JP6467567B2 - Surface change analysis system - Google Patents

Description

  The present invention relates to a ground surface change analysis system for analyzing a change in the ground surface at a certain time and a time different from this time.

  A laser scanner is installed in the aircraft, and the laser scanner irradiates the ground with laser light while flying the aircraft. The distance to the ground obtained from the time difference from the laser light reflected from the ground, GPS surveying instrument, IMU (inertia) Aircraft laser surveying is known as a surveying technique for precisely examining the altitude of the ground and the shape of the topography from the position information of the aircraft obtained from the measuring device.

For example, Patent Document 1 (Japanese Patent No. 2012-256230) discloses a DTM estimation method for estimating altitude data only on the ground surface (Digital Terrain Model) for a predetermined range based on laser scanner data on the ground surface by an aircraft. A river region is extracted by connecting pixels having no data in the unit grid in the predetermined range, and a first DTM is set for the data excluding the river region by setting a first maximum allowable slope value. And the local gradient is calculated from the estimated DTM. If the gradient exceeds a predetermined value, a second maximum allowable gradient value larger than the first maximum allowable gradient value is set and the DTM is estimated again. A method is disclosed.
Japanese Patent No. 2012-256230

  The aerial laser surveying as described above has a problem that enormous costs and preparations are required, and the surveying is not easy. Therefore, conventionally, it has been impossible to easily grasp the surface change immediately after the occurrence of a disaster such as a landslide, debris flow, heavy snowfall or avalanche. If it becomes possible to grasp the ground surface change immediately after the occurrence of disasters such as landslides, debris flows, heavy snowfalls and avalanches, it can contribute to disaster prevention, etc., but this has been a problem in the past.

The present invention solves the problems as described above, and the ground surface change analysis system according to the present invention is a preparatory step for preparing a plurality of aerial photographs obtained by photographing the ground surface from different positions by a camera mounted on the flying object. A reference coordinate setting step for setting a plurality of reference coordinates based on an actual measurement amount in a plurality of aerial photographs prepared in the preparation step; and extracting feature points in the aerial photograph prepared in the preparation step; 3D distribution data calculation step for calculating the three-dimensional distribution data of the ground surface, and the three-dimensional distribution data of the ground surface based on the three-dimensional distribution data of the ground surface calculated in the three-dimensional distribution data calculation step. 3D point cloud data calculation step for calculating 3D point cloud data of the ground surface having a higher density than the distribution data, and the reference coordinate setting step. Based on the reference coordinates, the coordinates of the point cloud in the 3D point cloud data on the ground surface calculated in the 3D point cloud data calculating step are calculated, and the coordinate calculated to obtain the coordinate calculated 3D point cloud data 3D point cloud data acquisition step, and the first coordinate calculated 3D point cloud data is acquired based on a plurality of aerial photographs acquired in the first period. Based on a plurality of aerial photographs acquired at a second time different from the first time, second coordinate calculated three-dimensional point cloud data is acquired, the first coordinate calculated three-dimensional point cloud data, and the first The difference between the two coordinate-calculated three-dimensional point cloud data is calculated and displayed.

  Moreover, the ground surface change analysis system according to the present invention is characterized in that the display is performed by color-coding according to the magnitude of the difference.

  The ground surface change analysis system according to the present invention is characterized in that the reference coordinates are three or more points.

  The ground surface change analysis system according to the present invention is characterized in that the reference coordinates are obtained by an actually measured amount by a total station.

  The ground surface change analysis system according to the present invention is characterized in that the reference coordinates are obtained by an actual measurement amount by a global navigation satellite system.

  Further, the ground surface change analysis system according to the present invention is configured such that the reference coordinates used when acquiring the first coordinate calculated 3D point cloud data based on the plurality of aerial photographs acquired at the first time are the second time. Based on the plurality of aerial photographs acquired in the above, the reference coordinates used when acquiring the second coordinate calculated 3D point cloud data are the same.

  The ground surface change analysis system according to the present invention is characterized in that Structure from Motion technology is used for the three-dimensional distribution data calculation step.

  The ground surface change analysis system according to the present invention is characterized in that a multi-view stereo technique is used for the three-dimensional point cloud data calculation step.

  In the ground surface change analysis system according to the present invention, the flying object is an unmanned aerial vehicle.

  According to the surface change analysis system according to the present invention, it is possible to quickly grasp the surface change immediately after the occurrence of a disaster such as a landslide, debris flow, heavy snowfall or avalanche, and the analysis result obtained quickly can be used for disaster prevention and search. It can be used for support.

