JP2005106906A - Altitude data generation method and altitude data generation program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To generate altitude data with respect to lattice points near a step region such as precipice, and also generate the altitude data obtained by correcting the altitude of the lattice points near the step region by using the altitudes of triangulation points and the control points. <P>SOLUTION: A plurality of proximity points which are located on altitude lines or the step region and satisfies prescribed conditions are detected for each lattice point and, concerning the first kind of lattice points that do not contain the proximity points on the step region among the detected plurality of proximity points, the altitudes of the lattice points are determined based on the locations and altitudes of the plurality of proximity points. Concerning the second kind of lattice points that contain the proximity points on the step region among a plurality of the proximity points, at least another proximity point which satisfies other prescribed conditions is additionally detected and the altitude of the selected lattice point is determined based on the location and the altitude of the at least the other proximity point which is additionally added. Furthermore, the altitudes determined concerning the triangulation points and the lattice points near the control points are corrected based on the altitudes of the triangulation points and the control points. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a contour map on a contour map that describes contour lines for a map including a step area symbol representing a step area such as a cliff, and a plurality of specific points whose positions and altitudes are specified, such as a triangular point or a reference point. The present invention relates to an elevation data generation method, an elevation data generation program, and an elevation data generation device for generating elevation data of lattice points of each mesh obtained by dividing the map into a plurality of meshes from contour line sequence data representing

Contour line sequence data, which is data representing contour lines, is generated from a contour map mainly describing contour lines. A method for generating contour line sequence data in this way is known per se. The contour point sequence data is approximated by a large number of connected polygonal lines, and a number of points on the polygonal line are directed from the start point to the end point by a process called vectorization. This is a sequence of points representing the two-dimensional position and elevation of each point. A contour map representing contour lines is divided into a large number of meshes, and elevation data representing the coordinates and elevations of the grid points of each mesh are generated from a large number of contour line sequence data for the numerous contour lines. The generation of contour point sequence data from the contour map is usually executed separately from the generation of elevation data. In this specification, a point on a contour line indicates a point included in the contour line sequence data. Further, a point on a line segment connecting a pair of adjacent points in the contour line sequence data may be referred to as a point included in the contour line sequence data. Further, a point on the contour line represented by the contour point sequence data may be referred to as a point on the contour point sequence data, a point on the contour point sequence, or a point on the contour line for simplification.

When generating elevation data from conventional contour line data, the terrain near the contour line is estimated by some method from the situation of the contour lines around the grid point whose elevation is to be obtained, and the elevation of the grid point is calculated. As estimation methods at this time, there are linear interpolation and curve interpolation that consider elevation interpolation in a section of terrain, curved surface interpolation that estimates terrain in more detail in three dimensions, and the like. An example of a method for generating altitude data using linear interpolation is described in Patent Document 1, for example. An example of curved surface interpolation is shown in Patent Document 2, for example. Although linear interpolation is easy to calculate, it is assumed that the altitude changes linearly, so a result slightly different from the actual topography is often obtained. Curve interpolation and curved surface interpolation can estimate altitude more realistically than linear interpolation, and can generate smooth three-dimensional data. Various examples of the curve interpolation method have been proposed. For example, the steepest azimuth method is described in Non-Patent Document 1 below.
JP-A-4-293078 Japanese Patent Laid-Open No. 9-50538 Prima et al. 1, “Development of algorithm for generating high-precision DEM”, Photogrammetry and Remote Sensing, 2001, Vol. 40, No. 5, p. 52-62

  In the prior art, the elevation data of the grid points is determined based on the contour point sequence data for the contour map. However, in real terrain, there are many areas such as cliffs, dikes or steep slopes where there are steps where the altitude changes so rapidly that they cannot be represented by contour lines. Such areas are shown on the contour map using special symbols. Hereinafter, such a region is referred to as a step region, and a symbol for representing it is referred to as a step region symbol. In the prior art, altitude data is determined ignoring the presence of such a step region. However, the step region affects the altitude of surrounding grid points. Therefore, the elevation data determined without considering the step region has a problem that the elevation of the grid points around the step region is not accurate.

  In addition, the contour map data normally used for generating contour line data generally includes data indicating the position and altitude of a specific point such as a triangular point or a reference point in addition to the contour line data. However, when the contour data is generated from the contour map data in the prior art, the data regarding these specific points is not used. For this reason, the altitudes of the grid points in the vicinity of these specific points may be values that seem to be contradictory in view of the altitudes of these specific points. In particular, in places where it is difficult to determine the altitude accurately only with contour lines, such as the top of a mountain, an altitude that is significantly different from the altitude value of a specific point provided at the top of the mountain may be determined.

Accordingly, a first object of the present invention is to provide altitude data that makes it possible to generate more accurate altitude data from contour line data, reflecting step areas such as cliffs, embankments, and steep slopes existing on a map. generating method and to provide elevation data generation program.
A second object of the present invention is an altitude data generation method and altitude data generation capable of generating altitude data more accurately by reflecting altitudes of specific points such as triangular points and reference points existing on a map. it is to provide a program.

In order to achieve the first object, an elevation data generation method according to the present invention described in claim 1 is characterized in that each of a plurality of contour lines included in a two-dimensional map image including contour lines and step region symbols is represented by a point sequence. Represents the contour line point sequence data stored in advance in the storage device and the point region representing the step region represented by the step region symbol, and represents the map from the step region representative point sequence data stored in advance in the storage device. Is an altitude data generation method executed by the processing device for generating altitude data indicating the altitude of each grid point of the grid point group obtained by dividing the grid into grids.
Furthermore, the method, the a pre-Symbol like contours point sequence data based on the step area representative point sequence data, for each grid point, on at least one of said plurality of contour point sequence or the stepped area representative point on the column a detecting step of detecting a respectively positioned a predetermined condition is satisfied more proximity points, for each grid point, proximity positioned in the stepped area representative points on the column in a plurality of adjacent points detected by the detecting step a determining step of determining whether or not the points are included among the plurality of grid points, the proximity points located in said stepped area representative points on the column in a plurality of adjacent points detected by the detecting step For the first type of grid points determined in the determining step if the first type of grid points is not included, the elevation of the first type of grid points is determined based on the positions and elevations of the plurality of adjacent points. Determining step and said plurality Among the grid points, the second type of grid points wherein it is determined that the proximity point on the step area representative point sequence into a plurality of adjacent points detected by the detecting step is included in the determination step , rather than to the stepped area representative points on the column, it is between a pair of contour points adjacent columns, other predetermined condition is satisfied, to add at least one adjacent lattice points of the lattice point And an additional detection step to detect and the position and altitude of at least one neighboring point on the contour line sequence of any of the plurality of neighboring points detected in the detecting step with respect to the second type grid point When the second elevation to determine the elevation of the second type of grid points on the basis of said detected by the additional at least one proximity grid point positions, in the respective elevation of the set of contour point sequence A determination step. .
Thereby, even when the step region is included in the map, the altitude of the lattice point in the vicinity can be determined.

In order to achieve the second object, an elevation data generation method according to the present invention described in claim 2 is characterized in that each of the plurality of contour lines included in a two-dimensional map image including a plurality of contour lines and a plurality of specific points is provided. are expressed as a sequence of points, representing the position and altitude of the previously stored contour point sequence data in the storage device of the plurality of specific points, from the specific point data previously stored in the storage device divides the map grid This is an altitude data generation method executed by the processing device for generating altitude data indicating the altitude of each grid point of the grid point group obtained in this way. The method further based on the previous SL like contours point sequence data, for each grid point, at least located on each of the two predetermined first condition is satisfied more proximity points of the plurality of contour lines point sequence a first detection step of detecting, based on the position and altitude of the plurality of adjacent points detected by said first detection step for the grid point, a determination step of determining altitude of the lattice point, before Symbol etc. high A second detection step of detecting at least one proximity point that is located on any contour line sequence and satisfies a predetermined second condition for each specific point based on the line point sequence data and the specific point data; A third detection step for detecting a lattice point that should be corrected for elevation, satisfying a predetermined third condition and satisfying a predetermined third condition; a position and elevation of the specific point; and the specific point For the second test Detected in step, on the basis of the position and elevation of the at least one adjacent point of the specific point, the position of the third detected for the specific point detection step was the near grid point, the And a correction step for correcting the altitudes of adjacent grid points .
As a result, it is possible to generate more accurate elevation data that reflects the elevation of a specific point such as a triangular point or a reference point.

In order to achieve the first object of the present invention, a program according to the present invention as set forth in claim 3 is configured such that each of a plurality of contour lines included in a two-dimensional map image including contour lines and step region symbols is represented by a point sequence. Represents the contour line point sequence data stored in advance in the storage device and the point region representing the step region represented by the step region symbol, and represents the map from the step region representative point sequence data stored in advance in the storage device. Is an altitude data generation program for generating altitude data indicating the altitude of each grid point of the grid point group obtained by dividing the grid into grids.
The present program is based on the previous SL like contours point sequence data and the stepped area representative point sequence data, for each grid point, at least one of the upper or the stepped area representative point on the columns of the plurality of contour lines point sequence located respectively detecting a predetermined condition is satisfied more proximity points for each grid point, near point located in said stepped area representative points on the column in a plurality of adjacent points detected by the detecting step a determining step of determining whether or not are included among the plurality of grid points, the proximity points located in said stepped area representative points on the column in a plurality of adjacent points detected by said detection step includes A first altitude determination step for determining the altitude of the first type of grid points based on the positions and altitudes of the plurality of adjacent points for the first type of grid points determined in the determination step if not Compilation It is intended to be executed by the over data.
Furthermore, the program, among the plurality of grid points, said is discriminated by the discriminating step and the proximity point on the step area representative point sequence is included in a plurality of adjacent points detected by the detecting step and for the second type of grid points, rather than to the stepped area representative points on the column, it is between a pair of contour points adjacent columns, certain other conditions are met, the at least one of said grid points An additional detection step of adding and detecting two adjacent grid points, and the second type of grid points are on any one of the contour point sequences among the plurality of proximity points detected in the detection step At least one of the position and altitude of the adjacent point, the position of which said additional to said detected at least one proximity lattice points, each of said pair of contour point sequence elevation and in of the second type based The second elevation that determines the elevation of the grid points It is intended to execute a constant step, to the computer.
Thereby, it is possible to determine the altitude of the second type grid point located in the vicinity of the step region even if the step region exists.

