JP2001133311A - Water level measurement method and water level measurement system - Google Patents

Abstract

(57) [Summary] In a water level measurement by image processing, a measurement error when a camera is installed at an inclined angle with respect to an object to be measured is corrected, and a water level measurement with the same accuracy as in a parallel state is performed. Realization. An image in which a water mark 3 and an inclined plate 4 are set is captured by a camera 2, image processing is performed on a water surface boundary from the inclined plate image by a water level measuring device, and converted into image coordinates on a scale of the water mark. Then, the water level on the ground is calculated by converting the coordinates to a world coordinate system. In advance, a coordinate conversion error caused by the inclination angle θ of the camera line of sight 102 is obtained for each scene 23 of the water mark 3, and the error is corrected by using this in online measurement. High-precision water level measurement is possible even when the camera installation position conditions are poor, such as in dams.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a water level measuring method and system for measuring the water level of rivers, lakes, seas, dams and the like by image processing.

[0002]

2. Description of the Related Art Safety management is performed by automatically measuring water levels of rivers, lakes, seas, dams, and the like. However, the fluctuation range of these water levels is usually several meters, up to a dozen meters, and therefore accurate. Measurement and maintenance are often difficult.

In recent years, the present inventors have been working on the development of a water level measuring system by image processing, and have described a series of inventions during this period in Japanese Patent Application Laid-Open Nos. Hei 7-333039 and Hei 8-0149992.
JP-A-8-145765, JP-A-9-16107
6, JP-A-10-062231, JP-A-10-33
2334, JP-A-11-030546, JP-A-11-110546
-072370, JP-A-11-118585 and the like.

The water level measurement by the above image processing is performed by setting a water mark having a scale perpendicular to the water surface and a slope plate having no scale on the water surface, taking the set image by a TV camera, and processing the image of the slope plate. Then, the boundary position between the inclined plate and the water surface on the image is obtained, and the water surface boundary position of the water mark is geometrically obtained based on the boundary position.

FIG. 17 shows such a geometric relationship.
That is, the water surface boundary 7 of the inclined plate 4 is obtained by image analysis of the water surface reflection image 4 ′ and the like, and the water surface boundary 8 of the water mark 3 is obtained from the geometric relationship with the inclined plate 4. One side 3 of the water mark 3
A water surface boundary 8 of -3 is thus obtained. Watermark 3
When the water surface boundary 8 is determined, characters and scales near the boundary 8 can be image-recognized to read the water level. However, since the length of the water mark is as long as 20 m, the minimum scale of the water mark is about 10 cm, which is insufficient in accuracy. Also, even if the minimum scale of the water mark is sufficient in accuracy, the measurement environment with the influence of dirt and waves is severe, and it is difficult to recognize detailed information such as display scale every time. .

Therefore, in the above invention, a reference point for determining the image coordinate system at the time of starting the system is set on the water mark image. That is, the reference points 5 and 6 are set on the side of the water mark 3-3, the conversion formula between the world coordinate system and the image coordinate system is obtained, and the water level of the water surface boundary 8 is determined regardless of the scale. Interpolation is performed from one or two of the reference points 5 and 6 on the image to obtain the actual water level converted to ground. It is to be noted that the reference point at the start of the system is ideal if all the scales on the screen can be finely taught to the system. However, the number of scenes is large and the work is difficult, and the program becomes complicated. In practice, a method is employed in which two reference points are taught to the system for each scene.

[0007]

The method of measuring the water level by the above-mentioned image processing can be measured from a distance without installing a precision instrument near the running water, which is very convenient for maintenance and maintenance. Has been applied to the site. However, the required accuracy of the measured water level (minimum measurement scale: 1c
In order to achieve m), there is a problem caused by the measurement target and the installation conditions of the camera as follows.

The smaller the camera field of view is, the better the resolution is, but on the other hand, there is a disadvantage that the frequency of controlling the camera with respect to the fluctuation of the water level increases. From the required measurement accuracy, an appropriate camera scene is practically about 2 to 4 m, and the image resolution is 0.5 to 1
cm. Also, the minimum scale displayed on the water mark needs to be visually identifiable from a distance, and the minimum display scale memory of the water mark installed in a dam or the like is about 10 cm.

