A method for improving landslide early warning stage discrimination based on adaptive time window

Abstract

The application discloses a method for improving landslide early warning stage discrimination based on an adaptive time window. The application sets multiple fixed time windows to calculate tangent angle time curves, selects an optimal time window in which a coincidence rate first meets a threshold requirement by using the coincidence rate of the tangent angle time curves, and realizes the discrimination of the landslide early warning stage. The method can greatly reduce the influence of data monitoring frequency on the early warning result, and improve the accuracy of the landslide early warning stage discrimination and the universality of the early warning method.

Description

Technical Field

[0001] This invention relates to the field of alarm technology for responding to disaster events, and specifically to a method for improving the determination of landslide early warning stages based on adaptive time windows. Background Technology

[0002] The currently popular method for determining the landslide early warning stage is the tangent angle method based on the surface deformation time curve. This method is based on Saito's three-stage landslide deformation theory and has been successfully applied to landslide early warning in areas such as Heifangtai, Gansu. The time window for the tangent angle in this method's calculation formula is the time interval of the monitoring data, which presents two problems: 1) The tangent angle value is highly sensitive to the time window, and the time window is related to the monitoring frequency, so changes in the monitoring frequency can easily lead to errors in the tangent angle calculation; 2) The deformation characteristics of different types of disasters (such as shallow and deep landslides) vary greatly, making it difficult to find a fixed time window suitable for all scenarios.

[0003] Furthermore, most successful applications of this early warning method are achieved by combining data monitored by ground-based GNSS equipment. If data monitored by other equipment (such as ground-based interferometric radar) is used, different early warning results may be generated due to different data frequencies. Summary of the Invention

[0004] In view of this, the present invention provides a method for improving the judgment of landslide early warning stage based on adaptive time window. By comparing the tangent angle curves under different time windows, the optimal time window is selected to realize the judgment of landslide early warning stage.

[0005] The method for improving landslide early warning stage discrimination based on adaptive time window of the present invention includes:

[0006] S1. Perform continuous real-time monitoring of the scene to obtain the deformation time curve; set multiple fixed time windows, calculate the tangent angle of the deformation time curve under each fixed time window, move the fixed time window to obtain the tangent angle curve corresponding to each fixed time window;

[0007] S2. Sort the fixed time windows in ascending order and calculate the overlap rate of the tangent angle curves under adjacent fixed time windows in turn; the fixed time window corresponding to the first time the overlap rate exceeds the set threshold B is the optimal warning time window.

[0008] S3. Use the tangent angle corresponding to the optimal warning time window as the warning tangent angle to determine landslide warnings.

[0009] Preferably, in S1, the calculation method for the tangent angle under a fixed time window Δt is as follows:

[0010] First, calculate the cumulative deformation S. i Average rate B i :

[0011]

[0012] Among them, S1, S i These are time points t1 and t2 in the deformation time curve, respectively. i The cumulative deformation corresponding to each moment;

[0013] Then, use the cumulative deformation S i Divided by average speed B i To obtain T with dimensions consistent with time t i :

[0014]

[0015] Then t i At time t, the deformation-time curve is within a fixed time window Δt (Δt = t). i -t i-n The tangent angle α under) i for:

[0016]

[0017] A preferred method for calculating the overlap rate of tangent angle curves within adjacent fixed time windows is as follows:

[0018] Calculate the difference in tangent angles on the tangent angle curves corresponding to adjacent time windows at the same time. If the difference is less than or equal to a set threshold A, it is considered that the two tangent angle curves overlap at that time. The ratio of the overlap time of the two tangent angle curves to the total time is the overlap rate of the two curves.

[0019] Preferably, the set threshold A is 3.

[0020] Preferably, the set threshold B is 80%.

[0021] Preferably, in step S1, the deformation time curve is obtained using ground-based GNSS equipment or ground-based interferometric radar.

[0022] Preferably, in step S1, ground-based interferometric radar is used to acquire the surface cumulative deformation of the monitoring scene; the tangent angle is determined based on the surface cumulative deformation, specifically including:

[0023] S101, Design multiple deformation thresholds based on the maximum value in the cumulative surface deformation;

[0024] S102, Obtain the area-time curves corresponding to each deformation threshold:

[0025] For each deformation threshold, the total area of ​​pixels whose cumulative deformation exceeds the deformation threshold is calculated in real time. Each time point corresponds to a total area value of pixels that exceeds the deformation threshold, which forms an area-time curve as time progresses.

