How to measure bathymetry

Abstract

To provide a method for measuring the topography of a water bottom, which can measure the topography of a water bottom with high accuracy even when the topography of the water bottom is measured using both a laser measuring device mounted on an aircraft and a sonar mounted on a ship. [Solution] In this method for measuring the water bottom topography, a measuring member 7 having a laser reflector is installed underwater above the water bottom in a measuring member installation step. A first measurement step for measuring the water bottom topography using a laser measuring instrument 3 includes a reflector measurement step for measuring the position of the laser reflector using the laser measuring instrument 3, and a second measurement step for measuring the water bottom topography using a sonar 5 includes a measuring member measurement step for measuring the position of the measuring member 7 using the sonar 5.

Description

[Technical Field]

[0001] The present invention relates to a method for measuring the topography of the bottom of a body of water such as a sea or lake. [Background technology]

[0002] A measurement method for measuring the elevation of the bottom of a body of water using a laser measurement device mounted on an aircraft is known (see, for example, Patent Document 1). In the measurement method described in Patent Document 1, the elevation of the bottom of a body of water is measured using a green laser beam emitted from the laser measurement device. Also, a bathymetric surveying method for measuring the topography of the seabed using a sonar mounted on a survey vessel is known (see, for example, Patent Document 2). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2019-66519 [Patent Document 2] Japanese Patent Application Publication No. 10-332825 Summary of the Invention [Problem to be solved by the invention]

[0004] The sound waves emitted from a sonar mounted on a ship spread out in a fan shape around the sonar in the water, and the range of the sound waves increases as the water depth increases. Therefore, in deep water, it is possible to efficiently measure the topography of the bottom using a sonar mounted on a ship. However, in shallow water, it is difficult to efficiently measure the topography of the bottom using a sonar mounted on a ship.

[0005] In contrast, when a laser measuring device mounted on an aircraft is used, it is possible to efficiently measure the topography of the water bottom even in shallow water.However, in deep water, the amount of laser light that is emitted from the laser measuring device mounted on an aircraft and reflected off the water bottom before reaching the laser measuring device decreases, making it difficult to accurately measure the topography of the water bottom using a laser measuring device mounted on an aircraft in deep water.

[0006] Furthermore, even in places with poor water transparency, the amount of laser light emitted from the aircraft-mounted laser measuring device, reflected by the water bottom, and then reaching the laser measuring device is reduced, making it difficult to accurately measure the water bottom topography using an aircraft-mounted laser measuring device, even in places with poor water transparency.In contrast, it is possible to accurately measure the water bottom topography using a ship-mounted sonar, even in places with poor water transparency.

[0007] The inventors of the present application have been considering measuring the water bottom topography using both an aircraft-mounted laser measuring device and a ship-mounted sonar in order to measure the water bottom topography efficiently and accurately, regardless of water depth or water transparency. However, when combining the results of the water bottom topography measured by the laser measuring device and the results of the water bottom topography measured by the sonar, if the relative positions of the water bottom topography measured by the laser measuring device and the water bottom topography measured by the sonar are shifted, it is difficult to measure the water bottom topography with high accuracy.

[0008] Therefore, the object of the present invention is to provide a method for measuring the topography of the seabed that can accurately measure the topography of the seabed, even when measuring the topography of the seabed using both a laser measuring device installed on an aircraft and a sonar installed on a ship. [Means for solving the problem]