On the other hand, in measuring the water level of a dam or the like, the water level measurement range often exceeds 20 m. For example, a water mark is installed on a vertical concrete wall upstream of the dam, and a camera is installed on the opposite bank. . In such a case, the camera line of sight is approximately 10 to 40 degrees with respect to the horizontal plane. In other words, the plane containing the camera line of sight and the water mark is not vertical,
It is installed in an inclined state. Therefore, the surface including the water mark (this coordinate system is referred to as the world coordinate system and is represented by $ 0)
Is not parallel to the camera imaging surface (the image information of this imaging surface developed on the image memory is referred to as an image coordinate system and is denoted by Δg).

In order to detect a water surface position from a camera image and obtain a water level on the ground, coordinate conversion between the world coordinate system # 0 and the image coordinate system #g is required. In order to obtain a relational expression between two coordinates, two reference points are set in advance on the water mark image at the time of system startup as described above, and the image coordinate system positions of the two reference points and the world coordinate system are set. The position is measured, and the conversion formula between the two coordinates is obtained. In this case, in the above-described related art, the return expression (linear) of both coordinate systems is obtained assuming that the two coordinate systems are parallel. If they are not parallel, a non-linear relational expression will result, and a complicated relational expression will be incorporated into the water level measuring device, which is not practical.

However, since the actual two coordinate planes are inclined, when a linear conversion equation is used, an error due to the conversion occurs at positions other than the two reference points, and the camera's line of sight is on a horizontal plane like a dam. 1cm when inclined more than 20 degrees
It was found that the measurement accuracy was not satisfactory.

It is an object of the present invention to provide a water level measuring method and system capable of overcoming the above-mentioned problems of the prior art and capable of measuring accurately even when the side surface to be measured and the camera imaging surface are inclined.

[0013]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention captures an image of a water mark installed at a water level measurement position with a camera, and determines the boundary position between the water surface detected by image processing and the image. In a water level measuring method for calculating a water level on an image in association with a water mark and calculating a water level (elevation) on the ground by performing coordinate conversion from an image coordinate system to a world coordinate system, Measurement errors caused by non-parallel surfaces are corrected for each camera scene of the water mark measurement unit where the camera tilt angle changes.

In addition, two or more reference points are set in advance on the water mark of the image for each camera scene, and the values of the respective reference points associated with the water mark are stored, and at least one reference point is stored. Is obtained by interpolating the water level at the boundary position. As a result, the measurement accuracy can be improved even when the scale is dirty or the scale is coarse.

Further, correction data indicating the measurement error on the image coordinates is obtained and stored in advance so that the measurement error at the reference point is minimized (0), and the water level on the ground is calculated from the water level on the image. At the time of conversion, correction is performed with reference to the correction data. Thereby, complicated calculation processing online can be avoided, and the water level can be corrected at high speed.

A water level measurement system to which the method of the present invention is applied includes a water mark installed at a water level measurement position, a camera for capturing an image of the water mark from a distance, an image display device, and an image display device. In a water level measurement system that includes a water level measurement device that performs image processing and a water level measurement process, and a camera control device that controls a camera attitude, the water level measurement device includes a camera scene of a water mark measurement unit that is changed by the camera control device. A reference water level setting function for setting at least two reference points for each time, and correcting a measurement error generated according to a camera tilt angle when converting a water level in an image coordinate system into a water level (elevation) on the ground in a world coordinate system. Water level correction data creation function and image processing of the captured image to detect the boundary position with the water surface,
From this boundary position, the water level on the image is obtained using the reference point, and the water level on this image is calculated as the water level on the ground (elevation).
A water level measurement function is provided for performing correction using the correction data by the water level correction data creation function when converting to the water level.

The operation of the present invention will be described. In the present invention, input information of the geometrical positional relationship between the camera and the water mark,
The error amount of the water level measured on the camera image is calculated from the above geometrical relationship. This error amount is used as correction data to correct the water level measurement result converted into the world coordinate system. This enables accurate water level measurement even when the camera imaging surface and the surface of the water mark (measurement surface) are not parallel, that is, even when the camera's line of sight is inclined.

This correction is generally a nonlinear and complicated calculation. However, in a method in which a reference point is set on the water mark image for each measurement scene and the image and water level are obtained from this reference point, this correction data can be obtained in association with the reference point at system startup. The correction can be performed only by reading the correction data at the time of online water level measurement. Therefore, a simple linear coordinate transformation equation can be used for the algorithm of the water level measurement as in the prior art. As a result, high-precision water level calculation can be performed at high speed, and the margin of camera installation at a site having a large camera inclination angle, such as a dam, is increased.

