Contour line interpolation algorithm with fusion of vector interpolation and TIN reconstruction

Abstract

The invention discloses a contour line interpolation algorithm fusing vector interpolation and TIN reconstruction. The contour line interpolation algorithm comprises the following steps: S1, contour line vector interpolation; s2, performing contour vector rarefaction; s3, reconstructing a contour line; and S4, performing interpolation thinning contour line correction. According to the algorithm provided by the invention, a fusion strategy of a vector interpolation method and a TIN reconstruction method is adopted, the advantages are made up of the disadvantages, a vector interpolation contour line is taken as a substrate, the defects of the contour line are corrected by means of a TIN reconstruction contour line, an ideal contour line interpolation result is comprehensively obtained, and the improvement of the existing method is realized.

Description

Technical Field

[0001] The present invention relates to terrain construction and conversion technology and three-dimensional analysis technology in geographic information space analysis technology, and in particular to a contour line interpolation algorithm. Background Art

[0002] Contours are a type of isovalue lines, which are closed curves formed by connecting ground points with equal elevations. They are the main form of expression and expression tool of landforms, and one of the most basic and core geographic information elements. Contour interpolation is an important topic in contour data processing, and has outstanding application value in the fields of aerial survey production of geographic information elements, topographic map reduction, and public version map processing and compilation.

[0003] The interpolation methods of contour lines can be generally divided into three categories: vector interpolation, digital elevation model (DEM) reconstruction, and irregular triangulated network (TIN) reconstruction. The basic principle of vector interpolation is to establish auxiliary line segments similar to strip triangulated networks between adjacent original contour lines, linearly interpolate the passing points of the desired contour lines on each auxiliary line segment in turn, and connect each passing point in sequence to obtain the interpolated contour lines. The overall ideas of DEM reconstruction and TIN reconstruction are relatively similar. Both interpolate the passing points of the desired contour lines based on the elevation space of regular grid points or irregular triangle vertices, and connect each passing point in sequence to obtain the interpolated contour lines. The three methods have their own advantages and disadvantages.

[0004] Among the three types of contour interpolation methods, the advantage of vector interpolation is that the contour lines are smooth, but the disadvantage is that the contour lines of special landforms are distorted, which is specifically manifested as abnormal contour rings in saddle and beam areas. The advantages of DEM reconstruction and TIN reconstruction are both in the expression of landform details, and TIN reconstruction is better at reflecting landform structural characteristics. However, the contour lines generated by both methods are fragmented, which is specifically manifested as jitter, sawtooth and independent rings. Summary of the invention

[0005] The object of the present invention is to provide a contour interpolation algorithm that integrates vector interpolation and TIN reconstruction, which can make up for the defects and shortcomings of the above-mentioned vector interpolation and TIN reconstruction interpolation methods.

[0006] To achieve the above purpose, a contour interpolation algorithm combining vector interpolation and TIN reconstruction is provided, which includes the following steps: S1, Contour vector interpolation: including Construct a terrain surface based on the original contour lines combined with the range lines of the target area; extract the center line of the terrain surface; extract the hanging points of the center line of the terrain surface; eliminate the center line of the terrain surface that intersects with the hanging points; determine the terrain type of the terrain surface based on the elevation relationship between the edge line of the terrain surface and the adjacent terrain surface; assign elevation values ​​to the center line of the terrain surface according to the terrain type of the terrain surface, and generate vector interpolation contour lines; S2, Contour vector thinning: including Based on the vector interpolation contour lines, the contour lines whose elevations are multiples of the contour intervals of the proposed thinned contour lines are selected to generate interpolated thinned contour lines; the first curve and the counting curve are redefined according to the contour intervals of the interpolated thinned contour lines; S3, Contour reconstruction: including Construct TIN based on original contour lines; generate reconstructed contour lines based on TIN at the same contour interval as the interpolated thinned contour lines; S4, interpolation and thinning contour correction: including The interpolated thinned contour lines and the reconstructed contour lines are spatially superimposed; the lines in the interpolated thinned contour lines that do not intersect with the reconstructed contour lines are screened out.

