JP2012174067A - Method and device for drawing map polygon - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide 'a method and a device for drawing polygons' by which a gap is not generated between adjacent polygons when parts satisfying predetermined conditions with less peripheral shapes of the polygons are thinned among element points constituting the circumference in order to smooth the polygon display.SOLUTION: For all polygons of a drawn map, element points forming circumferences of the respective polygons are acquired, and edges are set for the respective polygons. For the element points constituting the edges, when predetermined conditions showing that variation of the peripheral shapes of the polygons is less is satisfied, thinning processing for deleting the element points is performed. When the thinning processing for deleting the element points is performed and when the edges match to edges constituting polygons adjacent to the polygons to which the thinning processing is performed at present, the above deletion is also reflected on the adjacent polygons since the element points are also automatically deleted. This processing is performed to all the edges and all the polygons.

Description

  The present invention relates to a map polygon drawing method for thinning and displaying element points forming the periphery of a polygon when drawing a polygon as a map background when displaying a map on a display, and more particularly to an apparatus for implementing the method. Implement a map polygon drawing method and method that can eliminate a gap caused by performing thinning processing on one side of adjacent polygons while not performing thinning processing on the other side. Relates to the device.

  In order to display a map, in addition to displaying it as a map book, in recent years, it has been often displayed on displays such as personal computers and navigation devices, personal digital assistants, mobile phones, etc. by converting the map into electronic data. By making such a map into electronic data, any point in the world can be freely displayed at any scale and with a favorite display method.

  In addition to recording electronic data maps on various data recording media such as DVDs and memory cards, they can be imported into various information devices through the Internet, etc., but such map data often has various scale levels. The road is divided into a coordinate set of nodes expressed by longitude and latitude. When displaying such a map, in addition to the road display layer, a polygon display layer for displaying the background on the map such as roads, buildings, facilities, sea, rivers, forests, mountains, etc. on the map screen, as well as the city name Many layers of data such as administrative data such as administrative district names, road names, intersection names, facility names, and facility icons and information data display layers for displaying map symbols are displayed in an overlapping manner. .

  The data for displaying the polygons is important display data for displaying the map in a manner that is easy for the user to understand, friendly, and attractive. This polygon data is prepared based on satellite photographs and survey maps, and when this polygon data is displayed on the map, the display data processing may be greatly burdened and the map drawing performance deteriorates. Therefore, the thinning process of the element points constituting the periphery of the polygon is performed so as to reduce the map drawing processing burden as much as possible.

  The thinning-out process of the element points forming the periphery of such a polygon is mainly performed as shown in FIG. In the example shown in FIG. 11, when a polygon P as shown in FIG. 11A exists, when a part of the element point 2 in FIG. 11 protrudes, the element point of the protruding part is thinned out. Whether or not the element point is deleted and thinned out when a predetermined condition indicating that there is little change in the shape of the surrounding polygon is satisfied. The conditions at that time are performed as shown in FIG.

  That is, first, the relationship between the element point 2 and the element point 3 on both sides of the element point 2 is measured, the angle α at the element point 2 is measured, and the α is a predetermined angle αa such as 170 degrees, for example. It is determined whether it exists between 180 degrees.

  Secondly, in the example shown in FIG. 11, a perpendicular line is drawn from the element point 2 to a straight line connecting the element point 1 and the element point 3 on both sides of the element point 2, and the length L at that time, that is, the element point 2 Is measured to determine whether the length L is equal to or less than a predetermined length La as a maximum value threshold. When both conditions are satisfied, the element point 2 is thinned out. ing. Even if such a determination condition satisfies the first condition, it is not preferable to thin out the element points when the distance between the element points 1 and 3 adjacent to the element point 2 is large.

  In the processing, the angle α is measured on the polygon side with the counterclockwise direction as the forward direction. Accordingly, in FIG. 11A, in the illustrated example, the element point 2 protrudes from the polygon, and therefore the angle α is 180 degrees or less, whereas the polygon in which the element point 2 is a recess, contrary to the illustration. In this case, since the angle α exceeds 180 degrees, the thinning process of the element point 2 is not performed in that case.

  As a result of the above processing, as shown in FIG. 11C, (1) when the angle α between the adjacent element points 1 and 3 is α1 for the element point 2 and is larger than the predetermined angle αa and not more than 180 degrees. (2) When the length L1 of the perpendicular to the straight line connecting adjacent element points is smaller than the predetermined length La, the element points are thinned out as shown in FIG. And 3 only. The part of the element point 2 that satisfies the condition for selecting the element points to be thinned out can be said to be a part with little change in the surrounding shape of the polygon. In addition to the above, various methods have been proposed as conditions for performing the thinning process.

  As a result of the thinning process of the element points as described above, many element points of the polygon are thinned out, the burden of polygon display processing is reduced, and the display of the entire map is accelerated, thus improving the map display speed of a specific point In addition, smooth display can be performed in scroll display from the current map display, change in map display scale, and the like.

