SPS file elevation abrupt change correction method

Abstract

The invention belongs to the technical field of seismic exploration data processing, and particularly relates to an SPS file elevation abrupt change correction method. The method comprises the following steps: identifying a sudden change elevation point in an SPS file; according to the DEM elevation at the sudden change elevation point and the original elevation around the sudden change elevation point in the SPS file, or according to the DEM elevation at the sudden change elevation point and the elevation points around the sudden change elevation point and the original elevation around the sudden change elevation point in the SPS file, performing interpolation correction on the sudden change elevation of the sudden change elevation point to obtain a correction value of the sudden change elevation; and replacing the abrupt change elevation value in the SPS file with the abrupt change elevation correction value to complete elevation abrupt change correction, so that the elevation abrupt change in the SPS file is rapidly and accurately corrected.

Description

Technical Field

[0001] This invention belongs to the field of seismic exploration data processing technology, specifically relating to a method for correcting elevation abrupt changes in SPS files. Background Technology

[0002] SPS (Shell Processing Support Format for Land 3D Surveys) is an internationally recognized standard format for seismic exploration auxiliary data. With the development of seismic processing technology, the demand for reprocessing and utilizing historical seismic data has increased. However, SPS files of historical seismic data may contain errors or be lost due to subsequent data processing, editing, and storage. If some elevation data in an SPS file is incorrect or missing, the difference between the incorrect elevation and the surrounding elevation values ​​will be significant. When an elevation is missing, that elevation will be recorded as 0. Therefore, the manifestation of incorrect or missing elevation data is a sudden elevation change. Consequently, the static correction results calculated based on this elevation change data will also be incorrect, leading to inaccurate imaging of subsurface structures and affecting the effectiveness of seismic exploration for oil and gas exploration. Therefore, the problem of correcting elevation changes in historical seismic data SPS files urgently needs to be solved to improve the accuracy of seismic imaging based on historical data.

[0003] Patent application CN114543753A discloses a method for correcting the topographic DEM of subsidence and fissure areas. Addressing the problem of missing fissure elevation information in the Digital Elevation Model (DEM) of subsidence and fissure areas, this method utilizes a drone to acquire centimeter-level high-resolution optical remote sensing images of the subsidence and fissure area, delineates the fissure centerline, and then uses the similarity theorem of triangles to calculate the elevation correction value of each grid cell on both sides of the fissure centerline, thus obtaining the elevation of the subsidence and fissure area's topographic DEM. This method requires re-acquiring DEM data using a drone and delineating the fissure centerline, then directly interpolating the DEM elevation to obtain the fissure elevation information. However, for historical seismic data, the re-acquisitioned elevation data may differ significantly from the historically determined elevations, and the final fissure centerline elevation is obtained through simple linear interpolation, resulting in low accuracy. Furthermore, due to time and cost constraints, re-surveying and acquiring the elevation data may not be possible. If DEM elevation data is directly extracted from recent DEM elevation maps to replace abrupt elevation changes in SPS files, significant errors will occur in the elevation correction results. This is because the DEM elevations in digital elevation maps inherently differ from actual survey data, and the DEM elevations are recent data. Furthermore, the actual ground elevations differ considerably from those measured decades ago due to human activities such as landfilling and excavation, and natural landslides. Therefore, existing methods for correcting elevation abrupt changes cannot quickly and accurately correct elevation abrupt changes in SPS files. Summary of the Invention

[0004] The purpose of this invention is to provide a method for correcting elevation abrupt changes in SPS files, in order to solve the problem that existing methods cannot quickly and accurately correct elevation abrupt changes in SPS files.

[0005] To address the aforementioned technical problems, this invention provides a method for correcting elevation abrupt changes in SPS files, comprising:

[0006] Identify abrupt elevation changes in SPS files;

[0007] The abrupt elevation of the abrupt elevation point is corrected by interpolation based on the DEM elevation at the abrupt elevation point and the original elevation around the abrupt elevation point in the SPS file, or based on the DEM elevation at the abrupt elevation point and the original elevation around the abrupt elevation point in the SPS file. The corrected value of the abrupt elevation is obtained by interpolation.