[0019]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 shows an example of a dam water level measurement system to which the present invention is applied. This system includes a water level measuring device main body 1, a video input device 2 such as a TV camera, and a water mark 3, which is an imaging target.
It comprises a water level marking facility consisting of a set of inclined plates 4 and a camera control device 5.

In order to automatically measure the water surface 51 of the dam reservoir, an image from the camera 2 is taken into the image processing device 1 and image analysis is performed to obtain a water level. The upstream wall 50 of the dam is a plane perpendicular to the water surface 51 here, and the water mark 3 is installed. The water mark 3 is equipment conventionally used for visually observing the water surface of the dam, and defines the relative water level between the water level of the dam and a reference point on the ground. An inclined plate 4 is provided to make it easy to recognize the position of the water surface by image processing. In the present invention, since the water surface position on the water mark 3 is to be read, the inclined plate 4 is not an essential component.

The camera 2 is installed on the opposite shore where the water mark 3 is seen from the front as much as possible. Usually, it is installed on the roof of the dam management building, so it is 10m more than the top of the dam on the opposite bank.
It is a position higher by about m to 20 m. The distance between the camera 2 and the water mark 3 is about 50 m to 100 m. The depth of the dam, which is the part to be measured, depends on the size of the dam, but is between 10 m and 6 m.
It is about 0 m. The larger the field of view of the camera, the wider the water level in one scene can be handled, so the frequency of camera control due to the fluctuation of the water level is reduced. However, since the resolution of the image is reduced and the measurement accuracy is disadvantageous, the size of the camera scene has a limit from the accuracy, and is practically 2 m.
About 4 m. Now, the measurement depth range is 10m-60.
Assuming that m and the field of view are 4 m, the camera control device 5 controls the camera attitude according to the water level fluctuation, and captures a plurality of camera scenes 23 necessary for water level measurement.

Here, the geometric relationship between the camera line of sight 102 and the surface to be measured (water mark 3) will be described. Assuming that the distance between the camera 2 and the surface to be measured is 100 m and the water depth is 30 m, an approximate value of the camera viewing angle θ can be obtained by Expression 1.

[0023]

Θ = tan ~ ¹ ((Y1 + Y2) / X0) = tan ~ ¹ ((30 + 15) / 100) = 24 ° where Y1: measured water depth, Y2: camera mounting height from the dam upper surface (Y2 = 15 m) X0: horizontal distance between the camera and the dam wall.

As described above, the camera 2 for measuring the water level is installed obliquely downward, and is used while adjusting the inclination angle θ by changing the water level. Therefore, the camera imaging plane (ζg coordinate plane) and the measured plane (the plane including the water mark 3 and the ζ0 coordinate plane) are not parallel to each other, and the tilt angle θ is changed by camera control.
For this reason, in water level measurement using images, camera images (ζ
The water surface position measured on the (g coordinate plane) is subjected to coordinate conversion on the plane to be measured (ζ0 coordinate plane). However, since the two coordinate systems are not parallel, a non-linear coordinate conversion formula is obtained.

FIG. 2 shows the configuration of the water level measuring device main body according to one embodiment, which comprises a CPU 6, a main memory 7, a bus 8, an image processor 9, and an image memory 10. The image dedicated processor 9 takes in the image from the camera 2 and performs image processing. The image memory 10 stores a raw image from the camera 2 and an image processing result image. The image processing result is displayed on the video display unit 12.
Will be displayed. The CPU 6 has a function of executing water level measurement processing software based on the image processing result, and instructs the camera control device 5 to control the attitude of the camera according to the measured water level. Further, a reference point is set based on an input from the man-machine interface 53.

FIG. 3 (FIG. 1) shows the software configuration of the water level measuring function according to one embodiment of the present invention. This software is stored on the main memory 7 and has a CPU
6 and executed. This software function is roughly divided into a reference water level setting function 13, a water level measurement function 14, and a water level correction data creating means 11.

The reference water level setting function 13 comprises a first reference point setting means 15, a second reference point setting means 16, and a distance conversion coefficient calculation means 17. Water level measurement function 14
Is an online water level measurement processing function. The camera image capturing means 18, the water level detecting means 19, the water level correcting means 2
0, a water level calculation means 21 and the like, details of which will be described later with reference to FIG.

