A method and device for extracting river fracture points

Abstract

The present invention discloses a method and device for extracting river crack points, the method comprising: reading the profile data of the river from which the crack points are to be extracted to form a curve L1; smoothing the curve L1 to obtain a curve L2; calculating the intersection of L1 and L2 and storing it in an intersection set; (4) using the intersection in the intersection set as a segmentation point to segment the L1 curve; reading a segment and determining whether the segment is an upward convex curve, if so, extracting the point in the segment that is farthest from the starting point in a straight line and storing it in the candidate crack point set as a candidate crack point, re-sorting all the candidate crack points in the candidate crack point set from large to small according to the distance; extracting a subset that meets the requirements from large to small according to a preset number of crack points or a preset distance threshold, which is the crack point extraction result required by the user. The present invention is more efficient and more accurate.

Description

Technical Field

[0001] The invention relates to the field of information technology applications, and in particular to an automatic extraction method for river fracture points based on a river longitudinal profile. Background Art

[0002] The fracture point is the sharp turning point between the gentle slope section and the steep slope section on the longitudinal section of the riverbed. Its formation is closely related to the upstream erosion of the river, the structural uplift of the riverbed, and the change of lithology. The fracture point often appears in the form of rapids, turbulent beaches, waterfalls, etc. in the river channel. The fracture point is one of the important geomorphological indicators reflecting the development of valley water system, structural uplift, erosion rate, fault activity, etc. The rapid and accurate extraction of river fracture points has important research significance and application value.

[0003] For a long time, the research on crack points has mostly relied on field surveys. Due to the limitations of terrain conditions and human resources, field surveys can only be limited to small watersheds of a certain scale, making it difficult to conduct detailed surveys on a large scale. Some existing automatic crack point acquisition methods still have shortcomings or deficiencies such as high algorithm complexity, low efficiency, and low accuracy. Therefore, it is necessary to develop a crack point extraction method with higher efficiency and accuracy. Summary of the invention

[0004] Purpose of the invention: In view of the problems existing in the prior art, the present invention provides a method and device for extracting river fracture points with higher efficiency and accuracy.

[0005] Technical solution: The method for extracting river crack points of the present invention comprises:

[0006] (1) Reading the profile data of the river where the fracture point is to be extracted to form a curve L1;

[0007] (2) Smoothing the curve L1 according to a preset smoothing window parameter k to obtain a smoothed curve L2;

[0008] (3) Calculate the intersection of curve L1 and smooth curve L2 and store them in the intersection set Intersections;

[0009] (4) Using the intersection points in the intersection set Intersections as segmentation points, the L1 curve is segmented and stored in the segment set Sections;

[0010] (5) Read a segment from the segment set Sections and determine whether the segment is an upward convex curve. If so, execute step (6); otherwise, execute step (7);

[0011] (6) Extract the point in the segment that is farthest from the starting point of the segment curve and store it as a candidate crack point in the candidate crack point set TKickPoint = {(p i ,di )|i=1,…,u}; where p i is the i-th candidate split point, d i The crack point p i The distance to the straight line determined by the endpoint of the curve segment, u is the number of candidate crack points

[0012] (7) Return to step (5) until all segments in Sections are processed;

[0013] (8) re-sorting all candidate crack points in the set TKickPoint according to the distance from large to small to obtain a sequential candidate crack point set STKickPoint;

[0014] (9) According to the preset number of crack points or the preset distance threshold, a subset of KickPoints that meet the requirements is extracted from the set STKickPoint from large to small, which is the crack point extraction result required by the user.

[0015] Furthermore, step (1) specifically includes:

[0016] Read the profile data of the river where the crack point is to be extracted, and take each point in the profile data as a point of the curve L1 to form a curve L1 = {p i |i=1,...,n}, n is the number of points in the river profile data, p i is the i-th point in curve L1 and its coordinates.

[0017] Furthermore, step (2) specifically includes:

[0018] (2-1) According to the preset smoothing window parameter k, extract the first point p1 to the first point p2 in the curve L1. Points As the first point sp1 to the second point sp2 of the smooth curve L2 Points

[0019] (2-2) For the first Points To Points After smoothing according to the following formula, the smoothed curve L2 is Points To Points points;

[0020]

[0021] In the formula, (sp i，x , sp i，y ) represents the i-th point p in the curve L1i The coordinates of the smoothed point, i.e. the i-th point sp of the smoothed curve L2 i The coordinates of (p i，x , p i，y ) represents the i-th point p in the curve L1 i The coordinates of , n represents the number of points of the curve L1 and the smooth curve L2;

[0022] (2-3) Extract the last part of curve L1 point, as the last point of curve L2 points, thus obtaining a smooth curve L2.

