JP7774482B2 - River flow estimation system - Google Patents

Description

This invention relates to technology for estimating river flow rates, and more specifically to a river flow rate estimation system that can estimate the flow rate of a river based on images obtained by photographing the river.

It is useful to know the amount of water flowing in a river (flow rate), and it is extremely important to understand river flow rate, especially when flooding due to heavy rain is predicted. For over 100 years, the basic method for measuring flow rate during floods has been float observation. This float observation method involves dropping a float into the river and observing the time it takes for it to flow down a certain distance to determine the flow rate, and then multiplying this flow rate by the cross-sectional area of the river (the part through which water flows) to determine the flow rate. Furthermore, float observation requires a minimum of five observers, which means it is very labor-intensive.

On the other hand, in cases where it is difficult to dispatch many observers, such as rivers in mountainous regions, river flow is generally observed using the cross-section measurement method. With this method, the river cross section is measured at intervals of several centimeters, which requires a minimum of two to three observers, and the time required for observation at one location is estimated to be 15 to 30 minutes. In other words, determining river flow using the cross-section measurement method requires a great deal of effort, just like float observations.

It is possible to measure flow directly using measuring equipment without relying on float observations or cross-sectional measurement methods, but using measuring equipment during floods is dangerous, and even if the measuring equipment were permanently installed, there is a risk of it being damaged or readings being missed, so this is not a realistic method.

In recent years, therefore, attempts have been made to install cameras or video cameras in noteworthy locations on rivers and use the images and videos to determine river flow rates. For example, Patent Document 1 proposes technology for determining river flow rates by capturing images of a river at two or more time periods and using these images to perform PIV (Particle Image Velocimetry) analysis.

Japanese Patent Application Laid-Open No. 2008-216010

Until now, the mainstream method for determining river flow rate has been to first determine the flow velocity and then calculate the flow rate. For example, in float observations, the speed of the float is measured, and in Patent Document 1, PIV analysis is performed to determine the river flow velocity, and the river flow rate is then calculated by multiplying the flow velocity by the cross-sectional area of the river.

However, measuring river flow velocity using float observations requires a great deal of effort and does not always result in an accurate flow velocity. Furthermore, even if PIV analysis is performed as in Patent Document 1, accurate flow velocity may not always be obtained depending on the image conditions. And if accurate flow velocity cannot be obtained, it is naturally impossible to accurately determine the river flow rate.

The objective of the present invention is to solve the problems of the past, namely, to provide a river flow estimation system that uses images obtained by photographing a river and can determine river flow rate without calculating flow velocity.

The present invention focuses on the fact that the flow rate of a river contained in a photographed image can be estimated by adjusting the image of a flow simulation so that it resembles an image obtained by photographing the river, and is an invention based on an unprecedented concept.

The river flow estimation system of the present invention is a system that estimates the flow rate of a river based on observation images of the river, and is equipped with a flow simulation means and a display control means. The flow simulation means is a means for calculating the river water level at various locations using a 3D topographical model, and the display control means is a means for displaying a rendered image (an image in which the river and the 3D topographical model are superimposed) while changing the viewpoint and line of sight. The display control means displays the rendered image according to the viewpoint and line of sight that are further set so that the river water level matches that calculated by the flow simulation means. Furthermore, when the flow rate of the river is set, the flow simulation means calculates the river water at each location that corresponds to a river in the 3D topographical model. The flow rate of the river contained in the observation image can then be estimated by comparing the observed image with the rendered image while changing the flow rate set in the flow simulation means.

The river flow rate estimation system of the present invention can further include a field of view adjustment means. This field of view adjustment means adjusts the viewpoint and line of sight of the display control means so that the drawn image has a field of view that is approximately the same (including the same) as that of the observed image.

The river flow estimation system of the present invention can further include a photography specification input means and a drawing specification calculation means. The photography specification input means is a means for inputting the photography position and photography direction of the observation image, and the drawing specification calculation means is a means for determining the viewpoint and viewing direction of the drawn image based on the photography position and photography direction input by the photography specification input means. In this case, the display control means displays the drawn image according to the viewpoint and viewing direction determined by the drawing specification calculation means.