[0026] S103. For each fixed time window, calculate the tangent angle of the area-time curve corresponding to each deformation threshold at the current moment. The largest of the tangent angles of the area-time curves corresponding to each deformation threshold is the tangent angle at the current moment corresponding to the fixed time window.

[0027] Preferably, in step S101, N deformation thresholds are designed in the following manner:

[0028] The maximum cumulative deformation value S in the monitoring scenario during the current measurement period max When ≤100mm, Deformation threshold S k =10·k, k=1~N, Indicates rounding down;

[0029] The maximum cumulative deformation value S in the monitoring scenario during the current measurement period max When >100mm, Deformation threshold

[0030] Preferably, in S103, the deformation threshold S k The corresponding area-time curve A k The method for calculating the tangent angle of (t) is as follows:

[0031] First, calculate the area-time curve A. k (t) from the initial time t1 to each time t i average speed B k,i Then, by dividing the area by the average velocity, the ordinate A of the area-time curve is plotted. k,i Transformed to T with dimensions consistent with the horizontal axis time t k,i T is calculated using an adaptive time window method. k,i The optimal time window for the time curve, T k,i The slope within the optimal time window is the area-time curve A. k (t) at t i Tangent angle α at time k,i .

[0032] Preferably, in S4, there are four warning levels: attention level θ1≤α<θ2, warning level θ2≤α<θ3, alert level θ3≤α<θ4, and alarm level α≥θ4; where θ1∈[35°,45°], θ2∈[40°,50°], θ3∈[60°,80°], and θ4∈[70°,90°], and simultaneously satisfy θ1<θ2<θ3<θ4; where α is the warning tangent angle.

[0033] Beneficial effects:

[0034] This invention addresses the tangent angle time window problem in the deformation time curve tangent angle early warning method by proposing an adaptive time window approach. This method calculates the tangent angle time curve using multiple fixed time windows and selects the optimal time window based on the overlap rate of the tangent angle time curves, where the overlap rate first meets the threshold requirement. This allows for the determination of the landslide early warning stage. This method significantly reduces the impact of data monitoring frequency on the early warning results, improves the accuracy of landslide early warning stage determination, and enhances the universality of the early warning method.

[0035] The method of determining whether tangent angles coincide by the distance between the tangent angles corresponding to the curves at the same time is simple and easy to operate.

[0036] An overlap rate greater than 80% can be considered the optimal time window, reducing computational load and increasing accuracy.

[0037] When using ground-based interferometric radar to acquire the cumulative surface deformation of the monitoring scene, the tangent angle can also be determined based on the cumulative surface deformation. Compared with the traditional early warning method based on single-point deformation information, the method using area time series curves can identify the overall trend of landslide surface deformation. Its early warning information is more comprehensive and accurate, which can effectively improve the accuracy of landslide early warning stage judgment. Attached Figure Description

[0038] Figure 1 The curves are the cumulative deformation time curve and the tangent angle α curve for multiple time windows, where (a) 8 min; (b) 1 / 2 / 3 / 4 / 5 h; (c) 4 / 5 / 6 / 7 / 8 / 9 / 10 h.

[0039] Figure 2 The overlap rate of the tangent angle α curve under multiple time windows.

[0040] Figure 3 An improved landslide early warning stage discrimination based on adaptive time windows.

[0041] Figure 4 This is for the original landslide warning stage.

[0042] Figure 5 This is a flowchart of the present invention.

[0043] Figure 6This is a flowchart of the method for calculating the tangent angle based on the area-time curve. Detailed Implementation

[0044] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0045] This invention provides a method for improving landslide early warning stage discrimination based on adaptive time windows, the flowchart of which is shown below. Figure 5 As shown, the specific steps include the following:

[0046] 1. Calculate the tangent angle α time curve under multiple fixed time windows.

