A method for realizing debris flow early warning by extracting profile with single-line laser radar

Abstract

The application provides a method for realizing debris flow early warning by using single-line laser radar to extract profile, and the method comprises the following steps: collecting point cloud data of a U-shaped section profile of a debris flow channel by a single-line laser radar sensor in real time; obtaining a horizontal coordinate and a vertical coordinate corresponding to each point cloud in a rectangular coordinate system; obtaining a normalized horizontal coordinate and a normalized vertical coordinate of each point cloud in the rectangular coordinate system; obtaining an elevation difference value of each normalized point cloud; obtaining a turning point judgment threshold; finding two point clouds whose normalized elevation difference values are greater than or equal to the turning point judgment threshold, and taking the two found point clouds as two turning points of the U-shaped section profile of the debris flow channel; judging whether the elevation difference value of the debris flow channel at the current moment is greater than a debris flow early warning critical threshold, if yes, judging that the current moment is a debris flow event, and triggering a debris flow event alarm; otherwise, judging that the current moment is a non-debris flow event, and not triggering the debris flow event alarm.

Description

Technical Field

[0001] This invention relates to the field of debris flow early warning technology, and in particular to a method for debris flow early warning using single-line lidar to extract contours. Background Technology

[0002] Debris flow monitoring mainly focuses on debris flow early warning. Currently, debris flow early warning relies primarily on a combination of manual monitoring and automated equipment. This involves monitoring the temporal changes in elevation within the debris flow channel area to determine if a debris flow event has occurred. For example, using a fixed mud level gauge to monitor height changes in the debris flow area for an extended period, if the measured height difference exceeds the debris flow threshold, a debris flow event is considered to have occurred.

[0003] However, the accuracy of mud level gauge data is easily affected by interference. As it is a surface monitoring system with a large monitoring range, it is easy to misidentify disturbances such as slope changes near debris flow channels as debris flow events, which can easily lead to false alarms. Summary of the Invention

[0004] This invention provides a method for debris flow early warning by extracting contours using single-line lidar, which can solve the technical problem that the accuracy of mud level measurement data is easily affected by interference and prone to false alarms in the prior art.

[0005] This invention provides a method for debris flow early warning using single-line lidar to extract contours, the method comprising:

[0006] A single-line lidar sensor is placed on one side of the debris flow channel being monitored, with the measurement direction of the lidar sensor perpendicular to the flow direction of the debris flow channel, and the measurement angle of the lidar sensor fully covering the debris flow channel.

[0007] The radar sensor collects point cloud data of the U-shaped cross-sectional profile of the debris flow channel in real time. The point cloud data includes angle and distance values ​​in spherical coordinates.

[0008] Perform coordinate transformation on each point cloud data at the current moment to obtain the x-coordinate and y-coordinate of each point cloud in the rectangular coordinate system; where the y-coordinate is the elevation value of each point cloud.

[0009] Smoothing and normalization are performed on the x-coordinate and y-coordinate of each point cloud in the Cartesian coordinate system to obtain the normalized x-coordinate and y-coordinate of each point cloud in the Cartesian coordinate system.

[0010] The normalized elevation difference of each point cloud is obtained based on the normalized ordinate of each point cloud in the Cartesian coordinate system.

[0011] The threshold for determining inflection points is obtained based on the normalized x and y coordinates of each point cloud in a Cartesian coordinate system.

[0012] Find two point clouds whose normalized elevation difference is greater than or equal to the inflection point judgment threshold, and use the two point clouds as the two inflection points of the "U"-shaped cross-sectional profile of the debris flow channel; the area between the two inflection points is the channel area, and the area outside the two inflection points is the slope area.

[0013] The average of the ordinates of all point clouds between the two inflection points is taken as the elevation of the debris flow channel at the current moment.

[0014] The difference between the current elevation of the debris flow channel and the previous elevation is taken as the difference in the current elevation of the debris flow channel.

