the reflective target body 1 uses a color or a coating material that reflects near-infrared light well. The diameter of the reflective target body 1 is designed similarly to the conventional antenna cover of the electronic reference point 70.

Subsequently, laser measurement is carried out by the aircraft 10 on the flight route (step 82). As a result, laser measurement data such as round-trip time data of laser light, GNSS data, and IMU data is acquired.

Subsequent processing is similar to the processing in the above-described embodiment, the error between the center position coordinate of the sphere calculated from the footprint and the position coordinate of the electronic reference point is calculated, and the average error of a plurality of errors is calculated. It is calculated (steps 83 to 86).

The position coordinates of the electronic reference point 70 may be received in advance by the data analysis device 100 or may be received at the time of calculating the error.

With the above processing, by effectively utilizing the existing electronic reference point 70, the measurement error in laser measurement can be calculated easily and highly accurately.

Moreover, the reflective target body 1 may be installed in a GNSS surveying instrument. As shown in FIG. 9, it may be attached as a cover body to the tip of the reflective target body GNSS surveying instrument 90.

The GNSS surveying instrument 90 is an instrument that receives radio waves from satellites in static observation and the like. As shown in FIG. 9, the reflective target body 1 can be attached as a cover body of an antenna at the upper end of the GNSS surveying instrument.

FIG. 10 is a flowchart showing the operation flow of the laser measurement system when the reflective target body 1 is attached to the electronic reference point 70.

As shown in the figure, first, an operator attaches the reflection target body 1 as an antenna cover of the GNSS surveying instrument 90, and aligns the center of the antenna with the center of the reflection target body 1 (step 101). Similar to the above-described embodiment, the reflective surface 1a of the reflective target body 1 uses a color or a coating material that reflects near-infrared light well. The diameter of the reflective target body 1 is designed like the conventional antenna cover of a GNSS surveying instrument.

Subsequently, laser measurement is carried out by the aircraft 10 on the flight route (step 102). As a result, laser measurement data such as round-trip time data of laser light, GNSS data, and IMU data is acquired.

Subsequent processing is the same as the processing in the above-described embodiment, and an error between the center position coordinate of the sphere calculated from the footprint and the position coordinate measured by the GNSS surveying instrument 90 is calculated. The average error is calculated (steps 103 to 106).

Note that the survey (position coordinate acquisition) by the GNSS survey instrument 90 may be received in advance by the data analysis device 100, or may be received when the above error is calculated.

With the above processing, by effectively utilizing the existing GNSS surveying instrument 90, the measurement error in laser measurement can be calculated easily and highly accurately.

Further, the surveying tripod 2, the electronic reference point 70, and the GNSS surveying instrument 90 described above may be used in combination. That is, in calculating the average error for the plurality of reflection target bodies 1, the plurality of reflection target bodies 1 are attached to the surveying tripod 2, the electronic reference point 70, and the GNSS surveying instrument 90. It does not matter if there are mixed items.

In the above-described embodiment, the data analysis device 100 calculates the center coordinates and the radius of the virtual sphere B based on the measured values of the footprints of the four lasers. Here, when the radius of curvature of the reflection target body 1 (radius of the original spherical body B) is known in advance, the data analysis apparatus 100 compares the calculated radius with the known radius of the spherical body B. You may judge the degree of coincidence that you are doing. Accordingly, the data analysis device 100 can determine the accuracy of the calculated position coordinate error.

In the above-described embodiment, the example in which the present invention is applied to the aerial laser measurement system is shown, but the present invention may be applied to the laser measurement system using an artificial satellite. Further, the reflection target body 1 of the present invention can be applied to an MMS (Mobile Mapping System) using a vehicle (such as an automobile) traveling on the ground. Since the reflection target body 1 has a side surface having a sufficient area with the diameter of the sphere B as the width and the radius as the height, not only the laser light emitted from the sky like an aviation laser but also the MMS like Even when the laser light is emitted from the lateral direction, it is possible to secure four or more footprints required for calculating the center position coordinates.

Also, the same reflective target may be used in both the aerial laser metrology system and the MMS. That is, in the predetermined area where the reflection target body 1 is installed, the laser measurement process by the aircraft is executed at the same time as the laser measurement process by the vehicle is executed on the ground, and the error in the position coordinates is the same in each process. It may be calculated using the target body 1.

DESCRIPTION OF SYMBOLS 1... Reflective target body 1a... Reflective surface 1b... Cylindrical member 2... Surveying tripod 2a... Fixed rod 10... Aircraft 11... Laser range finder 12... GNSS receiver 13... IMU
70... Electronic reference point 90... GNSS surveying instrument 100... Data analysis device 110... CPU
180... Storage unit B... Virtual sphere

Claims (8)

A laser measuring device capable of irradiating a laser beam on the ground and measuring the position of the footprint of the laser beam by the reflected light from the ground,
A surveying tripod installed on a reference point having known coordinates on the ground, or a GNSS surveying instrument installed on the ground having the known coordinates or attached to an electronic reference point, and a hemisphere that divides a sphere of a predetermined radius into two equal parts. A reflective target having a body shape and capable of reflecting the laser light,
Based on each three-dimensional position coordinate calculated from at least four reflected lights that are estimated to be emitted from the laser measurement device and reflected by the reflection target body, the center position coordinate of the sphere is calculated and calculated. A laser measurement system comprising: a calculation device capable of calculating an error from a difference between a center position coordinate and the known coordinate. The laser measurement system according to claim 1, wherein
The laser measuring system, wherein the calculating device calculates the center position coordinate of the sphere by using the least square method based on each three-dimensional position coordinate calculated from the at least four reflected lights. The laser measurement system according to claim 1 or 2, wherein
The laser measurement system, wherein the reflection target body has a female screw that can be screwed into a fixed rod provided on the head of the survey tripod. The laser measurement system according to claim 1 or 2, wherein
The laser measurement system in which the reflective target body is attached as a cover body at the tip of the GNSS surveying instrument or the electronic reference point. The laser measurement system according to any one of claims 1 to 4,
The calculation device calculates center position coordinates and radius of the sphere based on each of the three-dimensional position coordinates, and determines whether the calculated radius matches a predetermined radius of the sphere Laser measurement system. The laser measurement system according to any one of claims 1 to 5,
The reflection target body is attached to each of the plurality of surveying tripods, the GNSS surveying instrument, or the electronic reference point existing in a predetermined area,
The laser measuring system, wherein the calculating device calculates a plurality of the errors with respect to the plurality of reflective target bodies, and calculates an average error of the plurality of calculated errors. The laser measurement system according to claim 6, wherein
A laser measurement system in which the calculation device corrects a measurement result by the laser measurement device based on the calculated average error. Irradiating a laser beam on the ground, irradiating a laser from a laser measuring device capable of measuring the position of the footprint of the laser beam by reflected light from the ground,
A surveying tripod installed on a reference point having known coordinates on the ground, or a GNSS surveying instrument having the known coordinates installed on the ground or attached to an electronic reference point, and a hemisphere that divides a sphere with a predetermined radius into two equal parts. A three-dimensional position coordinate is calculated from each of at least four reflected lights that have a body shape and are estimated to be reflected by a reflection target that can reflect the laser light,
Calculate the center position coordinates of the sphere based on the calculated three-dimensional coordinates,
A laser measuring method, wherein an error is calculated from a difference between the calculated center position coordinate and the known coordinate.

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