[0047] When calculating the tangent angle based on the deformation time curve, the calculated value of the tangent angle is highly sensitive to the time window. For example, a time window that is too small can easily cause the tangent angle to jump, while a time window that is too large can lead to a lag in early warning information. Furthermore, for deformation measurement equipment with different monitoring frequencies and deformation characteristics of different types of disasters, there is no fixed time window suitable for all conditions. This invention aims to select the optimal time window from multiple time windows.

[0048] The method for calculating the tangent angle under a single time window Δt is as follows:

[0049] First, calculate the cumulative deformation S. i Average rate B i :

[0050]

[0051] Among them, S1, S i These are time points t1 and t2 in the deformation time curve, respectively. i The cumulative deformation corresponding to each moment.

[0052] Then, use the cumulative deformation S i Divided by average speed B i To obtain T with dimensions consistent with time t i :

[0053]

[0054] Calculate T i The tangent angle (slope) α on the time curve within the time window Δt. i α i It is a dimensionless natural number.

[0055]

[0056] In equation (3), Δt is the tangent angle time window, and α i For t i The tangent angle at time S i ti S represents the cumulative deformation and time corresponding to the i-th monitoring data, respectively. i-1 t i-1 These represent the cumulative deformation and time corresponding to the (i-1)th monitoring data point, respectively.

[0057] Now, Δt is set to multiple fixed values, and the method for calculating the tangent angle is changed from formula (3) to formula (4).

[0058]

[0059] In equation (4), Δt is a fixed value, and the value of n depends on Δt.

[0060] Then select m fixed time windows:

[0061] Δt j =j,j=1,2,3,…,m (5)

[0062] In equation (5), Δt j The unit is h, and m is set according to the deformation frequency of the monitored object.

[0063] Calculate the time window Δt j The corresponding tangent angle α i,j This yields m tangent angle-time curves.

[0064]

[0065] 2. Calculate the coincidence rate of tangent angle curves.

[0066] Sort the fixed time windows in ascending order and calculate t at each time point. i Below, the difference in tangent angle C between adjacent time windows i,j :

[0067] C i,j =|α i,j -α i,j+1 | (7)

[0068] C i,j When ≤3, t is considered to be i Time α i,j Curve and α i,j+1 The ratio of the overlap time to the total time of curve information is α. i,j Curve and α i,j+1 The overlap rate C of the curves j (Formula (8)).

[0069]

[0070] 3. Selection of the optimal early warning time window

[0071] Time window Δtj The larger the value, the larger the tangent angle α. i,j The fewer jump phenomena there are, the more continuous the tangent angle curve is, and the higher the overlap rate C. j Larger. However, an excessively large time window can lead to a lag in early warning information. Curves with an overlap rate of 80% have high similarity, therefore when C j When ≥80% of the conditions are met for the first time, hour j is selected as the optimal warning time window.

[0072] 4. Early warning stage identification

[0073] The tangent angle corresponding to the warning time window is used as the warning tangent angle, and the warning stage is determined according to the correspondence between the tangent angle and the warning stage in Table 1.

[0074] Table 1. Correspondence between tangent angle and warning stage

[0075]

[0076] Note: Tangent angle threshold setting range: θ1∈[35°,45°], θ2∈[40°,50°], θ3∈[60°,80°], θ4∈[70°,90°], while satisfying θ1<θ2<θ3<θ4.

[0077] The deformation time curve of this invention can be obtained using ground-based GNSS equipment or ground-based interferometric radar (GB-InSAR).

[0078] Specifically, for monitoring using GB-InSAR, considering its technical advantage in monitoring surface deformation, and based on the characteristic of regular expansion of deformation areas during landslide development, a method for calculating the tangent angle based on area-time curves is proposed. By setting multiple deformation thresholds, the tangent angle calculation results from multiple deformation-time curves are fused to obtain the optimal tangent angle for landslide early warning stage identification. Compared to traditional early warning methods based on single-point deformation information, the method using area-time curves can identify the overall trend of landslide surface deformation, providing more comprehensive and accurate early warning information, and effectively improving the accuracy of landslide early warning stage identification. The specific method flow is as follows: Figure 6 As shown, the specific steps include the following:

[0079] S101, Design Deformation Threshold

[0080] GB-InSAR is used to monitor the scene and obtain the cumulative deformation of the scene within the current time window Δt. The maximum value S of the cumulative deformation of the scene within the current time window Δt is then used. max Design N deformation thresholds: The number and value of deformation thresholds can be determined empirically or through numerical simulation. This embodiment is designed as follows:

[0081] When S max When ≤100mm, Deformation threshold S k =10·k, k=1~N, This indicates rounding down to the nearest integer.