More specifically, the at least one adjacent lattice point detected in addition to the second type lattice point is the plurality of proximity points detected in the detection step for the second type lattice point. A set of contour point sequences that are on different sides with respect to the line connecting the at least one adjacent point and the second type grid points on any contour point sequence of points, and are adjacent to each other. A pair of closest lattice points is included in the lattice point of the second type in between . Thereby, even if there is a stepped region, it is possible to determine the altitude of a lattice point in the vicinity thereof relatively accurately. More specifically, the plurality of proximity points detected by the detection step for each grid point, when viewed from the grid point located in a plurality of steepest orientation, either contour point sequence or on the It includes a plurality of proximity points located on the step region representative point row . Thereby, the altitude can be determined relatively accurately according to the terrain.

More specifically, the plurality of proximity points detected in the detection step with respect to each grid point are proximity on one of the contour line sequences of the plurality of proximity points as viewed from the grid point. It further includes proximity points that are located farther from each of the one or a plurality of proximity points when viewed from the point, and that are located in the steepest direction with respect to each of the proximity points . As a result, the altitude can be determined more faithfully to the terrain.

In order to achieve the second object of the present invention, an elevation data generation program according to claim 6 is configured to calculate each of the plurality of contour lines included in a two-dimensional map image including a plurality of contour lines and a plurality of specific points. The map is divided into grids from contour point sequence data stored in advance in the storage device , represented by point sequences, and the specific point data stored in advance in the storage device, representing the positions and elevations of the plurality of specific points. An altitude data generation program for generating altitude data indicating the altitude of each grid point of the obtained grid point group. The present program is based on the previous SL like contours point sequence data, for each grid point, for detecting at least two respective positions to satisfy a predetermined condition a plurality of proximity points over the plurality of contour lines point sequence the 1 is a program for causing a computer to execute a detection step and a determination step of determining an altitude of the grid point based on the positions and altitudes of the plurality of proximity points detected in the first detection step for the grid point. . Furthermore, the program, based on the previous SL like contours point sequence data and the specific point data, for each particular point, either positioned contour point on the column satisfies a predetermined condition at least one adjacent point A second detection step for detecting, a third detection step for detecting a grid point that satisfies a predetermined condition and is close to the specific point and whose altitude is to be corrected, and the position and altitude of the specific point; detected by the second detecting step with respect to the specific point, the position and altitude of said at least one adjacent point of the specific point, and is detected the proximity with respect to the specific point in the third detection step A program for causing a computer to execute a correction step of correcting the altitude of the adjacent grid points based on the positions of the grid points .
This makes it possible to generate altitude data that has been corrected to match the position and altitude of specific points such as triangular points and reference points.

More specifically, in the invention of claim 7 , when any one specific point is on the inclined ground, the second detection step relates to the specific point as the at least one adjacent point on the inclined ground. , A plurality of proximity points located on different contour line point sequences are detected, and the grid points that are detected in the third detection step with respect to the specific points are to be corrected for the elevations, are grid points on the inclined ground. In the correction step, the position and altitude of the specific point, the positions and altitudes of the plurality of proximity points detected in the second detection step, and the specific point detected in the third detection step. based on the position of the adjacent grid points, to correct the elevation of the adjacent grid points. Alternatively, in the invention of claim 8, when one of the specific point is on level ground, the at least one adjacent point is detected by the second detecting step with respect to the specific point is on the level ground, and one is one of the near points on Kano contour point sequence, is detected by the third detecting step with respect to the specific point, the grid point to be corrected the altitude, Ri Oh lattice points on the flat, The correction step includes the position and altitude of the specific point, the position of the one adjacent point detected in the second detection step, and the proximity detected for the specific point in the third detection step. based on the position of the grid point, it is Rukoto to correct the altitude of the adjacent grid points. In this way, it is possible to generate altitude data in which the altitudes of the grid points on the inclined land or the flat ground are corrected so as to match the altitude of the specific point.

Therefore, according to a desirable mode of the present invention, even if there is a step region such as a cliff, a bank, or a steep slope existing on the map, it is possible to generate elevation data for lattice points in the vicinity of this region.
Furthermore, according to another desirable aspect of the present invention, more accurate elevation data is generated by reflecting the elevation of a specific point such as a triangular point or a reference point existing on a map to the elevation of a neighboring grid point. It becomes possible.

DESCRIPTION OF EMBODIMENTS Hereinafter, an embodiment of an elevation data generation method, an elevation data generation program, and an elevation data generation apparatus according to the present invention will be described with reference to the drawings.
FIG. 1 is a schematic block diagram of an embodiment of an elevation data generation apparatus according to the present invention. 1 represents contour line sequence data representing each of a plurality of contour lines included in a two-dimensional map image including contour lines and step area symbols, and step area representative points representing the step areas represented by the step area symbols. It is an altitude data generation device that generates altitude data indicating the altitude of each grid point of a grid point group obtained by dividing the map into a plurality of meshes from column data. The generation device 1 includes a processing device 10 realized by, for example, a personal computer or a workstation, an auxiliary storage device 20 such as a magnetic disk storage device, and an input / output device 30. The input / output device 30 includes an input device 31 including a keyboard and a pointing device such as a mouse, a display device 32 such as a CRT display device, and a printer 33.

  The processing device 10 incorporates an altitude data generation program 40. The altitude data generation program 40 includes processing units such as a step area extraction unit 41, a steepest azimuth search unit 42, an altitude calculation unit 43, and an altitude correction unit 44, and generates altitude data indicating altitudes of lattice points from contour line sequence data. To do. The processing device 10 corrects the functional block for extracting the step area, the functional block for searching for the steepest direction, the functional block for calculating the altitude, and the altitude when each processing unit in the altitude data generation program 40 is executed. It operates as a plurality of functional blocks called functional blocks. Therefore, in the processing device 10, corresponding functional blocks are realized by these processing units of the program 40. Therefore, the step area extraction unit 41, the steepest azimuth search unit 42, the altitude calculation unit 43, and the altitude correction unit 44 realize one embodiment of the altitude data generation device 1 according to the present invention. The altitude data generation program 40 implements one embodiment of the program according to the present invention, and is recorded in a recording medium or stored in the auxiliary storage device 20 via a network and executed by the processing device 10. . The elevation data generation program 40 can be recorded on a recording medium or sold via a network. The procedure in which the processing apparatus 10 executes the altitude data generation program 40 to generate altitude data realizes one embodiment of the altitude data generation method according to the present invention.

  The auxiliary storage device 20 stores contour line sequence data 21A, grid point data 21B, triangle point data 22A, reference point data 22B, contour line map image data 23, and standard pattern group 24 for step area symbol image detection in advance. Are used to generate step area symbol image data 25, step area representative point sequence data 26, peripheral point data list 27, steepest azimuth data 28, and altitude data 29.

The contour line sequence data 21 </ b> A is data composed of a plurality of point lines positioned on each polygonal line and the altitude value representing the elevation of the contour line by approximating each of the contour lines in the contour map with a polygonal line. In the present specification, the contour line sequence data 21A may be simply referred to as a contour line 21A. The grid point data 21B is data indicating two-dimensional coordinates (x, y) of a plurality of grid points when the contour map data is divided into a plurality of meshes. The triangular point data 22A and the reference point data 22B are data representing the coordinates and altitude of the triangular point and the reference point on the contour map, respectively. In the present embodiment, it is assumed that the contour line sequence data 21A, the triangular point data 22A, and the reference point data 22B are already generated from the contour map and stored in the auxiliary storage device 20.

  The contour map image data 23 is map image data showing contour lines. FIG. 2 shows some examples of such contour map image data 23. FIG. 4A is an example of contour map image data representing an inclined land, FIG. 4B is an example of contour map image data having a step region, and 260 is an example of a step region symbol. It is. FIG. 6C shows an example of contour map image data representing a flat land near the top of the mountain, for example. In the figure, the contour line C1 represents an elevation of the flat ground. In FIG. 2, the triangular point and the reference point are not shown for the sake of simplicity.

  Returning to FIG. 1, the elevation data generation program 40 executes the step area extraction unit 41 when activated. The step region extraction unit 41 extracts step region symbol image data 25 representing the step region symbol image from the contour map image data 23. When the contour map image data 23 is shown in FIG. 2B, step area symbol image data 25 indicating the step area symbol 260 as shown in FIG. 3A is extracted from the contour map image data 23. The image data 25 is data representing the step region symbol image by a binary bitmap.

  The step region symbol is a symbol representing a cliff or the like shown in the legend of the map image, and may vary depending on the map. In the case of FIG. 2B, the step region symbol image roughly indicates the position of the cross section of the step region. The first long line segment to be represented is a line figure in which a plurality of short line segments having one end on the line segment are arranged on the higher elevation side when viewed from the long line segment. Therefore, the step region symbol image is a step region It varies depending on the shape of the cross section and the width of the step region. In the present embodiment, pattern matching is used to extract such a step region symbol image. The step area symbol image detection standard pattern group 24 stored in the auxiliary storage device 20 includes a plurality of partial standard patterns representing a part of images constituting the step area symbol image. FIG. 4A shows examples of various standard patterns included in the standard pattern group 24 for detecting the step area symbol image. The standard pattern group 24 includes partial standard patterns oriented in various directions. A plurality of patterns obtained by changing the pattern directions shown in FIG. 5B may be added as partial standard patterns. As the pattern recognition technique, for example, the technique introduced in Noboru Funakubo, “Pattern Recognition”, 1991, Kyoritsu Publishing Co., Ltd., p. 15-22 can be used.

