JP2020112462A - Meander method aviation laser measurement method - Google Patents

Abstract

To provide a meander method aviation laser measurement method that can efficiently perform an aviation laser measurement with respect to meandering linear objects while maintaining conventional measurement accuracy.SOLUTION: A meandering method aviation laser measurement method of the invention disclosed in the present application is the method that measures linear objects by an aviation laser while flying meanderingly, and comprises a measurement plan step, a reference point set-up step, a measurement step, and an adjustment calculation step. The measurement step of these steps performs an aviation laser measurement while taking meandering flight on the basis of a planned flight course. The measurement plan step, when a curve angle in flight exceeds a threshold, divides the flight course and plans a flight course made of a plurality of division flight courses. When moving among different division flight courses, after getting away from the preceding division flight course, an air plane gets off the flight course once, takes turning flight, and then approaches the subsequent division flight course.SELECTED DRAWING: Figure 6

Description

The present invention is a technique relating to a method for measuring a linear object (hereinafter, referred to as “linear object”) such as a river, a road, a railroad, a coastline, and more specifically, along a meandering linear object. The present invention relates to a method of measuring with an aerial laser while meandering flight.

Up to now, aerial photogrammetry has been the mainstream method for measuring features over a wide area, but nowadays laser measurement, satellite image measurement, or synthetic aperture radar measurement is used. Various measurement methods have appeared, and it has become possible to appropriately select a suitable method according to the situation. The term "feature" as used herein is a generic term for all "objects" existing on the ground, such as artificial objects such as bridges and office buildings, or natural objects such as rivers, the sea, and forests.

Among these, aerial laser measurement is a method in which an aircraft flies above a target feature to be measured and receives a reflected wave of a laser pulse applied to the target feature for measurement. In this case, usually, the aircraft is equipped with a positioning device such as GNSS (Global Navigation Satellite System) and an inertial surveying device such as IMU (Internal Measurement Unit), and a measurement point (laser pulse is measured by a time difference between a laser pulse irradiation time and a reception time). The distance to the reflected point) can be obtained, and the irradiation position (x, y, z) and the irradiation posture (ω, φ, κ) at the time of laser pulse irradiation can be recorded by GNSS and IMU. As a result, It is possible to acquire the three-dimensional coordinates of the measurement point.

In addition, since conventional near-infrared laser measurement uses a near-infrared pulse laser (wavelength 1064 nanometer: nm), the laser pulse is reflected on the water surface and the feature on the bottom of the water cannot be measured. Aviation laser measurement, which can acquire objects (that is, water depth), has come to be used. This method is called ALB (Airborne Laser Bathymetry), and a green pulse laser (wavelength 532 nm) emitted from an aircraft passes through the water and is reflected from the bottom of the water, which enables sounding.

Due to such technical progress, aviation laser measurement has been widely used in recent years, and many new techniques relating to aviation laser measurement have been proposed accordingly. For example, in Japanese Patent Application Laid-Open No. 2004-242242, there is disclosed a technique capable of grasping a space sandwiched between features by performing a characteristic analysis process on a large amount of point cloud data obtained by aviation laser measurement (in particular, waveform data WFD). is suggesting.

JP, 2015-200615, A

By the way, when carrying out the aviation laser measurement, the flight course (hereinafter, simply referred to as “flying course”) is planned in advance, and then the flight is actually performed and the measurement is performed. This flight course is planned so that the aircraft flies in a straight line, and a plurality of flight courses are set so as to cover the target measurement range. Therefore, when performing aerial laser measurement over a range that spreads in a plane, it is possible to measure very efficiently by flying in a straight line, but on the other hand, when targeting a meandering linear object such as a river or road, The flying of the shape is rather inefficient.

In FIG. 9, a linear flight course is planned for a meandering river. Five straight courses (C1 to C5) planned on the left side of the figure and five straight courses planned on the right side of the figure. A straight course (C6 to C10) is shown. As can be seen from this figure, if a linear flight course is planned for a meandering linear object, the number of flight courses will increase, which will increase flight time and measurement costs.