FIG. 4 shows a flow of a processing procedure by the reference water level setting function 13 and the water level correction data creating means. This process is an offline process that is executed only once when the system is started. First, geometric position information of the camera 2 and the water mark 3 is input (step A).

FIG. 6 is an explanatory diagram showing the geometric relationship between the camera scene and the camera. Horizontal distance X0 between camera 2 and target, elevation level 22 between camera 2 and ground reference point
, The elevation difference H1 between the first reference point 26 and the elevation level 22 of the ground reference point, the elevation difference H2 between the second reference point 27 and the elevation level 22 of the ground reference point, and the like. The geometric relationship between the camera scene 23 and the camera 2 can be described. Such geometric data is measured in advance and is input as initial processing. FIG. 7 is a table showing a data configuration of the above-described geometric relationship.

Next, a process for adjusting the camera to the target scene is performed (step B). 8 and 9 show the relationship between the water mark 3, the camera scene 23, and the center coordinates thereof. In order to predefine the camera center position by the elevation value for each scene number, as shown in FIG. 8, n camera scenes that can cover the entire length of the water mark 3 are defined in advance, and each camera scene is defined. Is assigned a scene number. Also, as shown in FIG. 9, the elevation value of the scene center point is set in a table for each scene number, and for example, the camera direction is adjusted so that the camera scene center position YC in FIG. 8 becomes the set position. I do. This operation is performed by the operator operating the camera posture while watching the screen. When the adjustment of the camera position is completed, the camera posture information is registered as preset information.
The preset number is stored in association with the scene number.

After setting the camera scene, the camera image is taken into the image memory and displayed on the monitor screen (step D). The operator operates the man-machine interface 53 while watching the monitor screen to determine the first reference point on the screen (Step E). What is at an appropriate position on the scale of the water mark 3 may be specified as the first reference point 26. That is, by instructing an appropriate scale of the water mark 3 with a cursor or the like, the coordinate value on the image coordinate system ζg is taken in, and the value visually read from the scale of the water mark 3 as the reference point position is set. input. In this way, the relationship between the position of the first reference point on the image (coordinate system #g) and the position in the world coordinate system (coordinate system # 0) is input.

Next, an input relating to the second reference point 27 is made. The operation is the same as that for the first reference point (step F). Then, the world coordinate system of the two reference points (coordinate system 基準
0) and the distance (the number of pixels) in the image coordinate system (coordinate system # 0) on the image (step G), and from the calculation result, the world coordinate system (coordinate system # 0) and the image coordinate system ( Coordinate system ζ
The distance conversion coefficient ε between g) is obtained by Expression 2 (Step H).

[0033]

## EQU2 ## DIST: distance between two reference points on world coordinate system ζ0, dist: distance between two reference points on image coordinate system ζg.

The above input values and calculation results are stored as in the data tables of FIGS. 7 and 9 (steps J to K). Further, water level measurement error correction data is created and stored for each scene (step L). The process of creating the water level measurement error correction data will be described later in detail with reference to FIG.

The initial processing of one scene is completed as described above. The same is applied to the next scene processing, and the above series of processing is repeated until it is determined that all scenes have been completed (step C). In some cases, processing of all scenes cannot be performed at once. In that case, the program may be divided and executed at an appropriate time. For example, a scene that could not be processed due to the relationship between the amount of water stored in the dam may be performed at a time when the water level at which the water can be processed is reached.

FIG. 10 defines an intermediate coordinate system necessary for explaining the software processing. 100 is a plane including the water mark 3 (coordinate system # 0), 101 is a plane perpendicular to the camera's line of sight.
Normal to the vertical plane passing through the intersection O of 0 and the camera center C, 10
2 is a camera line of sight (straight line CO), 103 is the vertical axis of the ζ0 coordinate system, and 105 is an arbitrary water surface position (the surface of the water mark, ie, on the ζ0 coordinate system). Reference numeral 110 denotes a coordinate system assumed in front of the camera (hereinafter, referred to as a coordinate system # 2), which assumes a coordinate system connecting the same image formed on the camera imaging plane (coordinate system #g) to this plane. , A plane perpendicular to the camera line of sight 102. 111 is the vertical axis in the ζ2 coordinate system, 112
Is the intersection between the line connecting the camera center C and the water surface position 105 and the plane 110, 113 is the intersection between the line connecting the camera center C and the first reference point 26 and the plane 110 forming the coordinate system ζ2, 114 is the camera center C and the This is the intersection (線 2 coordinate system) of the line connecting the two reference points 26 and the plane 110 forming the coordinate system ζ2.