  FIG. 5 is a schematic flowchart of the processing of the step area extraction unit 41. First, all the partial images that match each partial standard pattern are detected from the contour map image data 23 (step S411), and the positional relationship that forms the step region symbols continuously from the positional relationship of the detected partial images. The partial images and the order of connecting them are determined, and the partial images are connected according to the determination result to obtain a bitmap image indicating the step region symbol image (step S412). Bitmap data representing this image is stored in the auxiliary storage device 20 as the step region symbol image data 25 (step S413). Further, the step region extraction unit 41 determines step region representative point sequence data 26 representing the obtained step region symbol image data 25 and stores it in the auxiliary storage device 20 (step S414). Thereafter, it is determined whether there is an unextracted step region symbol image (step S415). If so, the above processing is repeated, and the processing of the step region extraction unit 41 ends when extraction of all step region symbol images is completed. To do.

  The step region representative point sequence data 26 is a point sequence on a polygonal line representing the extracted step region symbol image, and the position coordinates (x, y) of a plurality of points constituting the representative point sequence data are set from the start point to the end point. The data is connected in the order up to. When there are a plurality of step area symbols on the contour map image, a step area symbol image is extracted for each, and from the step area symbol image data 25 representing each extracted step area symbol image, a step area representative point sequence is extracted. Data 26 is generated.

For each step region symbol image data 25, the step region representative point sequence data 26 can be defined in various ways. For example, when the step region symbol image is FIG. 3A, as shown in FIG. 3B, a broken line 26A connecting the dots indicated by the black circles at the center position of the short line segment included in the step region symbol image is displayed. Data representing the included point sequence can be used as the step region representative point sequence data 26. Alternatively, as shown in FIG. 5C, the data of the point sequence on the broken line 26B connecting the points indicated by black circles at the heads of the plurality of short line segments constituting the step region symbol image is used as the step region representative point sequence. It may be used for data 26. Alternatively, as shown in FIG. 4D, a point sequence included in a broken line 26C that connects points indicated by black circles at the intersections of the long line segment and the short line segment included in the step region symbol image can also be used. Furthermore, as shown in FIG. 6 (e), the outer periphery of the step region symbol includes the two broken lines 26B and 26C and short line segments 26D and 26E shown in FIGS. A closed polyline may be used. Furthermore, instead of the closed polyline representing the outer periphery of the step region symbol, when the step region symbol is configured to indicate the actual range or another data indicating the presence of the step region on the map, When there is a step area corresponding to each step area on the map, the step area representative point sequence data of the step area is preferably a closed point sequence indicating the existence range of the step area. In this specification, it is not distinguished whether the grid point, the steepest azimuth point in the vicinity of the grid point, or any other point of interest is located on the step region point sequence or in any one of the step regions. It may be referred to as being located on the step region point sequence or on the step region. Alternatively, it may be referred to as being located on the step region point sequence data. Further, the step region representative point sequence data 26 may be simply referred to as a step region representative point sequence 26 or a step region 26.

  FIG. 6 is a diagram schematically showing the step region representative point sequence data 26 obtained for the step region symbol 260 of FIG. Hereinafter, the point sequence data representing the image illustrated in FIG. 6 is used as the step region representative point sequence data 26.

  In the present embodiment, the step region symbol image data 25 indicating the step region symbol image on the contour map image data 23 is automatically extracted by using pattern matching. The contour map image data 23 is displayed on the screen, the operator visually finds the step region symbol image, and the point sequence on the step region symbol image representing the step region symbol image is designated. The region extraction unit 41 may generate the step region symbol image data 25.

Returning to FIG. 1, the altitude data generation program 40 being executed executes the steepest direction searching unit 42 after the step area extracting unit 41 is executed. Elevation data generating apparatus 1 according to the present invention, based on the equal contours point sequence data and the step area representative point sequence data, for each grid point, a predetermined positioned on the contour point sequence or stepped area representative point on the column first A plurality of proximity points satisfying one condition are detected. Further, for each grid point, it is determined whether or not a plurality of proximity points detected in the detection step include a proximity point located on the step region representative point sequence .

Specifically, the steepest azimuth search unit 42 examines the situation of surrounding contour lines for each grid point, and each grid point is located on the contour line sequence or step region representative point sequence, and the predetermined first As one condition, a plurality of proximity points in the direction with the steepest inclination are detected. More specifically, the main purpose of the steepest azimuth searching unit 42 is a point in which each grid point has the steepest inclination and is in a pair of opposite directions on the contour point sequence (hereinafter referred to as a pair of contour points). is sometimes referred to as steepest cardinal points) detects p1, position and elevation of p2, is in steep direction most similarly inclined with respect to each of the steepest cardinal points, and on one contour point sequence This is to detect the positions and altitudes of points q1 and q2 that are far from the original lattice point (hereinafter sometimes referred to as the secondary steepest azimuth point or the next steepest azimuth point ). When the points on the step region representative point sequence become the steepest azimuth points or secondary steepest azimuth points instead of the points on the contour lines, the positions of these points are detected.

  Further, the steepest direction searching unit 42 determines the attribute of the lattice point based on the above detection result. The attribute is an attribute that represents the type of grid point, and in the present embodiment, an attribute that represents the type of position of the grid point is used. Specifically, attributes such as an inclined point, a flat point, a step region adjacent point, and a step region point are used. The steepest azimuth searching unit 42 generates the steepest azimuth data 28 as a processing result and stores it in the auxiliary storage device 20.

  FIG. 7 is a diagram illustrating an example of the steepest azimuth data 28. One row of this data corresponds to one grid point, and each row includes a coordinate 280 of the corresponding grid point, an attribute 281, a steepest azimuth p1 coordinate 282, a p1 altitude 283, and a steepest azimuth p2 coordinate 284. , P2 altitude 285, secondary steepest direction q1 coordinate 286, q1 altitude 287, secondary steepest direction q2 coordinate 288, and q2 altitude 289.

FIG. 8 is a schematic flowchart of processing of the steepest direction searching unit 42. The processing of the steepest azimuth searching unit 42 can be applied to a contour map image having a step region as compared with the steepest azimuth method described in Non-Patent Document 1. First, the storage area of the steepest azimuth data 28 is secured in the auxiliary storage device 20 so as to have the data structure illustrated in FIG. 7, and the lattice point data stored in advance in the auxiliary storage device 20 at the lattice point coordinates 280. 21B (FIG. 1) is stored (step S421). Next, one of the grid points whose attributes are not determined is selected (step S422). Hereinafter, the lattice point is referred to as a selected lattice point. First, it is determined whether or not the selected grid point is a point on the step area representative point sequence 26 (step S423). If so, the step area point is set as the attribute of the grid point in the steepest azimuth data 28. Store (step S424). Hereinafter, the lattice point having this attribute may be referred to as a step region point or a step region lattice point. The processing of the lattice points ends, and the process moves to step S429.

If it is determined in step S423 that the selected grid point is not on the step region representative point sequence 26, a line from the selected grid point to a plurality of directions, for example, 16 directions, is checked in order to examine the situation around the selected grid point. The points that first intersect the contour line sequence 21A or the step region representative point sequence 26 are examined as peripheral points. The coordinates and elevations of the 16 intersections obtained here are paired with information for identifying the selected grid point, for example, the coordinates of the selected grid point, as the peripheral point data list 27 (FIG. 1) for the selected grid point. Store ( step S425). As described above, the peripheral point data list 27 is generated when each grid point is selected for each grid point. If any of the peripheral points is an intersection of a line segment extending from the selected grid point and the step region representative point sequence, it indicates that it is an intersection with the step region representative point sequence 26 instead of the elevation, and A specific value that is impossible as an altitude is stored.

Next, it is determined whether or not all the peripheral points are intersections with the contour point sequence and their elevations are the same (step S426). When all the peripheral points are intersections with the contour point sequence and their elevations are the same, the grid point can be considered to be located on a flat ground, and in the following, the grid point is treated as being on the flat ground. Therefore, the elevation of the selected grid point is the same as the elevation of the surrounding points. However, when there is a triangular point or a reference point in the vicinity of the selected grid point later, as the preparation for correcting the altitude of the selected grid point, the steepest azimuth point p1 closest to the selected grid point among the above peripheral points And the steepest azimuth point p2 among the points in the opposite direction as viewed from the selected grid point, are detected as the steepest azimuth points with respect to the selected grid point, and the coordinates and altitudes of those points are The steepest azimuth p1 coordinate 282, p1 altitude 283, steepest azimuth p2 coordinate 284, and p2 altitude 285 with respect to the selected grid point in the azimuth data 28 (FIG. 7) are stored (step S427A), and a flat spot is stored as the attribute 281. (Step S427B). Below, the grid point of this attribute may be called a flat spot or a flat grid point. The process relating to the selected grid point ends here, and the process moves to step S429.

If it is determined in step S426 that any of the peripheral points is an intersection with a different contour line sequence or an intersection with a step region representative point sequence , the selected grid point is not on the ground. At this time, among the 16 peripheral points, they are either on contour line sequences of different elevations or on different step region representative point sequences , or one is on the contour line sequence and the other is the step region representative. The steepest azimuth point p2 that is on the point sequence and is opposite to the steepest azimuth point p1 when viewed from the selected lattice point and the steepest azimuth point p1 of the selected lattice point is set as the steepest azimuth point with respect to the selected lattice point. The coordinates and altitudes of these points are detected and stored in the steepest azimuth data 28 in association with the selected grid points (step S427C). When any of the points p1 and p2 is on the step region representative point sequence , a specific value representing the step region point is stored as the altitude as in the case described above.