For a meandering linear object, it is possible to plan a flight course that meanders along the linear object. However, at a location where the meandering angle is large, the aircraft becomes low-speed flight (hovering in the case of a rotary wing), so the attitude measurement accuracy by the IMU is reduced, and the measurement point density is reduced or missing due to an increase in the rolling angle of the aircraft. Alternatively, it is conceivable that the GNSS reception situation deteriorates, and as a result, the measurement accuracy significantly decreases. Therefore, heretofore, no example was found in which aerial laser measurement was performed while meandering flight along a meandering linear object.

An object of the present invention is to solve a conventional problem, that is, a meandering aviation laser measurement method capable of efficiently performing aviation laser measurement on a meandering linear object while maintaining the conventional measurement accuracy. Is to provide.

The present invention focuses on the point of planning a flight course such as a meandering flight along a linear object, and dividing the flight course in the case of extremely bending and planning with a plurality of divided flight courses. The invention was made based on an idea that has never existed before.

The meandering aviation laser measuring method of the present invention is a method of measuring a linear object with an aviation laser while flying along a meandering linear object, and includes a measurement planning step, a reference point setting step, a measuring step, and an adjustment calculation. It is a method including steps. Among these, in the measurement planning process, the flight course and the installation position of the reference point at the time of performing the aviation laser measurement are planned, and in the reference point installation process, the reference point is installed based on the installation position planned in the measurement planning process. Further, in the measurement process, aviation laser measurement is performed while meandering flight based on the flight course planned in the measurement planning process, and in the adjustment calculation process, adjustment calculation is performed on the measurement point group acquired in the measurement process. In the measurement planning process, we plan a flight course that makes a meandering flight along a linear object, and if the bending angle during flight exceeds a threshold value, divide the flight course and consist of a plurality of divided flight courses. Plan. In the measurement process, when moving between different divided flight courses, the vehicle exits the preceding divided flight course, turns off the flight course, and then turns to enter the subsequent divided flight course.

The meandering aerial laser measurement method of the present invention may be a method of planning the installation positions of the reference points so that the reference points are located at two positions on both sides of the linear object in the bending portion where the bending angle during flight exceeds the threshold value. ..

The meandering aerial laser measurement method of the present invention may be a method of planning two or more flight courses so as to fly on both sides of a linear object.

The meandering aviation laser measuring method of the present invention can be a method of measuring a meandering river. In this case, in the measurement planning process, in addition to the flight course to fly on both sides of the river, a river flight course to fly over the river is planned. When flying on this river flight course, in addition to near infrared, green laser is also used. Use to do aviation laser measurement.

The meandering aviation laser measurement method of the present invention extracts an accuracy deterioration measurement point based on the measurement results and reference points obtained in two or more flight courses, and removes the accuracy deterioration measurement point before performing adjustment calculation. It can also be a method of doing.

The meandering aviation laser measurement method of the present invention may be a method of performing adjustment calculation after dividing the divided flight course into a plurality of calculation blocks.

The meandering aviation laser measuring method of the present invention has the following effects.
(1) Since a meandering flight is performed along a linear object, flight time and measurement cost can be suppressed, that is, aviation laser measurement can be efficiently performed.
(2) If the vehicle makes an extreme turn, the flight course is divided and planning is made with multiple divided flight courses, so it is possible to avoid slow flight of the aircraft and increase of the Rolling angle even in a location with a large meandering angle. Aviation laser measurement can be performed while maintaining accuracy.
(3) The coordinate of the point cloud can be obtained with higher accuracy by performing the adjustment calculation after further dividing the divided flight course into a plurality of calculation blocks.

The top view which shows a meandering river. The flowchart which shows the main processes of the meandering aviation laser measuring method of this invention. The flowchart which shows each process of a measurement plan process. A model diagram showing a flight course on the right bank side, a flight course on the left bank side, and a river flight course that are planned linearly along a meandering river. (A) is a model diagram illustrating a case in which an angle threshold for determining a refraction point is set to 90°, and (b) is a model illustrating a case in which an angle threshold for determining a refraction point is set to 60°. Fig. The model diagram which shows the 1st division flight course and the 2nd division flight course which are set up by dividing a basic flight course into two inflection points. The flowchart which shows each process of a measurement process. The flowchart which shows each process of a calculation process. Plan view showing 10 linear flight courses planned for a meandering river.