The river flow rate estimation system of the present invention has the following effects.
(1) The flow rate can be determined simply by acquiring observation images. For example, by permanently installing a camera on-site, unmanned operation and labor saving can be achieved. As a result, observation costs can be reduced and observers are not placed in dangerous situations.
(2) Furthermore, since the flow rate can be grasped simply by installing a camera on-site, it can be applied in a variety of locations.
(3) Even if the angle of view of the camera installed on-site is changed, the image of the flow simulation can be adjusted to flexibly accommodate the change.
(4) Since there is no need to calculate the flow velocity, it is possible to avoid the inconvenience of calculating an inaccurate river flow rate due to an inaccurate flow velocity.

1 is a block diagram showing the main configuration of a river flow rate estimation system according to the present invention; 1A is a photograph showing an example of an observed image, and FIG. 1B is a model diagram showing an example of a drawn image. FIG. 3 is a flowchart showing an example of a main processing flow of the river flow rate estimation system according to the first embodiment. FIG. 10 is a flowchart showing an example of a main processing flow of the river flow rate estimation system in the second embodiment.

An example of an embodiment of the river flow estimation system of the present invention will be explained with reference to the drawings.

Figure 1 is a block diagram showing the main components of the river flow estimation system 100 of the present invention. As shown in this figure, the river flow estimation system 100 of the present invention is configured to include a flow condition simulation means 101 and a display control means 102, and can also be configured to include a field of view adjustment means 103, a photography specification input means 104, a drawing specification calculation means 105, an image acquisition means 106, a display means 107, an observed image storage means 108, and a three-dimensional terrain model storage means 109.

The flow regime simulation means 101, display control means 102, angle of view adjustment means 103, photography parameter input means 104, and drawing parameter calculation means 105 that constitute the river flow estimation system 100 of the present invention can be manufactured as dedicated devices, or a general-purpose computer device can be used. This computer device includes a processor such as a CPU, memory such as ROM and RAM, and may further include input means such as a mouse and keyboard, and display means such as a display, and can be configured, for example, as a personal computer (PC) or server.

The observation image storage means 108 and the 3D terrain model storage means 109 can be stored in the storage device of a general-purpose computer (e.g., a PC), or can be built on a database server. If built on a database server, they can be placed on a local network (LAN: Local Area Network), or they can be used as a cloud server that stores data via the Internet.

Below, we will provide a detailed explanation of each of the main elements that make up the river flow estimation system 100.

(Image Acquisition Means)
The image acquisition means 106 acquires images (hereinafter referred to as "observation images") obtained by photographing the river as still images or videos, and can be equipped with a digital camera, a digital video camera, a smartphone, a tablet PC, or the like. Figure 2(a) shows an example of an observation image. Observation images can be acquired using the image acquisition means 106 carried by the observer, or using the image acquisition means 106 of a so-called fixed camera permanently installed on-site, or satellite images can also be used. The still images and videos acquired by the image acquisition means 106 are stored in the observation image storage means 108 (Figure 1). Note that the observation images taken by the image acquisition means 106 of the fixed camera may be transmitted via communication means and then stored in the observation image storage means 108.

(3D terrain model memorizer)
The three-dimensional terrain model storage means 109 is a means for storing a three-dimensional terrain model (hereinafter referred to as a "3D terrain model"). Here, a 3D terrain model is a representation of terrain, including features, using three-dimensional coordinates (i.e., constituent points), and is a terrain model typified by a digital surface model (DSM) or a digital elevation model (DEM). A 3D terrain model is typically composed of small areas obtained by dividing a target planar area. These small areas are also called meshes, and are formed by dividing the area into, for example, orthogonal grids, and each small area has a representative point. Because a three-dimensional point cloud (i.e., constituent point cloud) obtained by measurement is often random data (data with an irregular arrangement on a plane), geometric calculations are often performed to assign heights to the representative points of the small areas. Examples of calculation methods include the TIN (Triangulated Irregular Network) method, which finds height using an irregular triangular network formed from random data, the nearest neighbor method, which uses the nearest laser measurement point, as well as the inverse distance weighting (IDW) method, the Kriging method, and the averaging method.