[0009] In order to solve the above problems, the method for measuring the topography of the bottom of a body of water of the present invention is a method for measuring the topography of the bottom of a body of water, comprising: a measuring member installation step of installing a measuring member having a laser reflector that reflects laser light emitted from a laser measuring device underwater above the bottom of the water at the location to be measured; and a step of measuring the topography of the bottom of the water using the laser measuring device mounted on an aircraft flying above the location to be measured. a step of measuring the position of the laser reflector by a laser measuring device, The first measurement step is to measure the topography of the bottom of the water using a sonar mounted on a ship sailing on the water at the measurement location. a measuring member measuring step for measuring the position of the measuring member by sonar A second measurement step The method includes a correction necessity determination step for determining whether or not at least one of the first measurement result, which is a measurement result of the water bottom topography measured in the first measurement step, and the second measurement result, which is a measurement result of the water bottom topography measured in the second measurement step, needs to be corrected based on the measurement result of the reflecting unit measurement step and the measurement result of the measuring member measurement step; and a correction step for correcting at least one of the first measurement result and the second measurement result based on the measurement result of the reflecting unit measurement step and the measurement result of the measuring member measurement step, when it is determined that correction is needed in the correction necessity determination step, and the first measurement result after correction when the first measurement result is corrected in the correction step is referred to as the corrected first measurement result. and a combining step of combining the first measurement result and the second measurement result when the second measurement result is corrected in the correction step, the first measurement result and the second measurement result are combined if it is determined in the correction necessity determining step that correction is not necessary, combining the corrected first measurement result and the corrected second measurement result if it is determined in the correction necessity determining step that correction of the first measurement result and the second measurement result is necessary, combining the corrected first measurement result and the second measurement result if it is determined in the correction necessity determining step that correction of only the first measurement result is necessary, and combining the first measurement result and the corrected second measurement result if it is determined in the correction necessity determining step that correction of only the second measurement result is necessary. It is characterized by:

[0010] In the method for measuring the water bottom topography of the present invention, a measuring member having a laser reflector is installed underwater above the water bottom in the measuring member installation step. Also, in the present invention, the first measurement step of measuring the water bottom topography using a laser measuring device mounted on an aircraft includes a reflector measurement step of measuring the position of the laser reflector using the laser measuring device, and the second measurement step of measuring the water bottom topography using a sonar mounted on a ship includes a measuring member measurement step of measuring the position of the laser reflector using the sonar.

[0011] Therefore, in the present invention, even if there is a misalignment between the relative positions of the water bottom topography measured by the laser measuring device and the water bottom topography measured by sonar, it is possible to correct at least one of the water bottom topography measurement results measured in the first measurement step and the water bottom topography measurement results measured in the second measurement step based on the measurement results of the reflecting portion measurement step and the measurement results of the measuring member measurement step. In other words, in the present invention, even if there is a misalignment between the water bottom topography measured by the laser measuring device and the water bottom topography measured by sonar, it is possible to correct the misalignment and accurately combine the water bottom topography measurement results measured by the laser measuring device and the water bottom topography measurement results measured by sonar. Therefore, by measuring the water bottom topography using the water bottom topography measurement method of the present invention, it is possible to accurately measure the water bottom topography even when measuring the water bottom topography using both a laser measuring device installed on an aircraft and a sonar installed on a ship.

[0013] In the present invention, it is preferable that the laser reflecting portion retro-reflects the laser light. This configuration allows the position of the laser reflecting portion to be measured more accurately by a laser measuring device in the reflecting portion measurement step. For example, even if a laser-reflecting member having a shape similar to the laser reflecting portion is present in the water near the laser reflecting portion, the position of the laser reflecting portion can be measured more accurately by a laser measuring device in the reflecting portion measurement step. Therefore, when correcting at least one of the measurement results of the water bottom topography measured in the first measurement step and the measurement results of the water bottom topography measured in the second measurement step, the correction can be performed more accurately.

[0014] In the present invention, for example, the aircraft is an unmanned aerial vehicle, and the ship is an unmanned ship. [Effects of the Invention]

[0015] As described above, by measuring the topography of the bottom of the water using the bottom topography measurement method of the present invention, it becomes possible to measure the topography of the bottom of the water with high accuracy, even when measuring the topography of the bottom of the water using both a laser measuring device mounted on an aircraft and a sonar mounted on a ship. [Brief explanation of the drawings]

[0016] [Figure 1] 1 is a schematic diagram for explaining a method for measuring bottom topography according to an embodiment of the present invention; [Figure 2] FIG. 2 is a plan view of the measuring member shown in FIG. [Figure 3] FIG. 10 is a plan view of a measuring member according to another embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0017] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0018] (Method of measuring bottom topography) Fig. 1 is a schematic diagram for explaining a method for measuring bottom topography according to an embodiment of the present invention, Fig. 2 is a plan view of the measuring member 7 shown in Fig. 1.