[0008] Replace the elevation abrupt change values ​​in the SPS file with the corrected elevation abrupt change values ​​to complete the elevation abrupt change correction.

[0009] Furthermore, the interpolation correction employs co-kriging interpolation.

[0010] Furthermore, the formula for interpolation correction using the co-kriging interpolation method is as follows:

[0011]

[0012] in, This is the correction value for the abrupt elevation change, where n is the number of elevation points surrounding the abrupt elevation change point in the SPS file, and z is the value for z. i Let x be the original elevation value of the i-th spatial point surrounding the abrupt elevation point in the SPS file, and m be the number of elevation points in the DEM used for interpolation correction. When m = 1, x j x represents the DEM elevation value at the point of abrupt elevation change, where m > 1. j λ represents the DEM elevation values ​​at the abrupt elevation change point and its surrounding elevation points. i and b j The weights to be estimated are obtained by solving the Kriging system equations.

[0013] Furthermore, the method for identifying abrupt elevation points in the SPS file is as follows: extract the DEM elevation corresponding to the coordinates in the SPS file, subtract the extracted DEM elevation from the SPS file elevation to obtain the elevation difference, and identify abrupt elevation points based on the elevation difference.

[0014] Furthermore, the method for identifying abrupt elevation changes based on elevation differences is as follows: an elevation difference grayscale image is generated based on the elevation difference, a detection threshold is set, and an edge detection algorithm is used to detect the elevation difference grayscale image to obtain the abrupt elevation changes.

[0015] Furthermore, the edge detection algorithm is the Canny edge detection algorithm. The maximum threshold of the Canny edge detection algorithm is the gradient value calculated when the difference in elevation between adjacent points is within 8%, and the minimum threshold is the gradient value calculated when the difference in elevation between adjacent points is within 5%.

[0016] Furthermore, the method also includes quality control of the corrected values ​​of the abrupt elevation changes, determining whether they meet the quality control requirements. If they do, the corrected values ​​of the abrupt elevation changes are used as the final corrected values ​​of the abrupt elevation changes; otherwise, the detection threshold and / or interpolation parameters are adjusted, and the elevation abrupt change identification and correction are repeated until the quality control requirements are met. The quality control requirements are: replacing the abrupt elevation values ​​in the SPS file with the corrected values ​​of the abrupt elevation changes to obtain the corrected SPS file elevation; replacing the abrupt elevation values ​​in the SPS file with the corrected values ​​of the abrupt elevation changes to obtain the corrected SPS file elevation; and the corrected SPS file elevation does not contain any abrupt elevation points.

[0017] The beneficial effects of the above technical solution are as follows: This invention is an improved invention. After identifying abrupt elevation changes in the SPS file, it can determine the erroneous and lost elevations that need to be corrected in the SPS file. Based on the original elevation values ​​around the abrupt elevation changes obtained from the SPS file and the DEM elevation at the abrupt elevation changes, or based on the original elevation values ​​around the abrupt elevation changes obtained from the SPS file and the DEM elevation at the abrupt elevation changes and their surrounding elevations, interpolation correction is performed to determine the elevation correction value of the abrupt elevation changes. This makes the obtained correction value of the abrupt elevation changes more accurate and reliable, and eliminates the need to re-photograph the elevation values ​​at the elevation abrupt changes, thus improving the correction efficiency and accuracy. It effectively improves the accuracy of static correction calculations during the reprocessing of historical seismic data and can effectively support the effect of historical seismic data reprocessing. Attached Figure Description

[0018] Figure 1 This is a flowchart of the SPS file elevation change correction process according to an embodiment of the method of the present invention;

[0019] Figure 2 This is a schematic diagram illustrating the Canny edge detection principle of an embodiment of the method of the present invention;

[0020] Figure 3 This is an SPS file elevation grayscale image of an embodiment of the method of the present invention;

[0021] Figure 4 This is a schematic diagram of DEM digital elevation map extraction according to an embodiment of the method of the present invention;

[0022] Figure 5 This is a grayscale image of the DEM elevation obtained by extracting the DEM digital elevation map according to an embodiment of the method of the present invention.