Further, when at least one of the above p1 and p2, for example, p1 is positioned on the contour line sequence , the point p1 is processed on the contour line sequence positioned around the point p1 by the same processing as step S425 or Sixteen peripheral points located on the step region representative point sequence are further detected, and among these peripheral points, the point is in the steepest direction as viewed from the point p1, and the selected lattice point is as viewed from the point p1. The secondary steepest azimuth point q1 in the reverse direction is detected as the secondary steepest azimuth point with respect to the selected lattice point. Similarly, when the point p2 is located on the contour point sequence , the corresponding secondary steepest azimuth point q2 is detected. The coordinates and altitudes related to these points q1 and q2 are stored in the secondary steepest direction q1 coordinate 286, q1 altitude 287, secondary steepest direction q2 coordinate 288, and q2 altitude 289 for the selected grid point in the steepest direction data 28. Let When any of the points q1 and q2 is on the step region representative point sequence , a specific value representing the step region point is stored as the altitude as in the case described above (step S427D). As can be seen from the above, when either of the steepest azimuth points p1 and p2 is a point on the step region representative point sequence, the secondary steepest azimuth point q1 or q2 with respect to that point is not detected.

  It is determined whether or not a step region point is included in the points p1, p2, q1, q2 with respect to the selected grid point obtained as described above (step S428A). This determination can be made based on whether or not the elevation of each of the points p1, p2, q1, and q2 with respect to the selected grid point is a specific value that represents the step region point. If none of the points p1, p2, q1, and q2 with respect to the selected grid point is a step area point, the selected grid point is on a normal slope with no step area nearby, and the slope point is the steepest attribute. Store in the azimuth data 28 (step S428B). Hereinafter, the grid point having this attribute may be referred to as an inclined point or an inclined ground grid point. At this time, the route connecting points p1 and q1 is the steepest route with respect to the contour line where each is located, and the route connecting points p2 and q2 is the steepest route with respect to the contour line where each is located. If any of the points p1, p2, q1, q2 with respect to the selected grid point is a step area point, the step area adjacent point is stored in the steepest azimuth data 28 as an attribute of the selected grid point (step S428C). Hereinafter, the lattice point having this attribute may be referred to as a step region adjacent point or a step region adjacent lattice point. When the process for the selected grid point is completed as described above, it is determined whether or not there is an unprocessed grid point (step S429). If there is an unprocessed grid point, the process returns to step S421, and the unprocessed grid point is processed. When there is no grid point, the processing of the steepest azimuth search unit 42 ends.

FIG. 9 is a diagram illustrating an example of a contour map image including selected grid points having various attributes. FIG. 5A shows an example of a contour map image when the selected grid point s0 is a flat grid point having an elevation specified by the contour line sequence data 241. When the selected grid point s0 is a flat spot, the steepest bearing points p1 and p2 are detected, but the secondary steepest bearing points q1 and q2 are not detected. FIG. 6B shows the steepest azimuth points p1 and p2 and the secondary steepest azimuth points q1 and q2 when the selected grid point s0 is on a sloping ground and there is no step region in the vicinity thereof. An example is shown. FIG. 4C shows an example in which the selected grid point s0 is on a slope and is a step region adjacent point having a step region representative point sequence 26 in the vicinity thereof. In this example, the steepest azimuth points p1 and p2 are detected with respect to the selected lattice point s0, and the corresponding secondary steepest azimuth point q1 is detected because the point p1 is on the contour point sequence . Since the point p2 is on the step region representative point sequence 26, the secondary steepest azimuth point q2 with respect to the point p2 is not detected.

Returning to FIG. 1, when the processing of the steepest azimuth search unit 42 ends, the altitude data generation program 40 represents a step region representative among a plurality of adjacent points detected with respect to the lattice point. For the first type of lattice points that do not include the adjacent points located on the point sequence , the elevation of the first type of lattice points is determined based on the positions and elevations of the plurality of adjacent points. However, among the plurality of grid points, for the second type grid points in which the proximity points on the step region representative point sequence are included in the plurality of proximity points detected for the grid points, Used in place of the neighboring points on the area representative point sequence , additionally detected at least one other neighboring point that is not on the step area representative point sequence and is not detected on the stepped area representative point sequence, and at least the additional point is detected. The altitude of the second type grid point is determined based on the position and altitude of at least one other adjacent point.

  More specifically, the elevation data generation program 40 executes the elevation calculation unit 43 for determining the elevation of each grid point. The altitude calculation unit 43 determines the altitude of each grid point based on the steepest azimuth data 28 generated by the steepest azimuth search unit 42. In the present embodiment, the altitudes of grid points that are adjacent to the step region are determined in consideration of the presence of the step region. That is, the altitude calculation unit 43 calculates the altitude according to a different procedure depending on the attribute of each grid point determined by the steepest direction searching unit 42. When calculating the altitude of grid points that are adjacent to the step region, data of surrounding inclined grid points are used. For this reason, first, the altitude of the inclined grid point is calculated, and then the altitude of the grid point having other attributes is calculated.

  FIG. 10 is a schematic flowchart of the processing of the altitude calculation unit 43. First, an inclined ground grid point whose attribute is an inclined point and whose altitude is not determined is selected (step S431A). This selection is a grid point whose attribute is an inclined point in the steepest azimuth data 28, and an altitude is not stored for a grid point having the same coordinates in the altitude data 29 (FIG. 1). This can be done by detecting.

  After that, based on the data regarding the steepest azimuth points p1 and p2 and the secondary steepest azimuth points q1 and q2 determined for the selected inclined ground point, the altitude calculation for the inclined point is performed to calculate the altitude of the lattice point. An equation is determined (step S431B), the determined altitude calculation formula is used to determine the altitude of the inclined grid point, and the determined altitude is stored in the altitude data 29 (FIG. 1) as the altitude of the grid point. (Step S431C). Details of these steps S431B and S431C will be described later. Thereafter, it is determined whether or not there is an inclined grid point whose attribute is the inclined point and the altitude is not determined (step S431D). If there is, the process returns to step S431A and the above processing is repeated. If not, the process moves to step S432A.

  In step S432A, a flat grid point whose attribute is a flat point and whose altitude is not determined is selected. After that, for the selected flat grid point, the altitude of the steepest azimuth point p1 or p2 determined for the grid point is stored as it is in the altitude data 29 (FIG. 1) as the altitude of the grid point ( Step S432B). Thereafter, it is determined whether or not there is still a flat grid point whose attribute is a flat spot and the altitude is not determined (step S432C). If there is, the process returns to step S432A and the above processing is repeated. If not, the process moves to step S433A.

  In step S433A, step area adjacent grid points whose attributes are step area adjacent points and whose altitude is not determined are selected. Next, it is determined whether or not both of the steepest azimuth points p1 and p2 determined with respect to the lattice point that is the adjacent step region adjacent point are step region points (step S433B). This determination can be made based on whether or not the elevations of the points p1 and p2 in the steepest azimuth data 28 corresponding to the selected grid point are specific values that do not represent a normal elevation. When both p1 and p2 are step region points, the selected lattice point is located in the region sandwiched between the two step regions, and the contour lines in the vicinity are farther than those step regions. Since the altitude of the grid point cannot be automatically determined, a specific value indicating that the altitude cannot be determined is stored in the altitude data 29 instead of the altitude of the grid point, or the altitude data 29 is input by the user to input the altitude. (Step S433C). When the user determines the altitude, the user estimates and inputs the altitude of the selected grid point based on the position of the two step areas, the position of the contour line around the step area, and the altitude. Thereafter, the process proceeds to step S433D.

  When it is determined in step S433B that at least one of p1 and p2 is not a step region point, the step region adjacent point altitude calculation unit 50 that calculates the altitude of the grid point that is the step region adjacent point is activated. Details of the processing will be described later. Thereafter, the process proceeds to step S433D. In step S433D, it is determined whether or not there is still a step region adjacent grid point whose attribute is the step region adjacent point and the altitude is not determined, and if there is, return to step S433A and repeat the above processing. If not, the process moves to step S434A.

  In the present embodiment, the altitude of the grid point whose attribute is the step region point is not calculated. Therefore, a specific value indicating that the altitude cannot be determined instead of the altitude is stored in the altitude data 29 for the grid point whose attribute is the step area point and the altitude is not determined. For this reason, in step S434A, step area grid points whose attributes are step area points and whose altitude is not determined are selected. Next, a specific value indicating that the altitude cannot be determined is stored in the altitude data 29 for the selected grid point which is the step area point (step S434B). Thereafter, it is determined whether or not there is still a grid point whose attribute is the step region adjacent point and the altitude is not determined (step S434C), and if there is, returns to step S434A and repeats the above processing. If not, the processing of the altitude calculation unit 43 ends.

FIG. 11 is a diagram for explaining an example of determining the elevation calculation formula for the sloped point in step S431B of FIG. 10 and the calculation of the elevation of the sloped grid point in step S431C. In FIG. 4A, the horizontal axis represents coordinates S on a straight line in which broken lines connecting points q2, p2, p1, and q1 are arranged on the contour line sequence while maintaining the distance between the points. Points Sq2, Sp2, Sp1, and Sq1 represent positions on the corresponding straight line corresponding to the points q2, p2, p1, and q1 on the polygonal line, respectively, and S0 is a selected lattice point s0 that is an inclined ground lattice point. Represents the position on the straight line with respect to. The origin of the coordinates of the straight line (horizontal axis) may be determined as an arbitrary point.

  L1, L21, L22, and L3 are respectively the distance between the points Sp1 and Sq1, the distance between the points S0 and Sp1, the distance between the points Sp2 and S0, and the distance between the points Sq2 and Sp2. Represents the distance. The vertical axis represents the altitude, and hp1, hp2, hq1, and hq2 represent the altitudes at the points p1, p2, q1, and q2, respectively, and these altitudes are contour line sequence data 21A as the altitudes of the contour lines that pass through the respective points. Is already stored in the steepest direction data 38 corresponding to the selected grid point. H1, H2, and H3 represent an elevation difference between points q1 and p1, an elevation difference between points p1 and p2, and an elevation difference between points p2 and q2, respectively.