An example of an embodiment of the meandering aviation laser measuring method of the present invention will be described with reference to the drawings. The present invention is a method of measuring a meandering linear object with an aviation laser, and the meandering linear object can be implemented on any feature such as a river, a road, a railroad, or a coastline. Here, an example in which the river RV shown in FIG. 1 is targeted will be described.

1. Overall Overview First, an overview of the meandering aviation laser measurement method of the present invention will be described with reference to FIG. FIG. 2 is a flow chart showing the main steps of the meandering aerial laser measurement method of the present invention. As shown in this figure, first, like the conventional method, a measurement plan is prepared (Step 100). In this measurement planning process, the contents necessary for aviation laser measurement, such as the flight course when performing aviation laser measurement and the installation position of the reference point, are planned. When the measurement plan is created, the reference points are set according to the plan (Step 200).

When the preparations up to this point are completed, aviation laser measurement is performed while actually flying according to the planned flight course (Step 300). Then, the flight course is divided into a plurality of blocks (hereinafter referred to as "calculation blocks"), and adjustment calculation (bundle adjustment method, polynomial method, independent model method, etc.) is performed using the point cloud data in adjacent calculation blocks. After that (Step 400), the position and shape of the river RV are output on a drawing, a map or the like. Hereinafter, the meandering aviation laser measurement method of the present invention will be described in more detail for each main step.

2. Measurement Planning Process FIG. 3 is a flowchart showing each process of the measurement planning process (Step 100 in FIG. 2). In the measurement planning process, first, a basic flight course is planned (Step 101). This flight course FC is planned linearly along the meandering river RV as shown in FIG. 4, and there are two flight courses, a flight course FCR along the right bank side and a flight course FCL along the left bank side. You should plan on FC. Of course, one flight course FC can be planned, or three or more flight courses FC can be planned according to the measurement target and the measurement purpose. In addition, in order to grasp the water bottom of the river RV, in addition to the flight course FCR on the right bank side and the flight course FCL on the left bank side, a river flight course FCO flying above the river RV is planned. When flying on this river flight course FCO, that is, when measuring (depth-measuring) the water bottom topography of the river RV, it is desirable to use ALB for irradiating a green pulse laser.

When the basic flight course FC is planned, it is determined whether or not there is an extremely curved portion (hereinafter referred to as a "refraction point") on the flight course FC (Step 102). As described above, at the inflection point, the aircraft becomes low-speed flight (hovering in the case of a rotary wing), so the attitude measurement accuracy by the IMU is reduced, or the measurement point density is reduced or missing due to an increase in the rolling angle of the aircraft. The GNSS reception situation is likely to deteriorate, and as a result, the measurement accuracy may be significantly reduced. In view of this, in the present invention, at the inflection point, instead of meandering along the river RV, the course is once out (out of the flight course), and the series of flight courses FC planned in Step 101 is divided at the inflection point. ..

In determining the refraction point, a directional axis in the flight course FC before the change (hereinafter, referred to as “first direction axis”) and a directional axis in the flight course FC after the change (hereinafter, “second direction axis”) Then, when the included angle θ exceeds a predetermined threshold value (hereinafter, referred to as “angle threshold value”), the point can be determined as a refraction point. The angle threshold value is set to 90° in a) and the angle threshold value is set to 60° in Fig. 5B. Therefore, in the case of Fig. 5A, the first direction axis AX1 and the second direction axis AX1 are set. If the included angle θ with the direction axis AX2 is 90° or more, it is determined to be a “refraction point”, and in the case of FIG. 5B, the included angle θ between the first direction axis AX1 and the second direction axis AX2 is 60. If it is equal to or more than °, it is judged as a "refraction point".