[0023] Figure 6 This is a grayscale image showing the elevation difference between the DEM elevation and the SPS file in an embodiment of the method of the present invention.

[0024] Figure 7 This is a schematic diagram of the Canny edge detection results for SPS file elevation in an embodiment of the method of the present invention;

[0025] Figure 8 This is a schematic diagram of the elevation difference Canny edge detection results in an embodiment of the method of the present invention;

[0026] Figure 9 This is an SPS file elevation grayscale image without abrupt elevation changes, representing an embodiment of the method of the present invention.

[0027] Figure 10 This is a diagram showing the abrupt elevation changes after CoKriging interpolation correction in an embodiment of the method of the present invention.

[0028] Figure 11 This is a modified SPS file elevation grayscale image from an embodiment of the method of the present invention;

[0029] Figure 12 This is a grayscale image showing the difference between the elevation of the SPS file and the elevation of the DEM, as described in an embodiment of the method of the present invention.

[0030] Figure 13 This is a schematic diagram of the Canny edge detection results of the difference between the elevation of the modified SPS file and the elevation of the DEM in an embodiment of the method of the present invention;

[0031] Figure 14 This is an SPS file elevation map of a verification example of the present invention;

[0032] Figure 15 This is a schematic diagram of DEM digital elevation map extraction as a verification example of the present invention;

[0033] Figure 16 This is a grayscale image of the DEM elevation of a verification example of the present invention;

[0034] Figure 17 This is a grayscale image of the elevation difference in a verification example of the present invention;

[0035] Figure 18 This is a diagram showing the results of abrupt elevation edge detection in a verification example of the present invention;

[0036] Figure 19 This is a modified SPS file elevation map of the verification example of this invention;

[0037] Figure 20 This is the static correction single-shot diagram obtained before the modification of the verification example of this invention;

[0038] Figure 21 This is a statically corrected single-shot diagram obtained after modification of the verification example of this invention;

[0039] Figure 22 This is a static calibration cross-sectional view obtained before the modification of the verification example of the present invention;

[0040] Figure 23 This is a statically corrected cross-sectional view obtained after modification of the verification example of the present invention. Detailed Implementation

[0041] To make the objectives, technical solutions, and advantages of the present invention clearer, the specific embodiments of the present invention will be further described below with reference to the accompanying drawings.

[0042] After identifying abrupt elevation changes in an SPS file, this invention determines the original elevation values ​​of accurate elevation points surrounding the abrupt elevation changes recorded in the SPS file. Based on the original elevation values ​​around the abrupt elevation changes obtained from the SPS file and the DEM elevation at the abrupt elevation changes extracted from the DEM digital elevation map, or based on the original elevation values ​​around the abrupt elevation changes obtained from the SPS file and the DEM elevations of the abrupt elevation changes and their surrounding elevation points, interpolation correction is performed to determine the corrected elevation value of the abrupt elevation changes. This makes the corrected values ​​of the abrupt elevation changes more accurate and reliable, and eliminates the need to re-photograph the elevation changes, improving correction efficiency and accuracy. It effectively enhances the accuracy of static correction calculations during the reprocessing of historical seismic data, and can effectively support the reprocessing of historical seismic data.

[0043] Method Implementation Examples

[0044] This invention provides a method for correcting elevation abrupt changes in SPS files. The implementation process of this method is as follows: Figure 1 As shown, the following detailed explanation uses a 3D seismic data SPS file from an old work area as an example.

[0045] 1. Identify abrupt elevation changes in SPS files.