The plane 100 (coordinate system # 0) including the water mark 3 intersects with the line of sight 101 at the intersection O. Surface 10 at intersection O
The normal 101 of 0 is horizontal. Normal line 101 and line of sight 102
Intersect at an angle θ. A plane passing through the point O and perpendicular to the line of sight is assumed to be a plane 120 (coordinate system # 1). Plane 100
A first reference point 26, a second reference point 27, and an arbitrary point A are set on (coordinate ζ0). Camera center point C and first
The intersection between the line segment connecting the reference points 26 and the plane 120 (coordinate system # 1) is 123. In addition, the intersection between the line segment or the extension line connecting the point C and the second reference point 27 and the surface 120 (coordinate system # 1) is defined as 124. Furthermore, the line intersects with a line segment or an extended line connecting the point C and an arbitrary point A at an intersection B of the surface 120 (coordinate system # 1).

The cursor is positioned on the image of the first reference point 26, and the position thereof is image-processed to obtain the position 11 on the coordinate system # 2.
Calculate as 3. Point 113 is the intersection of the line segment connecting point C and point 26 and surface 110 (coordinate system # 2). The plane 110 (coordinate system # 2) and the plane 120 (coordinate system # 1) are both
2 is a plane perpendicular to and parallel to 2. A point corresponding to the point 113 (on the coordinate system # 2) can be set as a point 123 on the coordinate system # 1.

Similarly, with respect to the second reference point,
Point 27 on the top (coordinate system $ 0), on surface 110 (coordinate system $ 2)
, And a point 124 on the surface 120 (coordinate system # 1) can be defined. Further, an arbitrary point A on the surface 100 (coordinate system # 0), a point 115 on the surface 110 (coordinate system # 2), and a surface 120
An upper point (coordinate system # 1) B125 can be defined.

The procedure for creating correction data (step L in FIG. 4) will be described using the above relationships. FIG. 5 shows the flow of the water level error correction data creation process. First, geometrically related data of a camera and a camera scene are fetched (step L10). The relevant data includes, for example, the horizontal distance X0 between the camera and the object, the elevation difference Y0 between the reference point on the ground and the camera, the elevation difference Yc between the reference point on the ground and the center of the camera scene, the reference point on the ground and the first There is an altitude difference H1 from the reference point, and an altitude difference H2 between the ground reference point and the second reference point, and there are those that change for each scene and those that do not change.

Next, the position 26 of the first reference point in the world coordinate system (coordinate system # 0) is determined from the screen. That is, the cursor is set on the scale selected as the first reference point, and at this time, the scale of the water mark selected at the first reference point 26 is input as a read value, and is set as the position 26 on the coordinate system # 0. It is stored (step L20). Then, the position of the cursor on the image scale is measured, and an image of the first reference point (coordinate system ζg or
The position 113 of the coordinate system # 2) is obtained (step L30).
Similarly, for the second reference point, the position 27 on the coordinate system # 0 and the position 114 on the image (the coordinate system #g or the coordinate system # 2) of the second reference point are obtained (steps L40 and L50). Note that the two reference point positions 123 and 124 on the coordinate system # 1 can be easily obtained by coordinate conversion using the distance conversion coefficient ε between the coordinate system # 2 and the coordinate system # 1.

The 2 on the coordinate system ζ1 thus obtained
A straight line connecting the points 123 and 124 is set to 121, and n between the two points is n.
Divide equally and calculate each coordinate. n is determined so that the interval is approximately 1 cm. That is, n = 100 when the distance between the two reference points is 1 m, n = 200 when the distance between the two reference points is 2 m, and n when the distance between the two reference points is 3 m
= 300.

Although the two reference points may be arbitrary, it is usually preferable to use the above-described method for determining n since a graduation of meters is used. The obtained coordinate data on the surface 120 (coordinate system # 1) is stored in the array H of Expression 3 (step L6).
0). Here, the data will be described only for the inner dividing point, but the outer dividing point may be calculated as needed.