  When a polygon is displayed in the map display, when a gap is generated between the polygons, the gap area is extracted, and the merge button is operated so that the gap can be merged with the adjacent polygon to be corrected. Such a technique is disclosed in Patent Document 1.

JP 2007-213524 A

  As described above, when drawing a map with electronic data, a technique for thinning out the element points forming the periphery of the polygon when the predetermined condition as described above is satisfied in order to reduce the display processing burden of the polygon serving as the background. Then, for example, gaps Sa and Sb as shown in FIG.

  That is, in the example shown in the drawing, as shown in FIG. 5A, when polygons A, B, and C are drawn using all element points, no gap is generated between the polygons. When the element point thinning process is performed, the polygon A is a portion where the element point thinning process is performed at a slight protruding portion, and the polygon B becomes a concave portion, and the element point thinning is performed at this portion. The example which did not exist is shown.

  Similarly, in the example shown in the figure, in the relationship between the polygon A and the polygon C, when the polygon C performs the thinning process of the element points at the slight protruding portion, the polygon A is a concave portion at that portion. In this example, element points are not thinned out in this portion. As a result, a gap Sb is generated here.

  The gap between the polygons generated by the thinning-out process of the element points of the polygons formed in this way is, for example, one sea polygon adjacent to another sea polygon in the sea polygon as shown in FIG. In the part R of the boundary of the polygon when connected to each other, it is hardly known in the wide area map display state as shown in the figure, but when enlarged and displayed as shown in FIG. The gaps Sa and Sb appear as a white background with no surrounding sea color.

  Although such a gap between polygons does not cause a big problem as a display of the map itself, the gap becomes more conspicuous as the map is enlarged, and the appearance of the map data is impressed and the appearance is not very good. For this reason, it has also been proposed to perform the process of filling the gap as in the above-mentioned patent document, but it requires an artificial operation for the process, and enormous effort is required to eliminate the gap between all polygons. Cost.

  In order to facilitate polygon display as described above, the process of thinning out the element points that form the periphery of the polygon is performed on the map data by the company providing the map data, and the map thus processed is processed. In addition to providing data, when raw data that has not been thinned out is provided, a map is displayed based on that data. For example, there is a case where the data is processed by a thinning software on a personal computer or navigation device. Yes.

  Therefore, when displaying polygons that are the background of a map, the present invention reduces the processing load of polygon display by thinning out the element points that form the periphery of the polygon under a predetermined condition. The present invention relates to a map polygon drawing method and an apparatus for executing the method, which can easily solve the problem that a gap is generated and the appearance of a map is deteriorated without requiring a trouble.

  In order to solve the above problems, the map polygon drawing method according to the present invention extracts all polygons included in a map to be drawn, acquires element points forming the periphery of each polygon for the extracted polygons, An element for map display is set when an edge is set at a part composed of a plurality of element points adjacent to each other for a polygon, and the element points constituting the edge satisfy a predetermined condition indicating that there is little change in the surrounding shape of the polygon. When a thinning process that deletes as a point is performed, and when the thinning process that deletes the element point is performed, the element point matches an element point that constitutes a polygon adjacent to the polygon that is currently being thinned. The thinning process is also performed to delete the element points of the adjacent polygon, and the thinning process is performed on all the element points constituting the specified edge, and then specified. The thinning process is performed on other edges constituting the polygon, the thinning process is performed on all the edges of the designated polygon, and then the element points are applied to all the extracted polygons. A thinning process is performed, and a polygon is drawn by the data subjected to the thinning process.

  According to another map polygon drawing method of the present invention, in the map polygon drawing method, after performing the thinning process on all edges of the specified polygon, polygons adjacent to the polygon are sequentially The thinning process is performed by designating.

  Further, in another map polygon drawing method according to the present invention, in the map polygon drawing method, at the time of setting the edge, at least the change in the surrounding shape of the polygon is small for the element points at the front and rear ends of the edge. An element point other than an element point satisfying a predetermined condition indicating the above is selected.

  According to another map polygon drawing method of the present invention, in the map polygon drawing method, when the edge is set, the element points at the front and rear ends of the edge have not only the predetermined condition but adjacent polygons. It is characterized by selecting changing element points.

  In addition, in the map polygon drawing method according to the present invention, when the edge is set in the map polygon drawing method, when the edge is in common with the edge of an adjacent polygon, the element points constituting the edge are: Corresponding data for corresponding element points in both polygons is created, and when the element point of one polygon is deleted by the thinning process, the thinning process is performed to delete the element point of the other polygon by the corresponding data. It is characterized by that.

  Further, in another map polygon drawing method according to the present invention, in the map polygon drawing method, when the element points of the one polygon are deleted by the thinning-out processing, the element points of the other polygon are determined by the correspondence data. When performing the thinning process, the element point is not subjected to the thinning process.

  Further, in another map polygon drawing method according to the present invention, in the map polygon drawing method, the predetermined condition indicating that the change in the surrounding shape of the polygon is small is formed by an element point adjacent to the indicated element point. The angle is within a predetermined angle.