[0023] Furthermore, step (3) specifically includes:

[0024] (3-1) For the curve L1, each two adjacent points form a line segment For the smooth curve L2, each two adjacent points form a line segment

[0025] (3-2) For any line segment and the corresponding line segment Calculate whether it satisfies the following formula. If so, it means that the line segment and line segments If they intersect, execute step (3-3); otherwise, execute step (3-4);

[0026] (p i，y -sp i，y )×(sp i+1，y -p i+1，y )<0,i∈[1,n-1]

[0027] In the formula, p i，y 、p i+1，y Represents the i-th point sp of curve L1 i , the i+1th point sp i+1 The y-axis coordinate, sp i，y 、sp i+1，y represents the i-th point sp of the smooth curve L2 i , the i+1th point sp i+1 y-axis coordinate, n represents the number of points of curve L1 and smooth curve L2;

[0028] (3-3) Calculate line segments The intersections between them are stored in the intersection set Intersections;

[0029] (3-4) Return to step (3-2) until all line segments are processed and the intersection set Intersections containing all intersection points is obtained.

[0030] Furthermore, step (5) specifically includes:

[0031] (5-1) Read a segment from the segment set Sections and record its starting point and end point as p s (x s ,y s ), p e (x e ,y e ), the point in the middle of the segment is denoted as p m (x m ,y m );

[0032] (5-2) Connect point p s (x s ,y s ) and point p e (x e ,y e ) to obtain the equation of the line L:

[0033] L:y=kx+b

[0034]

[0035] (5-3) According to point p m (x m ,y m ) is located above or below the linear equation L to determine whether the current segment is a convex curve or a concave curve. The specific judgment method is: if kx m -y m +b<0, then point p m (x m ,y m ) is above the straight line equation L, the current segment is an upward convex curve, and step (6) is executed; otherwise, point p m (x m ,y m ) is below the straight line equation L, the current segment is a concave curve, and step (7) is executed.

[0036] The device for extracting river fracture points of the present invention comprises a processor and a computer program stored in a memory and executable on the processor, and the method is implemented when the processor executes the program.

[0037] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages: (1) the algorithm is simple and the execution efficiency is high; (2) in view of the significant feature of the crack point that it is "at the sharp turning point between the gentle slope section and the steep slope section", based on the cross processing of the river profile line and its smooth curve, the convex river segment can be quickly identified, and then the river crack point can be efficiently and accurately identified, avoiding the influence of data noise to a certain extent, with a low probability of misjudgment and high accuracy; (3) the crack point is extracted from large to small according to the chord height feature of the convex curve, ensuring that the algorithm has a low probability of missed judgment. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 The river experimental data and the DEM of the region used in the present invention;

[0039] Figure 2 is a longitudinal section of the river R17 in the first embodiment;

[0040] Figure 3 It is a schematic diagram of the flow of the automatic identification method of river breakpoints provided by the present invention;

[0041] Figure 4 The original river and its smooth curve in Example 1 ((a) is the full picture, (b) is the partial enlarged picture);

[0042] Figure 5 The intersection points and the convex curve segments calculated in Example 1 ((a) is the full picture, (b) is the partial enlarged picture);

[0043] Figure 6 is the crack point extracted in Example 1;

[0044] Figure 7 is the crack point extracted from river R3 in Example 2;

[0045] Figure 8 It is the crack point extracted from river R9 in Example 3. DETAILED DESCRIPTION

[0046] Embodiment 1

[0047] In this example, the R17 river in Lushan Mountain was selected as the experimental data. Figure 1 The longitudinal section of the river is shown in Figure 2 The following further describes a specific embodiment in conjunction with the accompanying drawings.

[0048] This embodiment provides a method for identifying river breakpoints. Figure 3 As shown, the following steps are included:

[0049] (1) Read the profile data of the river where the fracture point is to be extracted to form a curve L1.

[0050] In this step, the profile data of the river to be fractured is read, and each point in the profile data is used as a point of the curve L1 to form a curve L1 = {p i |i=1,...,n}, n is the number of points in the river profile data, p i is the i-th point in the curve L1 and its coordinates. In this embodiment, n is 735.

[0051] (2) According to the preset smoothing window parameter k, the curve L1 is smoothed to obtain the smoothed curve L2, as shown in Figure 4 shown.

