A method for automatically generating river cross sections and feature extraction

Abstract

The application discloses a kind of automatically generated river section and feature extraction method, comprising: by specified numerical value, along the river center line / longitudinal axis line generation point, and point is set to number along river direction, and adjacent line recursive generation center line is given to these line number;According to the order of numbering, traverse point, and make perpendicular to its adjacent line;Generation perpendicular segment and the intersection of adjacent line, and these intersection points are given the numbering value consistent with point;With intersection point along the direction of existing perpendicular segment, continue to make perpendicular to its adjacent line;Respectively, the intersection of perpendicular segment and adjacent line is solved, and these intersection points are given the numbering consistent with the starting point of perpendicular segment;Until perpendicular segment reaches river boundary;According to center line number and the intersection point number of generated perpendicular segment, line segment is generated, and automatic section establishment is completed;Information extraction point is generated by the generated section line;Extract section two / three-dimensional grid data information.The application realizes the automatic section generation and attribute extraction of river with relatively severe width and curvature variation.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of spatial analysis, more particularly to a method for automatically generating river cross section and feature extraction. BACKGROUND

[0002] Obtaining accurate longitudinal and transverse sections is the basic data guarantee for section design. At present, with the development of laser point cloud, multi / hyperspectral aerial survey, hydrodynamic simulation and other technologies, more and more data presentation forms are in the form of dense points or grid data. How to simply present the change characteristics of these data along the river direction, dense section extraction is a selectable way. Generally, the sections are drawn manually. Although many studies have developed related automatic section programs based on AutoCAD, they are generally used for roads. Unlike roads, the width of the river changes, the change of the side line is relatively severe, and it is almost consistent with the change of the left and right sides of the road. The change of the left and right banks of the river is very different. The method based on the single center line vertical line of the road is seriously distorted when processing the river section, and the dense sections may intersect. Therefore, under this background, the present application provides a method suitable for automatic extraction of river longitudinal and transverse sections, and establishes a method for extracting the properties of the automatically generated dense sections. SUMMARY

[0003] The technical problem to be solved by the present application is that the existing automatic section generation method is seriously distorted when extracting the river section, and self-intersection may occur when the local change is severe. A method for automatically generating river section and feature extraction is provided.

[0004] The above object of the present application is achieved by the following technical scheme: a method for automatically generating river section and feature extraction, comprising the following steps:

[0005] S1, obtaining the side line through the planar river;

[0006] S2, if there is no thalweg data, generating the river center line through the side line or the planar river;

[0007] S3, generating points along the river center line / thalweg through the specified interval length sequence, single numerical value or proportion value, and setting numbers for the points along the river direction;

[0008] S4, recursively generating the center line with adjacent lines and assigning numbers to these lines;

[0009] S5, traversing the points in step S3 in the order of the numbers, and making perpendicular lines to the adjacent lines of the points;

[0010] S6, respectively finding the intersection points of the generated perpendicular line segments and the adjacent lines in step S5, and assigning the same number values to these points as the points in step S3;

[0011] S7, with the intersection point generated in step S6, continue to draw a perpendicular line to the adjacent line in the direction of the perpendicular line segment in step S5;

[0012] S8, respectively, find the intersection point of the perpendicular line segment and the adjacent line in step S7, and assign the same number to these points as the starting point of the perpendicular line segment;

[0013] S9, repeat steps S7 and S8 until the perpendicular line segment reaches the river boundary;

[0014] S10, generate a line segment according to the center line number and the intersection point number of the perpendicular line segment, if the line segment intersects, return to step S4, encrypt the center line between the river boundaries, and repeat the above steps, otherwise, complete the automatic establishment of the section;

[0015] S11, generate information extraction points at a specified distance, a specified ratio or a fixed value through the generated section line;

[0016] S12, through the generated information extraction points, the two / three-dimensional grid data information of the section can be extracted, and the results can be calculated by any weighting or other method and assigned to the point attribute on the river center line or the thalweg, to extract the information along the river direction.

[0017] Further, in step S3, either the thalweg or the center line can be selected, the center line is a substitute for the thalweg without data, when generating the section by specifying the interval length sequence, the number of generated sections is equal to the sequence length, and when a single value is specified, the default is to generate the section at equal distances.

[0018] Further, in step S4, in the process of recursively generating the center line, the line number is assigned to ensure that the order of the lines from the left bank to the right bank of the river can be finally determined.

[0019] Further, in step S11, through vector calculation, extraction points can be generated on the section line segment at any distance combination, which can be inconsistent with the points constituting the section.