[0007] According to the contour interpolation algorithm combining vector interpolation with TIN reconstruction, the target area is a topographic map area or a management area, and the range line is a topographic map outline or a management area boundary.

[0008] According to the contour interpolation algorithm combining vector interpolation with TIN reconstruction, in S1, the step of constructing a terrain surface based on the original contour lines and range lines includes: The original contour lines are intersected and interrupted with the range lines to enclose a surface area with elevation information, which includes the following terrain surfaces: a slope surface formed by two contour lines of different elevations, a positive saddle plane formed by two contour lines of the same elevation, a negative beam plane formed by two contour lines of the same elevation, a hilltop circular plane formed by a single contour line, and a valley circular plane formed by a single contour line.

[0009] According to the contour interpolation algorithm combining vector interpolation and TIN reconstruction, in S1, the centerline of the terrain surface is extracted using the central axis algorithm; Among the extracted center lines, the center line of the slope surface appears as a long strip line, and the center lines of the hilltop circular plane and the valley circular plane appear as short serrated lines.

[0010] According to the contour interpolation algorithm combining vector interpolation and TIN reconstruction, in S1, the extracted terrain surface centerline suspension points are the terrain surface centerline endpoints with a mutual overlap of 0; The center lines of the terrain surfaces that intersect with the hanging points and are eliminated are the center lines of the jagged hill circular plane and the valley circular plane.

[0011] According to the contour interpolation algorithm that integrates vector interpolation and TIN reconstruction, in S1, in the step of determining the terrain type of the terrain surface according to the elevation relationship between the terrain surface edge line and the adjacent terrain surface: if the elevations of the two terrain surface edge lines are different, the terrain type of the terrain surface is a slope surface; if the elevations of the two terrain surface edge lines are the same, the terrain type of the terrain surface is a positive terrain saddle plane or a negative terrain beam plane, and the distinction is made according to the elevation relationship between the peripheral adjacent terrain surfaces.

[0012] According to the contour interpolation algorithm integrating vector interpolation and TIN reconstruction, in S1, in the step of assigning elevation values ​​to the center line of the terrain surface according to the terrain type of the terrain surface: the elevation of the center line of the slope surface = the sum of the elevations of two adjacent contour lines / 2, the elevation of the center line of the plane of the positive topographic saddle = the elevation of any adjacent contour line - the original contour interval / 2, and the elevation of the center line of the plane of the negative topographic beam = the elevation of any adjacent contour line + the original contour interval / 2; the center line assigned with the elevation value constitutes the vector interpolation contour line.

[0013] According to the contour interpolation algorithm combining vector interpolation and TIN reconstruction, in S3, the step of constructing TIN based on the original contour includes: An unconstrained triangulated network is constructed based on the Delaunay law using discrete sampling points and elevation points of the original contour lines. Contour lines and terrain feature lines are embedded as constraints. The affected triangles are adjusted to generate a constrained triangulated network.

[0014] According to the contour interpolation algorithm combining vector interpolation and TIN reconstruction, in S3, the step of generating reconstructed contour lines based on TIN according to the same contour interval as the interpolated thinned contour lines includes: The passing points of the contour lines are reconstructed based on the spatial interpolation of the irregular triangle vertex elevations, and the reconstructed contour lines are obtained by sequentially connecting the passing points.

[0015] Beneficial effect: The algorithm proposed in the present invention adopts a fusion strategy of vector interpolation method and TIN reconstruction method, taking the advantages of both methods and making up for their shortcomings, taking vector interpolation contour lines as the basis, and correcting their defects with the help of TIN reconstruction contour lines, comprehensively achieving ideal contour interpolation results and realizing improvement over existing methods.

[0016] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The present invention is further described below in conjunction with the accompanying drawings and embodiments: Figure 1 is a flow chart of the method of the present invention; Figure 2 is the original contour diagram; Figure 3It is a schematic diagram of the superposition of the original contour lines and the vector interpolated thinned contour lines; Figure 4 It is a schematic diagram of the superposition of the original contour lines and the TIN reconstructed contour lines; Figure 5 It is a schematic diagram of superposition of vector interpolation thinning contour lines and TIN reconstruction contour lines; Figure 6 It is a schematic diagram of the superposition of vector interpolation thinning contour lines and final contour lines; Figure 7 This is a schematic diagram of the superposition of the original contour lines and the final contour lines.

