JP2006301601A - Device for generating map data - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a device for generating map data capable of improving attractiveness of a map while avoiding an increase in labor during automatic generation of road polygons used for map data. <P>SOLUTION: The device reads in network data 40 representing roads as node links and processes them to generate polygon data 50 including road polygons. The generation of the road polygons includes a stage of generating rectangular polygons giving a width to each link, a stage of edging the links, a stage of erasing unnecessary edge lines, etc. The map data generating device after generating the rectangular polygons discriminatingly uses terminal shape determining methods according to connection states between respective polygons and other polygons and shapes and properties of the both to determine a terminal shape of each polygon. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a technique for generating map data for drawing a map.

  The electronic map data is used for displaying a map on a screen of a computer, a navigation device or the like. This electronic map data is composed of various polygon data representing buildings, other features, roads, railways, and the like. Conventionally, in order to reduce the labor involved in generating map data, various techniques for automatically generating these polygon data, particularly polygon data for drawing a road have been proposed.

  For example, Patent Document 1 discloses a technique for automatically generating polygon data by using route search data, that is, network data composed of nodes and links, and giving each link data a width. . Also disclosed is a technique for smoothly shaping a portion where the generated polygons are connected in a polygonal line with a circular arc, or shaping a connection portion between polygons having different widths in a tapered shape. Patent Document 2 discloses a technique for generating edge data of a road by determining the vertical relationship of the road, such as whether it is an elevated road, after generating polygon data with a wide network data. .

Japanese Patent Laid-Open No. 6-83937 JP 2002-333829 A

  For electronic map data, there has been a demand for further improving the appearance of the map and further reducing the labor required for generation. For example, the road may be displayed in different colors depending on the type such as a national road or a prefectural road. When such color-coded display is performed, depending on the shape of each polygon at the intersection where the national road and the prefectural road are connected, unnatural color coding may be performed, which may impair the appearance of the map. In order to improve the appearance of such a part, if the operator has manually determined the shape of such a part, a great amount of labor is required for generating map data.

  As another example, consider the case where two roads are running relatively close together. For example, the case where the upper and lower lines are formed by separate links, or the case where another road is running under the elevated road are applicable. When polygons are automatically generated by giving such a link a width, the polygons constituting these two roads may overlap each other. In order to avoid a sense of incongruity in drawing the map, it is necessary to give priority to one of the overlapping polygons and delete the other edge line. In this case, in order to prevent the road edge line from becoming discontinuous, it is desirable to give priority to one of the two roads running side by side and to erase the other edge line uniformly. It is. Conventionally, such processing has to be determined manually by the operator, and a great deal of labor has been required. In view of these problems, an object of the present invention is to provide a technology for automatically generating road polygons that are less likely to cause discomfort in map drawing.

  The present invention can be configured as a map data generation device that generates map data for drawing a map. This map data generation apparatus inputs geometric data and attributes used for determining the shapes of a plurality of polygons used for drawing a road included in map data. Then, based on at least a part of the attribute of both the target road to be processed and the road to be connected to the target road (hereinafter referred to as “connected road”), the shape determined based on the geometric data, and the direction, It is selected which of a plurality of types of determination methods prepared in advance for determining the end shape of the road polygon is to be applied. Then, the map data generation device obtains the end shape of each polygon according to the geometric data in accordance with the selected determination method, and generates polygon data for drawing a road polygon. In this process, an option that neither determination method is applied may be included. In this case, the most primitive shape obtained from geometric data may be applied as it is as polygon data.

  The present invention can determine the end shape of the target road by a method most suitable for connection with the connection road by considering the attribute of the connection road and the like. For example, it is possible to use different terminal shape determination methods so as to reduce discomfort on the display. By doing so, it is possible to generate polygons with a relatively light load with less discomfort on the display.

  As the geometric data, original polygon data prepared in advance may be used, or data used by the map data generation device to generate polygon data may be used. As an example of the latter, for example, network data representing the connection state of roads with nodes and links may be used as geometric data, and the map data generation device may generate polygon data using this geometric data. A link represents a road with a line segment or a broken line, and a node is an end point of a link.

  The shape of the polygon can be determined based on the side line composed of a point group located at a predetermined distance from the link and the end shape. The distance is the length perpendicular to the link. Polygon data may be generated by obtaining polygonal line or line segment data representing the side line and the end shape and combining them. Alternatively, the provisional polygon data having a fixed width with each link serving as the axis of symmetry may be obtained once, and the final polygon data may be generated by correcting this end shape. The predetermined distance from the link or the width of the rectangular polygon can be determined, for example, based on attributes associated with the link, for example, information such as a road type such as a national road or a prefectural road, the number of lanes, and a road width.

  As described above, the map data generation apparatus obtains the end shape by using various determination methods. The term “selection” in this specification includes the presence / absence of shaping of the end shape in a broad sense. For example, an aspect of switching whether or not to perform end shape shaping processing according to various conditions is also included in the concept of the present invention. Will be included.

  The above-mentioned proper use can be performed under various conditions. For example, the selection may be made based on the difference in road type between the target road and the connection road. This mode includes not only the case of selecting only the difference in road type as a condition, but also the case of selecting in consideration of conditions other than the difference in road type.