[0015] Determine whether the difference in elevation between the debris flow channel and the current time exceeds the debris flow warning threshold. If so, determine that the current time is a debris flow event and trigger a debris flow event alarm; otherwise, determine that the current time is not a debris flow event and do not trigger a debris flow event alarm.

[0016] Preferably, the normalized elevation difference of each point cloud is obtained by the following formula:

[0017] K=y'(x' n-1 )+y'(x' n+1 )-2*y'(x' n )

[0018] In the formula, K is the normalized elevation difference of the nth point cloud, n is the current point cloud index, and x' n-1 、x' n 、x' n+1 These are the normalized x-coordinates of the (n-1), n, and n+1th point clouds, respectively, y'(x' n-1 ), y'(x' n ), y'(x' n+1 ) are the normalized elevation values ​​of the (n-1), n, and n+1 point clouds, respectively.

[0019] Preferably, the threshold for determining the inflection point is obtained using the following formula:

[0020]

[0021] In the formula, Thr is the threshold for judging the inflection point, (y'(x') i )-x' i ) max Let y'(x') be the maximum of the differences between the normalized elevation value and the corresponding normalized x-coordinate of any point cloud. i Let x' be the normalized elevation value of the i-th point cloud. i Let x be the normalized x-coordinate of the i-th point cloud, where i is any value from 1 to N, and N is the total number of point clouds.

[0022] Preferably, the elevation of the debris flow channel at the current moment is obtained by the following formula:

[0023]

[0024] In the formula, Y(t) is the elevation value of the debris flow channel at the current moment, and y(x) is the elevation value of the debris flow channel at the current moment. n The elevation value of the i-th point cloud.

[0025] Preferably, the difference in elevation of the debris flow channel at the current moment is obtained by the following formula:

[0026] Δy=Y(t)-Y(t-1)

[0027] In the formula, Δy is the difference in elevation of the debris flow channel at the current moment, and Y(t-1) and Y(t) are the elevation values ​​of the debris flow channel at the previous moment and the current moment, respectively.

[0028] By applying the technical solution of this invention, a single-line lidar sensor can be used to scan vertical debris flow channels to obtain the cross-sectional contour data of debris flow channels. Through contour inflection point recognition technology, the channel and slope areas can be separated, and the elevation changes of the debris flow area can be accurately observed, thereby achieving rapid and accurate identification of debris flow events and reducing the false alarm rate of debris flow events. Attached Figure Description

[0029] The accompanying drawings, which form part of this specification, are provided to further illustrate embodiments of the invention and, together with the textual description, explain the principles of the invention. It is obvious that the drawings described below are merely some embodiments of the invention, and those skilled in the art can obtain other drawings based on these drawings without any creative effort.

[0030] Figure 1 A flowchart is shown below illustrating a method for debris flow early warning based on contour extraction using a single-line lidar according to an embodiment of the present invention.

[0031] Figure 2 A schematic diagram of single-line lidar acquiring cross-sectional profile data of debris flow channels according to an embodiment of the present invention is shown.

[0032] Figure 3 A schematic diagram of the time-series elevation status of a debris flow channel outline provided according to an embodiment of the present invention is shown. Detailed Implementation

[0033] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0034] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to this application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0035] Unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps set forth in these embodiments do not limit the scope of the invention. It should also be understood that, for ease of description, the dimensions of the various parts shown in the drawings are not drawn to actual scale. Techniques, methods, and devices known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be considered part of the specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters in the following figures denote similar items; therefore, once an item is defined in one figure, it need not be further discussed in subsequent figures.

[0036] like Figure 1 As shown, this invention provides a method for debris flow early warning using single-line lidar to extract contours, the method comprising:

[0037] A single-line lidar sensor is placed on one side of the debris flow channel being monitored, with the sensor's measurement direction perpendicular to the flow direction. The sensor's measurement angle fully covers the debris flow channel. A schematic diagram of the data acquisition is shown below. Figure 2 As shown; the measurement angle range of the radar sensor is ±90°;

[0038] The radar sensor collects point cloud data of the "U"-shaped cross-sectional profile of the debris flow channel in real time. The point cloud data includes angle and distance values ​​in spherical coordinates. The acquisition frequency can be set to once per minute.