[0052] This step specifically includes:

[0053] (2-1) According to the preset smoothing window parameter k (k=15 in this embodiment), extract the first point p1 to the first point p2 in the curve L1. Points As the first point sp1 to the second point sp2 of the smooth curve L2 Points

[0054] (2-2) For the first Points To Points After smoothing according to the following formula, the smoothed curve L2 is Points To Points points;

[0055]

[0056] In the formula, (sp i，x , sp i，y ) represents the i-th point p in the curve L1 i The coordinates of the smoothed point, i.e. the i-th point sp of the smoothed curve L2 i The coordinates of (p i，x , p i，y ) represents the i-th point p in the curve L1 i The coordinates of , n represents the number of points of the curve L1 and the smooth curve L2;

[0057] (2-3) Extract the last part of curve L1 point, as the last point of curve L2 points, thus obtaining a smooth curve L2.

[0058] (3) Calculate the intersection of curve L1 and smooth curve L2 and store them in the intersection set Intersections.

[0059] This step specifically includes:

[0060] (3-1) For the curve L1, each two adjacent points form a line segment For the smooth curve L2, each two adjacent points form a line segment

[0061] (3-2) For any line segment and the corresponding line segment Calculate whether it satisfies the following formula. If so, it means that the line segment and line segments If they intersect, execute step (3-3); otherwise, execute step (3-4);

[0062] (p i，y - sp i，y )×(sp i+1，y - p i+1，y )<0,i∈[1,n-1]

[0063] In the formula, p i，y 、p i+1，y Represents the i-th point sp of curve L1 i , the i+1th point sp i+1 The y-axis coordinate, sp i，y 、sp i+1，y represents the i-th point sp of the smooth curve L2 i , the i+1th point sp i+1 y-axis coordinate, n represents the number of points of curve L1 and smooth curve L2;

[0064] (3-3) Calculate line segments The intersections between them are stored in the intersection set Intersections;

[0065] (3-4) Return to step (3-2) until all line segments are processed, and obtain the intersection point set Intersections = {ip j |j=1,...,m}, m is the number of intersection points. In this embodiment, m is 88.

[0066] (4) Using the intersection points in the intersection set Intersections as segmentation points, the L1 curve is segmented and stored in the segment set Sections.

[0067] (5) Read a segment from the segment set Sections and determine whether the segment is an upward convex curve. If so, execute step (6); otherwise, execute step (7). In this embodiment, there are 41 upward convex curve segments finally extracted, such as Figure 5 shown.

[0068] This step specifically includes:

[0069] (5-1) Read a segment from the segment set Sections and record its starting point and end point as p s (x s ,y s ), p e (x e ,y e ), the point in the middle of the segment is denoted as p m (x m ,y m );

[0070] (5-2) Connect point p s (x s ,y s ) and point p e (x e ,y e ) to obtain the equation of the line L:

[0071] L:y=kx+b

[0072]

[0073] (5-3) According to point P m (x m ,y m ) is located above or below the linear equation L to determine whether the current segment is a convex curve or a concave curve. The specific judgment method is: if kx m -y m +b<0, then point p m (x m ,y m ) is above the straight line equation L, the current segment is an upward convex curve, and step (6) is executed; otherwise, point p m (x m ,y m ) is below the straight line equation L, the current segment is a concave curve, and step (7) is executed.

[0074] (6) Extract the point in the segment that is farthest from the starting point in a straight line and store it as a candidate crack point in the candidate crack point set TKickPoint = {(p i , d i )|i=1,…,u}; among them, p i is the i-th candidate split point, di The crack point p i The distance to the straight line determined by the end point of the curve segment, u is the number of candidate break points. In this embodiment, the number of candidate break points km obtained is 41.

[0075] (7) Return to step (5) until all segments in Sections are processed.

[0076] (8) All candidate crack points in the set TKickPoint are reordered according to the distance from large to small to obtain the sequential candidate crack point set STKickPoint.

[0077] (9) According to the preset number of crack points or the preset distance threshold, a subset of KickPoints that meet the requirements is extracted from the set STKickPoint, which is the crack point extraction result required by the user. In this embodiment, when the distance threshold is 6, the final extracted river crack point result is as follows: Figure 6 shown.

[0078] This embodiment also provides a device for extracting river breakpoints, including a processor and a computer program stored in a memory and executable on the processor, wherein the processor implements the above method when executing the program.

[0079] Embodiment 2

[0080] The difference between this embodiment and the first embodiment is that the number of smoothing points is set to 15, the distance threshold is set to 8, and the river breakpoints finally extracted from the R16 river are as follows: Figure 7 The three extracted crack points are all located at the characteristic position where the river profile changes from gentle to steep, which is consistent with the expert judgment result.

[0081] Embodiment 3

[0082] The difference between this embodiment and the first embodiment is that the number of smoothing points is set to 15, the distance threshold is set to 5, and the river crack point result finally extracted by R12 is as follows: Figure 8 The eight crack points extracted are all located at the characteristic position where the river profile changes from gentle to steep, which is consistent with the expert judgment result.