[0020] Compared with the prior art, the method has the following advantages: the method is used for automatic extraction of sections of complex entities with river channel boundaries, and the surface data obtained by models or remote sensing means and the variation characteristics of the data along the direction thereof are obtained through the sections. The method of the present application considers the complexity of the river channel boundary, which is composed of complex multiple line segments, and the trend of the left and right bank lines is inconsistent, can adapt to the rapidly changing direction of the river channel, generate sections consistent with the width of the river channel, and avoid the self-intersection phenomenon caused by directly using the center line method, and realize the automatic section generation and attribute extraction of the river with relatively sharp width and curvature variation. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 Flow chart of the automatic generation of river section and feature extraction method of the present application;

[0022] Figure 2 The present application shows an example of complete calculation of river section, i.e. part of the Jinsha River;

[0023] Figure 3 The present application shows an example of automatic calculation of section;

[0024] Figure 4 The present application shows a two-dimensional test flow rate diagram to be extracted, and the color represents the flow rate;

[0025] Figure 5 The present application shows a longitudinal extraction result diagram of the river section. DETAILED DESCRIPTION

[0026] In order to facilitate those skilled in the art to understand and implement the present application, the present application will be further described in detail below in combination with examples, and it should be understood that the examples described herein are only used to illustrate and explain the present application, and are not used to limit the present application.

[0027] The automatic generation of river section and feature extraction method provided by the present embodiment, as shown in Figure 1 , includes the following steps:

[0028] S1, read the river data river, extract the left and right bank lines through programming or ArcGIS, respectively recorded as leftB and rightB.

[0029] Specifically, in the present embodiment, the river data river is part of the Jinsha River surface data, as shown in Figure 2 .

[0030] S2, obtain the center line of the river by the existing automatic extraction center line method (reference CN202110232297.4, an improved TIN-based vector data center line extraction method) or arcgis software, recorded as center1.

[0031] Specifically, when implementing step S2, those skilled in the art know that this step is implemented without the deep trunk line data, if there is deep trunk line data, this step can be skipped, and the corresponding deep trunk line is recorded as center1.

[0032] S3, specify the interval length sequence, single numerical value or proportional value, and there is no essential difference, taking a single interval distance value D as an example, along center1, generate a point set center1_p according to the specified distance interval, and set the number of center1_p in turn according to the direction of center1. Specifically:

[0033] S31, reading the center1 data by programming; wherein the programming includes but is not limited to C#, python, C++, etc.

[0034] S32, setting the initial total_length value as 0, traversing the line segment in center1, the length is recorded as L, if total_length+L<D, then total_length=total_length+L, if total_length+L>=D, then total_length=total_length-D, and the generated point is located on the line segment;

[0035] S33, setting the starting point of the line segment as p1(x1, y1) and the ending point as p2(x2, y2), then the generated point calculation method is:

[0036]

[0037] S34, recording the point coordinates, generating the point, increasing the number attribute, recording from 0 in turn, and increasing the identification attribute of the line, recording as "center1".

[0038] S4, generating the center line lc1 with the line leftB and center1, generating the center line rc1 with the line rightB and center1, generating the center line lc11 with the line center1 and lc1, generating the center line lc12 with the line lc1 and leftB, generating the center line rc11 with the line center1 and rc1, and generating the center line rc12 with the line rc1 and rightB. From left to right, there are 9 lines, as shown in Figure 3 , which are leftB, lc12, lc1, lc11, center1, rc11, rc1, rc12, and rightB respectively.

[0039] S5, traversing the point p in the center1_p point set, and making a perpendicular line to the adjacent line. Specifically:

[0040] S51, reading the p point coordinates (x, y), and the adjacent lines are lc11 and rc11.

[0041] S52, here you can choose to make a perpendicular line from p to center1 or make a perpendicular line from p to lc11 and rc11. Taking the perpendicular line from p to lc11 and lc12 as an example for demonstration.

[0042] Draw a perpendicular line from point p to lc11. Traverse the line segments in lc11. If the perpendicular line intersects a line segment and the distance between the point and all line segments in lc11 is the shortest, take the intersection point and denot it as plc11. If the perpendicular line intersects any line segment but the intersection point is not on the line segment, or the shortest perpendicular distance is greater than the shortest distance from point p to lc11, then take the endpoint of p that is closest to lc11 and denot it as plc11. The method for drawing a perpendicular line from point p to lc12 is the same, and the intersection point is denoted as prc11. This will not be repeated.

[0043] S6. Calculate and obtain the coordinates of plc11 and prc11, and assign them the same number as point p.

[0044] S61, let the coordinates of point p be (x, y). If plc11 is an endpoint of lc11, its coordinates can be directly obtained. If plc11 is the intersection of the perpendicular line from point p to lc11 and lc11, let plc11 lie on line segment K of lc11, with endpoints P1(x1, y1) and Pp2(x2, y2). Express the perpendicular line segment and K as a straight line in the form AX + BY = C, with coefficients denoted as (A1, B1, C1) and (A2, B2, C2), respectively. Then:

[0045]

[0046] B1 = 1

[0047]

[0048]

[0049] B2 = 1

[0050]

[0051] S62. Using (A1,B1,C1) and (A2,B2,C2), calculate the coordinates of plc11 as (plx11,ply11) using the following formula:

[0052]

[0053]

[0054] S63. Using the same method, the coordinates (prx11, pry11) of prc11 can be calculated.