[0082] When S max When >100mm, Deformation threshold

[0083] S102, Obtain the area-time curve

[0084] Deformation-time curves based on single-point monitoring can effectively identify the landslide hazard state at a point during slope deformation. However, after a significant slope failure, the deformation rate at a single point may slow down, but the deformation area may still continue to expand. Using area-time curves can more accurately identify the overall deformation trend of the landslide surface.

[0085] For the cumulative deformation within the time window Δt, for each deformation threshold S k Calculate the time t at each time point within the time window Δt. i The cumulative deformation exceeds S k The total area A of the pixels k,i All A within the time window Δt k,i The set of these is the area-time curve A. k (t). During the landslide development process, A k (t) is an increasing curve, A k The growth rate of (t) is the expansion rate of the deformed region.

[0086] S103, Calculate the tangent angle of the area time curve.

[0087] For each deformation threshold S k The corresponding area-time curve A k (t), calculate the area-time curve A k (t) from the initial time t1 to each time t i average speed B k,i (Formula (9)).

[0088]

[0089] Plot the vertical axis A of the area-time curve by dividing the area by the average velocity. k,i Transformed to T with dimensions consistent with the horizontal axis time t k,i (Formula (10)).

[0090]

[0091] Calculate t i The tangent angle (slope) α at time t is... k,i (Formula (11)), α k,i It is a dimensionless natural number.

[0092]

[0093] S104, Obtain the warning judgment tangent angle

[0094] t i At time t, each deformation threshold S k There is a corresponding tangent angle α k,i N deformation thresholds can yield N tangent angles, and the maximum tangent angle α is... i As the tangent angle of the time window (Formula (12)).

[0095]

[0096] Case

[0097] Taking the surface deformation data of the slope of the Jianshan Iron Mine in Shanxi Province monitored by ground-based interferometric radar as an example, the adaptive time window calculation and early warning process is as follows:

[0098] 1) The original data frequency is 8 minutes, and 10 fixed time windows are set (1h, 2h, 3h, 4h, 5h, 6h, ..., 10h). The tangent angle α curve under each time window is shown below. Figure 1 .Depend on Figure 1 (a) It can be seen that the tangent angle curve jump phenomenon when the original data frequency is used as the time window is very serious, and many false alarms will occur when the original method is used for early warning.

[0099] 2) Calculate the overlap rate of the tangent angle curves corresponding to 10 fixed time windows, such as... Figure 2 The tangent angle α curves of the 4h and 5h time windows coincide with each other to reach 80% first, therefore the adaptive time window is 4h.

[0100] 3) Use the tangent angle of the adaptive time window as the warning tangent angle. In Table 1, the tangent angle thresholds θ1, θ2, θ3, and θ4 are set to 40°, 50°, 75°, and 85°, respectively. The warning stage is determined based on Table 1 and the warning tangent angle values. Figure 3 Improved landslide early warning stage discrimination based on adaptive time window. Figure 4 This is a comparison of the original landslide early warning stage using an 8-minute time window. Figure 3 , 4 It is evident that the original early warning stage had issues with jumps and false alarms. By improving the adaptive time window, the early warning stage has become more continuous, stable, and reliable.

[0101] In summary, the above are merely preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. 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 improving landslide early warning stage discrimination based on adaptive time window, characterized in that, The application relates to a landslide early warning method, which comprises the following steps: S1, continuously and real-time monitoring a scene to obtain a deformation time curve; a plurality of fixed time windows are set, tangent angles of the deformation time curve in each fixed time window are calculated, the fixed time window is moved, and tangent angle curves corresponding to the fixed time window are obtained; S2, the fixed time windows are sorted in ascending order, and the coincidence rate of tangent angle curves in adjacent fixed time windows is calculated in sequence; when the coincidence rate exceeds a set threshold B for the first time, the fixed time window corresponding to the coincidence rate is the optimal early warning time window; the calculation method of the coincidence rate of the tangent angle curves in the adjacent fixed time windows is as follows: the tangent angle difference value of the tangent angle curves corresponding to the adjacent time windows at the same time is calculated, when the difference value is less than or equal to a set threshold A, it is considered that the two tangent angle curve information coincide; the ratio of the length of the two tangent angle curve information to the total length is the coincidence rate of the two curves; S3, the tangent angle corresponding to the optimal early warning time window is taken as a warning tangent angle, and landslide early warning discrimination is carried out.