  FIG. 4B shows a three-dimensional Hermitian function of the distance S on the broken line used as an example of a calculation formula for calculating the altitude of the lattice point s0. This function is used as the altitude calculation formula for the sloped point. FIG. 6C is a diagram showing conditions for determining the function f (S). Reference numerals 51 and 52 indicate that the elevations at the points p1 and p2 are the elevations hp1 and hp2 of the contour lines at the points p1 and p2, respectively, and α and β indicate average gradients described later.

When the Hermitian function is determined by the first-order difference method, α and β are given by reference numerals 55 and 56, respectively. Reference numeral 55 represents an average gradient α between the points p 2 and q 1, reference numeral 56 represents an average gradient β between the points q 2 and p 1, and reference numeral 53 represents a derivative of the function f (S) at the point p 1. (Gradient) is equal to the average gradient α, and reference numeral 54 indicates that the differential coefficient (gradient) of the function f (S) at the point p2 is equal to the average gradient β. Under these six conditions, the coefficients a, b, c, and d of the three-dimensional function shown in FIG. In this way, the altitude calculation formula for the inclination point is determined.

  In step S431B of FIG. 10, the inclination point elevation calculation formula shown in FIG. 11B is determined based on the above consideration. In step S431C of FIG. 10, the horizontal formula corresponding to the grid point s0 in the determined calculation formula is determined. By inputting the coordinate S0 on the axis, the elevation at the lattice point s0 is calculated.

  As described above, the altitude calculation unit 43, when the selected grid point is not the step region adjacent point, that is, any of p1, p2, q1, and q2 that are adjacent points that satisfy the predetermined first condition of the selected grid point. Is not a step region point, the altitude of the selected grid point is determined based on the position and altitude of those adjacent points.

FIG. 12 is a diagram illustrating an example of a contour map image in which a selected grid point is determined to be a step region adjacent point because one of the steepest azimuth points p1 and p2 corresponding thereto is a step region point. In the figure, the steepest cardinal points p1 is above contour C 2, other steepest cardinal points p2 indicates an example in which the stepped region point overlying stepped area representative point sequence 2 6 to the selected grid point s0. It is assumed that the secondary steepest bearing point q1 corresponding to the point p1 is on the contour line C1. The secondary steepest azimuth point q2 with respect to the point p2 is not detected.

FIG. 13 is a diagram illustrating an example of a contour map image in which a selected grid point is determined to be a step region adjacent point because at least one of the secondary steepest azimuth points q1 and q2 corresponding to the selected lattice point is a step region point. . In the figure, the steepest azimuth points p1 and p2 with respect to the selected grid point s0 are on the contour point sequence C5 and C6, respectively, and the secondary steepest azimuth point q2 is a step region point on the step region representative point sequence 26. An example is shown. It is assumed that the secondary steepest azimuth point q1 is on the contour line C7. In the figure, points A and B are inclined ground grid points closest to the point q2 and located on both sides of the line segment connecting the points p2 and q2, and the points p 1a , p 2a , q 1a , and q 2a are lattice points. A steepest azimuth point for A and a secondary steepest azimuth point. Points p 1b , p 2b , q 1b and q 2b are the steepest azimuth point and the second steepest azimuth point with respect to the lattice point B. Note that the elevation calculation unit 50 for the step region adjacent point is described below even when the point q2 is a step region point instead of the point q1, or when both the points q1 and q2 are both step region points. The description in the case where is a step region point can be applied.

  FIG. 14 is a schematic flowchart of the processing of the step area adjacent point elevation calculation unit 50. First, it is determined whether or not at least one of the steepest azimuth points p1 and p2 with respect to the selected grid point s0 is a step region point (step S501). In the case of FIG. 12, the steepest bearing point p2 is a step region point, and in FIG. 13, neither p1 nor p2 is a step region point.

In the case as shown in FIG. 12, the steepest azimuth point p2 of the selected grid point is the step region point, and it is difficult to accurately estimate the altitude. Therefore, it is difficult to estimate the altitude of the selected grid point s0. For this reason, in the present invention, the selected grid point s0 that is determined to be adjacent to the step area adjacent point because it is located in the vicinity of the step area point (p2) is another condition that satisfies the predetermined second condition of the selected grid point. The proximity point is detected, and the altitude of the selected grid point is determined based on at least the position and altitude of the other proximity point. More specifically, the terrain around the selected grid point, which is the adjacent point of the step area, is estimated to be close to the terrain at the inclined grid point, which is an inclined point located in the vicinity, except for the step area. . Therefore, when one of the two steepest azimuth points p1 and p2 with respect to the selected grid point is a step area point, the altitude calculation unit 43 adds a grid point that is the nearest ground grid point to the selected grid point. To detect.
In this case, the altitude calculation formula for the inclined grid points located on one side is used in the case where the altitude calculation formula for the plurality of inclined grid points located on both sides of the line segment connecting the selected grid point s0 and the steepest bearing point p2 is used. It is considered that the altitude of the selected grid point can be estimated more accurately than the case. For this reason, in the present embodiment, the elevation of the selected grid point is estimated using an elevation calculation formula for a pair of inclined ground grid points located on both sides of the line segment connecting the selected grid point s0 and the steepest bearing point p2. .

  At that time, the length of the polygonal line passing through the neighboring inclined grid point is usually different, and when the length of the polygonal line passing through the selected inclined grid point is longer than the length of the polygonal line passing through the neighboring inclined grid point, To determine the elevation of the selected grid point reflecting the topography around the grid point, extend the length of the polyline that passes through the nearby inclined grid point to be equal to the length of the polyline that passes through the selected grid point. It is desirable to use an altitude calculation formula for neighboring grid points. Conversely, when the length of the polygonal line passing through the selected grid point is shorter than the length of the polygonal line passing through the neighboring inclined grid point, the length of the polygonal line passing through the neighboring inclined grid point is equal to the length of the polygonal line passing through the selected grid point. It is desirable to use the altitude calculation formula of the neighboring grid points by shortening.

  Therefore, in the present embodiment, the two steepest azimuth points located on both sides of the selected grid point, the range of coordinates of the polygonal line connecting the selected grid point, and the steepest azimuth points located on both sides of the neighboring inclined grid point So that the range of coordinates on the polygonal line connecting the slope and the slope grid point is matched, for example, from 0 to 1, the latter length and coordinates are matched to the former length and coordinates, and the elevation relative to the slope grid point in the vicinity Use formulas.

  That is, if it is determined in step S501 that one of p1 and p2 (for example, p2) is a step region point, the process moves to step S502, where the two inclined slopes closest to the lattice point are selected for the selected lattice point. A pair of inclined ground grid points A and B located on both sides of a line connecting the points p1 and p2 are detected.

Altitude calculation formulas fa (Sa) and fb (Sb) for calculating the respective altitudes of the detected sloped grid points A and B have already been determined in step S431B of FIG. Here, Sa represents coordinates on a broken line passing through the steepest azimuth points p 1a and p 2a and the secondary steepest azimuth points q 1a and q 2a with respect to the point A. Similarly, Sb represents coordinates on a broken line passing through the steepest azimuth points p 1b and p 2b and the secondary steepest azimuth points q 1b and q 2b with respect to the point B. In step S503, instead of the variable Sa of the function fa (S a ), a function fap1p2 (Sa ′) that uses a variable Sa ′ normalized to be 0 to 1 between the points p 1a and p 2a is obtained. It is generated from fa (S a ). Similarly, instead of the variable Sb of the function fb (S b ), the function fb1p2 (Sb ′) that uses the variable Sb ′ normalized to be 0 to 1 between the points p 1b and p 2b is changed to the function fb. Generate from (S b ).

Next, in step S504, these two functions are added with weights, and a function f (S0 ′) for obtaining the elevation of the selected grid point s0 is determined as in the following equation (1).
f (S0 ′) = (ka / (ka + kb)) × fap1p2 (S0 ′)
+ (Kb / (ka + kb)) × fbp1p2 (S0 ′) (1)
Here, ka and kb are the distances on the contour line sequence from the selected grid point s0 to the nearest inclined grid points A and B, respectively, and S0 ′ is the selected grid on the polygonal line passing through the selected grid point s0. The coordinates of the points, S0 ′, are normalized so that the values are 0 and 1 at the points p2 and p1 on the horizontal axis corresponding to the broken line, respectively.

Next, in step S505, the coordinate S0 ′ of the selected grid point s0 is input to the obtained function variable, the elevation is obtained, and stored in the elevation data 29. Thus, even when the selected grid point is a step region adjacent point, the altitude can be obtained. In this way, the process of the step area adjacent point elevation calculation unit 50 when either of the steepest azimuth points p1 and p2 is the step area adjacent point ends. In this manner, the elevation of the selected grid point adjacent to the step region point p2 can be determined using the elevation calculation formula for the nearby inclined ground grid point. Adjacent selected grid points in the case where the point p1 is a step region point can be similarly determined using an elevation calculation formula for an inclined ground grid point in the vicinity of the point p1.
In Equation 1, as ka, a distance from the selected grid point s0 to a point on the polygonal line passing through the inclined ground grid point A having the same value as the variable S0 ′ may be used. The same applies to Kb. Further, as the inclined ground lattice points in the vicinity of the selected lattice point, more inclined ground lattice points than the pair of inclined ground lattice points as described above may be used.