  Further, in another map polygon drawing method according to the present invention, in the map polygon drawing method, the predetermined condition indicating that the change in the surrounding shape of the polygon is small is that a perpendicular line dropped on a straight line connecting adjacent element points is used. 2. The polygon drawing method according to claim 1, wherein the length is within a predetermined range.

  Another map polygon drawing method according to the present invention is characterized in that, in the map polygon drawing method, the thinned data is stored in a database as map display data.

  Another map polygon drawing method according to the present invention is characterized in that, in the map polygon drawing method, the thinned data is stored in a database as map display data.

  In order to solve the above problems, the map polygon drawing apparatus according to the present invention extracts a thinning process polygon extracting means for extracting all the polygons included in a map to be drawn, and a polygon extracted by the thinning process polygon extracting means. For each polygon extracted by the polygon peripheral forming element point acquiring means for acquiring the element points forming the peripheral edge of each polygon and the thinning processing polygon extracting means, an edge is formed at a portion composed of a plurality of adjacent element points. When the polygon peripheral edge setting means for setting the image and the element points constituting the edge set by the polygon peripheral edge setting means satisfy a predetermined condition indicating that there is little change in the polygon peripheral shape, the map display element points Element point thinning processing means for performing thinning processing to be deleted, and the element point thinning processing means deletes element points. If the element point matches an element point that constitutes a polygon adjacent to the polygon currently being thinned, the thinning process is also performed to delete the element point of the adjacent polygon. And performing the thinning process on all element points constituting the designated edge, and then performing the thinning process on other edges constituting the designated polygon. The thinning process is performed on all the edges of the image, and then the element points are thinned out on all of the extracted polygons, thereby generating data for drawing the polygons.

  Another map polygon drawing apparatus according to the present invention is the map polygon drawing apparatus, wherein the element point thinning processing unit performs the thinning process on all edges of the designated polygon. The thinning process is performed by sequentially specifying polygons adjacent to the polygon.

  According to another map polygon drawing apparatus of the present invention, in the map polygon drawing apparatus, in the polygon peripheral edge setting means, at the time of setting the edge, at least the element points at the front and rear ends of the edge An element point other than an element point that satisfies a predetermined condition indicating that there is little change in the surrounding shape is selected.

  In the map polygon drawing apparatus according to the present invention, in the map polygon drawing apparatus, the polygon peripheral edge setting means may set the predetermined condition for the element points at the front and rear ends of the edge when the edge is set. In addition to the above, element points where adjacent polygons change are selected.

In the map polygon drawing apparatus according to the present invention, in the map polygon drawing apparatus, when the edge is set by the polygon peripheral edge setting means in the element point thinning processing means, the edge of the polygon adjacent to the edge is set. When it is in common with an edge, for each element point constituting the edge, create corresponding data for the corresponding element point in both polygons,
When the element point of one polygon is deleted by the thinning process, the thinning process of deleting the element point of the other polygon by the correspondence data is performed.

  In the map polygon drawing apparatus according to the present invention, in the map polygon drawing apparatus, when the element point thinning processing unit deletes the element point of the one polygon by the thinning processing, the corresponding data Thus, when the thinning process of the element point of the other polygon is performed, the thinning process is not performed for the element point.

  In the map polygon drawing apparatus according to the present invention, the predetermined condition indicating that the change in the surrounding shape of the polygon is small in the map polygon drawing apparatus is formed by an element point adjacent to the designated element point. The angle is within a predetermined angle.

  Further, in another map polygon drawing apparatus according to the present invention, in the map polygon drawing apparatus, the predetermined condition indicating that the change in the surrounding shape of the polygon is small is that a perpendicular line dropped on a straight line connecting adjacent element points. The length is within a predetermined range.

  In another map polygon drawing apparatus according to the present invention, the thinned data is stored in a database as map display data in the map polygon drawing apparatus.

  In another map polygon drawing apparatus according to the present invention, the thinned data is stored in a database as map display data in the map polygon drawing apparatus.

  Since the present invention is configured as described above, when displaying polygons that are the background of a map, when thinning out the element points that form the periphery of the polygons under a predetermined condition in order to reduce the processing burden of polygon display, Then, it becomes possible to easily solve the problem that a gap is generated between adjacent polygons and the appearance of the map is deteriorated without requiring any trouble.

It is a functional block diagram of the Example of this invention. It is an operation | movement flowchart of the Example. It is an operation | movement flowchart of the element point thinning-out process performed in the Example. It is a figure which shows the example of the element point for every polygon. It is a figure which shows the example of the edge setting process of an adjacent polygon. It is a figure which shows the example of the element point correspondence table | surface of the edge for every polygon. It is a figure which shows the example of the thinning-out process of the polygon A. It is a figure which shows the example of the thinning-out process of the polygon B performed after that. It is a figure which shows the example of the thinning-out process of the polygon C performed after that. It is a figure which shows the state before the thinning process by this invention, and after a process. It is a figure which shows the example of the thinning-out process of the polygon component point proposed conventionally. It is explanatory drawing of the state which a clearance gap produces between polygons as a result of the same process. It is a figure which shows the actual example which a clearance gap produces between conventional polygons.

  Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a functional block diagram of a map polygon drawing apparatus according to the present invention that performs processing for preventing gaps between adjacent polygons, particularly when performing thinning processing of element points that form the periphery of a polygon. 1 is a functional block diagram that is primarily shown and that allows the invention to be implemented in various ways. In addition, in the same figure, the function part which performs each function can be said to be a means which performs each function.

  In the example of the apparatus that performs the thinning process of the element points that form the periphery of the display polygon in FIG. 1, the thinning process target selection unit 1 that mainly selects the target of the thinning process of the element points, and the thinning process target The thinning processing target selected by the selection unit 1 is provided with an element point thinning processing unit 2 that actually performs the thinning processing.

  In FIG. 1, for example, the both operate in cooperation with each other, and when the thinning process is performed on the polygon selected by the thinning process target selection unit 1, the edges therein, and the element points constituting the polygon as described later, the same When the processing for the next element point of the edge and all the element points of the same edge is completed, the same processing is performed for the next edge, and when the edge processing is completed, the other edges of the polygon are selected in order. Thus, the processing is completed for other polygons that require the current processing.

  The thinning processing target selection unit 1 includes a thinning processing polygon extraction unit 3 for extracting all polygons included in a map to be processed from now on. The thinning process polygon designation unit 4 finally designates all polygons of the map, but in order to perform the process in order, the polygons to be processed are designated in an appropriate order.

  The polygon edge forming element point acquisition unit 5 acquires all the element points that form the edges of the specified polygons and the polygons directly adjacent to the specified polygons as will be described later. Conventionally, these data are organized and recorded in the original data for displaying each polygon.

  The adjacent polygon detection unit 6 detects adjacent polygons for the polygons specified by the thinning processing polygon specification unit 4 as described above. The polygon edge forming element point acquisition unit 5 also performs processing for acquiring element points for these polygons as described above. As a result, when the polygon designated by the thinning processing polygon designation unit 4 is the polygon A as shown in FIG. Polygon detector 6 detects polygon B and polygon C.

  The polygon edge forming element point acquisition unit 4 acquires 24 element points of element points A1 to A24 for the polygon A and 17 element points of B1 to B17 for the polygon B. For C, 18 element points C1 to C18 are acquired.

  The polygon peripheral edge setting unit 7 sets an edge that forms a polygon peripheral edge for the polygon specified by the thinning processing polygon specifying unit 3 and the polygon detected by the adjacent polygon detection unit 6. The “edge” at this time is a predetermined condition such as an element point where an adjacent element point is bent by, for example, 10 degrees or more for each polygon, or a part where the adjacent polygon changes at that part although there is no large bend. A peripheral portion connecting characteristic element points is detected. Thereby, the “edge” as described above is determined.

  By such edge detection processing, in the example shown in FIG. 4, the element points A1 to A8 are substantially straight for the polygon A as shown in FIG. With respect to this edge, the counterclockwise direction in the polygon A is set as the forward direction, and similarly, the element points A8 to A14 are set as the edge 2.

  Also, when the element point A16 portion is bent at 10 degrees or less, this is not used as the end of the edge, and for the element point A17 portion, the adjacent polygon changes from polygon B to polygon C. Element points A14 to A17 are defined as edge 3 as end portions of the edge. As for the element point A18, like the element point A16, when it is a slight bend of, for example, 10 degrees or less, this is not used as the edge of the edge. Further, since the element points A20 to A1 are substantially on a straight line, this peripheral portion is set as the edge 5.

  Similarly, for the polygon B which is an adjacent polygon, since the edge 3 set in the polygon A is a common edge, the element points B1 to B4 are the element points of the edge 3. From this edge to the polygon B in the forward direction, the element points B4 to B6 are the edge 6, the element points B6 to B10 are the edge 7, and the bending of the element point B12 portion is small. Therefore, the element points B10 to B14 are set as the edge 8.

  Since the element points B14 to B1 of the polygon B are substantially linear, this is referred to as an edge 9. The edge 9 is a polygon adjacent to the polygon A and is configured in common with the element points C4 to C8 in the polygon C adjacent to the polygon B.

  Regarding the polygon C, the element points A17 to A20 are configured in the polygon A for the edge 4 of the polygon A, whereas the element points C1 to C4 are configured in common. The element points C4 to C8 of the polygon C constitute the edge 9 together with the element points B14 to B1 of the polygon B as described above.

  Since the element point C11 is less bent, it is not used as the edge of the edge, and the element points C8 to C15 are set as the edge 10. The element points CC15 to C1 are edges 11. As described above, a series of edges are set for the designated polygon A and the polygons B and C that are adjacent to the designated polygon A.