[0046] Since historical seismic data SPS files are often processed as contiguous pieces, with shot-receiver point files containing hundreds of thousands of lines of data, improving the accuracy and speed of elevation abrupt change correction requires first improving the accuracy and speed of abrupt elevation change identification. This invention extracts DEM elevation data by projecting SPS coordinates onto a DEM digital elevation map, then calculates the difference between the SPS file elevation and the DEM elevation, and identifies abrupt elevation points based on this difference. For example, an abrupt change threshold can be set; when the elevation difference at a point exceeds the threshold, that point is identified as an abrupt elevation change point. Furthermore, when part of the SPS file's elevation is missing, the missing elevation is assigned a value of 0. Because the elevation difference at the missing or erroneous points in the SPS file differs significantly from the DEM elevation data, while the difference between the normal elevation in the SPS file and the DEM elevation data is smaller, using the elevation difference between the two for abrupt change identification yields more accurate results.

[0047] As a preferred implementation, to improve the accuracy and speed of identification, this invention visualizes the elevation difference, generates a grayscale image of the elevation difference, sets a detection threshold, and uses an edge detection algorithm to detect the elevation difference grayscale image to obtain the abrupt elevation change points. Visualization solves the carrier problem for identifying elevation abrupt changes, and the edge detection algorithm can quickly and accurately locate the position of the abrupt elevation change and extract its coordinates. The specific process is as follows:

[0048] S1: Extract coordinates and elevations from the SPS file, perform visualization processing, and draw a grayscale elevation map of the SPS file.

[0049] Obtain the SPS text file, extract the x and y coordinates and elevation data B of the shot points or receiver points, use data B to create a scatter plot and visualize the scatter plot, and then create a grayscale elevation map of the SPS file, such as... Figure 3 As shown in the figure (the horizontal axis is the east coordinate and the vertical axis is the north coordinate, as is the case for all figures with coordinates in the appendix of the instruction manual), the overall elevation changes of the work area can be seen from this figure. Two elevations are obviously abnormally high and one is obviously abnormally low. This figure shows obvious areas of elevation change, but it is difficult to distinguish less obvious changes.

[0050] S2: Obtain the DEM digital elevation map, and use the coordinate file obtained in S1 to perform coordinate projection to extract the DEM elevation of the corresponding coordinates.

[0051] Extract data C from data B, containing only x and y coordinates. Project data C (white dots) onto a DEM digital elevation map (e.g., a 5m resolution DEM digital elevation map). Figure 4 As shown, the DEM elevation data D is extracted and visualized to create a DEM elevation grayscale map, as shown below. Figure 5 As shown.

[0052] S3: Subtract the elevation from the DEM elevation extracted in S2 from the elevation from the SPS file extracted in S1 to obtain the elevation difference, and then visualize the elevation difference by drawing a grayscale image of the elevation difference between the DEM elevation and the SPS file. In this embodiment, the elevation difference is obtained by subtracting the elevation extracted in S1 from the DEM elevation extracted in S2, and then visualized by drawing a grayscale image of the elevation difference, such as... Figure 6 As shown.

[0053] S4: Set a detection threshold and use an edge detection algorithm to detect the elevation difference obtained in S3, quickly and automatically detecting abrupt elevation changes and extracting the coordinates of the points where the elevation changes occur. In this embodiment, considering the speed and accuracy of identifying abrupt elevation changes, the Canny edge detection algorithm is used to detect the elevation difference obtained in S3. The Canny edge detection algorithm aims to accurately detect edges in digital images, minimizing false detections while ensuring accurate edge localization. The detection steps are as follows:

[0054] (1) Apply Gaussian filtering to smooth the image and reduce noise;

[0055] (2) Calculate the gradient values ​​of the image using the Sobel operator, including the gradient magnitude and direction;

[0056]

[0057]

[0058] Among them, G x With G y The results are gradient edge detection results in the horizontal (x) and vertical (y) directions, respectively. A is the original image, and the two matrices are Sobel operator templates.