As described above, when one of the points p1 and p2 (for example, p2) that is the proximity point of the selected grid point s0 is on the step region representative point sequence , the altitude calculation unit 43 sets the other proximity points close to the point p2. The grid points A and B, which are inclined ground grid points, are additionally detected, and the altitude of the second type grid point is determined based on the positions and altitudes of the other adjacent points (A and B) detected additionally. Has been decided. More specifically, using the altitude calculation formula determined for the polygonal line connecting the two steepest azimuth points (pa1 and pa2 or pb1 and pb2) for each of the points A or B and the grid point A or B. Thus, an altitude determination formula for the selected grid point is determined. Further, the altitude of the selected grid point s0 is determined based on the coordinates of the selected grid point on the broken line connecting the adjacent grid points p1 and p2 with respect to the selected grid point s0 and the selected grid point and the determined altitude determination formula. Yes. Since the coordinates of the selected grid point are normalized, and the normalized coordinates depend on the positions of the proximity points p1 and p2 and the selected grid point s0, the altitude of the selected grid point is the proximity. It is detected depending on the positions of the points p1 and p2.

  If it is determined in step S501 that neither of the points p1 and p2 is a step region adjacent point, it is determined from the definition of the step region adjacent point, and at least the secondary steepest azimuth point q1 or q2 with respect to the selected grid point is determined. One is a step area point. For example, in the case of FIG. 13, the point q2 is a step region point. In FIG. 12, one of the steepest azimuth points p2 of the selected grid point whose elevation is to be determined is on the stepped region, and the elevation of the selected grid point is replaced with another pair of inclined ground grid points instead of the point p2. It was determined. In FIG. 13, since the secondary steepest azimuth point q2 is on the stepped region, the altitude of the point q2 is estimated using a pair of inclined ground grid points in the vicinity of the point q2, as in FIG. It is expected that the elevation of the selected grid point can be determined using this.

  Therefore, in the step region adjacent point elevation calculation unit 50, when it is determined in step S501 that neither of the points p1 and p2 is a step region adjacent point as shown in FIG. 14, in step S506, the points q1 and q2 are calculated. It is determined whether or not any of them is a step region point. In the case of FIG. 13, it is determined that q2 is a step region point. In step S507, the same processing as in step S502 is performed on the determined step region point (q2 in FIG. 13), and nearby inclined ground grid points (grid points A and B in the case of FIG. 13) are detected. When the step area points determined in step S505 are both q1 and q2, the process of step S502 is executed for each.

Next, in step S508, with respect to the neighboring inclined ground grid points (lattice points A and B in the case of FIG. 13) detected with respect to the secondary steepest azimuth point (for example, q2) determined as the step region point. The same processing as S503 is executed to determine a normalized altitude calculation formula for each point. Further, in step S509, processing similar to that in step S504 is performed, and an altitude calculation formula for a line segment that connects the steepest azimuth point (p2) corresponding to the secondary steepest azimuth point (for example, q2) determined as the step region point. To decide. Then, obtained in step S510, the coordinate values S0 'of the stepped region point to the resulting formula (e.g., q2) to input (0 in the case of FIG. 13), the stepped region point elevations (e.g., q2) And stored in the altitude data 29.

  In this way, even when the secondary steepest azimuth point q2 is a step region point, the altitude can be estimated, so that the altitudes of the points p1, p2, q1, and q2 can all be determined. Accordingly, in step S511, the altitude calculation formula for the slope is determined in the same manner as in step S431B in the case where the selected grid point is a grid point shown in FIG. 10, and in step S512, the same as step S431C in FIG. In addition, the elevation of the selected grid point may be determined according to the obtained calculation formula. In this way, the processing of the step area adjacent point elevation calculation unit 50 ends, and the processing of the elevation calculation unit 43 also ends.

  As can be seen from the above, even when one of the secondary steepest azimuth points q1 and q2 (for example, q2) of the selected grid point is located on the step region, other adjacent points that satisfy other predetermined conditions with respect to the selected grid point As a result, the sloped grid point closest to the point q2 is detected, and the altitude of the point q2 is determined depending on the position and elevation of the sloped grid point, and then based on the points p1, p2, q1, and q2. Therefore, the altitude of the selected grid point is determined depending on the altitude and position of the other adjacent points. Of course, the altitude of the selected grid point also depends on the positions of the points p1 and q1, the altitude, and the position of the point q2.

Returning to Figure 1, the elevation data generating apparatus 1 to display the each of the plurality of contour lines included in the two-dimensional map image which includes a plurality of specific points such as a plurality of contour lines and the triangular point or a reference point in the sequence of points from an equal height line point sequence data specific point data representing the position and altitude of the plurality of specific points, capable of generating altitude data indicating the elevation of each grid point of the grid point group obtained by dividing the map in a grid It is configured.

As already mentioned, elevation data generating apparatus 1, based on equal contours point sequence data, for each grid point, the position and detects a predetermined first condition is satisfied more proximity points on the contour point sequence The altitude of the grid point is determined based on the positions and altitudes of the plurality of proximity points detected for the grid point.

Elevation data generating apparatus 1 may further, based on the previous SL like contours point sequence data and the specific point data, the second condition is satisfied at least one adjacent position on the contour point sequence given for each particular point Detecting a point, detecting a lattice point close to the specific point satisfying a predetermined third condition for the specific point, detecting the position and altitude of the specific point, and the specific point Based on the position and altitude of the at least one adjacent point of the specific point, the altitude of the adjacent grid point detected with respect to the specific point can be corrected.
That is, the altitude data generation program 40 executes the altitude correction unit 44 to correct the altitude of the grid points in the vicinity of the specific point after the altitude calculation unit 43 determines the altitude. The altitude correction unit 44 corrects the altitude of the lattice points in the vicinity of the specific point based on the altitude indicated by the specific point data such as the triangular point data 22A and the reference point data 22B.

  FIG. 15 is a schematic flowchart of the processing of the altitude correction unit 44. First, correction range data Dmax, which is an existence range of surrounding grid points whose elevation is to be corrected based on specific point data such as triangular point data and reference point data, is input to the user by the input device 31 (FIG. 1). (Step S441). For example, the correction range data Dmax may indicate the radius of the circle when the correction range is a triangular point or a circular range centered on the reference point, and the correction range is a square region surrounding the triangular point or the reference point. In some cases, the length of one side or half thereof may be specified. In either case, the range may specify the number of grid points included in the length instead of specifying the radius or the length of one side or half thereof.

  Next, one of a number of specific points indicated by the triangular point data 22A and the reference point data 22B is selected (step S442). Hereinafter, the selected specific point may be referred to as a selected specific point. The process of the steepest direction searching unit 42 is executed for the selected specific point (step S443). As described above, by this process, the coordinates and altitudes of the steepest azimuth points p1 and p2 and the coordinates and altitudes of the second steepest azimuth points q1 and q2 and the attributes of the selected specific points are selected with respect to the selected specific point. It is determined whether the point is an inclined point, a flat point, a step region adjacent point, or a step region point.

Next, the attribute of the selected specific point is discriminated (step S444), and when the attribute is an inclined point, an altitude calculation formula for an inclined land specific point for calculating the altitude of the selected specific point is determined (step S445). This determination method will be described later. Next, an altitude correction formula for a nearby inclined grid point is determined based on the obtained calculation formula (step S446). This determination method will also be described later. Based on the obtained altitude correction formula, the altitudes of the sloped graticule points around the selected specific point that are initially specified and within the correction range Dmax are sequentially corrected (step S447). It should be noted that correction using this altitude correction formula is not performed for neighboring grid points, flat grid points, step area adjacent grid points, and step area grid points. Thereafter, it is determined whether or not there are unprocessed triangle points and reference points (step S448), and if there are any, the process returns to step S442. When there is no more, the processing of the altitude correction unit 44 ends. Therefore, the condition of the specific point to which the correction can be applied in step S447 is that the specific point is determined as the slope specific point by the steepest search unit. Further, the conditions of the neighboring grid points corrected in step S447 are the inclined ground grid points, and the distance from the selected specific point is within the range designated by the user in advance.

When it is determined in step S444 that the attribute of the selected specific point is a flat point, an elevation correction formula for a flat grid point is determined (step S449), and the flat grid around the selected specific point is determined as in step S447. The elevation of the point is corrected (step S450). Therefore, the condition for the specific point to which the correction in step S450 can be applied is that the specific point is determined as a flat spot by the steepest search unit. Further, the conditions of the neighboring grid points corrected in step S450 are grid points determined as flat spots, and the distance from the selected specific point is within the range designated by the user in advance. Even if grid points other than the flat grid points are in the vicinity of the selected specific point , the altitude is not corrected in step S450 .

  After step S450, the process proceeds to step S448. As a result of the determination in step S444, when the selected specific point is a grid point other than the inclined ground grid point and the flat ground grid point (for example, a step area adjacent grid point or a step area grid point), the elevation correction based on the selected specific point is performed. Without processing, the process proceeds to step S448.

  When the surrounding grid point is a step region adjacent point, the altitude is estimated using information such as the altitude and position of the surrounding inclined ground grid point, as already described. Therefore, further changing the estimation based on the altitude of the selected specific point results in a double estimation, and therefore a desired result is not always obtained. Therefore, in the present embodiment, correction of the altitude for the step area adjacent point using the altitude of the selected specific point is omitted. However, such correction may be performed. In particular, any selected specific point is located in the vicinity of a grid point that is a step region adjacent point, and the difference between the altitude determined by the altitude calculating unit 43 relative to the former and the altitude of the selected specific point is a predetermined limit. If it is larger, the altitude may be corrected appropriately according to the altitude of the selected specific point. However, when the selected grid point is a step area point, the altitude calculation unit 43 has not determined the altitude, so the altitude correction unit 44 does not correct the selected grid point that is the step area point. .

Figure 16 is a diagram for explaining the procedure for determining the use slopes specific point altitude formula in step S44 5 in Fig. 15. In FIG. 6A, the steepest azimuth searching unit 42 uses, as an example, the steepest azimuth points B and C and the secondary steepest azimuth points A and D located on the contour line sequence based on the selected specific point In. It indicates that the position and elevation have been determined. In the figure, these points are point A, point B, point C, and point D in order from the lowest elevation. When the selected specific point In is an inclined land specific point, the points A, B, C, and D are all inclined points and are not step region adjacent points or step region points.