  The polygon peripheral edge setting unit 7 shown in FIG. 1 performs the edge setting as described above, and the edge constituent element point detection unit 8 detects the element points of each polygon that constitutes each edge as described above. The thinning process edge instruction unit 9 instructs the edge for performing the thinning process on the polygon designated by the thinning process polygon designation unit 4 and the polygon detected by the adjacent polygon detection unit 6.

  The thinning process element point designating unit 10 sequentially instructs the element points constituting the edges of the edges designated by the thinning process edge instruction unit 9. In this way, for example, when performing thinning processing of element points for the polygon designated by the current thinning processing polygon designating unit 4, the thinning processing edge instruction unit 9 sequentially instructs the edges constituting the polygon, The thinning process element point instruction unit 10 sequentially instructs the element points constituting the edge in the polygon for the edge. After all the specified polygon edges have been processed for the polygons to be thinned out, the same thinning processing is performed on adjacent polygons and the element points that make up the same. Is processed.

  The element point thinning processing unit 2 performs a process of thinning out the element points designated as described above that satisfy a predetermined condition, and basically performs the processing of FIG. 11 shown in the conventional example. Do. Among them, the thinning availability determination processing unit 11 performs processing for determining whether or not to thin out element points, and the adjacent element point angle of FIG. 11 measured by the adjacent element point angle measuring unit 12 therein. The angle α is measured. Based on the measured value, the adjacent element point angle predetermined range discriminating unit 13 performs the condition (1) αa <α1 ≦, as shown in FIGS. 11B and 11C and as described in the explanation of FIG. It is determined whether or not 180 degrees is satisfied.

  In addition, in the perpendicular length measurement unit 18 to the straight line between adjacent element points, as shown in FIGS. 11B and 11C, and as described in the explanation of the same figure, the straight line connecting adjacent element points is connected. It is determined whether the length L1 of the perpendicular is shorter than a predetermined length La, that is, whether L1 <La. Accordingly, the thinning availability determination processing unit 11 determines whether or not the conditions of the thinning conditions (1) and ′ (2) are satisfied, and performs thinning processing when all the conditions are satisfied.

  In the thinning flag processing unit 16, when the thinning availability determination processing unit 10 determines that a specific element point is thinned out, in the illustrated example, data to be thinned and drawn is formed as map drawing data. Therefore, a thinning flag is set at the element point. After that, for all the polygons, it is determined whether or not all the element points of all the edges are thinned out, and after performing the thinning flag processing, the polygon display data forming unit 18 displays the data for displaying the polygons. Form.

  As a result of the processing as described above, a polygon consisting of a large number of element points as shown in FIG. 1A becomes the minimum element point as shown in FIG. As shown by edge 3 and edge 4 in the same figure, when the thinning process is performed on one of the adjacent polygons, the edge is thinned regardless of whether the other side is thinned. As a result, the gap as shown in FIG. 13A is not generated between adjacent polygons.

  These thinning processes will be described in more detail in order according to the operation flow of FIGS. In the example of the thinning process for the display polygon peripheral edge forming element point in FIG. 2, the process starts with extraction of the polygon to be thinned first (step S1). This processing is performed as described above by the thinning processing polygon extraction unit 3 in FIG.

  Thereafter, polygons to be thinned out are designated in order (step S2). This processing is performed by the thinning processing polygon specifying unit 4 in FIG. Next, the element point of the designated polygon is acquired (step S3). In this process, the polygon edge forming element point acquiring unit 5 in FIG. 1 acquires the element point for the polygon specified by the thinning process polygon specifying unit 4. It is done by.

  Next, an adjacent polygon is detected for the designated polygon (step S4). This processing is performed as described above in the adjacent polygon detector 6 shown in FIG. Thereafter, element points of adjacent polygons are acquired (step S5). This processing is performed by detecting element points for the polygons detected by the adjacent polygon detection unit 6 in the polygon edge forming element point acquisition unit 5 of FIG. By such processing, element points are acquired for each polygon as shown in FIG. 4 as described above.

  Thereafter, the edge of the polygon periphery including the common element point of the polygon adjacent to the designated polygon is set (step S6). This processing is performed as described above by the polygon peripheral edge setting unit 7 of FIG. As a result, the edge 1 to edge 11 as shown in FIG. 5 are set as described above.

  Next, an element point for each polygon is associated with each edge (step S7). This process is shown in FIG. 6, and edge 1 to edge 5 exist for polygon A, and all the element points constituting these edges correspond to the forward direction. Similarly, for polygon B, edges 3, 6, 7, 8, and 9 exist, and the element points constituting the polygon B are edge A and polygon A is forward in the counterclockwise direction from A14 to A17. This indicates that the element points of polygon B corresponding to the element points correspond to B4, 3, 2, 1 in the opposite direction. For polygon B, the other edges are in the forward direction.