[0055] S64. Assign points plc11 and prc11 the same number as point p, and record that they belong to lc11 and rc11 respectively.

[0056] S7, the vertical line is drawn from plcl to lc1, and the vertical line is drawn from prcl to rc1, the calculation method is similar to step S5, and no longer be repeated;

[0057] S8, the intersection points of the vertical line segment with lc1 and rc1 are calculated respectively, and the points are assigned the same number as the starting point of the vertical line segment, and it is recorded that they belong to lc1 and rc1 respectively;

[0058] S9, steps S7 and S8 are repeated until the vertical line segment reaches the river boundary leftB and rightB respectively;

[0059] S10, the points with the same number are connected in the order of the line segments leftB, lc12, lc1, lc11, center1, rc11, rc1, rc12, and rightB, respectively, to generate the cross section line, if there is intersection between the generated cross section lines, return to step S4, encrypt the center line between the river boundaries, and repeat the above steps, otherwise, the cross section is automatically established;

[0060] S11, the information extraction points are generated by the generated cross section line with a specified distance sequence, a specified ratio or a fixed value, or directly using the cross section line endpoints, in the case, the cross section line endpoints are directly used, other ways to generate information extraction points, the method is the same as step S3, and will not be repeated;

[0061] S12, through the generated information extraction points, combined with the coordinate information of the extraction points, the data information at the corresponding coordinates of the cross section two / three-dimensional grid or within a certain range can be extracted, and any weighting or other methods (other methods include but are not limited to bilinear interpolation, specified range average, kernel function calculation, etc.) can be used to calculate the results, and the results are assigned to the point attributes on the river center line or the thalweg, the information along the river direction is extracted, in the case, the two-dimensional flow velocity information calculated by the mike model is extracted, as shown in Figure 4 、 Figure 5 .

[0062] It should be pointed out that the specific embodiments described in the present application are only examples of the spirit of the present application. Those skilled in the art of the present application can make various modifications or supplements to the described specific embodiments or use similar ways to replace them, but will not deviate from the spirit of the present application or exceed the scope defined by the appended claims.

Claims

1. A method for automatically generating river cross-sections and feature extraction, characterized in that, The method comprises the following steps: S1, obtaining the edge line through the planar river; S2, if there is no thalweg data, generating the river center line through the edge line or the planar river; S3, generating points along the river center line / thalweg through a specified interval length sequence, a single numerical value or a proportional value, and setting numbers for the points in the river direction; S4, recursively generating the center line through adjacent lines and assigning numbers to the lines; S5, traversing the points in step S3 in the order of the numbers and making perpendicular lines to the adjacent lines; S6, respectively finding the intersection points of the generated perpendicular line segments and the adjacent lines in step S5, and assigning the same number values to the points as the points in step S3; S7, continuing to make perpendicular lines to the adjacent lines in the direction of the perpendicular line segments in step S5 through the intersection points generated in step S6; S8, respectively finding the intersection points of the generated perpendicular line segments and the adjacent lines in step S7, and assigning the same numbers to the points as the starting points of the perpendicular line segments; S9, repeating steps S7 and S8 until the perpendicular line segments reach the left and right edge lines of the river, respectively; S10, generating line segments according to the center line numbers and the intersection point numbers of the generated perpendicular line segments, returning to step S4 to encrypt the center line between the river edge lines and repeating the above steps if the line segments intersect, or completing the automatic establishment of the cross section otherwise; S11, generating information extraction points through the generated cross section lines at a specified distance, a specified proportion or a fixed numerical value; S12, extracting cross section two / three-dimensional grid data information through the generated information extraction points, taking any weighted calculation result and assigning it to the point attribute on the river center line or the thalweg to extract information in the river direction.

2. The method for automatically generating river cross-sections and feature extraction according to claim 1, wherein, In step S3, either the thalweg or the center line can be selected, and the center line is a substitute for the thalweg data. When generating cross sections through a specified interval length sequence, the number of generated cross sections is equal to the sequence length, and when a single numerical value is specified, the default is to generate cross sections at equal distances.

3. The method for automatically generating river cross-sections and feature extraction according to claim 1, wherein, In step S4, in the process of recursively generating the center line, the line numbers are assigned to ensure that the order of the lines from the left bank to the right bank of the river can be finally determined.

4. The method for automatically generating river cross-sections and feature extraction according to claim 1, wherein, In step S11, extraction points are generated on the cross section line segments at any distance combination through vector calculation, which can be inconsistent with the points constituting the cross section.

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