[0039] Perform coordinate transformation on each point cloud data at the current moment to obtain the x-coordinate and y-coordinate of each point cloud in the Cartesian coordinate system; where the y-coordinate is the elevation value of each point cloud; and the x-coordinate is the horizontal distance of each point cloud from the preset origin.

[0040] Smoothing and normalization are performed on the x-coordinate and y-coordinate of each point cloud in the Cartesian coordinate system to obtain the normalized x-coordinate and y-coordinate of each point cloud in the Cartesian coordinate system.

[0041] The normalized elevation difference of each point cloud is obtained based on the normalized ordinate of each point cloud in the Cartesian coordinate system.

[0042] The threshold for determining inflection points is obtained based on the normalized x and y coordinates of each point cloud in a Cartesian coordinate system.

[0043] Find two point clouds whose normalized elevation difference is greater than or equal to the inflection point judgment threshold, and use the two point clouds as the two inflection points of the "U"-shaped cross-sectional profile of the debris flow channel; the area between the two inflection points is the channel area, and the area outside the two inflection points is the slope area.

[0044] The average of the ordinates of all point clouds between the two inflection points is taken as the elevation of the debris flow channel at the current moment.

[0045] The difference between the current elevation of the debris flow channel and the previous elevation is taken as the difference in the current elevation of the debris flow channel.

[0046] Determine whether the difference in elevation between the debris flow channel and the current time exceeds the debris flow warning threshold. If so, determine that the current time is a debris flow event and trigger a debris flow event alarm; otherwise, determine that the current time is not a debris flow event and do not trigger a debris flow event alarm.

[0047] In this invention, when a debris flow event occurs, the debris flow channel changes, with debris flowing or accumulating, causing changes in the channel's elevation. By monitoring the temporal elevation changes of the debris flow channel, real-time early warning and judgment of debris flows can be achieved.

[0048] This invention utilizes a single-line lidar sensor to scan vertical debris flow channels, acquiring cross-sectional contour data of the debris flow channels. Through contour inflection point recognition technology, the channel and slope areas can be separated, allowing for precise observation of elevation changes in the debris flow area. This enables rapid and accurate identification of debris flow events, reducing the false alarm rate of debris flow events.

[0049] According to one embodiment of the present invention, point cloud data of debris flow channels are acquired in real time at a collection frequency of 1 minute / time. The point cloud data consists of spherical coordinates, including angle values ​​(θ) and distance values ​​(R). The point cloud data is converted into rectangular coordinate data (x, y) by the following formula to outline the contour of the debris flow channel.

[0050] x = R*sin(θ)

[0051] y = R * cos(θ)

[0052] Generally, debris flow outlines are "U"-shaped, meaning that the bottom of the debris flow channel and the slopes on both sides together form the debris flow outline. However, the main change in debris flow is the change in the elevation of the bottom of the debris flow channel. Slope data would increase the amount of data calculation. Therefore, it is necessary to separate the slope and the bottom of the debris flow channel in order to identify the changes in debris flow.

[0053] Starting with the morphological characteristics of debris flow contours, inflection points appear at the junction of the slope and the bottom of the gully. Identifying these inflection points allows for the separation of the slope from the bottom of the debris flow gully. First, the contour point cloud data is smoothed and filtered to remove interfering data and prevent the identification of local inflection points. Then, the point cloud data is normalized to obtain normalized data.

[0054] According to one embodiment of the present invention, the normalized elevation difference of each point cloud is obtained by the following formula:

[0055] K=y'(x' n-1 )+y'(x' n+1 )-2*y'(x' n )

[0056] In the formula, K is the normalized elevation difference of the nth point cloud, n is the current point cloud index, and x' n-1 、x' n 、x' n+1 These are the normalized x-coordinates of the (n-1), n, and n+1th point clouds, respectively, y'(x' n-1 ), y'(x' n ), y'(x' n+1 ) are the normalized elevation values ​​of the (n-1), n, and n+1 point clouds, respectively.