  Regarding the polygon C, the element point of the polygon A at the edge 4 is in the forward direction, whereas the element point of the polygon C is in the reverse direction by the same correspondence as described above. Similarly, for edge 9, when polygon B is in the forward direction, polygon C is in the reverse direction. The other edges of the polygon C are in the forward direction.

  For the edges constituting each polygon, the element points are shown for edges 1 to 11, respectively. Here, for example, the edge 3 of the polygon A and the edge 3 of the polygon B are common for the edge 3, and the edge 4 of the polygon A and the edge 4 of the polygon C are common for the edge 4. Regarding the edge 9, the edge 9 of the polygon B and the edge 9 of the polygon C are common.

  In the example of FIG. 2, the polygon element points are then thinned out as shown in FIG. In the example of the thinning process of the element points forming the periphery of the polygon shown in FIG. 3, the element points to be thinned first are sequentially designated (step S21). In the example shown in FIG. 3, it is determined whether or not a thinning flag has already been set for the element point designated thereafter (step S22).

  That is, the thinning flag is not yet set in the state that is initially activated in the process shown in FIG. 3, but after setting the thinning flag at the designated element point in step S28 described later in the subsequent process, step S29 is performed. When it is determined that the thinning check of all element points has not yet been performed, the process returns to step 21 and repeats the same processing by sequentially specifying new element points. Since it is not necessary to perform subsequent processing for the standing element point, the process returns to step S1 to instruct the next element point.

  When it is determined that the element point instructed in step S21 has not yet been thinned, the process proceeds to step S23 to measure the angle α1 on the polygon side between the designated element point and the adjacent element points (step S23). That is, in order to determine the condition (1) in FIGS. 11B and 11C, the angle α1 is measured.

  Thereafter, in step S24, it is determined whether or not the measured angle α1 is within 180 degrees. If it is determined that the angle exceeds 180 degrees, the process skips to step S29 assuming that no thinning process is performed for this element point, and returns to step S21 when it is determined that all element points have not been thinned out yet. The next element point is indicated. On the other hand, when it is determined that the angle α1 is within 180 degrees, the process proceeds to step S25, where it is determined whether or not the measured angle α1 exceeds a predetermined angle αa such as 170 degrees.

  When it is determined that the angle α1 measured here is smaller than the predetermined angle αa, it is determined that the portion is not suitable for thinning because there is a certain degree of bending, and the process proceeds to step S29 to perform the operation. On the other hand, when it is determined that the measured angle exceeds the predetermined angle αa, the process proceeds to step S26, and the length L1 of the perpendicular to the straight line connecting the adjacent element points is measured (step S26).

  In this process, the measurement for determining the condition (2) in FIGS. 11B and 11C is performed as described above. Based on the measurement result, the length L1 of the perpendicular is a predetermined length in step S27. It is determined whether or not it is La or less. Here, when it is determined that the length of the perpendicular is not equal to or less than the predetermined length La, it is determined that there is a certain amount of bending at that portion and it is not suitable for thinning, and the process proceeds to step S29 to perform the above operation.

  When it is determined in step S27 that the perpendicular length L1 is equal to or shorter than the predetermined length La, it is a time when all of the conditions (1) and (2) in FIGS. 11B and 11C are satisfied. Proceeding to S28, a thinning flag is set for the designated element point. Thereafter, the process proceeds to step S29 when it is determined at step S24, step S25, or step S27 whether or not all element points have been thinned out, and returns to step S21 to return to the next element. The point instruction is continued, and when it is determined that the thinning check of all the element points has been performed, the process proceeds to step S30, and the series of processes ends.

  After performing the process as shown in FIG. 3 in step S8 of FIG. 2, the process proceeds to step S9, and the polygons to be thinned out are sequentially designated. Here, since the processing of the polygon designated first by the above processing is completed, the processing is subsequently performed on the adjacent polygon. The thinning process similar to that shown in FIG. 3 is also performed for the polygon so designated. At this time, when the thinning flag is set for the previous polygon, the thinning process is not performed for the next polygon. Processing shall be performed.

  Thereafter, it is determined whether or not all adjacent polygons of the designated polygon have been thinned out (step S11). When it is determined that all of the adjacent polygons have not been thinned out yet, the process returns to step S9, and the next The operation is repeated by sequentially instructing polygons. On the other hand, when it is determined in step S11 that all adjacent polygons have been thinned, the process proceeds to step S12, where it is determined whether all the thinned polygons have been processed. After the subsequent processing of the adjacent polygons of the designated polygon, the above operation of performing the thinning process in step S10 is repeated until all of the polygons adjacent to the specified polygon are instructed. After that, when thinning processing is performed for all the polygons, the process proceeds to step S13, and element polygons with thinning flags are thinned to create display polygons.

  In the present invention, a device having the functional blocks shown in FIG. 1 is operated in order according to the operation flow shown in FIG. 2 and FIG. 3, so that a desired function can be performed. After the element points for each polygon are associated with the edge, the process shown in FIG. 7 is performed for the designated polygon A at first.