[0059] The formula for calculating the gradient magnitude G is:

[0060]

[0061] The formula for calculating the gradient direction θ is:

[0062]

[0063] (3) Non-maximum suppression technique is used to eliminate false edge detections, making the edges clearer;

[0064] (4) Edge information is filtered using dual threshold detection, the principle of which is as follows: Figure 2As shown. Considering the influence of measured elevation on field static correction, the continuity and energy of the reflected wave phase axis decrease with the increase of the terrain elevation noise ratio. At a terrain elevation noise ratio of 5%, although the energy of the reflected wave decreases, the shape and width of the phase axis remain unchanged. However, at a noise ratio of 8%, some records show widening or weakening of the phase axis, and the phase axes of the reflected waves from the horizontal interface can no longer be superimposed to form a flat interface shape. Therefore, in this embodiment, when setting dual thresholds, the maximum threshold is selected based on the gradient value calculated within 8% of the difference in elevation between adjacent points, and the minimum threshold is selected based on the gradient value calculated within 5% of the difference in elevation between adjacent points. In other embodiments, settings can be configured according to usage requirements, and the location of abrupt elevation changes can be quickly and accurately identified and extracted by adjusting the detection threshold. Alternatively, edge detection can be directly performed on the SPS file's grayscale elevation image to extract the locations of abrupt elevation changes. When performing Canny edge detection directly on the SPS file's grayscale elevation image, the maximum threshold is the gradient value calculated when the elevation difference between adjacent points is within 8%, and the minimum threshold is the gradient value calculated when the elevation difference between adjacent points is within 5%. The Canny edge detection results for the SPS file elevation are shown below. Figure 7 As shown, Canny edge detection was performed on the elevation difference between the DEM elevation and the SPS file, with a maximum threshold of 8% and a minimum threshold of 5% for the difference in elevation between adjacent points. The edge detection results for the elevation difference between the DEM elevation and the SPS file are as follows. Figure 8 As shown, it can be seen that compared to Figure 7 , Figure 8 It can detect potential elevation abrupt changes in the upper left corner, resulting in more accurate and reliable detection results. According to... Figure 8 Based on the detection results, the sudden elevation F is quickly located, and the coordinates of the sudden elevation point are extracted.

[0065] 2. Based on the accurate original elevations around the abrupt elevation points in the SPS file, the DEM elevations at the abrupt elevation points extracted from the DEM digital elevation map, or based on the DEM elevations at the abrupt elevation points and their surrounding elevation points, and the original elevations around the abrupt elevation points in the SPS file, the abrupt elevations are interpolated and corrected.

[0066] In this embodiment, CoKriging interpolation is used to obtain accurate original elevation points around the abrupt elevation points in the SPS file (such as...). Figure 9 The elevation shown is used as a hard constraint, with the DEM elevation extracted from the DEM digital elevation map (such as...) Figure 5 As shown in the figure, the abrupt elevation change is corrected by interpolation using a soft constraint. The corrected result is H. The visualization of the abrupt elevation change result after CoKriging interpolation correction is shown in the figure. Figure 10As shown. The CoKriging interpolation method improves local interpolation accuracy by considering the correlation between multiple relevant spatial variables. Based on the covariance function, it finds the optimal weights to determine the interpolation result. The interpolation steps are as follows:

[0067] S1: Determine the location of the point to be interpolated, which is a point of sudden elevation change;

[0068] S2: Calculate the spatial weights of data points surrounding the abrupt elevation change point to the point to be interpolated. The spatial weights of the accurate original elevation points surrounding the abrupt elevation change point in the SPS file are the first weights, and the spatial weights of the DEM elevations are the second weights. Specifically, the formula for calculating the first weight A1 is as follows: The formula for calculating the second weight A2 is: Where n is the number of elevation points surrounding the abrupt elevation point in the SPS file, m is the number of elevation points in the DEM used for interpolation correction, and λ i and b j The weights to be estimated are obtained by solving the Kriging system equations. Under the condition of second-order stationarity, in order to ensure that the estimated values ​​are unbiased, To ensure greater accuracy, the first weight is greater than the second weight. In this embodiment, eight elevation points are selected around the abrupt elevation point in the SPS file, and eight elevation points are also selected around the abrupt elevation point in the DEM elevation data. In this case, n=8 and m=9. In other embodiments, the number of surrounding elevation points can be selected based on the calculation accuracy and calculation time.