[0057] According to one embodiment of the present invention, the inflection point judgment threshold is obtained by the following formula:

[0058]

[0059] In the formula, Thr is the threshold for judging the inflection point, (y'(x') i )-x' i ) maxLet y'(x') be the maximum of the differences between the normalized elevation value and the corresponding normalized x-coordinate of any point cloud. i Let x' be the normalized elevation value of the i-th point cloud. i Let x be the normalized x-coordinate of the i-th point cloud, where i is any value from 1 to N, and N is the total number of point clouds.

[0060] When K >= Thr, the point is determined to be an inflection point. In this invention, since the cross-sectional profile of the debris flow channel is "U" shaped, there must be two inflection points.

[0061] The debris flow channel contour data is composed of multiple lidar point clouds. For example... Figure 3 As shown, the dataset A{A1,A2...An} for the previous time (t-1) between the two inflection points and the dataset A'{A1',A2'...An'} for the current time (t) represent point cloud data of the debris flow channel contour at different times. Each point cloud data point (A1 or A1') contains an angle value (θ) and a distance measurement value (R). By calculating the angle and distance values, the elevation value of each point cloud can be obtained, and then the average elevation of all point clouds in the channel can be obtained, which can characterize the elevation of the debris flow channel at the current time. The elevation value of the debris flow channel at the current time can be obtained by the following formula:

[0062]

[0063] In the formula, Y(t) is the elevation value of the debris flow channel at the current moment, and y(x) is the elevation value of the debris flow channel at the current moment. n The elevation value of the i-th point cloud. According to one embodiment of the present invention, the difference in elevation of the debris flow channel at the current moment is obtained by the following formula:

[0064] Δy=Y(t)-Y(t-1)

[0065] In the formula, Δy is the difference in elevation of the debris flow channel at the current moment, which reflects the elevation change of the debris flow channel. Y(t-1) and Y(t) are the elevation values ​​of the debris flow channel at the previous moment and the current moment, respectively.

[0066] If Δy is greater than the debris flow warning threshold (T), a debris flow event alarm is triggered; otherwise, it is a non-debris flow event, as shown in the following formula. T needs to be set according to the specific warning scenario.

[0067]

[0068] In summary, this invention provides a method for debris flow early warning by extracting contours using a single-line lidar sensor. By using a single-line lidar sensor to scan vertically through debris flow channels, the cross-sectional contour data of the debris flow channels can be obtained. Through contour inflection point recognition technology, the channel and slope areas can be separated, and the elevation changes of the debris flow area can be accurately observed, enabling rapid and accurate identification of debris flow events and reducing the false alarm rate of debris flow events.

[0069] The parts of this invention not described in detail are techniques known to those skilled in the art.

[0070] In the description of this invention, it should be understood that the orientation or positional relationship indicated by directional terms such as "front, back, up, down, left, right", "horizontal, vertical, horizontal" and "top, bottom" is generally based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing this invention and simplifying the description. Unless otherwise stated, these directional terms do not indicate or imply that the device or element referred to must have a specific orientation or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on the scope of protection of this invention; the directional terms "inner" and "outer" refer to the inner and outer contours relative to the outline of each component itself.

[0071] For ease of description, spatial relative terms such as "above," "on top of," "on the upper surface of," "above," etc., are used herein to describe the spatial positional relationship of a device or feature as shown in the figures to other devices or features. It should be understood that spatial relative terms are intended to encompass different orientations in use or operation beyond the orientation of the device as described in the figures. For example, if the device in the figures were inverted, a device described as "above" or "on top of" other devices or structures would subsequently be positioned as "below" or "under" other devices or structures. Thus, the exemplary term "above" can include both "above" and "below." The device may also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatial relative descriptions used herein will be interpreted accordingly.