It is a figure explaining the structure of the flying body 101 which acquires the aerial photograph used with the ground surface change analysis system which concerns on embodiment of this invention. It is a figure which shows an example of a structure of the computer which implement | achieves a ground surface change analysis system based on the ground surface change analysis method which concerns on embodiment of this invention. It is a figure which shows the flowchart of the analysis process performed with the ground surface change analysis system which concerns on this invention. It is a figure which shows the subroutine which acquires the coordinate calculated 3D point cloud data of the ground surface change analysis system which concerns on this invention. It is a figure explaining the example of selection of the standard coordinates in an aerial photograph. It is a figure which shows an example of the mode of the measurement of the reference | standard coordinate by actual measurement. It is a figure which shows the example of a setting of the reference | standard coordinate (GCP; ground control point) in an actual aerial photograph. It is a figure which shows the example of a setting of the reference | standard coordinate (GCP; ground control point) in an actual aerial photograph. It is a figure which shows the example of a setting of the reference | standard coordinate (GCP; ground control point) in an actual aerial photograph. It is a figure which shows the aerial photograph of the 1st period before a debris flow disaster occurrence. It is a figure which shows the aerial photograph of the 2nd period after a debris flow disaster occurrence. It is the figure which displayed the difference of 1st coordinate calculated 3D point group data and 2nd coordinate calculated 3D point group data by color-coding.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. First, an example of a method for taking aerial photographs used in the ground surface change analysis system according to the present invention will be described. FIG. 1 is a diagram for explaining a configuration of a flying object 101 that obtains an aerial photograph used in a ground surface change analysis system according to an embodiment of the present invention, and shows a state in which an aerial photograph of the ground surface is taken by the flying object 101. Yes.

  In the following, a configuration for taking an aerial photograph will be described, but an aerial photograph capturing method with such a configuration is merely an example of an aerial photograph capturing method, and the ground surface change analysis system according to the present invention is It is also possible to use aerial photographs acquired by other photographing methods.

  In FIG. 1, reference numeral 101 denotes an aircraft capable of autonomous flight. Here, an unmanned aerial vehicle is assumed as the flying object 101, but an aerial photograph may be taken using a manned aircraft.

  A control device (not shown) is installed on the ground, and the control device is capable of data communication with the flying object 101, and controls the flight of the flying object 101, sets and changes a flight plan, and the flying object 101. The information collected by can be stored and managed.

  As the flying object 101, for example, a helicopter as a small flying object that autonomously flies can be used. The flying object 101 (helicopter) is operated by remote control from the control device, or a flight plan is set from the control device to the control device of the flying object 101 (helicopter), and autonomous flight is performed according to the flight plan. It has become.

  The flying object 101 (helicopter) includes a fuselage 103 and a required number of propellers provided in the fuselage 103, for example, four propellers 104, 105, 106, 107 in total, front, rear, left, and right. Reference numerals 106 and 107 are individually connected to a first motor, a second motor, a third motor, and a fourth motor (all not shown). The driving of each of the first motor, the second motor, the third motor, and the fourth motor is controlled independently. Note that the propellers 104, 105, 106, and 107, the first motor, The two motors, the third motor, the fourth motor, etc. constitute the navigation means of the flying object.

  The aircraft 103 of the flying object 101 (helicopter) is provided with an imaging device 113 and a flying object control device (not shown). The imaging device 113 acquires digital image data. The imaging device 113 may be a camera that captures still images at predetermined time intervals, or may be a video camera that continuously captures images. The imaging device 113 is provided on the lower surface of the machine body 103. Further, the imaging device 113 has a CCD and a CMOS sensor, which are a collection of pixels, as an imaging device, and acquires digital image data (aerial photograph) from the air with this imaging device. Can be done.

  The aerial photograph data acquired by the imaging device 113 may be configured to be wirelessly transmitted to a control device on the ground, or stored in a medium (not shown), and the flying object 101 (helicopter). You may make it collect from this media after landing.

In addition, acquiring an aerial photograph with the imaging device 113 mounted on the flying object 101 (helicopter) as described above does not require a large-scale preparation or the like, and can capture an aerial photograph relatively easily and inexpensively. Although it is an important matter in realizing the ground surface change analysis system according to the present invention, the ground surface change analysis system according to the present invention is not necessarily required to use an aerial photograph using the flying object as described above. There is no. That is, the ground surface change analysis system according to the present invention can also be realized using an aerial photograph acquired by a flying object such as a conventional manned airplane or artificial satellite.