[0044]

HH0 (i) = coordinate of point 123 + i * Δ
(I = 0, n) where Δ = distance between two points (on coordinate system ζ1) / n Next, each point (array HH0) on the surface 120 and the camera center C
To obtain the intersection with the surface 100 (step L7).
0). The coordinate values of the intersection (coordinate values on the coordinate system # 0) are stored in the array GS (i = 0, n) (step L7).
0).

FIG. 11 shows a method of calculating an intersection A between the plane 100 (coordinate system # 0) and a line segment connecting the camera center C and each equally divided point. Let point B be one of the equally divided points on plane 120 (coordinate system # 1). For example, OB = HH0 (i). Assuming that the camera center is C, the point A is the intersection of the line connecting the camera center C and the point B on the surface 120 with the surface 100;
OA = GS. Angle δ between line of sight 102 and line AC
Is calculated from Equation 4.

[0046]

[Number 4] AS = AOcos (θ) OS = AOsin (θ) CS = OC-OS = SQRT (X0 2 + Y0 2) -AOsi
n (θ) Tan (δ) = AS / CS = AOcos (θ) / (SQRT (X0 2 +
^{Y0 2) -AOsin (θ))} δ = Tan ~ 1 (AOcos (θ) / (SQRT (X0 2 + Y0 2) -A
Osin (θ))) The OC is known from the horizontal distance X0 and the altitude difference Y0, and the above relationship between AO and δ is obtained. Thus, the OB / OA relationship is derived as shown in Equation 5.

[0047]

OB = ST + OT OT = AOcos (θ) AT = AOsin (θ) BT = ATtan (δ) = AOsin (θ) tan (δ) OB = BT + OT = AOsin (θ) tan (δ) + ACos (θ) OB / OA = HH0 (i) / GS (i) = sin (θ) tan
(δ) + cos (θ) Further, HH0 (i) / GS (i) can be converted into Equation 6 as a function of θ and δ.

[0048]

GS (i) = HH0 (i) / (sin (θ) tan
(δ) + cos (θ)) From this, the correction data HOSEI is obtained as shown in Expression 7.

[0049]

HOSEI (i) = GS (i) -HH0 (i)
(I = 0, n) Therefore, every time the water level is measured, the water level correction means 20 can perform the above calculation to correct the water level. However, since these calculations are complicated and time-consuming, it is not preferable to incorporate them into an online measurement program.

By the way, HH0 (i) is position information on the image coordinate system, while GS (I) gives correct position coordinates on the world coordinate system. Therefore, the correction data HOS of equation 7
EI (i) can be determined in advance as a function of position in the image coordinate system.

FIG. 12 shows a relation table between the coordinates (the number of pixels of the Y coordinate) from the origin in the image coordinate system and correction data, and FIG. 13 shows a characteristic curve based on the first reference point. The correction data HOSEI (i) is an actual calculation example for a certain site, but becomes 0 at the positions of two reference points as shown in the figure.

As described above, since the correction data can be calculated in advance when setting two reference points, in this embodiment, the correction data for each scene is calculated when the necessary geometric data is input. And is stored as a correction data table as shown in FIG. Therefore, at the time of online water level measurement, it is only necessary to read the water level correction data table, no complicated calculation processing is required, and highly accurate water level calculation can be performed at high speed.

FIG. 14 shows an example of a camera image. The camera image 31 is displayed on the display device 12. Image origin 4
1 is usually the upper left corner. Watermark 3 image 32, inclined plate 4
, An image 34 of the first reference point, an image 35 of the second reference point, and the like. The coordinates 36 of the first reference point (h
1) and the coordinate 37 (h2) of the second reference point are the number of pixels from the origin 41, respectively.

FIG. 15 shows a flowchart of the online processing of water level measurement. When a camera image is captured at a sampling cycle (step a), the water surface boundary is detected by image processing or the like (step b), and the water surface boundary is image coordinate y on the scale of the water mark.
(Step c), and the water surface position y is converted into a world coordinate system to obtain a water level (step d).

FIG. 16 shows an example of measuring the water surface position. The image 32 of the water mark 3, the image 33 of the inclined plate 4, and the water surface position 40 (indicated by y). The detection of the water surface position 40 by the image processing can be obtained from the intersection of the real image of the inclined plate 4 and the virtual image due to refraction or reflection on the water surface.

Next, the water level correction data table is read out, and the water level calculated in step d is corrected (step e). If the water level correction data is in the image coordinate system, correction is performed before step d.

