A monocular camera based dry beach measurement method

Abstract

The application provides a kind of dry beach measurement method based on monocular camera, including three major parts of obtaining beach top elevation and tailing pond water level elevation, calculating dry beach length and calculating dry beach slope, using camera to shoot tailing pond dry beach image, through manual auxiliary point selection waterline position, the length of dry beach is automatically calculated;Through liquid level meter, the change of tailing pond reservoir water level is monitored in real time;The beach top elevation is monitored;Under the condition that dry beach length, reservoir water level and beach top elevation are known, the dry beach slope is inversely calculated according to trigonometric function.The application scheme has the characteristics of low cost, easy to implement and high precision.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of mine monitoring, and particularly relates to a dry beach measurement method based on a monocular camera. BACKGROUND

[0002] The tailings pond is a special water conservancy project for storing tailings sand and beneficiation wastewater. The tailings sand is generally discharged in a low-lying valley, and a dam is built in the gap of the mountain. The tailings pond of the flat type tailings pond can also be built by building a dam on four sides. The tailings pond accident is extremely harmful.

[0003] The dry beach length is an important index affecting the safe operation of the tailings pond. It not only affects the height of the tailings dam saturation line and the safety of the tailings dam superhigh, but also determines the flood control capacity of the tailings pond. The insufficient dry beach length will seriously affect the safety of the tailings pond.

[0004] At present, the automatic measurement methods of the dry beach of the tailings pond mainly include the following methods:

[0005] (1) Laser ranging and angle measuring method. Assuming that the slope of the dry beach of the tailings pond is uniform, a laser range finder and an inclinometer are arranged on a typical section. The distance and angle of two or more points on the surface of the dry beach are measured by the laser range finder, and the length of the dry beach is calculated by fitting the dry beach section. The principle of this method is simple, and the cost of the monitoring system is low. However, due to the extremely low reflectivity of the dry beach, the laser range finder often cannot measure the distance normally, so the practical application effect of this method is poor.

[0006] (2) Three-dimensional laser scanner measurement method. The three-dimensional point cloud data of the dry beach is obtained by using a high-precision three-dimensional laser scanner, and the dry beach length is measured by using the point cloud data of the dry beach through professional software or algorithm. This method can accurately measure the length of the dry beach, but the three-dimensional laser scanner used for measurement is expensive, and it is difficult to be widely applied.

[0007] (3) Cross ratio invariance method. Three marker points are placed on the dry beach, and the three marker points are ensured to be on a straight line. Then, a camera is used to shoot the dry beach image containing all the marker points. The length of the dry beach is calculated by using the principle of cross ratio invariance in the projection change. This method is simple to operate, but since the tailings pond is continuously discharging tailings sand, the marker points cannot be kept for a long time, and it is very difficult to practice.

[0008] (4) Slope calculation method. The height of the dry beach is measured by using a height measuring device such as an ultrasonic level meter, and then the slope value of the dry beach is calculated by using a geometric algorithm. Then, the length of the dry beach is calculated combined with the monitoring data of the water level of the tailings pond. This method is a commonly used method, but since the environment of the tailings pond is poor, it is difficult to ensure that the ultrasonic level meter is always perpendicular to the horizontal plane, and the stability of the measurement data will be affected.

[0009] (5) seepage calculation method, the method assumes that the tailing dam is homogeneous and the same body, the saturation line in the dam body does not consider the ups and downs of the dry beach surface, the size of the slope, has very high linearity, the accurate intersection line of the dry beach surface and the water line is fitted from the saturation line obtained from real-time monitoring, and the length of the dry beach is obtained. The assumption condition of the method does not highly coincide with the actual situation, and in actual application, the dry beach length calculated by the method is greatly different from the dry beach length measured by manual measurement.