  Next, the configuration of a computer that executes a ground surface change analysis system according to the present invention that analyzes changes in the ground surface based on aerial photographs acquired by the imaging device 113 of the flying object 101 (helicopter) as described above will be described. To do.

  FIG. 2 is a diagram showing an example of the configuration of a computer that realizes a ground surface change analysis system based on the ground surface change analysis method according to the embodiment of the present invention. In FIG. 2, 10 is a system bus, 11 is a CPU (Central Processing Unit), 12 is a RAM (Random Access Memory), 13 is a ROM (Read Only Memory), 14 is a communication control unit that controls communication with an external information device, 15 is an input control unit such as a keyboard controller, 16 is an output control unit, 17 is an external storage device control unit, 18 is an input unit composed of input devices such as a keyboard, pointing device, and mouse, 19 is an output unit such as a printing device, Reference numeral 20 denotes an external storage device such as an HDD (Hard Disk Drive), 21 denotes a graphic control unit, and 22 denotes a display device.

  In FIG. 2, the CPU 11 searches for and acquires data by communicating with an external device according to a program ROM stored in the ROM 13 or a program stored in the large-capacity external storage device 20. Processing of output data in which graphics, images, characters, tables, etc. are mixed is executed, and management of a database stored in the external storage device 20 is further executed.

  Further, the CPU 11 comprehensively controls each device connected to the system bus 10. The program ROM in the ROM 13 or the external storage device 20 stores an operating system program (hereinafter referred to as OS) that is a basic program for controlling the CPU 11. The ROM 13 or the external storage device 20 stores various data used when performing output data processing or the like. The RAM 12 as a main memory functions as a main memory, work area, and the like for the CPU 11.

  The input control unit 15 controls the input unit 18 from a keyboard or a pointing device (not shown). The output control unit 16 performs output control of the output unit 19 such as a printer.

  The external storage device control unit 17 is an external storage device 20 such as an HDD (Hard Disk Drive) or a floppy disk (FD) that stores a boot program, various applications, font data, user files, editing files, printer drivers, and the like. Control access to. A system program for realizing the ground surface change analysis method of the present invention is stored in the external storage device 20 as described above. The graphic control unit 21 is configured to perform drawing processing on information to be displayed on the display device 22.

  Further, the communication control unit 14 controls communication with an external device via a network, thereby acquiring data required by the system from a database held by an external device on the Internet or an intranet, It is configured to be able to send information to an external device.

In addition to an operating system program (hereinafter referred to as OS) that is a control program for the CPU 11, the external storage device 20 is installed with a system program for operating the ground surface change analysis system of the present invention on the CPU 11 and data used in the system program. Saved and remembered.

  As data used in the system program for realizing the ground surface change analysis method of the present invention, it is basically assumed that the data is stored in the external storage device 20, but in some cases, these data are It is also possible to configure to acquire from an external device on the Internet or an intranet via the communication control unit 14. The data used in the system program for realizing the ground surface change analysis method of the present invention can also be obtained from various media such as a USB memory, a CD, and a DVD.

  Next, the ground surface change analysis method according to the present invention that can be executed by the computer having the above system configuration will be described below. The ground surface change analysis system according to the present invention, as an outline, analyzes the change of the ground surface between the first time and the second time different from the first time, visualizes this, and displays it by the display device 22 or the like. To display.

  Here, in the analysis process of the ground surface change analysis system according to the present invention, there is a significant change in the ground surface between the aerial photograph according to the first period and the aerial photograph according to the second period after the first period. The analysis of the ground surface in a certain case is assumed. In addition, as the second period, for example, a period after the occurrence of a disaster such as a landslide, debris flow, heavy snowfall or avalanche is assumed, and as the first period, a period before the occurrence of the disaster is assumed.

  In the ground surface change analysis system according to the present invention, an aerial photograph is prepared so that it can be processed as digital data. However, only an analog photograph can be prepared as an aerial photograph related to the first period before the disaster occurs. In such a case, it may be scanned into digital data. If the aerial photograph according to the second period is acquired based on the aerial photograph acquisition method described above using the flying object 101 (helicopter), an aerial photograph based on appropriate digital data can be obtained.

  Hereinafter, analysis processing in the ground surface change analysis system according to the present invention will be described. FIG. 3 is a diagram showing a flowchart of analysis processing executed by the ground surface change analysis system according to the present invention.

