A contour interpolation method integrating vector interpolation and TIN reconstruction

Abstract

The present invention discloses a contour interpolation method that combines vector interpolation and TIN reconstruction, which comprises the following steps: S1, vector interpolation of contours; S2, thinning of contour vectors; S3, contour reconstruction; S4, correction of interpolated and thinned contours. The method proposed by the present invention adopts a fusion strategy of vector interpolation method and TIN reconstruction method, making use of their respective advantages and compensating for their respective disadvantages. With the vector-interpolated contours as the basis, the defects are corrected by means of TIN-reconstructed contours, and an ideal contour interpolation result is obtained comprehensively, realizing the improvement of the existing method.

Description

Technical Field

[0001] The present invention relates to three-dimensional analysis technologies in terrain construction and conversion technologies and geographic information spatial analysis technologies, and particularly relates to a contour interpolation method. Background Art

[0002] A contour is a type of isoline, which is a closed curve formed by connecting ground points with equal elevations. It is the main manifestation 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 prominent application value in fields such as aerial survey production of geographic information elements, topographic map compilation, and processing and compilation of public version maps.

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

[0004] Among the three categories of contour interpolation methods, the advantage of the vector interpolation method is that the generated contour line is smooth, and the disadvantage is that the contours of special landforms are distorted, specifically manifested as abnormal loops of contours in areas such as saddles and ridges. The advantages of both the DEM reconstruction method and the TIN reconstruction method lie in the expression of landform details, and the TIN reconstruction method is better at reflecting the landform structure characteristics. However, both the contours generated by the two methods have fragmentation phenomena, specifically manifested as jitter, sawtooth, and independent loops. Summary of the Invention

[0005] The purpose of the present invention is to provide a contour interpolation method that combines vector interpolation and TIN reconstruction, which can make up for the defects and deficiencies of the above-mentioned vector interpolation and TIN reconstruction methods alone.

[0006] To achieve the above purpose, a contour interpolation method that combines vector interpolation and TIN reconstruction is provided, which includes the following steps:

[0007] S1. Contour vector interpolation: including

[0008] Construct a terrain surface based on the original contour lines and the boundary line of the target area; extract the center line of the terrain surface; extract the hanging points of the center line of the terrain surface; remove the center line of the terrain surface that intersects with the hanging points; determine the terrain type of the terrain surface according to the elevation relationship between the terrain surface boundary line 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 to generate vector interpolated contour lines.

[0009] S2. Contour vector thinning: including

[0010] Based on the vector interpolated contour lines, select the contour lines with elevations that are multiples of the contour interval of the contour lines to be thinned, and generate interpolated and thinned contour lines; redefine the primary contour and the index contour according to the contour interval of the interpolated and thinned contour lines.

[0011] S3. Contour reconstruction: including

[0012] Construct a TIN based on the original contour lines; generate reconstructed contour lines based on the TIN with the same contour interval as the interpolated and thinned contour lines.

[0013] S4. Correction of interpolated and thinned contour lines: including

[0014] Spatially superimpose the interpolated and thinned contour lines with the reconstructed contour lines; screen out the lines in the interpolated and thinned contour lines that do not intersect with the reconstructed contour lines.

[0015] According to the contour interpolation method that combines vector interpolation and TIN reconstruction, the target area is a topographic map area or a management area, and the boundary line is the map border of the topographic map or the boundary of the management area.

[0016] According to the contour interpolation method that combines vector interpolation and TIN reconstruction, in S1, the step of constructing a terrain surface based on the original contour lines and the boundary line includes:

[0017] Intersect and break the original contour lines with the boundary line, and enclose to form a surface area with elevation information. The surface area includes the following terrain surfaces: the slope surface formed by two contour lines with different elevations, the positive landform saddle plane formed by two contour lines with the same elevation, the negative landform ridge plane formed by two contour lines with the same elevation, the hilltop circular plane formed by a single contour line, and the valley circular plane formed by a single contour line.

[0018] According to the contour interpolation method that combines vector interpolation and TIN reconstruction, in S1, use the central axis algorithm to extract the center line of the terrain surface;

[0019] Among the extracted center lines, the center line of the slope surface appears as a long strip, and the center lines of the hilltop circular plane and the valley circular plane appear as short toothed lines.

[0020] According to the contour interpolation method that combines vector interpolation and TIN reconstruction, in S1, the hanging points of the center line of the terrain surface extracted are the end points of the center line of the terrain surface with an overlap degree of 0;

[0021] The center lines of the terrain surfaces that intersect with the hanging points and are removed are the center lines of the toothed mountain top annular plane and the valley annular plane.

[0022] According to the contour interpolation method that combines vector interpolation and TIN reconstruction, in S1, in the step of judging the terrain category of the terrain surface based on the terrain surface edge line and the elevation relationship of adjacent terrain surfaces: 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 landform saddle plane or a negative landform ridge plane, and the distinction is made according to the elevation relationship of the surrounding adjacent terrain surfaces.