When a refraction point is confirmed on the flight course FC planned in Step 101, the flight course FC is divided at this refraction point as shown in FIG. 6 (Step 103). In FIG. 6, the flight course FC is divided into two by setting the first flight division block DB1 (area indicated by the broken line) and the second flight division block DB2 (area also indicated by the broken line) on the flight course FC. Therefore, the flight course in the first flight division block DB1 is set as the first division flight course FC1, and the flight course in the second flight division block DB2 is set as the second division flight course FC2.

Further, as shown in FIG. 6, a third divided flight course FC3 is set between the first divided flight course FC1 and the second divided flight course FC2. That is, the entire flight course FC is planned by connecting the first divided flight course FC1, the third divided flight course FC3, and the second divided flight course FC2 in this order (Step 104). The third divided flight course FC3 is, so to speak, a buffer section for avoiding flight at a steep angle, and is planned in a region outside the flight course FC planned in Step 101. More specifically, as shown in FIG. 6, after exiting the preceding first divided flight course FC1, turn outside the flight course FC and smoothly enter the second divided flight course FC2. Split flight course FC3 is planned.

The series of steps (Step 101 to Step 104) described so far are performed for each planned flight course FC. For example, in the case shown in FIG. 4, Steps 101 to 104 are repeatedly performed for each of the right bank flight course FCR, the left bank flight course FCL, and the river flight course FCO.

When the entire flight course FC connecting the first divided flight course FC1, the third divided flight course FC3, and the second divided flight course FC2 is determined, the installation position of the reference point is planned (Step 105). The installation position of the reference point is extremely important for ensuring a predetermined measurement accuracy in the aviation laser measurement. In particular, when performing meandering flight as in the present invention, the installation position of the reference point has a great influence on the measurement accuracy. Therefore, as a result of various studies including simulations, the inventors can perform measurement with high accuracy if one or more reference points are installed near the refraction part and on both banks of the river RV. I found that I could do it. Specifically, as shown in FIG. 6, in the area where the first flight division block DB1 and the second flight division block DB2 overlap, one or more locations are provided on each of the right bank side and the left bank side of the river RV (in FIG. 6, It is advisable to plan to arrange the reference points PS at one place each.

3. Measuring Process FIG. 7 is a flowchart showing each process of the measuring process (Step 300 in FIG. 2). In the measurement process, aviation laser measurement is performed while flying according to a flight course FC that is planned in advance. Specifically, as shown in FIG. 6, when flying along the same first divided flight course FC1 (that is, in the first divided flight block DB1), fly along the meandering river RV (Step 301). When the vehicle exits the first divided flight course FC1 (Step 302), it turns outside the flight course FC according to the third divided flight course FC3 (Step 303) and enters the second divided flight course FC2 (Step 303). It should be noted that it is desirable to stop the irradiation of the laser pulse during the flight according to the third divided flight course FC3. In this way, when moving between different divided flight courses (first divided flight course FC1 to second divided flight course FC2 in FIG. 6), the preceding divided flight course (first divided flight course in FIG. 6) After exiting FC1), the vehicle once turns in an area outside the flight course FC, and then enters the subsequent divided flight course (the second divided flight course FC2 in FIG. 6).

The series of steps (Step 301 to Step 304) described so far are performed for each planned flight course FC. For example, in the case shown in FIG. 4, the steps from Step 301 to Step 304 are repeated for each of the right bank flight course FCR, the left bank flight course FCL, and the river flight course FCO.

4. Calculation Step When the measurement step (Step 300 in FIG. 2) is performed, calculation processing is executed on the point cloud data that is the measurement result in order to output the position and shape of the river RV to a drawing, map, or the like. FIG. 8 is a flowchart showing each step of the calculation step (Step 300 in FIG. 2). As shown in this figure, when calculating the point cloud data, the measured range is divided into two or more calculation blocks (Step 401). The calculation is not performed for the entire measurement range collectively but for each calculation block in order to improve the calculation accuracy by performing the calculation for each range having similar position and orientation information.