[0019] The underwater topography measurement method of this embodiment is a method for measuring the topography of the bottom of the sea, lake, etc. In this embodiment, a laser measuring device 3 mounted on an aircraft 2 flying above the location to be measured and a sonar 5 mounted on a ship 4 sailing on the water surface of the location to be measured are used. In addition, a measuring member 7 having a laser reflector 6 that reflects laser light emitted from the laser measuring device 3 is used to measure the underwater topography. The aircraft 2 is an unmanned aerial vehicle (drone) remotely controlled by radio. The ship 4 is an unmanned ship remotely controlled by radio. Specifically, the ship 4 in this embodiment is a radio-controlled boat. In the following description, the aircraft 2 will be referred to as the "drone 2" and the ship 4 will be referred to as the "radio-controlled boat 4."

[0020] The laser measuring device 3 includes a light emitting unit that emits laser light toward the bottom of the water, and a light receiving unit that receives the laser light emitted from the light emitting unit and reflected by the bottom of the water. The laser measuring device 3 in this embodiment emits green laser light (green laser). The laser measuring device 3 emits laser light 50 times per second while changing the emission direction of the laser light so that the emission direction of the laser light forms an ellipse when viewed from above the drone 2. Note that the laser measuring device 3 may also emit laser light while changing the emission direction of the laser light so that the emission direction of the laser light forms a straight line when viewed from above the drone 2.

[0021] The sonar 5 includes a transmitting unit that emits sound waves and a receiving unit that receives sound waves emitted from the transmitting unit and reflected by the bottom of the water. The sonar 5 emits, for example, ultrasonic waves. The sound waves emitted from the sonar 5 spread in a fan shape underwater, with the sonar 5 at the center. The measuring member 7 includes a substrate 8 formed, for example, in the shape of a rectangular or square flat plate. The laser reflecting unit 6 in this embodiment is a retroreflective sheet that retroreflects laser light. The laser reflecting unit 6 (retroreflective sheet) is formed in the shape of a circular sheet and is attached to one surface of the substrate 8. When viewed in the thickness direction of the substrate 8, the center of the circular laser reflecting unit 6 coincides with the center of the rectangular or square substrate 8.

[0022] The method for measuring the water bottom topography includes a measuring member installation step in which a measuring member 7 is installed underwater above the water bottom at the measurement location, a first measurement step in which the water bottom topography is measured using a laser measuring device 3 mounted on a drone 2, and a second measurement step in which the water bottom topography is measured using a sonar 5 mounted on a radio-controlled boat 4. In the following description, the measurement results of the water bottom topography measured in the first measurement step will be referred to as the "laser measurement results," and the measurement results of the water bottom topography measured in the second measurement step will be referred to as the "sonar measurement results."

[0023] In the measuring member installation step, an operator installs the measuring member 7 in water. In the measuring member installation step, the measuring member 7 is installed so that the thickness direction of the substrate 8 formed in a flat plate shape coincides with the up-down direction (vertical direction) and so that the laser reflecting portion 6 faces upward. The measuring member 7 is installed so that the laser reflecting portion 6 is located at a depth at which the laser light emitted from the laser measuring instrument 3 reaches the laser reflecting portion 6. In the measuring member installation step, for example, the measuring member 7 is fixed onto a predetermined base 9, thereby installing the measuring member 7 in water above the bottom of the water. The base 9 is firmly fixed to the bottom of the water so that the measuring member 7 does not move in the water.

[0024] In the first measurement step, a laser beam is emitted downward from the laser measuring device 3 mounted on the drone 2. In the first measurement step, the topography of the water bottom is measured based on the reception results by the laser measuring device 3 of the laser beam emitted from the laser measuring device 3 and reflected by the water bottom. The first measurement step includes a reflecting portion measurement step in which the laser measuring device 3 measures the position of the laser reflecting portion 6. In the reflecting portion measurement step, the horizontal position and the up-down position of the laser reflecting portion 6 are measured based on the reception results by the laser measuring device 3 of the laser beam emitted from the laser measuring device 3 and reflected by the laser reflecting portion 6. In this embodiment, the position of the center of the laser reflecting portion 6 is measured.