[0083] The above disclosures are only several preferred embodiments of the present invention, which cannot be used to limit the scope of the present invention. Therefore, equivalent changes made according to the claims of the present invention are still within the scope of the present invention.

Claims

1. A method for extracting river fracture points, characterized in that The method includes: (1) Reading the profile data of the river where the fracture point is to be extracted to form a curve L1; (2) Smoothing the curve L1 according to a preset smoothing window parameter k to obtain a smoothed curve L2; (3) Calculate the intersection of curve L1 and smooth curve L2 and store them in the intersection set Intersections; (4) Using the intersection points in the intersection set Intersections as segmentation points, the L1 curve is segmented and stored in the segment set Sections; (5) Read a segment from the segment set Sections and determine whether the segment is an upward convex curve. If so, execute step (6); otherwise, execute step (7); (6) Extract the point in the segment that is farthest from the starting point in a straight line and store it as a candidate crack point in the candidate crack point set TKickPoint; (7) Return to step (5) until all segments in Sections are processed, and obtain the candidate crack point set TKickPoint = {(p i , d i )|i=1,…,u}; among them, p i is the i-th candidate split point, d i The crack point p i The distance to the straight line determined by the endpoint of the curve segment, u is the number of candidate crack points; (8) re-sorting all candidate crack points in the set TKickPoint according to the distance from large to small to obtain a sequential candidate crack point set STKickPoint; (9) According to the preset number of crack points or the preset distance threshold, a subset of KickPoints that meet the requirements is extracted from the set STKickPoint, which is the crack point extraction result required by the user; Step (2) specifically includes: (2-1) According to the preset smoothing window parameter k, extract the first point p1 to the first point p2 in the curve L1. Points As the first point sp1 to the second point sp2 of the smooth curve L2 Points (2-2) For the first Points To Points After smoothing according to the following formula, the smoothed curve L2 is Points To Points points; In the formula, (sp i,x , sp i,y ) represents the i-th point p in the curve L1 i The coordinates of the smoothed point, i.e. the i-th point sp of the smoothed curve L2 i The coordinates of (p i，x , p i,y ) represents the i-th point p in the curve L1 i The coordinates of , n represents the number of points of the curve L1 and the smooth curve L2; (2-3) Extract the last part of curve L1 point, as the last point of curve L2 points, thus obtaining a smooth curve L2.

2. The method for extracting river fracture points according to claim 1, characterized in that: Step (1) specifically includes: Read the profile data of the river where the crack point is to be extracted, and take each point in the profile data as a point of the curve L1 to form a curve L1 = {p i |i=1,...,n}, n is the number of points in the river profile data, p i is the i-th point in curve L1 and its coordinates.

3. The method for extracting river fracture points according to claim 1, characterized in that: Step (3) specifically includes: (3-1) For the curve L1, every two adjacent points form a line segment For the smooth curve L2, each two adjacent points form a line segment (3-2) For any line segment and the corresponding line segment Calculate whether it satisfies the following formula. If so, it means that the line segment and line segments If they intersect, execute step (3-3); otherwise, execute step (3-4); (p i，y -sp i，y )×(sp i+1,y -p i+1,y )<0,i∈[1,n-1] In the formula, p i,y 、p i+1，y Represents the i-th point sp of curve L1 i , the i+1th point sp i+1 The y-axis coordinate, sp i,y 、sp i+1,y represents the i-th point sp of the smooth curve L2 i , the i+1th point sp i+1 y-axis coordinate, n represents the number of points of curve L1 and smooth curve L2; (3-3) Calculate line segments The intersections between them are stored in the intersection set Intersections; (3-4) Return to step (3-2) until all line segments are processed and the intersection set Intersections containing all intersection points is obtained.

4. The method for extracting river fracture points according to claim 1, characterized in that: Step (5) specifically includes: (5-1) Read a segment from the segment set Sections and record its starting point and end point as p s (x s ,y s ), p e (x e ,y e ), the point in the middle of the segment is denoted as p m (x m ,y m ); (5-2) Connect point p s (x s ,y s ) and point p e (x e ,y e ) to obtain the equation of the line L: L:y=kx+b (5-3) According to point p m (X m ,y m ) is located above or below the linear equation L to determine whether the current segment is a convex curve or a concave curve. The specific judgment method is: if kx m -y m +b<0, then point p m (x m ,y m ) is above the straight line equation L, the current segment is an upward convex curve, and step (6) is executed; otherwise, point p m (X m ,y m ) is below the straight line equation L, the current segment is a concave curve, and step (7) is executed.

5. A device for extracting river fracture points, comprising a processor and a computer program stored in a memory and operable on the processor, characterized in that: When the processor executes the program, the method according to any one of claims 1 to 4 is implemented.

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