[0023] According to the contour interpolation method that combines 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 category of the terrain surface: the elevation of the slope surface center line = (the sum of the elevations of two adjacent contour lines) / 2, the elevation of the positive landform saddle plane center line = the elevation of any adjacent contour line - the original contour interval / 2, the elevation of the negative landform ridge plane center line = the elevation of any adjacent contour line + the original contour interval / 2; the center lines with assigned elevation values form vector interpolation contour lines.

[0024] According to the contour interpolation method that combines vector interpolation and TIN reconstruction, in S3, the steps of constructing a TIN based on the original contour lines include:

[0025] Construct an unconstrained triangular network based on the discrete sampling points and elevation points of the original contour lines using the Delaunay rule; embed the contour lines and terrain feature lines as constraint conditions; adjust the affected triangles to generate a constrained triangular network.

[0026] According to the contour interpolation method that combines vector interpolation and TIN reconstruction, in S3, the steps of generating reconstructed contour lines based on the TIN at the same contour interval as the interpolated and thinned contour lines include:

[0027] Based on the passing points of the reconstructed contour lines interpolated in the elevation space of the vertices of the irregular triangles, sequentially connect each passing point to obtain the reconstructed contour lines.

[0028] Beneficial effects: The method proposed in the present invention adopts a fusion strategy of vector interpolation method and TIN reconstruction method, making use of their respective advantages and compensating for their deficiencies. With the vector interpolation contour lines as the basis, the defects are corrected by means of TIN reconstructed contour lines, and an ideal contour interpolation result is comprehensively obtained, realizing the improvement of the existing methods.

[0029] Additional aspects and advantages of the present invention will be given in part in the following description, become apparent in part from the following description, or be learned through the practice of the present invention. Brief Description of the Drawings

[0030] The present invention will be further described below in conjunction with the drawings and embodiments:

[0031] Figure 1 is a flowchart of the method of the present invention;

[0032] Figure 2 is a schematic diagram of the original contour line;

[0033] Figure 3 is a schematic diagram of the superposition of the original contour line and the vector interpolated and thinned contour line;

[0034] Figure 4 is a schematic diagram of the superposition of the original contour line and the TIN reconstructed contour line;

[0035] Figure 5 is a schematic diagram of the superposition of the vector interpolated and thinned contour line and the TIN reconstructed contour line;

[0036] Figure 6 is a schematic diagram of the superposition of the vector interpolated and thinned contour line and the final contour line;

[0037] Figure 7 is a schematic diagram of the superposition of the original contour line and the final contour line.

[0038] Figure 2-7 Among them, the gray thin line represents the original contour line, the black thin line represents the vector interpolated and thinned contour line, the black dotted line (dotted line) represents the TIN reconstructed contour line, and the black thick line represents the final contour line. Detailed Embodiments

[0039] This part will describe in detail the specific embodiments of the present invention. The preferred embodiments of the present invention are shown in the drawings. The function of the drawings is to supplement the description of the text part of the specification, enabling people to 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 protection scope of the present invention.

[0040] In the description of the present invention, understandings such as greater than, less than, exceeding, etc. are understood as not including the number itself, and understandings such as above, below, within, etc. are understood as including the number itself. If there is a description of first and second, it is only for the purpose of distinguishing technical features and cannot be understood as indicating or implying relative importance or implicitly indicating the quantity of the indicated technical features or implicitly indicating the sequence relationship of the indicated technical features.

[0041] In the description of the present invention, unless otherwise clearly defined, terms such as "setting", "installation", "connection", etc. should be understood in a broad sense, and those skilled in the art can reasonably determine the specific meanings of the above terms in the present invention in combination with the specific content of the technical solution.

[0042] Referring to Figure 1-7 , a contour interpolation method that combines vector interpolation and TIN reconstruction, which includes the following steps:

[0043] S1. Contour vector interpolation: including

[0044] Construct a terrain surface based on the original contour lines and the boundary 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; judge the terrain type of the terrain surface according to the terrain surface boundary line and the elevation relationship of adjacent terrain surfaces; assign elevation values to the center line of the terrain surface according to the terrain type of the terrain surface to generate vector interpolated contour lines.

[0045] S2. Contour vector thinning: including

[0046] Based on the vector interpolated contour lines, screen out all the contour lines with elevations that are multiples of the contour interval of the contour lines to be thinned, and generate interpolated and thinned contour lines; redefine the index contour and the major contour according to the contour interval of the interpolated and thinned contour lines.

[0047] S3. Contour reconstruction: including

[0048] Construct a TIN based on the original contour lines; generate reconstructed contour lines based on the TIN with the same contour interval as the interpolated and thinned contour lines.

[0049] S4. Correction of interpolated and thinned contour lines: including

[0050] Spatially superimpose the interpolated and thinned contour lines with the reconstructed contour lines; screen out the short lines in the interpolated and thinned contour lines that do not intersect with the reconstructed contour lines (i.e., cause abnormal loops).