  In FIG. 3, when the analysis process is started in step S100, subsequently, in step S101, a step of preparing a plurality of aerial photographs acquired in the first period is executed. In this step, it is assumed that several aerial photographs are prepared before the occurrence of disasters such as landslides, debris flows, heavy snowfalls and avalanches causing ground deformation. Here, hereinafter, when preparing aerial photographs, it is required to prepare a plurality of aerial photographs obtained by photographing the ground surface to be analyzed from different positions. The same applies to the step of preparing an aerial photograph for the second period described later.

  Subsequently, in step S102, a subroutine for obtaining coordinate-calculated three-dimensional point cloud data is executed based on the aerial photograph at the first time prepared in the previous step S101.

  Hereinafter, such a subroutine will be described. FIG. 4 is a diagram showing a subroutine for acquiring coordinate-calculated three-dimensional point cloud data in the ground surface change analysis system according to the present invention.

  In FIG. 4, when the coordinate-calculated three-dimensional point cloud data acquisition subroutine is started in step S200, a plurality of aerial photographs at the corresponding time are referred to in step S201.

In step S202, a step of setting reference coordinates in the aerial photograph is executed. The setting of the reference coordinates in such an aerial photograph will be described.

  In the ground surface change analysis system according to the present invention, it is possible to calculate accurate three-dimensional point cloud data coordinates by performing digital data processing after setting reference coordinates in a plurality of aerial photographs based on actual measurement amounts. It is like that. As described above, setting the reference coordinates based on the actually measured amount in the data of the aerial photograph is a part of the important constituent requirement in the ground surface change analysis system according to the present invention. Such reference coordinates are also referred to as a ground control point (GCP).

  Here, a specific method for setting the coordinate position of the reference coordinate will be described. The aerial photograph itself is not geographical information but image information. Therefore, an operation for setting a reference coordinate (GCP; ground control point) at an easily specified location in the aerial photograph is performed. In setting the reference coordinate, it is particularly preferable to perform based on an actually measured amount. In the ground surface change analysis system according to the present invention, it is important. As a result, it is possible to accurately grasp the difference in the ground surface at two periods.

  FIG. 5 is a diagram for explaining an example of selecting reference coordinates in an aerial photograph. FIG. 5 (A) shows an example of an aerial photograph, and FIG. 5 (B) shows a partially enlarged view thereof. In the aerial photograph, a point that is selected as a reference coordinate (GCP; ground control point) may be selected as a standard that is easily recognized by the aerial photograph.

  For example, the point selected as the reference coordinate (GCP; ground control point) may be a corner of a pedestrian crossing road surface sign or the like. In FIG. 5B, a portion suitable as such a reference coordinate (GCP; ground control point) is surrounded by a dotted line. FIG. 6 is a diagram illustrating an example of a state in which the position coordinates of the reference coordinates (GCP; ground control point) are actually measured by the total station 120.

  As shown in FIG. 6, the three-dimensional coordinates of points that are easy to recognize in the aerial photograph, such as the end of a road marking on a pedestrian crossing, are obtained by actual measurement, and the reference coordinates (GCP; ground control point) in the aerial photograph are obtained. Set as. Here, the method of actually measuring the three-dimensional coordinates of the reference coordinates (GCP; ground control point) is not limited to the method using the total station, and any other method can be used. For example, the reference coordinates (GCP; ground control point) can be surveyed by a global navigation satellite system such as GPS.

  As described above, the reference coordinates (GCP; ground control point), which are three-dimensional coordinates obtained from the actual measurement amount, are set in the aerial photograph data.

  7 to 9 are diagrams showing an example of setting reference coordinates (GCP; ground control point) in an actual aerial photograph. In the example of FIGS. 7 to 9, the road surface display in the parking lot is selected as a place that can be easily recognized by an aerial photograph, and is used as a reference coordinate (GCP; ground control point). 7 to 9 are a plurality of aerial photographs obtained by photographing a predetermined area of the ground surface from different positions. In each aerial photograph, the same reference coordinates (GCP; ground control point) measured as described above are set. This makes it possible to obtain three-dimensional geographic information from each image information.

  The reference coordinates (GCP; ground control point) as described above need to be set at least 3 points in the aerial photograph, but the reference coordinates (GCP; ground control point) are more than 4 points. Precise ground surface analysis is possible.