(Flow simulation means)
The flow regime simulation means 101 is a means for calculating, when an operator sets a desired river flow rate, the river water level at each position based on the river flow rate and a 3D topographical model, and can also be used as a means for calculating the flow velocity in addition to the river water level. Specifically, it is a means for calculating the river water level at each position by having an electronic calculator (computer) execute calculation processing using a program. Note that the program used by the flow regime simulation means 101 can be any of a variety of conventional programs, including commercially available products.

(Display control means)
The display control means 102 is a means for outputting an image in which a river and a 3D topographical model are superimposed (hereinafter referred to as a "drawn image") to a display means 107 such as a display. An example of the drawn image is shown in FIG. 2(b). The display control means 102 can also display the drawn image so that it matches the river water level calculated by the flow condition simulation means 101, and can further display the drawn image so that it is a bird's-eye view according to a set viewpoint and line of sight. This display control means 102 also causes a computer to execute processing using a conventional program, and can be implemented using the same program as the flow condition simulation means 101.

(Field of view adjustment means)
As described above, the display control means 102 can display the drawn image so as to be a bird's-eye view according to the set viewpoint and line of sight direction. The angle-of-view adjustment means 103 is a means for setting the viewpoint and line of sight direction of the drawn image to be displayed by the display control means 102. This allows the display control means 102 to display the drawn image while appropriately changing the viewpoint and line of sight direction, and adjust the drawn image so as to become an image desired by the operator. To set the viewpoint and line of sight direction, for example, the operator can set the viewpoint and line of sight direction by operating the angle-of-view adjustment means 103 while checking the drawn image displayed on the display (display means 107). In this case, it is preferable to use a pointing device (such as a mouse, touch panel, pen tablet, touchpad, trackpad, or trackball), a keyboard, or the like as the angle-of-view adjustment means 103.

One of the technical features of the present invention is that the angle of view of an observation image and a drawn image is approximately the same (including coincidence), thereby estimating the river flow rate in the observation image. Here, the angle of view includes the range (size) and attitude (shape) of features (part of a 3D terrain model) included in the image (observation image or drawn image), as well as the shape of the river (particularly the river water level). In other words, if the range and attitude of the features and the shape of the river included in the observation image and the drawn image are approximately the same, then the angle of view of the observation image and the drawn image will be approximately the same. Furthermore, if the angle of view of the observation image and the drawn image are approximately the same, then the river flow rate when the river water level related to the drawn image is calculated can be estimated to be the flow rate of the river included in the observation image.

The angle-of-view adjustment means 103 can also be configured to set camera specifications (orientation elements) such as the camera's focal length, screen distance, principal point position deviation, and various distortions (radial distortion, asymmetric distortion, etc.) in addition to the viewpoint and line-of-sight direction of the drawn image. This allows the display control means 102 to display a drawn image based on the river water level, 3D terrain model, viewpoint and line-of-sight direction, and camera specifications from the flow condition simulation means 101 as given conditions, allowing the drawn image to be displayed in a way that better matches the angle of view of the observed image.

When the operator operates the angle-of-view adjustment means 103 while checking the drawn image displayed on the display (display means 107) so that the angle of view of the observed image and the drawn image roughly matches, it is advisable to display the observed image on the display as well. For example, the observed image shown in Figure 2(a) is displayed along with the drawn image shown in Figure 2(b), and the set river flow rate is changed and the viewpoint and line of sight are changed so that the angle of view of the drawn image matches that of the observed image.