[0010] Therefore, a dry beach measurement method with low cost, easy implementation and high precision is developed to solve the problems in the prior art. SUMMARY

[0011] The present application aims to provide a dry beach measurement method with low cost, easy implementation and high precision, uses a camera to shoot a tailing pond dry beach image, manually selects a water line position by manual assistance, automatically calculates the length of the dry beach, monitors the change of the tailing pond water level by a liquid level meter, monitors the beach top elevation, and inversely calculates the dry beach slope according to a trigonometric function under the condition that the dry beach length, the tailing pond water level and the beach top elevation are known. The specific technical scheme is as follows:

[0012] A dry beach measurement method based on a monocular camera, comprising the following steps:

[0013] Obtaining the beach top elevation and the tailing pond water level elevation, specifically: obtaining the beach top elevation H D and the tailing pond water level elevation H W by a detection device;

[0014] Calculating the dry beach length, specifically comprising:

[0015] Step 1, adjusting the position of the camera and the camera holder;

[0016] Step 2, shooting by using the camera on the camera holder, and obtaining a corrected dry beach image;

[0017] Step 3, obtaining the plane coordinates of the point P(i,j) on the water line in the real world and the distance between the point P and the camera according to the corrected dry beach image obtained in step 2:

[0018] The plane coordinates of the point P(i,j) in the real world are as follows:

[0019]

[0020] Wherein: X and Y are the coordinate positions of the point P(i,j) on the X axis and the Y axis in the real world, H C is the elevation of the camera, and ω are as follows:

[0021]

[0022] FOV H FOV (Field of View) is the horizontal field of view of the camera. V From a vertical perspective, Img H For images taken by the camera, Img W Where α is the image width and α is the vertical angle of the camera's principal optical axis;

[0023] The distance D between the camera and point P is calculated using the following formula:

[0024]

[0025] Step 4: Calculate the length L of the dry beach using the following expression. P :

[0026]

[0027] Where: ρ is the horizontal alignment angle of the camera gimbal;

[0028] Step 5: Using the center point of the bottom edge of the corrected dry beach image as the origin, send rays in the ∈ direction, and calculate the intersection points P of the rays and the waterline in sequence. m The length of the dry beach is determined, and the minimum value is recorded as the length L of the dry beach monitored in this instance. B ;

[0029] The slope θ of the dry beach is calculated using the following formula:

[0030]

[0031] Preferably, obtaining the beach crest elevation and tailings dam water level elevation includes:

[0032] Use surveying equipment to regularly measure the beach crest elevation H. D ;

[0033] The water level H in the tailings dam was measured using a level gauge. W .

[0034] Preferably, step ① specifically includes:

[0035] The camera is calibrated to determine its intrinsic, extrinsic, and distortion parameters.

[0036] A vertical pole is installed on the top of the tailings dam, perpendicular to the horizontal plane. A camera pan-tilt unit is installed on the top of the pole. The camera pan-tilt unit can rotate horizontally and pitch, and automatically acquire the horizontal rotation angle ρ and the pitch angle β. The camera is mounted on the camera pan-tilt unit, and the initial direction of the camera's main optical axis is generally perpendicular to the direction of the dam.

[0037] Obtain relevant parameters, specifically including: camera elevation H. C The vertical angle α of the camera's principal optical axis is obtained using the expression α = 90° - β; the camera's horizontal field of view (FOV) is...H Vertical field of view (FOV) V Images captured by the camera are high-resolution (Img). H and image width Img W ;

[0038] Adjust the camera and camera gimbal, specifically: set the camera gimbal to rotate clockwise horizontally as positive, counterclockwise as negative, and tilt downwards as positive. Obtain the following value ranges for the horizontal alignment angle ρ, tilt angle β, and vertical angle α of the camera's principal optical axis:

[0039]

[0040]

[0041] Preferably, the corrected dry beach image in step ② is obtained by combining the camera's intrinsic parameters, extrinsic parameters, and distortion parameters from step ①.

[0042] Preferably, in step ⑤: ∈ = m × ε;

[0043] in: ε is the angle value of each ray rotation. The value of ε ranges from 1° to 10° and is divisible by 180°.

[0044] In addition to the objectives, features, and advantages described above, the present invention has other objectives, features, and advantages. The invention will now be described in further detail with reference to the figures. Attached Figure Description

[0045] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0046] Figure 1 This is a schematic diagram of camera height, pitch angle, field of view, and pixel size in a preferred embodiment of the present invention;

[0047] Figure 2 This is a schematic diagram of the camera setup for dry beach measurement in an embodiment of the present invention, wherein: Figure 2 (a) is the front view; Figure 2 (b) is a top view;

[0048] Figure 3 This is a schematic diagram of the spatial coordinates of waterline pixels in a preferred embodiment of the present invention.