In FIG. 6B, the horizontal axis represents coordinates S on a straight line in which broken lines connecting points A, B, C, and D are arranged on the contour line sequence while maintaining the distance between the points. Points Sa, Sb, Sc, and Sd represent the coordinates on the horizontal axis corresponding to points A, B, C, and D on the polygonal line, respectively, and Sin represents the horizontal to the selected specific point In that is an inclined point. Represents a coordinate on the axis. Although the origin of the coordinate on the horizontal axis may be determined arbitrarily in principle, the coordinates of the points Sb and Sc are set to 0 and 1 in order to correct the altitude of the surrounding grid points described later. It is better to normalize the coordinates of the horizontal axis.

  L1, L21, L22, and L3 are the distance between the point Sc and the point Sd, the distance between the point Sin and the point Sc, the distance between the point Sb and the point Sin, and the distance between the point Sa and the point Sb, respectively. Represents the distance. The vertical axis represents the altitude, and ha, hb, hc, and hd represent the altitudes at points A, B, C, and D, respectively, and these altitudes are contour line sequence data 21A as the altitudes of the contour lines that pass through the respective points. Is given by. Hin is the altitude of the selected specific point In, and this altitude is given by the specific point data. H1, H21, H22, and H3 represent an elevation difference between points D and C, an elevation difference between points C and In, an elevation difference between points In and B, and an elevation difference between points B and A, respectively.

  An example of a function fr (S) used as an example of an expression representing the inclination near the selected specific point In is a function effective for points Sb to Sin on the horizontal axis, as indicated by 60 in FIG. It is given by fr1 (S) and a function fr2 (S) effective for Sc from the point Sin on the horizontal axis. Each of the functions is a three-dimensional Hermitian function of the distance S on the broken line (that is, on the horizontal axis with respect to the broken line), as illustrated in FIG. 11B. A set of these two functions is used as an altitude calculation formula for the slope specific point.

  FIG. 4D is a diagram showing conditions for determining the functions fr1 (S) and fr2 (S). Reference numerals 61 and 62 indicate that the elevations at the points B and In are contour elevations hb and hin at the points B and In, respectively, and reference numerals 63 and 64 indicate differential coefficients (gradients) at the points B and In of the function fr1. Indicates that the values β and γ are designated in advance. Reference numerals 65 and 66 indicate that the elevations at the points In and C are the elevations hin and hc of the contour lines at the points In and C, respectively, and reference numerals 67 and 68 indicate the differential coefficients (gradients) at the points In and C of the function fr2. Indicates that the values γ and α are designated in advance.

  When the Hermitian functions fr1 and fr2 are determined by the first-order difference method, the α, β and γ are given by reference numerals 69, 70 and 71, respectively. Reference numeral 69 represents an average gradient α between the points In and D, reference numeral 70 represents an average gradient β between the points A and In, and reference numeral 71 represents an average gradient γ between the points B and C. . Reference numeral 63 indicates that the gradient of the function fr1 (S) at the point B is equal to the average gradient β, and reference numeral 64 indicates that the gradient of the function fr1 (S) at the point In is equal to the average gradient γ. Indicates that the gradient of the function fr2 (S) at the point In is equal to the average gradient γ, and reference numeral 68 indicates that the gradient of the function fr2 (S) at the point C is equal to the average gradient α. Under these conditions, the coefficients a, b, c and d of the two three-dimensional functions called functions fr1 (S) and fr2 (S) are determined. Thus, the functions fr1 (S) and fr2 (S) are determined, and the altitude calculation formula fr (S) for the slope specific point is also determined.

Figure 17 is a diagram for explaining the procedure for using the above-obtained slope specific point for the altitude calculation equation fr (S), determines a slope for the altitude correction equation in step S44 6 in FIG. 15 is there. In the figure, the selected specific point In, the steepest azimuth points B and C determined for the selected specific point In, the lattice point R to be corrected for the altitude located in the vicinity of the selected specific point In, and the maximum of the lattice points. Steep bearing points pr1 and pr2 are shown.

The elevation correction formula for the inclined ground grid point representing the corrected altitude of the correction target grid point R is given by the following formula fm (S).
fm (S) = (1−D / Dmax) × fr (S) + (D / Dmax) × f (S) (2)
Here, f (S) is an altitude calculation formula for an inclined grid point that gives an altitude on the polygonal line connecting the points pr1 and pr2 of the correction target grid point R, and is determined in step S431B of FIG. The coordinates on the straight line are normalized so that the coordinates for the points pr1 and pr2 on the line when the broken line is extended to a straight line are 0 and 1. In the above equation 2, as the value of the variable S, the coordinate value S0 of the correction target grid point R on the broken line is used. f r (S) is determined in step S44 5, is altitude formula gradient specific point for the selected specific point. This variable S is also determined to have values 0 and 1 corresponding to points B to C. Dmax indicates the correction application range data initially designated by the user, and D represents the distance from the selected specific point In to the target grid point R.

According to Equation 2, when D = 0, fm (S) is equal to fr (S) and coincides with the elevation of the point on the broken line passing through the selected specific point, and when D = Dmax, fm It can be seen that (S) is equal to f (S) and is not corrected. When D = Dmax / 2, fm (S) is (fr (S) + f (S)) / 2. Therefore, it can be seen that the influence of the altitude of the selected specific point decreases according to the distance from the selected specific point. The distance D is not limited to the distance D defined as described above, and other values may be used. Needless to say, the correction formula 2 itself may be changed. When the correction target grid point R is a grid point that is an inclined point, the above equation 2 is an altitude correction formula for the inclined ground grid point determined in step S446 of FIG.

FIG. 18 is a diagram illustrating a procedure for determining the elevation correction formula for a flat ground grid point in step S449 of FIG. 15 executed when the selected specific point is a flat spot. In FIG. 5A, it is assumed that the lattice point R is on the flat ground within the contour line C1 on the contour point sequence having the contour lines C1, C2, and the like. In the figure, pr1 and pr2 are examples of two steepest azimuth points detected with respect to the lattice point R. When the selected specific point In is determined to be a flat spot as a result of executing the steepest azimuth searching unit 42 while ignoring the altitude of the selected specific point In during the execution of the altitude correcting unit 44 of FIG. The altitude of the grid point R can be corrected based on the positional relationship between the selected specific point In and the lattice point R to be corrected in the vicinity thereof, the altitude of the selected specific point, and the altitude of the flat land. Since the selected specific point In is displayed as a point existing on the map on which the contour lines are described, the selected specific point In is also represented as a point on the plane on which the lattice point R is located in the figure. For the following explanation of altitude correction, the point located in the vertical direction of this specific point In, the point having the altitude of this specific point is shown as In *, and the altitude is corrected in the vertical direction of the grid point R. The point after this is shown as R *.

  Specifically, a line connecting the selected specific point In and the lattice point R is extended to the rear of the lattice point R to detect the intersection Q with the contour line C1. Actually, the intersection point Q may be located far from the selected specific point In depending on the shape and position of the contour line C1, but the intersection point Q does not depend on the distance between the point and the selected specific point In. The selected specific point In for correcting the altitude of the grid point in the vicinity of the selected specific point In is the same as the adjacent points B and C detected when the selected grid point shown in FIG. Think of it as a close point. Since the point Q is a point on the contour line C1, the altitude is equal to the altitude hpt indicated by the contour line C1. The distance D from the selected specific point In is used as a variable along the straight line 80 on the plane connecting the selected specific point In and the point Q. The elevation of the point on the straight line 90 located in the vertical direction of the selected specific point In and connecting the point In * having the elevation of the specific point In and the point Q is corrected to the point at the distance D on the straight line 80. Can be used in a correction formula representing Reference numeral 72 in FIG. 6B is an altitude correction formula indicating the corrected altitude fm (D) represented by the straight line 90.

FIG. 6C shows conditions regarding the correction formula fm (D). First, as indicated by reference numeral 73, the corrected altitude fm is equal to the altitude hin of the selected specific point at the selected specific point In. Reference numeral 74 indicates that the corrected altitude fm at the point Q is equal to the altitude hpt of the original contour line C1. Under these conditions, the coefficients a and b of the correction formula indicated by reference numeral 72 are determined. As a result, assuming that the distance from the selected specific point In to the point Q is Dq, the altitude correction formula fm (D) at the position of the distance D is expressed by the symbol 75 in FIG. When the distance between the grid point R and the selected specific point In is Dr, the corrected altitude for the grid point R, that is, the altitude fm (Dr) of the point R * is as shown by reference numeral 76 in FIG. Become.
The present invention is not limited to the above embodiments, modifications within the scope not changing the gist of the invention may also be modified not needless to say. For example, in the above embodiment, in order to determine the position of the lattice point, a plurality of points on the contour line in the vicinity of the lattice point are determined by the steepest azimuth method. May be determined.

1 is a schematic block diagram of an embodiment of an elevation data generation apparatus according to the present invention. It is a figure which shows some examples of contour map image data. It is a figure which shows the example of a level | step difference area | region symbol image and a level | step difference area | region representative point sequence . It is a figure which shows the example of the standard pattern group for level | step difference area | region symbol image detection. It is a schematic flowchart of the process of a level | step difference area extraction part. It is a figure which shows a level | step difference area | region representative point sequence typically. It is a figure which shows the example of the steepest direction data. It is a schematic flowchart of a process of the steepest direction search part. It is a figure which shows the example of the contour map image containing the grid point of various attributes. It is a schematic flowchart of the process of an altitude calculation part. It is a figure for demonstrating the example of the determination of the altitude calculation formula for inclination points, and the calculation of the altitude of an inclination point. FIG. 10 is a diagram illustrating an example of a contour map image in which a selected grid point is determined to be a step region adjacent point because one of the corresponding two steepest azimuth points is a step region point. It is a figure which shows the example of the contour map image from which the selected grid point is judged to be a step area adjacent point because at least one of the corresponding two secondary steepest bearing points is a step area point. It is a schematic flowchart of the process of the height calculation part for level | step difference area | region adjacent points. It is a schematic flowchart of the process of an altitude correction | amendment part. It is a figure for demonstrating the procedure which determines the altitude calculation formula for slope specific points in FIG. It is a figure for demonstrating the procedure which determines the elevation correction formula for slope specific points in FIG. It is a figure explaining the procedure which determines the elevation correction formula for flat land specific points performed when a selection specific point is a flat point.