[0069] S3: Calculate the contribution rate of surrounding data points to the interpolation point, and use the covariance function to determine the contribution rate of surrounding data points to the interpolation point;

[0070] S4: Use the contribution rate of surrounding data points to the interpolation point to estimate the value of the interpolation point;

[0071] The interpolation correction formula is as follows:

[0072]

[0073] in, z is the correction value for abrupt elevation changes. i x is the original elevation value of the i-th spatial point surrounding the abrupt elevation point in the SPS file, when m=1. j x represents the DEM elevation value at the point of abrupt elevation change, where m > 1. j The elevation values ​​are the DEM values ​​at the abrupt elevation change points and their surrounding elevation points.

[0074] 3. Replace the abrupt elevation values ​​in the SPS file with the corrected elevation values ​​H, resulting in the corrected SPS file elevation data I. The visualization result is shown below. Figure 11 As shown, the correction of the abrupt elevation changes in the SPS file is completed.

[0075] 4. Quality control of elevation correction.

[0076] Quality control requirements are set, and the correction values ​​for abrupt elevation changes are subjected to quality control to determine whether they meet the requirements. If they do, the correction values ​​for abrupt elevation changes are used as the final abrupt elevation change correction values. If they do not meet the requirements, the detection threshold and / or interpolation parameters of the edge detection algorithm are adjusted. The interpolation parameters refer to the first weight in the CoKriging interpolation method. The identification and correction of elevation abrupt changes are repeated until the quality control requirements are met. The quality control requirements are: replace the abrupt elevation values ​​in the SPS file with the correction values ​​for abrupt elevation changes to obtain the corrected SPS file elevation. The corrected SPS file elevation should not contain any abrupt elevation points. In this embodiment, the difference between the corrected SPS file elevation data I and the DEM elevation data D is calculated to obtain the difference J between the corrected SPS file elevation and the DEM elevation. The data J is visualized, and the visualization result is as follows. Figure 12 As shown. For Figure 12 Edge detection was performed using the Canny edge detection algorithm. A large threshold was set at an 8% elevation difference between adjacent points. No abrupt elevation changes were detected, indicating compliance with quality control results. Correction values ​​for abrupt elevation changes were output. The detection results are as follows: Figure 13 As shown.

[0077] Verification Example

[0078] The following describes the SPS file elevation change correction method introduced in this invention, which is used to detect and repair an SPS file containing elevation changes in historical seismic data. The static correction effects on single shots and profiles before and after repair are analyzed. Figure 14-19 It is the process of identifying and correcting abrupt elevation changes. The original SPS file is as follows: Figure 14 As shown; project the coordinates from the SPS file onto the DEM digital elevation map (e.g.) Figure 15 As shown in the figure, the extracted DEM elevation is obtained, as follows. Figure 16 As shown; subtracting the DEM elevation from the SPS file elevation yields the following result: Figure 17 The elevation difference is shown; the Canny edge detection algorithm is used to perform edge detection on the elevation difference, and the result of the abrupt elevation edge detection is obtained, such as... Figure 18 As shown, the coordinates of the abrupt change region and its elevation point are extracted; the elevation of the abrupt change region is corrected using the CoKriging interpolation method, and the corrected elevation values ​​are used to replace the abrupt change elevation values ​​in the SPS file to obtain the corrected SPS file elevation, as shown. Figure 19 As shown, the abrupt elevation changes in the SPS file have been accurately corrected. A comparison of the effects before and after static correction is performed on one of the permutations, as shown below. Figure 20 and Figure 21As shown, the static correction before elevation correction exhibits significant initial arrival fluctuations and discontinuities in the phase axis. The static correction after elevation correction shows a marked improvement. The corresponding effects of the profile elevation correction before and after are shown in the figures. Figure 22 and Figure 23 As shown, the continuity of the phase axis is significantly improved. The results demonstrate that this method is efficient, objective, and accurate, and the elevation correction is highly reliable, solving the static correction problem in seismic processing caused by abrupt elevation changes and ensuring accurate imaging of subsurface structures.