  As described above, after setting the reference coordinates (GCP; ground control point) based on the actual measurement amount in the plurality of aerial photographs in step S202, the process proceeds to step S203, and three-dimensional distribution data is calculated from the plurality of aerial photographs. In such a three-dimensional distribution data calculation step of step S203, it is preferable to use the structure from motion technique.

  The Structure from Motion technique is a technique for calculating the three-dimensional distribution data of the ground surface by extracting feature points in aerial photographs and associating a plurality of aerial photographs. As such a three-dimensional distribution data calculation step, conventionally known algorithms described in JP2013-120133A, JP2014-120079A, and the like can be used.

  Next, in step S204, based on the three-dimensional distribution data calculated in step S203 above, three-dimensional point cloud data calculation for calculating three-dimensional point cloud data on the ground surface that is denser than the three-dimensional distribution data on the ground surface. Perform steps. In this three-dimensional point cloud data calculation step, it is preferable to use the multi-view stereo technique.

  Note that software such as Agisoft PhotoScan Pro can be used in the three-dimensional distribution data calculation step in step S203 and the three-dimensional point cloud data calculation step in step S204.

  In step S205, the position coordinates of all point groups are calculated based on the three-dimensional point group data calculation step obtained as described above and the set reference coordinates (GCP; ground control point). The coordinate-calculated 3D point cloud data is acquired. A conventionally well-known algorithm can be used as an algorithm for acquiring coordinate-calculated three-dimensional point group data from the three-dimensional point group data calculating step and reference coordinates (GCP; ground control point).

  The coordinate-calculated three-dimensional point cloud data acquired based on the aerial photograph at the first time is referred to as first coordinate-calculated three-dimensional point cloud data.

  In step S206, the process returns to the original routine.

  Returning from the subroutine to the main routine, subsequently, in step 103 of FIG. 3, a step of preparing a plurality of aerial photographs acquired at the second time is executed. In this step, it is assumed that multiple aerial photographs are prepared after disasters such as landslides, debris flows, heavy snowfalls, and avalanches that cause deformation of the ground surface. To obtain an aerial photograph after the occurrence of a disaster, the aerial photograph 101 (helicopter) as described above can be used to take an aerial photograph relatively easily and inexpensively.

  Subsequently, in step S104, a subroutine for obtaining coordinate-calculated three-dimensional point cloud data is executed based on the aerial photograph at the second time prepared in the previous step S103.

  This subroutine is the same as that described above except that it is executed on the basis of the aerial photograph at the second time, but a more preferred embodiment of the subroutine will be described.

In step S202, it has been described that the operation of setting reference coordinates (GCP; ground control point) in the aerial photograph is performed. Here, reference coordinates (GCP; ground control points) set for a plurality of aerial photographs acquired in the first period and reference coordinates (GCP; ground control points) set for a plurality of aerial photographs acquired in the second period. ) Are more preferably the same.

  In other words, the points to be selected as reference coordinates (GCP; ground control point) and measured are assumed to be characteristic places such as pedestrian crossings in places that have not been damaged by disasters such as landslides, debris flows, heavy snowfalls and avalanches. Good.

  By the way, when the acquisition of the coordinate-calculated 3D point cloud data obtained based on the sky photograph at the second time is completed by the subroutine, the process returns to the main routine.

  The coordinate-calculated three-dimensional point cloud data acquired based on the aerial photograph at the second time is referred to as second coordinate-calculated three-dimensional point cloud data.

  Now, returning to the main routine of FIG. 3, the first coordinate-calculated 3D point cloud data acquired based on the plurality of aerial photographs acquired at the first time and the plurality of data acquired at the second time. A difference from the second coordinate-calculated three-dimensional point cloud data acquired based on the aerial photograph is calculated.

  In step S <b> 106, for example, it is color-coded according to the difference, and is displayed on the display device 22 or output from the output unit 19. In order to visualize the magnitude of the difference, not only a color-coded display but also a shade display can be employed. Any other method can be used as long as the difference can be visualized.

  In step S107, the analysis process ends.

According to the surface change analysis system according to the present invention as described above, it is possible to quickly grasp the surface change immediately after the occurrence of a disaster such as a landslide, debris flow, heavy snowfall or avalanche, and the analysis result obtained quickly can be obtained. It can be used for disaster prevention and search support.
(Example)
The debris flow disaster that occurred in Hiroshima in August 2014 was analyzed by the surface change analysis system according to the present invention.