  In the example of thinning-out processing of the polygon A shown in FIG. 7, the constituent edges 1 to 5 of the polygon A are configured by element points as shown respectively. For example, the edge 1 is almost straight and other adjacent polygons Since there is no influence or the like, thinning processing is performed for elements other than the element points 1 and 8 that are the element points at the front and rear ends. In FIG. 7, the element points 1 to 8 at this time indicate that the corresponding element points of the polygon A are A1 to A8. The same element point correspondence table is shown below.

  The edge 2 of the polygon A is also subjected to thinning processing except for the element points at the front and rear ends. The edge 3 is composed of the common element points of the polygon A and the polygon B, but this part can be subjected to the thinning process of the element point 2, that is, A15 by the process in the polygon A. As a result, in the polygon B having the corresponding element point, a flag for thinning processing is set for the element point B3 of this portion. Thereafter, as will be described later, it is assumed that the thinning process has already been performed in the process using the polygon B, so that the thinning process is not particularly necessary.

  As for the edge 4 of the polygon A, as shown in FIG. 12B showing the conventional example, the thinning process is not performed on the element point 2 (A19) which is the bottom of the concave portion of this portion. However, after that, in the process of the polygon C shown in FIG. 9, the element point 2 is thinned out. The thinning process can be performed for the element point 3 (A19). For the edge 5, thinning processing is performed except for the edges at the front and rear ends.

  As a result, as shown in FIG. 7B, when the polygon A is composed of edges and component points as shown in FIG. 7B, the element points are arranged as shown in FIG. As for the edge 3 portion, the element points are thinned out by processing of the polygon A, and as a result, this portion is linearized. At the same time, since this process is also reflected on the polygon B side, the element points B2 and B3 of the polygon B are also thinned out. As a result, the polygons A and B are adjacent to each other without a gap.

  FIG. 8 shows the thinning-out process for the polygon B performed after the above-described processing of FIG. 7. With respect to the edge 3, the element points B2 and B3 are thinned out by the thinning-out process of the polygon A as described above. ing. As other specially mentioned edges, there is an edge 9 which is an edge common to the polygon C, but the element points are thinned out as shown in the processing of the polygon B to be processed first, and the correspondence of the polygon C is thereby performed. The thinning flag is set at the element points C4, 5, 6, 7, and 8 to be thinned out.

  As a result of the processing, as shown in FIG. 4B, for each element point of each edge of the polygon B, the edge 3 is thinned out by the processing of the polygon A as shown in FIG. For 9, the thinning process here is reflected in the polygon C.

  In the thinning process of the polygon C shown in FIG. 9, only the element point 3 is thinned out for each element point of the polygon A corresponding to the edge 4 in common in the edge 4 in particular. In this polygon C, as shown in FIG. 12 (b) showing the conventional example, the thinning process can be performed on the element point 2 as well. Therefore, the element point 2 (AA18, C3) can also be thinned out here. As a result, the element point A18 of the polygon A corresponding to the element point C3 of the polygon C is also reflected in this thinning. The edge 9 is thinned out in the processing of the polygon B as described above.

  As a result, finally, as shown in FIG. 9C and an enlarged view of the map display state as shown in FIG. As shown in FIG. 5, no gap is generated at the portion where the gap is generated between the polygons, and the conventional problem can be solved. In addition, all of this processing can be automated, and data that has been subjected to all thinning processing can be easily obtained. In addition, when the original data before thinning is provided, the device that draws the map can quickly display the polygon by the software that performs the above processing.

DESCRIPTION OF SYMBOLS 1 Thinning process object selection part 2 Element point thinning process part 3 Thinning process polygon extraction part 4 Thinning process polygon designation | designated part 5 Polygon peripheral formation element point acquisition part 6 Adjacent polygon detection part 7 Polygon peripheral edge setting part 8 Edge Formed element point detection unit 9 Thinning process edge instruction unit 10 Thinning process element point instruction unit 11 Decimation availability determination processing unit 12 Adjacent element point angle meter side unit 13 Adjacent element point angle predetermined area determination unit 14 Adjacent element point Perpendicular line length measurement unit 15 Perpendicular length less than predetermined value determination unit 16 Thinning flag processing unit 17 Thinning flag detection unit 18 Polygon display data forming unit

Claims (20)