The calculation block can be set by directly using the flight division block (the first flight division block DB1 or the second flight division block DB2 shown in FIG. 6) or can be set by further dividing the flight division block. Can also be set. In the flight division block, it becomes meandering flight and its flight attitude changes, but normally, if the range where the flight attitude changes multiple times in the same flight course is subject to adjustment calculation as it is, the parameters will be detailed in that flight course. Cannot be set. By further dividing the flight division block (for example, dividing the position at which the flight attitude changes at the boundary) and performing adjustment calculation etc. using the division range as a calculation block, detailed parameters can be set, and as a result, The accuracy of the calculated coordinates is improved.

By the way, in the present invention, since the meandering flight is performed, the flight speed thereof tends to be relatively low, and it is possible to acquire high-density point cloud data as compared with normal flight measurement. On the other hand, as shown in FIG. 4, when performing aviation laser measurement on two or more flight courses (a flight course FCR on the right bank side, a flight course FCL on the left bank side, and a river flight course FCO), the measurement results and criteria of multiple flight courses If verification is performed based on the point PS, it is possible to extract a measurement point whose accuracy is obviously deteriorated (hereinafter referred to as “accuracy deterioration measurement point”). In meandering flight, there is a possibility that there will be a clear deterioration in accuracy. Therefore, if the acquired high-density point cloud data is directly calculated, the data will be included. If the accuracy deterioration measurement points are extracted in advance and the accuracy deterioration measurement points are removed from the acquired point cloud data (Step 402) and then adjustment calculations are performed (Step 403), the accuracy of the calculated coordinates and the like should be improved. It becomes possible to be suitable.

INDUSTRIAL APPLICABILITY The meandering aerial laser measuring method of the present invention can be particularly effectively used for measuring meandering linear objects such as coastlines, roads, and railroads as well as rivers. According to the present invention, it is possible to measure rivers and shorelines more efficiently, and as a result, it is possible to take appropriate measures against flooding caused by rivers, that is, prevent flood disasters before they occur. Considering that the above can be achieved, the present invention can be said to be not only industrially applicable but also expected to make a great social contribution.

AX1 1st direction axis AX2 2nd direction axis DB1 1st division block DB2 2nd division block FCR Right bank side flight course FCL Left bank side flight course FCO River flight course FC1 1st division flight course FC2 2nd division Flight course FC3 Third split flight course PS Reference point RV river

Claims (6)

A method for measuring a linear object with an aviation laser while flying along a meandering linear object,
A measurement planning process that plans the flight course when performing aviation laser measurement and the installation position of the reference point,
Based on the installation position planned in the measurement planning process, a reference point setting step of setting a reference point,
Based on the flight course planned in the measurement planning step, a measurement step of performing aerial laser measurement while meandering flight,
An adjustment calculation step of performing adjustment calculation for the measurement point group acquired in the measurement step,
In the measurement planning step, while planning the flight course such as meandering flight along the linear object, when the bending angle during flight exceeds a threshold value, the flight course is divided into a plurality of divided flight courses. Plan the flight course
In the measuring step, when moving between the different divided flight courses, after exiting the preceding divided flight course, once turning off the flight course and then entering the subsequent divided flight course,
A meandering aviation laser measurement method characterized by the above. In the measurement planning step, the installation positions of the reference points are planned so that they are located at two positions on both sides of the linear object in the bending portion where the bending angle during flight exceeds a threshold value.
The meandering aviation laser measuring method according to claim 1, wherein In the measurement planning step, two or more flight courses are planned so as to fly on both sides of the linear object,
The meandering aviation laser measuring method according to claim 1 or 2, characterized in that. The linear object is a river,
In the measurement planning process, in addition to the flight course to fly on each side of the river, planning a river flight course to fly over the river,
In the measuring step, when flying on the river flight course, an aerial laser measurement is performed using a green laser,
The meandering aviation laser measuring method according to claim 3, wherein In the adjustment calculation step, the accuracy deterioration measurement point is extracted based on the measurement results obtained in two or more of the flight courses and the reference point, and the adjustment calculation is performed after removing the accuracy deterioration measurement point.
The meandering aviation laser measuring method according to claim 3 or 4, characterized in that. In the adjustment calculation step, the adjustment calculation is performed after dividing the divided flight course into a plurality of calculation blocks,
The meandering aviation laser measuring method according to any one of claims 1 to 5.

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