[0051] Based on the above steps, the final contour lines can be generated. The processing and generation of the final contour lines adopt a fusion strategy, learning from each other's strengths and compensating for each other's weaknesses. Taking the vector interpolated contour lines as the base, and using the TIN reconstructed contour lines to correct their defects, an ideal contour interpolation result is comprehensively obtained, achieving a significant improvement over the existing methods.

[0052] Specifically, in S1, the target area can be a standard topographic map area or a management area (such as a management area defined by administrative division, etc.). Based on this, the boundary line can be the map border of the standard topographic map or the boundary of the management area.

[0053] In S1, the steps of constructing a terrain surface based on the original contour lines and the range lines specifically include the following: Intersect and break the original contour lines and the range lines to enclose and form a surface region with elevation information. The surface region is a closed surface or a plane, and it usually includes the following terrain surfaces: a slope formed by two contour lines with different elevations, a positive landform saddle plane formed by two contour lines with the same elevation, a negative landform ridge plane formed by two contour lines with the same elevation, a hilltop circular plane formed by a single contour line, and a valley circular plane formed by a single contour line. According to the classification principle of the above terrain surfaces, the standard topographic map sheet or the management area is thus divided and constructed into several different types of terrain surfaces.

[0054] 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 appears as a long strip, and there may be abnormal contour loops in the center lines of the positive landform saddle plane and the negative landform ridge plane. The center lines of the hilltop circular plane and the valley circular plane appear as short toothed lines.

[0055] In S1, the hanging points of the extracted center lines of the terrain surface are the end points of the center lines of the terrain surface with an overlapping degree of 0, which are used for the spatial overlay analysis and extraction of the center lines of the toothed hilltop circular plane and the valley circular plane in the subsequent steps.

[0056] In S1, the center lines of the terrain surface that intersect with the hanging points and are to be removed are the center lines of the toothed hilltop circular plane and the valley circular plane. Among them, after the center lines of the toothed hilltop 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 surface that intersect with the hanging points are removed.

[0057] In S1, in the step of judging the terrain type of the terrain surface according to the terrain surface boundary line and the elevation relationship of the adjacent terrain surfaces: If the elevations of the two terrain surface boundary lines are different, the terrain type of the terrain surface is a slope; if the elevations of the two terrain surface boundary lines are the same, the terrain type of the terrain surface is a positive landform saddle plane or a negative landform ridge plane, and it 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 boundary line, it is judged as a positive landform ridge plane, and vice versa as a negative landform saddle plane. Among them, the center lines of the toothed hilltop circular plane and the valley circular plane are removed in the previous step and do not participate in the subsequent step of assigning elevation values to the center lines of the terrain surface. Therefore, it is not necessary to judge the terrain types of the hilltop circular plane and the valley circular plane here.

[0058] In S1, in the step of assigning elevation values to the centerlines of terrain surfaces according to the terrain surface terrain categories: the elevation of the slope centerline = (the sum of the elevations of two adjacent contour lines) / 2, the elevation of the saddle plane centerline of positive landforms = the elevation of any adjacent contour line - the original contour interval / 2, and the elevation of the ridge plane centerline of negative landforms = the elevation of any adjacent contour line + the original contour interval / 2. In this way, the contour interval between the original contour lines and the vector interpolated contour lines is 1 / 2 of the original contour line contour interval. The centerlines with assigned elevation values form vector interpolated contour lines, and these vector interpolated contour lines have a new contour interval with the original contour lines, which can be used for the operation of the contour line thinning step.

[0059] In S2, in the step of screening out the contour lines whose elevations are multiples of the contour interval of the contour lines to be thinned, for the screened-out contour lines, their elevations can be divided evenly by the contour interval of the interpolated and thinned contour lines.

[0060] In S3, a TIN is constructed based on the original contour lines. If there are elevation points and terrain feature lines, they are jointly constructed. Specifically, first, an unconstrained triangular network is constructed based on the discrete sampling points and elevation points of the original contour lines according to the Delaunay rule; then the contour lines and terrain feature lines are embedded as constraint conditions; and the affected triangles are locally adjusted to generate a constrained triangular network.

[0061] In S3, the steps of generating reconstructed contour lines based on the TIN at the same contour interval as the interpolated and thinned contour lines include: interpolating the passing points of the reconstructed contour lines in the elevation space of the vertices of the irregular triangles, and sequentially connecting each passing point to obtain the reconstructed contour lines.

[0062] The above has described the embodiments of the present invention in detail with reference to the accompanying drawings. However, the present invention is not limited to the above embodiments, and various changes can be made without departing from the gist of the present invention within the scope of knowledge possessed by those of ordinary skill in the art.

Claims

1. A contour interpolation method 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 method combining vector interpolation and TIN reconstruction according to claim 1, 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 method 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 method combining vector interpolation and TIN reconstruction according to claim 1, 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 method combining vector interpolation and TIN reconstruction according to claim 1, 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 method combining vector interpolation and TIN reconstruction according to claim 1, 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 method combining vector interpolation and TIN reconstruction according to claim 1, 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 method combining vector interpolation and TIN reconstruction according to claim 1, 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 method 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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