[0049] Figure 4 This is a schematic diagram of the selection of waterline points in a preferred embodiment of the present invention;

[0050] Figure 5 This is a schematic diagram illustrating the principle of dry beach length calculation in a preferred embodiment of the present invention;

[0051] Figure 6 This is a schematic diagram of the calculation of dry beach monitoring parameters in a preferred embodiment of the present invention. Detailed Implementation

[0052] The embodiments of the present invention will be described in detail below with reference to the accompanying drawings. However, the present invention can be implemented in many different ways as defined and covered by the claims.

[0053] Example:

[0054] A method for measuring dry beach based on a monocular camera includes the following steps:

[0055] Step S1: Obtain the beach crest elevation and tailings dam water level elevation. Specifically, the beach crest elevation H is obtained by detecting the elevation using detection equipment. D and tailings dam water level H W In this embodiment, it is preferable to use surveying equipment (such as a total station) to periodically measure the elevation of the beach top, and to install radar level gauges or ultrasonic level gauges at appropriate locations within the tailings dam, such as drainage wells and drainage chutes, to measure the water level elevation of the tailings dam.

[0056] Step S2: Calculate the length of the dry beach, specifically including:

[0057] Step ①: Adjust the position of the camera and camera gimbal. In this embodiment, the preferred method is:

[0058] The camera is calibrated (using conventional methods) to determine its intrinsic, extrinsic, and distortion parameters.

[0059] A vertical pole is installed on the top of the tailings dam, perpendicular to the horizontal plane. A camera pan-tilt unit is mounted on the top of the pole. This camera pan-tilt unit can rotate horizontally and pitch, and automatically acquires the horizontal rotation angle ρ and the pitch angle β. The camera is mounted on this camera pan-tilt unit (i.e., a camera is placed at a suitable location on the top of the tailings dam to capture images of the dry beach; see details). Figure 1 and Figure 2 The initial direction of the camera's main optical axis is generally perpendicular to the direction of the dam body; here, a fixed-focus industrial camera from the existing technology is preferred.

[0060] Obtain relevant parameters, specifically including: camera elevation H. C The vertical angle α of the camera's principal optical axis is obtained using the expression α = 90° - β; the camera's horizontal field of view (FOV) is... H Vertical field of view (FOV) V Images captured by the camera are high-resolution (Img). H (in pixels) and image width Img W (Unit: pixels);

[0061] Adjust the camera and camera gimbal, specifically: set the camera gimbal to rotate clockwise horizontally as positive, counterclockwise as negative, and tilt downwards as positive. Obtain the following value ranges for the horizontal alignment angle ρ, tilt angle β, and vertical angle α of the camera's principal optical axis:

[0062]

[0063]

[0064] In this embodiment: when the value of α is appropriate, the waterline of the dry beach should be near the middle of the dry beach image captured by the camera. In actual application, the above effect can be achieved by adjusting the tilt angle of the camera gimbal.

[0065] Step 2: Take a picture using the camera on the camera gimbal (real-time shooting). Combine the camera's intrinsic parameters, extrinsic parameters, and distortion parameters from Step 1 to obtain the corrected dry beach image.

[0066] Step ③: Set point P(i,j) to be a point on the waterline, and set the horizontal coordinates of the camera's XOY projection point on the real-world horizontal plane to (0,0). See details. Figure 3 Based on the corrected dry beach image obtained in step ②, obtain the real-world planar coordinates of point P(i,j) above the waterline and the distance of the camera from point P:

[0067] The real-world planar coordinates of point P(i,j) are as follows:

[0068]

[0069] Where: X and Y are the coordinates of point P(i,j) on the X-axis and Y-axis in the real world, respectively, and H... C For the camera's elevation, And ω are as follows:

[0070]

[0071] The distance D between the camera and point P is calculated using the following formula:

[0072]

[0073] Step 4: Let P(X,Y) be the real-world plane coordinates of point P on the dry beach waterline (see details). Figure 4 The length L of the dry beach is calculated using the following expression. P :

[0074]

[0075] Step 5: In the dry beach image, with the principal optical axis as 90°, rotate clockwise to the bottom right corner of the image (180°), then the bottom left corner is 0°. Using the center point of the bottom edge of the corrected dry beach image as the origin, send rays in the ∈ direction, and calculate the intersection points P of the rays and the waterline. m The length of the dry beach (see details) Figure 5 The minimum value is recorded as the dry beach length L of this dry beach monitoring. B Where: ∈=m×ε, ε is the angle value of each ray rotation. The value of ε ranges from 1° to 10° and is divisible by 180°.