  FIG. 10 is a diagram showing an aerial photograph of the first period before the occurrence of a debris flow disaster. The first aerial photograph was taken in 2008 by a digital aerial survey camera.

  FIG. 11 is a diagram showing an aerial photograph of the second period after the occurrence of a debris flow disaster. The aerial photograph of the second period was taken with an unmanned air vehicle 101. The ground altitude at the time of shooting was 150 m, and 5500 aerial photographs were obtained by 14 flights.

  As the reference coordinates (GCP; ground control point), the common coordinates in the first period and the second period were obtained by the actual measurement amount of 30 points, and the position coordinates of these 30 points were set in each aerial photograph. In addition, the global navigation satellite system was used for the actually measured amount of the reference coordinates (GCP; ground control point).

  As software, Agisoft PhotoScan Pro was used.

  FIG. 12 shows an analysis result by the ground surface change analysis system according to the present invention. FIG. 12 is a diagram showing the difference between the first coordinate calculated 3D point group data and the second coordinate calculated 3D point group data in different colors.

  As shown in FIG. 12, according to the ground surface change analysis system according to the present invention, the height change distribution in the affected area can be accurately grasped, and can be used for decision making such as search and removal of earth and sand. Met.

10 ... System bus 11 ... CPU (Central Processing Unit)
12 ... RAM (Random Access Memory)
13 ... ROM (Read Only Memory)
DESCRIPTION OF SYMBOLS 14 ... Communication control part 15 ... Input control part 16 ... Output control part 17 ... External storage device control part 18 ... Input part 19 ... Output part 20 ... External storage device 21 ... Interface unit 21 ... Graphic control unit 22 ... Display device 101 ... Aircraft 103 ... Airframes 104, 105, 106, 107 ... Propeller 113 ... Imaging device 120 ... Total station 130 ... Target

Claims (9)

A preparation step of preparing a plurality of aerial photographs taken from different positions on the ground surface by a camera mounted on the flying object,
A reference coordinate setting step for setting a plurality of reference coordinates based on an actually measured amount in a plurality of aerial photographs prepared in the preparation step;
Extracting a feature point in the aerial photograph prepared in the preparation step, and associating a plurality of aerial photographs, thereby calculating three-dimensional distribution data of the ground surface;
A three-dimensional point cloud data calculating step for calculating three-dimensional point cloud data of the ground surface having a higher density than the three-dimensional distribution data of the ground surface based on the three-dimensional distribution data of the ground surface calculated in the three-dimensional distribution data calculating step;
Based on the reference coordinates set in the reference coordinate setting step, the coordinates of the point cloud in the 3D point cloud data of the ground surface calculated in the 3D point cloud data calculation step are calculated, and the coordinate calculated 3D points Coordinate-calculated 3D point cloud data acquisition step for acquiring group data;
Perform each step consisting of
Based on a plurality of aerial photographs acquired in the first period, the first coordinate calculated 3D point cloud data is acquired,
Based on a plurality of aerial photographs acquired at a second time different from the first time, obtain second coordinate calculated 3D point cloud data,
A ground surface change analysis system that calculates and displays a difference between the first coordinate-calculated three-dimensional point group data and the second coordinate-calculated three-dimensional point group data. The ground surface change analysis system according to claim 1, wherein the display is performed by color-coding according to the difference. The ground surface change analysis system according to claim 1 or 2, wherein the reference coordinates are three or more points. The ground surface change analysis system according to any one of claims 1 to 3, wherein the reference coordinates are obtained by an actually measured amount by a total station. The ground surface change analysis system according to any one of claims 1 to 4, wherein the reference coordinates are obtained by an actually measured amount by a global navigation satellite system. Based on a plurality of aerial photographs acquired in the second period based on a plurality of aerial photographs acquired in the second period, the reference coordinates used when acquiring the first coordinate calculated 3D point cloud data are based on the plurality of aerial photographs acquired in the first period. 6. The ground surface change analysis system according to claim 1, wherein the ground surface change analysis system is the same as the reference coordinates used when acquiring the second coordinate-calculated 3D point cloud data. The ground change analysis system according to any one of claims 1 to 6, wherein a structure from motion technique is used in the three-dimensional distribution data calculation step. The ground surface change analysis system according to any one of claims 1 to 7, wherein a multi-view stereo technique is used in the three-dimensional point cloud data calculation step. The ground surface change analysis system according to any one of claims 1 to 8, wherein the flying body is an unmanned aerial vehicle.