The processing result thus detected is stored or transferred (step f). The necessity of updating the scene is determined based on the position of the water level (step g), and when the update is required, another scene is changed by camera control. The above processing is repeated. A sampling cycle of about once every two seconds is usually sufficient, but can be arbitrarily determined as needed.

As described above, according to this embodiment, the inclination angle of the camera with respect to the water mark at a site such as a dam is large, and the geometrical relationship between the water mark in the world coordinate system and the water mark image in the image coordinate system is obtained. Even when the coordinate conversion error due to the target non-parallelism cannot be ignored, it is possible to measure an accurate ground water level corrected according to the inclination angle with respect to the water level obtained from the camera image.

Further, according to the water level correcting means of this embodiment, when setting a reference point on an image for each scene at the time of starting up the system, a correction value corresponding to a pixel position is obtained. The online processing of the measurement does not require any complicated calculations and can detect the water level with high accuracy at high speed. Therefore, accurate measurement of the water level can be easily realized even in a system in which a camera and a target have a complicated structure including a plurality of camera scenes.

[0060]

According to the present invention, when the water level is detected by processing the image of the water mark, the conversion from the image coordinate system to the world coordinate system is performed by changing the line of sight of the camera with respect to the water mark. Since the error in the case of having is corrected, the water level can be measured with high accuracy without deteriorating the measurement accuracy even when the camera installation position condition is poor. As a result, camera installation conditions can be relaxed at sites such as dams.

[Brief description of the drawings]

FIG. 1 is a schematic explanatory diagram of a water level measurement system to which the present invention is applied.

FIG. 2 is a configuration diagram of a water level measuring device according to one embodiment of the present invention.

FIG. 3 is a block diagram showing processing functions of the water level measuring device of FIG. 2;

FIG. 4 is a flowchart showing off-line processing (reference water level setting processing, correction data creation processing) among the processing functions of FIG. 3;

FIG. 5 is a flowchart showing water level error correction data creation processing.

FIG. 6 is an explanatory diagram showing a geometric relationship between a camera and a water level measurement target object.

FIG. 7 is an explanatory diagram showing the contents of geometrical relation data set during a reference water level setting process.

FIG. 8 is an explanatory diagram showing a range of a water mark and a setting of a camera scene.

FIG. 9 is a table showing correspondence between scene numbers and scene center elevation values.

FIG. 10 is an explanatory diagram of a conversion error between coordinate systems caused by a tilt angle of a camera line of sight.

FIG. 11 is a partial detailed view of FIG. 10;

FIG. 12 is an explanatory diagram showing an example of a water level correction data table.

FIG. 13 is a graph showing characteristics of water level accuracy correction data.

FIG. 14 is an explanatory diagram showing an example of a camera image when two reference points are set.

FIG. 15 is a flowchart showing the online processing procedure of the water level measurement processing.

FIG. 16 is an explanatory diagram showing an example of a camera image at the time of water level measurement.

FIG. 17 is an explanatory diagram of a principle of detecting a water level from image processing of a water mark and an inclined plate.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Water level measuring device, 2 ... Camera, 3 ... Water mark, 4 ... Inclined plate, 5 ... Camera control device, 6 ... CPU, 7 ... Main memory,
8 Bus, 9 Image processor, 10 Image memory, 11 Image display device, 12 Water level correction data creation means, 13 Reference water level setting function, 14 Water level measurement function, 1
Reference numeral 5: first reference point setting means, 16: second reference point setting means, 17: distance conversion coefficient calculating means, 18: camera image capturing means, 19: water level detecting means, 20: water level correcting means, 2
1 ... water level calculation means, 22 ... elevation of ground reference point, 23 ... range of camera scene of measured part, 26 ... first reference point in water mark, 27 ... second reference point in water mark, 3
Reference numeral 1 denotes a screen of the camera image of the measured part, 32 denotes a water mark on the screen, 33 denotes an inclined plate on the screen, 34 denotes a scale used as a first reference point on the screen, and 35 denotes a second scale on the screen. , A scale used as a reference point, 36... Y-direction coordinate value h1 in the image coordinate system of the first reference point, 37... Y-direction coordinate value h2, 38 in the image coordinate system of the second reference point, initial setting Geometry data table, 39: water level correction table, 41: origin of image coordinate system, 50: dam concrete wall, 51: water surface, 1
00: vertical plane including water mark 3 (ζ0 coordinate system), 101:
A horizontal line on the vertical plane passing through the intersection O of the camera line of sight and the vertical plane # 0 and the camera center C, 102 ... the line of sight of the camera (straight line CO),
105: water surface position (point A, surface of the water mark); 110: surface perpendicular to the camera line of sight assumed in front of the camera (ζ2 coordinate system); 112: line between camera center C and water surface position 105 and surface 110 Intersection point 113: Intersection point between a line connecting the camera center C and the first reference point 26 and the plane 110 forming the coordinate system ζ2, 1
14... Intersection (の 2 coordinate system) of a line connecting camera center C and second reference point 26 and plane 110 forming coordinate system ζ2, 120.
A plane passing through the point O and perpendicular to the line of sight ({1 coordinate system), 121 ...}
Vertical axis of one coordinate system, 123... Intersection of line connecting camera center C and first reference point 26 and plane 120 forming coordinate system ζ1;
4: Intersection of line connecting camera center C with second reference point 27 and plane 120 forming coordinate system ζ1 (ζ1 coordinate system) 125: Intersection of line connecting camera center C and water surface position 105 and plane 120 (B ).