[0018] Figure 2-7 In the figure, the thin grey lines represent the original contours, the thin black lines represent the vector interpolation thinned contours, the dashed black lines (dotted lines) represent the TIN reconstructed contours, and the thick black lines represent the final contours. DETAILED DESCRIPTION

[0019] This section will describe in detail the specific embodiments of the present invention. The preferred embodiments of the present invention are shown in the accompanying drawings. The purpose of the accompanying drawings is to supplement the description of the text part of the specification with graphics, so that people can intuitively and vividly understand each technical feature and the overall technical solution of the present invention, but it cannot be understood as a limitation on the scope of protection of the present invention.

[0020] In the description of the present invention, words such as greater than, less than, and exceeding are understood to exclude the number itself, and words such as above, below, and within are understood to include the number itself. If there is a description of first or second, it is only used for the purpose of distinguishing technical features, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features or implicitly indicating the order of the indicated technical features.

[0021] In the description of the present invention, unless otherwise clearly defined, terms such as setting, installing, connecting, etc. should be understood in a broad sense, and technicians in the relevant technical field can reasonably determine the specific meanings of the above terms in the present invention based on the specific content of the technical solution.

[0022] Reference Figure 1-7 , a contour interpolation algorithm combining vector interpolation and TIN reconstruction, comprising the following steps: S1, Contour vector interpolation: including Construct a terrain surface based on the original contour lines combined with the range lines of the target area; extract the center line of the terrain surface; extract the hanging points of the center line of the terrain surface; eliminate the center line of the terrain surface that intersects with the hanging points; determine the terrain type of the terrain surface based on the elevation relationship between the edge line of the terrain surface and the adjacent terrain surface; assign elevation values ​​to the center line of the terrain surface according to the terrain type of the terrain surface, and generate vector interpolation contour lines; S2, Contour vector thinning: including Based on the vector interpolation contour lines, all contour lines whose elevations are multiples of the contour intervals of the proposed thinned contour lines are screened out to generate interpolated thinned contour lines; the first curve and the counting curve are redefined according to the contour intervals of the interpolated thinned contour lines; S3, Contour reconstruction: including Construct TIN based on original contour lines; generate reconstructed contour lines based on TIN at the same contour interval as the interpolated thinned contour lines; S4, interpolation and thinning contour correction: including The interpolated thinned contour lines and the reconstructed contour lines are spatially superimposed; the short lines in the interpolated thinned contour lines that do not intersect with the reconstructed contour lines (i.e., cause abnormal rings) are screened out.

[0023] Based on the above steps, the final contour lines can be generated. The processing and generation of the final contour lines adopts a fusion strategy, taking the advantages of each other and making up for each other's weaknesses. The vector interpolation contour lines are used as the basis, and the defects of the contour lines are corrected with the help of TIN reconstructed contour lines. The ideal contour interpolation results are obtained comprehensively, which realizes a significant improvement over the existing methods.

[0024] Specifically, in S1, the target area may be a standard topographic map area or a management area (eg, a management area defined by administrative divisions, etc.), based on which, the range line may be a contour line of a standard topographic map or a boundary line of a management area.

[0025] In S1, the steps of constructing a terrain surface based on the original contour lines and the range lines specifically include the following contents: the original contour lines are intersected and interrupted with the range lines to enclose a surface domain with elevation information, and the surface domain is a closed surface or plane, which usually includes the following terrain surfaces: a slope surface formed by two contour lines of different elevations, a positive saddle plane formed by two contour lines of the same elevation, a negative beam plane formed by two contour lines of the same elevation, a mountain ring plane formed by a single contour line, and a valley ring plane formed by a single contour line. According to the above classification principles of terrain surfaces, the standard topographic map sheets or management areas are divided and constructed into several different types of terrain surfaces.

[0026] In S1, the central axis algorithm is used to extract the center line of the terrain surface. Among the extracted center lines, the center line of the slope surface appears as a long strip line, the center line of the positive topographic saddle plane and the negative topographic beam plane may have contour anomaly rings, and the center line of the hilltop ring plane and the valley ring plane appears as a short toothed line.