(Drawing specification calculation means)
As explained above, the angle of view of the drawn image and the observation image can be matched by adjusting the viewpoint and line of sight of the drawn image by the operator operating the angle-of-view adjustment means 103 (i.e., manually operating it), or the viewpoint and line of sight of the drawn image can be determined by calculation. In this case, the drawing parameter calculation means 105 calculates the viewpoint and line of sight of the drawn image based on the parameters (hereinafter referred to as "photography parameters") used when the observation image was captured. Note that these photography parameters are input by the photography parameter input means 104. For example, the operator can input the photography parameters by operating a keyboard or the like, or the photography parameters can be transmitted via communication means when the image acquisition means 106 captures an image.

The imaging specifications include at least the imaging position and imaging direction, and may also include camera specifications. The imaging position is the three-dimensional coordinates (X, Y, Z) of the imaging position (lens center) of the image acquisition means 106, and can be measured using conventional positioning technologies such as the Global Navigation Satellite System (GNSS) or Total Station (TS). The imaging direction is the optical axis direction of the image acquisition means 106, and is a value determined by the tilt (yaw, pitch, roll) relative to three orthogonal axes (e.g., the X-Y-Z axes), i.e., the rotation angle (ω, φ, κ) around each axis, and can be measured using an angular velocity sensor, geomagnetic sensor, IMU (Inertial Measurement Unit), etc.

In cases where the shooting specifications are input by the shooting specification input means 104 and the drawing specification calculation means 105 calculates the viewpoint and line of sight of the drawn image based on the shooting specifications, the display control means 102 naturally displays the drawn image as a bird's-eye view according to the calculated viewpoint and line of sight.

(Processing flow)
The following describes in detail the main processing of the river flow rate estimation system 100. The explanation will be divided into a form in which the operator sets the viewpoint and line of sight of the drawn image by operating the angle of view adjustment means 103 (hereinafter referred to as "first form"), and a form in which the viewpoint and line of sight calculated by the drawing parameter calculation means 105 are set (hereinafter referred to as "second form").

Figure 3 is a flow diagram showing an example of the main processing flow of the river flow estimation system 100 in the first form, with the center column showing the processing to be performed, the left column showing what is necessary for that processing, and the right column showing what results from that processing.

To estimate the flow rate of a river using the river flow rate estimation system 100 in the first embodiment, an observation image is first acquired as shown in Figure 3 (Step 200 in Figure 3). As mentioned above, the observation image can be acquired using an image acquisition means 106 carried by an observer, or it can be acquired using an image acquisition means 106 of a so-called fixed camera permanently installed on-site.

Once the observation image is acquired, the river flow rate is set by the operator (Step 211 in Figure 3). The flow regime simulation means 101 then calculates the river water level at each location based on the set river flow rate and the 3D terrain model read from the 3D terrain model storage means 109 (Step 212 in Figure 3).

Once the river water level is calculated, the operator sets the viewpoint and line of sight (Step 213 in Figure 3), and the display control means 102 outputs the drawn image to the display means 107 (Step 214 in Figure 3). Once the drawn image is displayed, the operator compares the drawn image with the observed image (Step 215 in Figure 3). If the range or orientation of the features (i.e., the background) within the field of view do not substantially match (including matching) (No in Step 215 in Figure 3), the operator changes the viewpoint and line of sight (Step 213 in Figure 3) and displays the drawn image (Step 214 in Figure 3), and then compares the drawn image with the observed image again (Step 215 in Figure 3). On the other hand, if the range or orientation of the features within the field of view substantially match (Yes in Step 215 in Figure 3), the river water level within the field of view of the drawn image and the observed image is compared (Step 216 in Figure 3).

If the river water level does not approximately match within the angle of view (No in Step 216 in Figure 3), the river flow rate is changed (Step 211 in Figure 3) and the series of processes (Steps 212 to 216 in Figure 3) are repeated again. However, there is no need to change the viewpoint or line of sight in this case. On the other hand, if the river water level within the angle of view approximately matches (Yes in Step 216 in Figure 3), the river flow rate when the river water level in the drawn image is calculated is determined to be the river flow rate included in the observed image (Step 217 in Figure 3).