2. The method for improving landslide warning stage discrimination based on adaptive time window according to claim 1, characterized in that, in the S1, the calculation method of the tangent angle in the fixed time window Delta t is as follows: First, the accumulated deformation S is calculated i at an average rate B i : Wherein, S1, S i are the accumulative deformations corresponding to the time t1 and t i in the deformation-time curve, respectively. Then, the accumulated deformation S is divided by the average rate B i i i :​​ Then t i The tangent angle a i of the deformation time curve at the fixed time window Δt (Δt = t i-n ) is: i ​ 3. The method for improving landslide warning stage discrimination based on adaptive time window according to claim 1, characterized in that, the set threshold A is 3.

4. The method for improving landslide warning stage discrimination based on adaptive time window according to claim 1, characterized in that, the set threshold B is 80%.

5. The method for improving landslide warning stage discrimination based on adaptive time window according to claim 1, characterized in that, in the S1, a ground GNSS device or a ground-based interferometric radar is adopted to obtain the deformation time curve.

6. The method for improving landslide warning stage discrimination based on adaptive time window according to claim 5, characterized in that, in the S1, a ground-based interferometric radar is adopted to obtain the surface cumulative deformation variable of the monitoring scene; the tangent angle is determined based on the surface cumulative deformation variable, and the method specifically comprises the following steps: S101, a plurality of deformation thresholds are designed according to the maximum value in the surface cumulative deformation variable; S102, area-time curves corresponding to each deformation threshold are obtained: for each deformation threshold, the total area of the pixel points exceeding the deformation threshold at the current time is calculated in real time; each time corresponds to a total area of the pixel points exceeding the deformation threshold, and with the passage of time, the area-time curve is formed; S103, for each fixed time window, the tangent angle of the area-time curve corresponding to each deformation threshold at the current time is calculated, and the maximum tangent angle of the area-time curve corresponding to each deformation threshold is the tangent angle of the fixed time window at the current time.

7. The method for improving landslide warning stage discrimination based on adaptive time window according to claim 6, characterized in that, in the S101, N deformation thresholds are designed in the following manner: Maximum accumulated deformation value S in the current measurement period monitoring scenario max ≤ 100 mm, Deformation threshold value S k = 10 · k, k = 1 ~ N, denotes rounding down; Maximum accumulated deformation value S in the current measurement period monitoring scenario max > 100 mm, Deformation threshold 8. The method for improving landslide warning stage discrimination based on adaptive time window according to claim 6 or 7, characterized in that, In S103, the deformation threshold S k The corresponding area-time curve A k The tangent angle of (t) is calculated as follows: First, calculate the area-time curve A. k (t) from the initial time t1 to each time t i average speed B k,i Then, by dividing the area by the average velocity, the ordinate A of the area-time curve is plotted. k,i Transformed to T with dimensions consistent with the horizontal axis time t k,i T is calculated using an adaptive time window method. k,i The optimal time window for the time curve, T k,i The slope within the optimal time window is the area-time curve A. k (t) at t i Tangent angle α at time k,i .

9. The method for improving landslide warning stage discrimination based on adaptive time window according to claim 1, wherein, in the S3, there are four early warning levels: attention level theta 1 <= alpha < theta 2, warning level theta 2 <= alpha < theta 3, alert level theta 3 <= alpha < theta 4 and alarm level alpha >= theta 4; wherein, theta 1 belongs to [35 DEG, 45 DEG], theta 2 belongs to [40 DEG, 50 DEG], theta 3 belongs to [60 DEG, 80 DEG], and theta 4 belongs to [70 DEG, 90 DEG], and theta 1 < theta 2 < theta 3 < theta 4 is satisfied; wherein, alpha is the warning tangent angle.

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