Explanation of symbols

260 ... step region representative symbol image, 26, 26A, 26B, 26C ... step region representative point sequence, p1, p2 ... steepest azimuth point, q1, q2 ... secondary steepest azimuth point, s0 ... lattice point, In ... triangle Point or reference point.

Claims (11)

From contour line sequence data representing each of a plurality of contour lines included in a two-dimensional map image including contour lines and step region symbols as point sequences, and step region representative point sequence data representing the step regions represented by the step region symbols. , An altitude data generation method for generating altitude data indicating the altitude of each grid point of a grid point group obtained by dividing the map into grids,
Based on the plurality of contour point sequence data and the step region representative point sequence data, for each grid point, a plurality of proximity points that are located on the contour point sequence data or the step region representative point sequence data and satisfy a predetermined condition are determined. A detection step to detect;
For each grid point, a determination step for determining whether or not a plurality of proximity points detected in the detection step includes a proximity point located on the step region representative point sequence data;
Of the plurality of grid points, the first type determined in the determination step that the plurality of proximity points detected in the detection step does not include a proximity point located on the step region representative point sequence data A first altitude determination step for determining the altitude of the first type of grid points based on the positions and altitudes of the plurality of adjacent points;
The second type of lattice determined in the determining step when the adjacent points on the step region representative point sequence data are included in the plurality of adjacent points detected in the detecting step among the plurality of lattice points. For the point, an additional detection step of adding and detecting other neighboring points of the grid point that do not exist on the step region representative point sequence data and satisfy other predetermined conditions;
A second altitude determination step for determining the altitude of the second type of grid points based on at least the positions and altitudes of the other adjacent points detected in addition to the second type of grid points;
The altitude data generation method characterized by including. A plurality of contour point sequence data representing each of the plurality of contour lines contained in a two-dimensional map image including a plurality of contour lines and a plurality of specific points, and specific point data representing the positions and elevations of the plurality of specific points From the altitude data generating method for generating altitude data indicating the altitude of each grid point of the grid point group obtained by dividing the map into grids,
A first detection step of detecting a plurality of proximity points located on the contour line sequence data and satisfying a predetermined first condition for each grid point based on the plurality of contour line sequence data;
A determination step of determining an altitude of the grid point based on the positions and altitudes of the plurality of proximity points detected in the first detection step for the grid point;
A second detection step of detecting at least one proximity point that is located on the contour line sequence data for each specific point and satisfies a predetermined second condition based on the plurality of contour line sequence data and the specific point data; ,
For the specific point, a third detection step for detecting a grid point that satisfies a predetermined third condition and is close to the specific point and whose altitude is to be corrected;
Based on the position and altitude of the specific point and the position and altitude of the at least one proximity point of the specific point detected in the second detection step with respect to the specific point, in the third detection step A correction step of correcting the altitude of the adjacent grid points detected with respect to the specific point;
The altitude data generation method characterized by including. From contour line sequence data representing each of a plurality of contour lines included in a two-dimensional map image including contour lines and step region symbols as point sequences, and step region representative point sequence data representing the step regions represented by the step region symbols. , An altitude data generation program for generating altitude data indicating the altitude of each grid point of the grid point group obtained by dividing the map into grids,
Based on the plurality of contour point sequence data and the step region representative point sequence data, a plurality of proximity points that are located on the contour point sequence data or the step region representative point sequence data for each grid point are detected. Detecting step to
For each grid point, a determination step for determining whether or not a plurality of proximity points detected in the detection step includes a proximity point located on the step region representative point sequence data;
Of the plurality of grid points, the first type determined in the determination step that the plurality of proximity points detected in the detection step does not include a proximity point located on the step region representative point sequence data A first altitude determination step for determining the altitude of the first type of grid points based on the positions and altitudes of the plurality of adjacent points;
The second type of lattice determined in the determining step when the adjacent points on the step region representative point sequence data are included in the plurality of adjacent points detected in the detecting step among the plurality of lattice points. For the point, an additional detection step of detecting by adding other adjacent points of the grid point that do not exist on the step region representative point sequence data and satisfy other constant conditions;
A second altitude determination step for determining the altitude of the second type of grid points based on at least the positions and altitudes of the other adjacent points detected in addition to the second type of grid points;
An altitude data generation program characterized by causing a computer to execute. The other proximity point that is detected in addition to the second type grid point includes a pair of grid points closest to the second type grid point. Elevation data generation program. The plurality of proximity points detected in the detection step with respect to each grid point are positioned in a plurality of steepest directions as viewed from the grid point, and are positioned on the contour line sequence data or the step region representative point sequence data. The altitude data generation program according to claim 3 or 4, comprising a plurality of proximity points. The plurality of proximity points detected in the detection step with respect to each lattice point are behind the plurality of proximity points located in the steepest azimuth as viewed from the proximity points on the contour line sequence data. The altitude data generation program according to claim 5, further comprising a proximity point located and located in the steepest direction. A plurality of contour point sequence data representing each of the plurality of contour lines included in a two-dimensional map image including a plurality of contour lines and a plurality of specific points, and specific point data representing the positions and elevations of the plurality of specific points From the elevation data generation program for generating elevation data indicating the elevation of each grid point of the grid point group obtained by dividing the map into grids,
A first detection step of detecting a plurality of proximity points located on the contour line sequence data and satisfying a predetermined first condition for each grid point based on the plurality of contour line sequence data;
A determination step of determining an altitude of the grid point based on the positions and altitudes of the plurality of proximity points detected in the first detection step for the grid point;
A second detection step of detecting at least one proximity point that is located on the contour point sequence data and satisfies a predetermined second condition for each specific point based on the plurality of contour point sequence data and the specific point data; When,
For the specific point, a third detection step for detecting a grid point that satisfies a predetermined third condition and is close to the specific point and whose altitude is to be corrected;
Based on the position and altitude of the specific point and the position and altitude of the at least one proximity point of the specific point detected in the second detection step with respect to the specific point, in the third detection step A correction step of correcting the altitude of the adjacent grid points detected with respect to the specific point;
An altitude data generation program characterized by causing a computer to execute. When any one of the specific points is on the inclined ground, with respect to the specific point, in the second detection step, as the at least one adjacent point, a plurality of adjacent points that are on the inclined ground and are located on the contour line sequence data Detect
The grid points to be corrected for the elevation detected in the third detection step with respect to the specific point are grid points on the inclined ground,
The correction step performs the correction based on the position and altitude of the specific point and the positions and altitudes of the plurality of adjacent points detected in the second detection step.
The altitude data generation program according to claim 7. When any specific point is on the ground, the at least one proximity point detected in the second detection step with respect to the specific point is a point on the level ground and on the contour line;
The grid point that is detected in the third detection step with respect to the specific point and whose altitude is to be corrected is a grid point on the flat ground.
The altitude data generation program according to claim 7. From the contour point sequence data representing each of a plurality of contour lines included in the two-dimensional map image including the contour line and the step region symbol as a point sequence, and the step region representative point sequence data representing the step region represented by the step region symbol. , An altitude data generation device that generates altitude data indicating the altitude of each grid point of a grid point group obtained by dividing the map into grids,
Based on the plurality of contour point sequence data and the step region representative point sequence data, for each grid point, a plurality of proximity points that are located on the contour line sequence data or the step region representative point sequence data and satisfy a predetermined condition are determined. Detecting means for detecting;
For each grid point, a determination unit that determines whether or not a plurality of proximity points detected by the detection unit includes a proximity point located on the step region representative point sequence data;
Of the plurality of grid points, the first type determined by the determination means that the plurality of proximity points detected by the detection means do not include a proximity point located on the step region representative point sequence data A first altitude determining means for determining the altitude of the first type of grid points based on the positions and altitudes of the plurality of adjacent points;
Of the plurality of grid points, a second type of grid that is determined by the determination means when a plurality of proximity points detected by the detection means includes a proximity point on the step region representative point sequence data. For the point, additional detection means for detecting by adding other adjacent points of the grid point that are not on the step area representative point sequence data and satisfy other predetermined conditions;
Second altitude determining means for determining the altitude of the second type of grid points based on the position and altitude of the other adjacent points detected in addition;
An altitude data generation device comprising: A plurality of contour point sequence data representing each of the plurality of contour lines included in a two-dimensional map image including a plurality of contour lines and a plurality of specific points, and specific point data representing the positions and elevations of the plurality of specific points From the elevation data generation device for generating elevation data indicating the elevation of each grid point of the grid point group obtained by dividing the map into grids,
First detecting means for detecting a plurality of proximity points that are located on the contour line sequence data and satisfy a predetermined first condition for each grid point based on the plurality of contour line sequence data;
Determining means for determining the altitude of the grid points based on the positions and altitudes of the plurality of proximity points detected by the first detection means for the grid points;
Second detection means for detecting at least one proximity point satisfying a predetermined second condition that is located on the contour point sequence data for each specific point based on the plurality of contour point sequence data and the specific point data; ,
For the specific point, a third detection unit that detects a lattice point that satisfies a predetermined third condition and is close to the specific point and whose elevation is to be corrected;
Based on the position and altitude of the specific point and the position and altitude of the at least one proximity point of the specific point detected by the second detecting unit with respect to the specific point, the third detecting unit Correction means for correcting the altitude of the adjacent grid points detected for the specific point;
An altitude data generation device comprising:

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