[0025] In the second measurement step, sound waves are emitted downward into the water from the sonar 5 mounted on the radio-controlled boat 4. In the second measurement step, the topography of the water bottom is measured based on the reception results of the sound waves emitted from the sonar 5 and reflected by the water bottom by the sonar 5. The second measurement step includes a measuring member measurement step in which the position of the measuring member 7 is measured using the sonar 5. In the measuring member measurement step, the horizontal and vertical positions of the measuring member 7 are measured based on the reception results of the sound waves emitted from the sonar 5 and reflected by the measuring member 7 by the sonar 5. In this embodiment, the position of the center of the upper surface of the measuring member 7 is measured. The second measurement step may be performed after or before the first measurement step. Furthermore, if there are no obstacles, the first and second measurement steps may be performed simultaneously.

[0026] The method for measuring the water bottom topography also includes a correction necessity determination process for determining whether or not it is necessary to correct at least one of the laser measurement results (i.e., the measurement results of the water bottom topography measured in the first measurement process) and the sonar measurement results (i.e., the measurement results of the water bottom topography measured in the second measurement process) based on the measurement results of the reflecting part measurement process and the measurement results of the measuring member measurement process, and a correction process for correcting at least one of the laser measurement results and the sonar measurement results when it is determined in the correction necessity determination process that correction is necessary.

[0027] As described above, in this embodiment, the center of the laser reflecting portion 6 coincides with the center of the substrate 8 when viewed in the thickness direction of the substrate 8. In the correction necessity determination step, the amount of deviation between the position of the center of the laser reflecting portion 6 measured in the reflecting portion measurement step and the position of the center of the upper surface of the measuring member 7 measured in the measuring member measurement step is calculated. For example, an operator inputs the measurement results of the reflecting portion measurement step and the measuring member measurement step into a personal computer and calculates the amount of deviation using predetermined software. Furthermore, in the correction necessity determination step, if the calculated amount of deviation is equal to or greater than a predetermined reference value, it is determined that correction is necessary, and if the calculated amount of deviation is less than the reference value, it is determined that correction is not necessary. The determination of whether correction is necessary is made, for example, by an operator.

[0028] If it is determined that correction is necessary in the correction necessity determination process, a correction process is performed. In the correction process, at least one of the laser measurement results and the sonar measurement results is corrected based on the measurement results of the reflecting portion measurement process and the measurement results of the measuring member measurement process. In the correction process, at least one of the laser measurement results and the sonar measurement results is corrected using software so that the center position of the laser reflecting portion 6 measured in the reflecting portion measurement process coincides with the center position of the upper surface of the measuring member 7 measured in the measuring member measurement process. For example, the sonar measurement results are corrected. In addition, for example, the laser measurement results and the corrected sonar measurement results are combined to obtain measurement results of the water bottom topography of the measured location, and the measurement results of the water bottom topography of the measured location are converted into three-dimensional data.

[0029] (Main effect of this form) As described above, in this embodiment, in the measuring member installation step, the measuring member 7 is installed underwater above the water bottom. Also, in this embodiment, the first measurement step of measuring the water bottom topography using the laser measuring device 3 mounted on the drone 2 includes a reflecting portion measurement step of measuring the position of the laser reflecting portion 6 using the laser measuring device 3, and the second measurement step of measuring the water bottom topography using the sonar 5 mounted on the radio-controlled boat 4 includes a measuring member measurement step of measuring the position of the laser reflecting portion 6 using the sonar 5.

[0030] Furthermore, in this embodiment, in the correction necessity determination step, it is determined whether or not at least one of the laser measurement result and the sonar measurement result needs to be corrected based on the measurement results of the reflecting part measurement step and the measurement results of the measuring member measurement step, and if it is determined that correction is necessary, in the correction step, at least one of the laser measurement result and the sonar measurement result is corrected based on the measurement results of the reflecting part measurement step and the measurement results of the measuring member measurement step. Specifically, in the correction step, at least one of the laser measurement result and the sonar measurement result is corrected so that the position of the center of the laser reflecting part 6 measured in the reflecting part measurement step and the position of the center of the upper surface of the measuring member 7 measured in the measuring member measurement step coincide.