[0027] In S1, the extracted topographic surface centerline hanging points are the topographic surface centerline endpoints with a mutual overlap of 0, which are used for spatial superposition analysis and extraction of the centerlines of the jagged hilltop annular plane and the valley annular plane in the subsequent steps.

[0028] In S1, the center lines of the terrain surfaces intersecting the suspension points are removed, i.e., the center lines of the toothed hill circular plane and the valley circular plane. After the center lines of the toothed hill circular plane and the valley circular plane are extracted at each location, their center lines are deleted, and this operation is repeated until all the center lines of the terrain surfaces intersecting the suspension points are removed.

[0029] In S1, in the step of judging the terrain category of the terrain surface according to the elevation relationship between the terrain surface edge line and the adjacent terrain surface: if the elevations of the two terrain surface edge lines are different, the terrain category of the terrain surface is a slope surface; if the elevations of the two terrain surface edge lines are the same, the terrain category of the terrain surface is a positive terrain saddle plane or a negative terrain beam plane, which can be further distinguished according to the elevation relationship of the surrounding adjacent terrain surfaces. Specifically, if the elevation of the surrounding adjacent terrain surface is less than the elevation of the terrain surface edge line, it is judged to be a positive terrain beam plane, otherwise it is a negative terrain saddle plane. Among them, the center line of the jagged hill ring plane and the valley ring plane is eliminated in the previous step, and it does not participate in the elevation value assigned to the center line of the terrain surface in the subsequent step. Therefore, it is not necessary to judge the terrain category of the hill ring plane and the valley ring plane here.

[0030] In S1, in the step of assigning elevation values ​​to the center line of the topographic surface according to the terrain type of the topographic surface: the elevation of the center line of the slope surface = the sum of the elevations of two adjacent contour lines / 2, the elevation of the center line of the plane of the positive topographic saddle = the elevation of any adjacent contour line - the original contour interval / 2, and the elevation of the center line of the plane of the negative topographic beam = the elevation of any adjacent contour line + the original contour interval / 2. In this way, the contour interval between the original contour line and the vector interpolated contour line is 1 / 2 of the contour interval of the original contour line. The center line assigned with the elevation value constitutes the vector interpolated contour line, which has a new contour interval with the original contour line and can be used for the operation of the contour line thinning step.

[0031] In S2, in the step of selecting contour lines whose elevations are multiples of the contour intervals of the contour lines to be thinned out, the elevations of the selected contour lines can evenly divide the contour intervals of the interpolated thinned out contour lines.

[0032] In S3, TIN is constructed based on the original contour lines. If there are elevation points and terrain feature lines, they are jointly constructed. Specifically, first, the original contour line discrete sampling points and elevation points are used to construct an unconstrained triangulation network based on the Delaunay law; then the contour lines and terrain feature lines are embedded as constraints; the affected triangles are locally adjusted to generate a constrained triangulation network.

[0033] In S3, the step of generating reconstructed contour lines based on TIN according to the same contour interval as the interpolated thinned contour lines includes: interpolating the passing points of the reconstructed contour lines based on the irregular triangle vertex elevation space, and sequentially connecting the passing points to obtain the reconstructed contour lines.

[0034] The embodiments of the present invention are described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the above embodiments. Various changes can be made within the knowledge scope of ordinary technicians in the technical field without departing from the purpose of the present invention.