Extract all polygons contained in the map to be drawn,
For the extracted polygons, obtain element points that form the periphery of each polygon,
For each polygon, set an edge at the part consisting of multiple element points adjacent to each other,
For the element points constituting the edge, when a predetermined condition indicating that there is little change in the surrounding shape of the polygon is satisfied, a thinning process for deleting as the map display element points is performed,
When the thinning process for deleting the element point is performed, if the element point matches the element point constituting the polygon adjacent to the polygon currently being thinned, the element point of the adjacent polygon is also deleted. To perform the thinning process,
After performing the thinning process on all element points constituting the designated edge, the thinning process is performed on other edges constituting the designated polygon, and all the specified polygons The thinning process is performed on the edge,
Thereafter, the element points are thinned out for all the extracted polygons,
A polygon drawing method, wherein a polygon is drawn by the data subjected to the thinning process.   2. The polygon drawing according to claim 1, wherein after performing the thinning process on all edges of the designated polygon, the thinning process is performed by sequentially designating polygons adjacent to the polygon. Method.   When setting the edge, element points other than an element point satisfying a predetermined condition indicating that there is little change in the surrounding shape of the polygon are selected for the element points at the front and rear ends of the edge. The polygon drawing method according to claim 1.   4. The polygon rendering method according to claim 3, wherein, when setting the edge, for the element points at the front and rear ends of the edge, in addition to the predetermined condition, an element point at which an adjacent polygon changes is selected. When the edge is set and the edge is in common with the edge of the adjacent polygon, for the element points constituting the edge, corresponding data for the corresponding element points in both polygons is created,
2. The polygon rendering method according to claim 1, wherein when the element point of one polygon is deleted by the thinning process, the thinning process of deleting the element point of the other polygon by the correspondence data is performed.   When the element point of the one polygon is deleted by the thinning process, when the element point of the other polygon is thinned by the corresponding data, the thinning process is not performed for the element point. The polygon drawing method according to claim 5.   2. The polygon rendering method according to claim 1, wherein the predetermined condition indicating that the change in the surrounding shape of the polygon is small is that an angle formed by an adjacent element point with respect to the designated element point is within a predetermined angle. .   2. The polygon drawing method according to claim 1, wherein the predetermined condition indicating that the change in the surrounding shape of the polygon is small is that the length of a perpendicular line drawn to a straight line connecting adjacent element points is within a predetermined range.   The polygon drawing method according to claim 1, wherein the thinned data is stored in a database as map display data.   The polygon drawing method according to claim 1, wherein the thinned data is stored in a database as map display data. A thinning process polygon extracting means for extracting all the polygons included in the map to be drawn;
For polygons extracted by the thinning processing polygon extraction means, polygon edge forming element point acquisition means for acquiring element points forming the edge of each polygon;
For each polygon extracted by the thinning processing polygon extracting means, a polygon peripheral edge setting means for setting an edge in a portion composed of a plurality of element points adjacent to each other;
Element points that are subjected to thinning processing to be deleted as element points for map display when a predetermined condition indicating that there is little change in the surrounding shape of the polygon is satisfied for the element points constituting the edge set by the polygon peripheral edge setting means A thinning processing means,
In the element point thinning processing means, when the thinning process for deleting an element point is performed, when the element point matches an element point constituting a polygon adjacent to the polygon currently being thinned, Perform the thinning process to delete the element points of the adjacent polygon,
After performing the thinning process on all element points constituting the designated edge, the thinning process is performed on other edges constituting the designated polygon, and all of the designated polygon methods are performed. The thinning process is performed on the edges of
After that, the polygon drawing apparatus is characterized in that data for drawing a polygon is created by performing thinning processing of the element points on all of the extracted polygons.   In the element point thinning processing means, after performing the thinning processing on all edges of the designated polygon, the thinning processing is performed by sequentially specifying polygons adjacent to the polygon. The polygon drawing apparatus according to claim 11.   In the polygon peripheral edge setting means, at the time of setting the edge, with respect to the element points at the front and rear ends of the edge, at least element points other than the element points satisfying a predetermined condition indicating that the change in the peripheral shape of the polygon is small. 12. The polygon rendering apparatus according to claim 11, wherein the polygon rendering apparatus is selected.   The polygon peripheral edge setting means, when setting the edge, for the element points at the front and rear ends of the edge, in addition to the predetermined condition, an element point at which an adjacent polygon changes is selected. 14. The polygon drawing apparatus according to 13. In the element point thinning processing means, when the edge is set by the polygon peripheral edge setting means, when the edge is in common with the edge of an adjacent polygon, the element points constituting the edge respectively correspond to both polygons. Create correspondence data for element points,
12. The polygon rendering apparatus according to claim 11, wherein when the element point of one polygon is deleted by the thinning process, the thinning process of deleting the element point of the other polygon is performed by the correspondence data.   In the element point thinning-out processing means, when the element point of the one polygon is deleted by the thinning-out process, when the element point of the other polygon is thinned out by the corresponding data, 16. The polygon drawing apparatus according to claim 15, wherein thinning processing is not performed.   12. The polygon rendering apparatus according to claim 11, wherein the predetermined condition indicating that the change in the surrounding shape of the polygon is small is that an angle formed by an adjacent element point with respect to the designated element point is within a predetermined angle. .   12. The polygon rendering apparatus according to claim 11, wherein the predetermined condition indicating that the change in the surrounding shape of the polygon is small is that the length of a perpendicular drawn to a straight line connecting adjacent element points is within a predetermined range.   The polygon drawing according to claim 1, wherein the thinned data is stored in a database as map display data. apparatus   12. The polygon rendering apparatus according to claim 11, wherein the thinned data is stored in a database as map display data.

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