[0031] Therefore, in this embodiment, even if there is a deviation in the relative positions of the water bottom topography measured by the laser measuring instrument 3 and the water bottom topography measured by the sonar 5, the deviation can be corrected in the correction process, and the laser measurement results and the sonar measurement results can be accurately combined. Therefore, if the water bottom topography is measured using the measurement method of this embodiment, it becomes possible to accurately measure the water bottom topography even when the water bottom topography is measured using both the laser measuring instrument 3 mounted on the drone 2 and the sonar 5 mounted on the radio-controlled boat 4.

[0032] In this embodiment, the laser reflector 6 retro-reflects the laser light. Therefore, in this embodiment, the position of the laser reflector 6 can be measured with higher accuracy by the laser measuring instrument 3 in the reflector measurement step. Therefore, in this embodiment, at least one of the laser measurement results and the sonar measurement results can be corrected with higher accuracy in the correction step.

[0033] (Other embodiments) In the above-described embodiment, the center of the laser reflecting portion 6 does not have to coincide with the center of the substrate 8 when viewed in the thickness direction of the substrate 8. Also, in the above-described embodiment, as shown in Fig. 3, the laser reflecting portion 6 may be formed in the same rectangular shape as the substrate 8. Also, various patterns as shown in Figs. 3(A) and (B) may be applied to the laser reflecting portion 6, which is a retroreflective sheet.

[0034] In the above-described embodiment, the base material 8 may be formed in a disk shape, or in a flat plate shape of a polygon other than a square. For example, the base material 8 may be formed in a disk shape having the same external shape as the laser reflecting portion 6. In addition, in the above-described embodiment, the base material 8 may be formed in a rectangular parallelepiped or cubic shape, or in a polygonal prism shape such as a cylindrical shape, a truncated cone shape, or a square prism shape, or in a polygonal prism shape such as a square prism shape.

[0035] In the above-described embodiment, the laser reflector 6 does not need to retro-reflect the laser light. Also, in the above-described embodiment, a manned aircraft may be used instead of the drone 2, and a manned ship may be used instead of the radio-controlled boat 4. [Explanation of symbols]

[0036] 2 Drones (aircraft) 3 Laser measuring instrument 4. Radio-controlled boats (ships) 5. Sonar 6 Laser reflector 7 Measuring parts

Claims

1. A method for measuring the topography of a water bottom, comprising: a measuring member installation step of installing a measuring member having a laser reflecting portion that reflects laser light emitted from the laser measuring device underwater above the bottom of the water at the measurement location; a first measurement step of measuring the topography of the bottom of the water using the laser measuring device mounted on the aircraft flying above the measurement location, the first measurement step including a reflector measurement step of measuring the position of the laser reflector using the laser measuring device; a second measurement step, which includes a step of measuring the topography of the bottom of the water using a sonar mounted on a ship sailing on the water at the measurement location, and a measuring member measurement step of measuring the position of the measuring member using the sonar; a correction necessity determination step for determining whether or not it is necessary to correct at least one of the first measurement result, which is the measurement result of the water bottom topography measured in the first measurement step, and the second measurement result, which is the measurement result of the water bottom topography measured in the second measurement step, based on the measurement results of the reflecting portion measurement step and the measurement results of the measuring member measurement step; a correction step of correcting at least one of the first measurement result and the second measurement result based on the measurement result of the reflecting portion measurement step and the measurement result of the measuring member measurement step when it is determined that correction is necessary in the correction necessity determination step; When the first measurement result is corrected in the correction step, the corrected first measurement result is defined as a corrected first measurement result, and when the second measurement result is corrected in the correction step, the corrected second measurement result is defined as a corrected second measurement result. A method for measuring bottom topography, comprising a synthesis step of combining the first measurement result and the second measurement result if it is determined in the correction necessity determination step that correction is not necessary, combining the corrected first measurement result and the corrected second measurement result if it is determined in the correction necessity determination step that correction of the first measurement result and the second measurement result is necessary, combining the corrected first measurement result and the second measurement result if it is determined in the correction necessity determination step that correction of only the first measurement result is necessary, and combining the first measurement result and the corrected second measurement result if it is determined in the correction necessity determination step that correction of only the second measurement result is necessary.

2. 2. The method for measuring bottom topography according to claim 1, wherein the laser reflector retro-reflects the laser light.

3. the aircraft is an unmanned aerial vehicle; 3. The method for measuring underwater topography according to claim 1, wherein the vessel is an unmanned vessel.

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