[0076] Step S3: Calculate the dry beach slope θ according to the following formula (see details). Figure 6 ):

[0077]

[0078] The details of applying the solution of this invention are as follows:

[0079] (1) Compared with the three-dimensional laser scanner method, the monocular dry beach measurement method adopted in this invention has a low cost and achieves a balance between economy and accuracy.

[0080] (2) Compared with laser ranging and angle measurement methods and cross-ratio invariant methods, the monocular dry beach measurement method adopted in this invention is easy to implement and does not require setting targets or other markers on the dry beach surface. The camera's photographs are not affected by the reflectivity of the dry beach surface, thus improving the stability of the system.

[0081] (3) Compared with the slope estimation method and the seepage estimation method, the monocular dry beach measurement method adopted in this invention can directly calculate the dry beach length based on the dry beach image. The measured value of the dry beach length is more accurate and closer to the value measured manually.

[0082] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for measuring dry beach based on a monocular camera, characterized in that, Includes the following steps: To obtain the beach crest elevation and tailings dam water level elevation, specifically: the beach crest elevation H is obtained through detection equipment. D and tailings dam water level H W ; Calculating the length of the dry beach includes: Step 1: Adjust the position of the camera and camera gimbal; Step 2: Take a picture using the camera on the camera gimbal and obtain the corrected image of the dry beach; Step ③: Based on the corrected dry beach image obtained in Step ②, obtain the real-world planar coordinates of point P(i,j) on the waterline and the distance of the camera from point P: The real-world planar coordinates of point P(i,j) are as follows: Where: X and Y are the coordinates of point P(i,j) on the X-axis and Y-axis in the real world, respectively, and H... C For the camera's elevation, And ω are as follows: FOV H FOV (Field of View) is the horizontal field of view of the camera. V From a vertical perspective, Img H For images taken by the camera, Img W Where α is the image width and α is the vertical angle of the camera's principal optical axis; The distance D between the camera and point P is calculated using the following formula: Step 4: Calculate the length L of the dry beach using the following expression. P : Where: ρ is the horizontal alignment angle of the camera gimbal; Step 5: Using the center point of the bottom edge of the corrected dry beach image as the origin, send rays in the ∈ direction, and calculate the intersection points P of the rays and the waterline in sequence. m The length of the dry beach is determined, and the minimum value is recorded as the length L of the dry beach monitored in this instance. B ; ∈ represents the angle of the sampling ray at the waterline point; The slope θ of the dry beach is calculated using the following formula:

2. The method for measuring dry beaches based on a monocular camera according to claim 1, characterized in that, Obtaining the beach crest elevation and tailings dam water level elevation includes: Use surveying equipment to regularly measure the beach crest elevation H. D ; The water level H in the tailings dam was measured using a level gauge. W .

3. The method for measuring dry beach based on a monocular camera according to claim 1, characterized in that, Step ① specifically includes: The camera is calibrated to determine its intrinsic, extrinsic, and distortion parameters. A vertical pole is installed on the top of the tailings dam, perpendicular to the horizontal plane. A camera pan-tilt unit is installed on the top of the pole. The camera pan-tilt unit can rotate horizontally and pitch, and automatically acquire the horizontal rotation angle ρ and the pitch angle β. The camera is mounted on the camera pan-tilt unit, and the initial direction of the camera's main optical axis is generally perpendicular to the direction of the dam. Obtain relevant parameters, specifically including: camera elevation H. C The vertical angle α of the camera's principal optical axis is obtained using the expression α = 90° - β; the camera's horizontal field of view (FOV) is... H Vertical field of view (FOV) V Images captured by the camera are high-resolution (Img). H and image width Img W ; Adjust the camera and camera gimbal, specifically: set the camera gimbal to rotate clockwise horizontally as positive, counterclockwise as negative, and tilt downwards as positive. Obtain the following value ranges for the horizontal alignment angle ρ, tilt angle β, and vertical angle α of the camera's principal optical axis:

4. The method for measuring dry beach based on a monocular camera according to claim 3, characterized in that, The corrected dry beach image in step ② is obtained by combining the camera's intrinsic parameters, extrinsic parameters, and distortion parameters from step ①.

5. The method for measuring dry beach based on a monocular camera according to any one of claims 1-4, characterized in that, In step ⑤: ∈=m×ε; in: ε is the angle value of each ray rotation. The value of ε ranges from 1° to 10° and is divisible by 180°.

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