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yoichi Takagi 5-2-1 Omikacho, Hitachi City, Ibaraki Prefecture Inside Hitachi Process Computer Engineering Co., Ltd. (72) Inventor Akio Tsujikawa 5-chome Omikamachi, Hitachi City, Ibaraki Prefecture No. 1 Inside Hitachi Ltd. Omika Works (72) Inventor Ken Saito 4-6 Kanda Surugadai, Chiyoda-ku, Tokyo Inside Hitachi Ltd. (72) Inventor Takayuki Yoneoka 5-chome Omikamachi, Hitachi City, Ibaraki Prefecture No. 1 Hitachi Process Computer Engineering Co., Ltd. F-term (reference) 2F014 FA04 2F065 AA02 AA24 CC00 EE00 FF04 FF09 FF26 FF61 JJ03 PP01 QQ00 QQ23 QQ24 QQ28

Claims (6)

[Claims] 1. An image of a water mark set at a measurement position of a water level is captured by a camera, and a boundary position between the water surface detected by image processing and the water surface is associated with a scale of the water mark in the image to obtain a water level on the image. Further, in a water level measuring method for calculating a water level (elevation) on the ground by performing coordinate conversion from an image coordinate system to a world coordinate system, a measurement error caused by the fact that the surface of the water mark is not parallel to the camera imaging surface is determined by a camera tilt. A water level measuring method, wherein the correction is performed for each camera scene of a water mark measuring unit whose angle changes. 2. The method according to claim 1, wherein two or more reference points are set in advance on the water mark of the image for each camera scene, and a value of each reference point associated with the water mark is stored. A water level measurement method, wherein a water level at the boundary position is obtained by interpolating from a value of at least one reference point. 3. The method according to claim 2, wherein correction data indicating a measurement error on image coordinates is obtained and stored in advance in such a relationship that the measurement error at the reference point is minimized, and the ground level is calculated from the water level on the image. A water level measurement method, wherein the water level is calculated with reference to the correction data when calculating the water level. 4. The water level measurement method according to claim 1, wherein the boundary position is detected by image processing of a real image and a virtual image of the inclined plate combined with the water mark. 5. A water mark installed at a water level measurement position,
In a water level measurement system including a camera that captures an image of a water mark from a distance, an image display device, a water level measurement device that performs image processing and a water level measurement process on the captured image, and a camera control device that controls a camera attitude, The water level measurement device has a reference water level setting function of setting at least two reference points for each camera scene of the water mark measurement unit that is changed by the camera control device, and a water level of the image coordinate system on the ground in the world coordinate system. A water level correction data generation function for correcting a measurement error generated according to the camera tilt angle when converting to a water level (elevation), and image processing of a captured image to detect a boundary position with the water surface, and from the boundary position, The water level on the image is obtained using the reference point, and when the water level on this image is converted into the water level (elevation) on the ground, the correction data by the water level correction data creation function is used. A water level measurement system, comprising: a water level measurement function for performing a correction using the water level. 6. The water level according to claim 5, wherein the water level correction data creating function is configured to calculate a correction value corresponding to a distance from the reference point and to store the correction value in a referable manner. Measurement system.