Figure 4 is a flow diagram showing an example of the main processing flow of the river flow estimation system 100 in the second form, with the center column showing the processing to be performed, the left column showing what is necessary for that processing, and the right column showing what results from that processing.

To estimate the flow rate of a river using the river flow rate estimation system 100 in the second embodiment, an observation image is first acquired as shown in Figure 4 (Step 200 in Figure 4). As mentioned above, the observation image can be acquired using an image acquisition means 106 carried by an observer, or it can be acquired using an image acquisition means 106 of a so-called fixed camera permanently installed on-site.

Once the observed image is acquired, the operator inputs the imaging specifications (Step 221 in Figure 4). The rendering specifications calculation means 105 then calculates the viewpoint and line of sight direction of the rendering image based on the imaging specifications (Step 222 in Figure 4).

Once the viewpoint and viewing direction of the drawn image are calculated, the river flow rate input by the operator is set (Step 223 in Figure 4). Once the river flow rate is set, the flow regime simulation means 101 calculates the river water level at each position based on the set river flow rate and the 3D terrain model read from the 3D terrain model storage means 109 (Step 224 in Figure 3).

Once the river water level is calculated, the display control means 102 outputs the drawn image to the display means 107 (Step 225 in Figure 4). Then, the drawn image and the observation image are compared, particularly with respect to the river water level, based on their angles of view (Step 226 in Figure 4).

If the angle of view (especially the river water level) of the drawn image and the observed image do not substantially match (No in Step 226 in Figure 4), the river flow rate is changed (Step 223 in Figure 4) and the series of processes (Steps 223 to 226 in Figure 4) are repeated. On the other hand, if the angle of view of the drawn image and the observed image substantially match (Yes in Step 226 in Figure 4), the river flow rate when the river water level of the drawn image was calculated is determined to be the flow rate of the river included in the observed image (Step 227 in Figure 4).

The river flow estimation system of the present invention is particularly useful for river administrators, including national and local governments. Considering that the present invention can quickly predict floods and other river-related water damage, thereby protecting many residents from disasters, the present invention is not only applicable to industry but is also expected to make a significant contribution to society.

100 River flow rate estimation system of the present invention 101 Flow regime simulation means (of river flow rate estimation system) 102 Display control means (of river flow rate estimation system) 103 View angle adjustment means (of river flow rate estimation system) 104 Photographing parameter input means (of river flow rate estimation system) 105 Drawing parameter calculation means (of river flow rate estimation system) 106 Image acquisition means (of river flow rate estimation system) 107 Display means (of river flow rate estimation system) 108 Observation image storage means (of river flow rate estimation system) 109 3D topographic model storage means (of river flow rate estimation system)

Claims (3)

A system for estimating the flow rate of a river based on observation images of the river, comprising:
A flow simulation means for calculating the river water level at each location using a three-dimensional topographical model;
a display control means for displaying a drawn image in which a river and a three-dimensional topographical model are superimposed while changing a viewpoint and a line of sight;
the display control means displays the drawn image so as to correspond to the river water level calculated by the flow condition simulation means and in accordance with a set viewpoint and line of sight direction;
the flow regime simulation means calculates the river water level at each position of the river in the three-dimensional topographical model when the flow rate of the river is set;
The flow rate of the river included in the observed image can be estimated by comparing the observed image with the drawn image while changing the flow rate set in the flow regime simulation means.
A river flow rate estimation system characterized by: further comprising a view angle adjusting means for adjusting a viewpoint and a line of sight direction of the display control means so that the drawn image has the same or substantially the same view angle as the observed image;
2. The river flow rate estimation system according to claim 1. an imaging parameter input means for inputting the imaging position and imaging direction of the observation image;
a drawing parameter calculation means for calculating a viewpoint and a line of sight direction of the drawing image based on the photographing position and the photographing direction input by the photographing parameter input means,
the display control means displays the drawn image according to the viewpoint and line of sight direction calculated by the drawing specification calculation means.
2. The river flow rate estimation system according to claim 1.