[0072] Furthermore, it should be noted that the use of terms such as "first" and "second" to define components is merely for the purpose of distinguishing the corresponding components. Unless otherwise stated, the above terms have no special meaning and therefore should not be construed as limiting the scope of protection of this invention.

[0073] 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 debris flow early warning using single-line lidar to extract contours, characterized in that, The method includes: A single-line lidar sensor is placed on one side of the debris flow channel being monitored, with the measurement direction of the lidar sensor perpendicular to the flow direction of the debris flow channel, and the measurement angle of the lidar sensor fully covering the debris flow channel. The radar sensor collects point cloud data of the "U"-shaped cross-sectional profile of the debris flow channel in real time. The point cloud data includes angle and distance values ​​in spherical coordinates. Perform coordinate transformation on each point cloud data at the current moment to obtain the x-coordinate and y-coordinate of each point cloud in the rectangular coordinate system; where the y-coordinate is the elevation value of each point cloud. Smoothing and normalization are performed on the x-coordinate and y-coordinate of each point cloud in the Cartesian coordinate system to obtain the normalized x-coordinate and y-coordinate of each point cloud in the Cartesian coordinate system. The normalized elevation difference of each point cloud is obtained based on the normalized ordinate of each point cloud in the Cartesian coordinate system. The threshold for determining inflection points is obtained based on the normalized x and y coordinates of each point cloud in a Cartesian coordinate system. Find two point clouds whose normalized elevation difference is greater than or equal to the inflection point judgment threshold, and use the two point clouds as the two inflection points of the "U"-shaped cross-sectional profile of the debris flow channel; the area between the two inflection points is the channel area, and the area outside the two inflection points is the slope area. The average of the ordinates of all point clouds between the two inflection points is taken as the elevation of the debris flow channel at the current moment. The difference between the current elevation of the debris flow channel and the previous elevation is taken as the difference in the current elevation of the debris flow channel. Determine whether the difference in elevation between the debris flow channel and the current time exceeds the debris flow warning threshold. If so, determine that the current time is a debris flow event and trigger a debris flow event alarm; otherwise, determine that the current time is not a debris flow event and do not trigger a debris flow event alarm.

2. The method according to claim 1, characterized in that, The normalized elevation difference of each point cloud is obtained using the following formula: K=y'(x' n-1 )+y'(x' n+1 )-2*y'(x' n ) In the formula, K is the normalized elevation difference of the nth point cloud, n is the current point cloud index, and x' n-1 、x' n 、x' n+1 These are the normalized x-coordinates of the (n-1), n, and n+1th point clouds, respectively, y'(x' n-1 ), y'(x' n ), y'(x' n+1 ) are the normalized elevation values ​​of the (n-1), n, and n+1 point clouds, respectively.

3. The method according to claim 1, characterized in that, The threshold for determining the inflection point is obtained using the following formula: In the formula, Thr is the threshold for judging the inflection point, (y'(x') i )-x' i ) max Let y'(x') be the maximum of the differences between the normalized elevation value and the corresponding normalized x-coordinate of any point cloud. i Let x' be the normalized elevation value of the i-th point cloud. i Let x be the normalized x-coordinate of the i-th point cloud, where i is any value from 1 to N, and N is the total number of point clouds.

4. The method according to claim 1, characterized in that, The elevation of the debris flow channel at the current moment can be obtained using the following formula: In the formula, Y(t) is the elevation value of the debris flow channel at the current moment, and y(x) is the elevation value of the debris flow channel at the current moment. n The elevation value of the i-th point cloud.

5. The method according to claim 1, characterized in that, The difference in elevation of the debris flow channel at the current moment can be obtained by the following formula: Δy=Y(t)-Y(t-1) In the formula, Δy is the difference in elevation of the debris flow channel at the current moment, and Y(t-1) and Y(t) are the elevation values ​​of the debris flow channel at the previous moment and the current moment, respectively.

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