Claims

1. A contour interpolation algorithm combining vector interpolation and TIN reconstruction, characterized in that: The steps include: S1, Contour vector interpolation: including Construct a terrain surface based on the original contour lines combined with the range lines of the target area; extract the center line of the terrain surface; extract the hanging points of the center line of the terrain surface; eliminate the center line of the terrain surface that intersects with the hanging points; determine the terrain type of the terrain surface based on the elevation relationship between the edge line of the terrain surface and the adjacent terrain surface; assign elevation values ​​to the center line of the terrain surface according to the terrain type of the terrain surface, and generate vector interpolation contour lines; S2, Contour vector thinning: including Based on the vector interpolation contour lines, the contour lines whose elevations are multiples of the contour intervals of the proposed thinned contour lines are selected to generate interpolated thinned contour lines; the first curve and the counting curve are redefined according to the contour intervals of the interpolated thinned contour lines; S3, Contour reconstruction: including Construct TIN based on original contours; Generate reconstructed contour lines based on TIN according to the same contour interval as the interpolated thinned contour lines; S4, interpolation and thinning contour correction: including The interpolated thinned contour lines and the reconstructed contour lines are spatially superimposed; the lines in the interpolated thinned contour lines that do not intersect with the reconstructed contour lines are screened out.

2. The contour interpolation algorithm combining vector interpolation and TIN reconstruction according to claim 1 is characterized in that: The target area is a topographic map area or a management area, and the range line is a contour line of a topographic map or a boundary line of a management area.

3. The contour interpolation algorithm combining vector interpolation and TIN reconstruction according to claim 2 is characterized in that: In S1, the steps of constructing a terrain surface based on the original contour lines and range lines include: The original contour lines are intersected and interrupted with the range lines to enclose a surface area with elevation information, which includes the following terrain surfaces: a slope surface formed by two contour lines of different elevations, a positive saddle plane formed by two contour lines of the same elevation, a negative beam plane formed by two contour lines of the same elevation, a hilltop circular plane formed by a single contour line, and a valley circular plane formed by a single contour line.

4. The contour interpolation algorithm combining vector interpolation and TIN reconstruction according to claim 1 is characterized in that: In S1, the centerline of the terrain surface is extracted using the central axis algorithm; Among the extracted center lines, the center line of the slope surface appears as a long strip line, and the center lines of the hilltop circular plane and the valley circular plane appear as short serrated lines.

5. The contour interpolation algorithm combining vector interpolation and TIN reconstruction according to claim 1 is characterized in that: In S1, the extracted terrain surface centerline suspension points are the endpoints of the terrain surface centerline with a mutual overlap of 0; The center lines of the terrain surfaces that intersect with the hanging points and are eliminated are the center lines of the jagged hill circular plane and the valley circular plane.

6. The contour interpolation algorithm combining vector interpolation and TIN reconstruction according to claim 1 is characterized in that: In S1, in the step of determining the terrain type of the terrain surface according to the elevation relationship between the terrain surface edge line and the adjacent terrain surface: if the elevations of the two terrain surface edge lines are different, the terrain type of the terrain surface is a slope surface; if the elevations of the two terrain surface edge lines are the same, the terrain type of the terrain surface is a positive terrain saddle plane or a negative terrain beam plane, and the distinction is made according to the elevation relationship of the peripheral adjacent terrain surfaces.

7. The contour interpolation algorithm combining vector interpolation and TIN reconstruction according to claim 1 is characterized in that: In S1, in the step of assigning elevation values ​​to the center line of the terrain surface according to the terrain type of the terrain surface: the elevation of the center line of the slope surface = the sum of the elevations of two adjacent contour lines / 2, the elevation of the center line of the plane of the positive terrain saddle = the elevation of any adjacent contour line - the original contour interval / 2, and the elevation of the center line of the plane of the negative terrain beam = the elevation of any adjacent contour line + the original contour interval / 2; the center line assigned with the elevation value constitutes a vector interpolation contour line.

8. The contour interpolation algorithm combining vector interpolation and TIN reconstruction according to claim 1 is characterized in that: In S3, the steps of constructing TIN based on the original contour lines include: An unconstrained triangulated network is constructed based on the Delaunay law using discrete sampling points and elevation points of the original contour lines. Contour lines and terrain feature lines are embedded as constraints. The affected triangles are adjusted to generate a constrained triangulated network.

9. The contour interpolation algorithm combining vector interpolation and TIN reconstruction according to claim 8, characterized in that: In S3, the steps of generating reconstructed contour lines based on TIN according to the same contour interval as the interpolated thinned contour lines include: The passing points of the contour lines are reconstructed based on the spatial interpolation of the irregular triangle vertex elevations, and the reconstructed contour lines are obtained by sequentially connecting the passing points.

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