Claims

1. A method for correcting elevation abrupt changes in SPS files, characterized in that, include: Identify abrupt elevation changes in SPS files; The abrupt elevation of the abrupt elevation point is corrected by interpolation based on the DEM elevation at the abrupt elevation point and the original elevation around the abrupt elevation point in the SPS file, or based on the DEM elevation at the abrupt elevation point and the original elevation around the abrupt elevation point in the SPS file. The corrected value of the abrupt elevation is obtained by interpolation. Replace the elevation abrupt change values ​​in the SPS file with the corrected elevation abrupt change values ​​to complete the elevation abrupt change correction.

2. The method for correcting elevation abrupt changes in SPS files according to claim 1, characterized in that, The interpolation correction employs co-kriging interpolation.

3. The method for correcting elevation abrupt changes in SPS files according to claim 2, characterized in that, The formula for interpolation correction using the co-kriging interpolation method is as follows: in, This is the correction value for the abrupt elevation change, where n is the number of elevation points surrounding the abrupt elevation change point in the SPS file, and z is the value for z. i Let x be the original elevation value of the i-th spatial point surrounding the abrupt elevation point in the SPS file, and m be the number of elevation points in the DEM used for interpolation correction. When m = 1, x j x represents the DEM elevation value at the point of abrupt elevation change, where m > 1. j λ represents the DEM elevation values ​​at the abrupt elevation change point and its surrounding elevation points. i and b j The weights to be estimated are obtained by solving the Kriging system equations.

4. The method for correcting elevation abrupt changes in SPS files according to claim 1, characterized in that, The method for identifying abrupt elevation points in the SPS file is as follows: extract the DEM elevation corresponding to the coordinates in the SPS file, subtract the extracted DEM elevation from the SPS file elevation to obtain the elevation difference, and identify abrupt elevation points based on the elevation difference.

5. The method for correcting elevation abrupt changes in SPS files according to claim 4, characterized in that, The method for identifying abrupt elevation changes based on elevation differences is as follows: an elevation difference grayscale image is generated based on the elevation difference, a detection threshold is set, and an edge detection algorithm is used to detect the elevation difference grayscale image to obtain abrupt elevation changes.

6. The method for correcting elevation abrupt changes in SPS files according to claim 5, characterized in that, The edge detection algorithm is the Canny edge detection algorithm. The maximum threshold of the Canny edge detection algorithm is the gradient value calculated when the difference in elevation between adjacent points is within 8%, and the minimum threshold is the gradient value calculated when the difference in elevation between adjacent points is within 5%.

7. The method for correcting elevation abrupt changes in SPS files according to claim 5, characterized in that, The method further includes quality control of the corrected values ​​of the abrupt elevation changes, determining whether they meet the quality control requirements. If they do, the corrected values ​​of the abrupt elevation changes are used as the final corrected values ​​of the abrupt elevation changes; otherwise, the detection threshold and / or interpolation parameters are adjusted, and the elevation abrupt change identification and correction are repeated until the quality control requirements are met. The quality control requirements are: replacing the abrupt elevation values ​​in the SPS file with the corrected values ​​of the abrupt elevation changes to obtain the corrected SPS file elevation, and the corrected SPS file elevation does not contain any abrupt elevation points.

Images