  There may be a plurality of connecting roads connected to the target road, such as an intersection. In such a case, the selection conditions may be switched between the case where the target road and the plurality of connection roads have the same road type and the other cases. For example, consider a case where a color or pattern for drawing a road is selected according to the road type. If all connected polygons have the same road type, all these polygons will be given a uniform pattern or color, so the end shape of each polygon has little effect on the appearance of the map. Don't give. On the other hand, when different kinds of polygons are included, the end shape of the polygons greatly affects the appearance of the map. According to the above-described aspect, by selecting the proper use condition depending on whether or not the road types of all the polygons are the same, the end shape is determined by a suitable method while considering factors such as ensuring appearance and reducing processing load. Can be done.

  Further, the processing may be selected depending on whether or not there is a road of the same type as the target road on the connection road. Further, when there are a plurality of connection roads as described above, not only the difference in road type between the target road and the connection road, but also the difference in road type between the connection roads may be considered. For example, the conditions for selection may be switched between when there are two or more connected roads with the same road type in the connected roads and in other cases.

  As another aspect, the selection may be made based on at least one of the difference between the widths of the target road and the connection road and the connection angle between the two. The connection angle refers to an angle formed by the symmetry axis of the polygon or an angle formed by the traveling direction of the road represented by the polygon. The appearance of the map can be improved by selecting the terminal shape in consideration of these geometric factors. Regarding the difference in width, for example, it may be divided into a case where the width of the target road and the connecting road is the same as the case where it is different, or the latter is further subdivided, and the width of the target road is wider than the width of the connecting road Alternatively, it may be divided into narrow cases.

  The end shape can be determined in various ways. As a first method, there is a method in which an intersection between the side lines of the target road and the connecting road is obtained, and a terminal shape is defined by a line segment connecting the intersections. Depending on the position of the intersection, there may be either a form in which a part of the rectangular end before determination is deleted, a form in which the rectangular end is extended, or a form in which a part is extended while deleting a part. When an acute corner is formed in the course of such processing, fillet processing for deleting the corner with an arc may be performed.

  Furthermore, when the connection angle between the target road and the connection road is relatively shallow and the intersection of the side lines is used, if the polygon shape becomes irregular, instead of such an intersection, the target road side on the survey line of the connection road The end shape of the target road may be determined using a point at a predetermined distance from the end point.

  As a second method, the end shape may be defined by connecting the side lines of the target road with broken lines so that the target road becomes a convex polygon. A convex polygon refers to a polygon having a convex end shape such as a shape in which none of the diagonal lines protrudes from the polygon. By using such a shape, it is avoided that the end shape of the target road looks unnatural due to differences in road type, width, connection angle, etc., at the connection part with other polygons such as an intersection part. be able to. The shape of the above-mentioned broken line can also be set by various methods. Furthermore, instead of the broken line, the end shape may be defined by connecting the side lines with a semicircular curve or other convex curve.

  Various methods can be used for the above-described terminal shape determination method and proper use conditions. Multiple roads are grouped in advance based on road name, type, traffic regulation, connection angle, uplink / downlink information, etc., and the terminal shape determination method is used properly depending on the presence or absence of grouped roads. Also good. The map data generation device of the present invention can be provided with a function for generating and managing polygon data for representing topographic shapes, buildings, and other features in addition to a function for generating road polygon data.

  Grouping can be performed under various conditions. For example, at least one of a road name and a traffic restriction attached to the road can be used. Roads with the same name and roads that are consistently restricted to one-way traffic, etc. are often recognized as continuous roads for social reasons, so these roads are grouped together. By doing so, it is possible to realize a map display in accordance with such a common belief. Further, in the Y-shaped branch, those having a shallow connection angle with respect to the target road are recognized as so-called “roads”, and these are grouped together. A “road” represents a series of roads that are usually recognized as one continuous road from the geometric shape. Hereinafter, in the present invention, the term "road" broadly represents a road that is recognized as a series of roads based on traffic restrictions, road names, types, etc. in addition to geometric shapes. . In the present invention, by grouping the roads in the broad sense in this way, it becomes possible to perform a uniform process in the polygonization process and the edge line process for the group. Appearance improves. In this specification, the expression “with connectivity” may be used as a concept similar to “the way”. With connectivity is an evaluation of the geometric shape of the road. Roads whose connection angle is equal to or smaller than a predetermined angle such as 30 degrees are expressed as “with connectivity”.

  When the road type is included in the attribute, grouping may be performed between roads having the same road type. All roads of the same type may be grouped, or a condition may be added to group some roads of the same type. As a general rule, it is often the same type that is recognized as a continuous road. In addition, expressions such as fill colors and patterns are often defined for each type. If grouping is performed within the same type, it is possible to unify the polygon data generation method along these actual conditions.

  When grouping, a connection angle between a plurality of polygons may be considered. The connection angle refers to an angle formed by the symmetry axis of the polygon or an angle formed by the traveling direction of the road represented by the polygon. In general, the smaller the connection angle, the higher the possibility that the road is recognized as a continuous road. Therefore, by considering the connection angle, it is possible to perform grouping according to such a common rule.

  Grouping can be used for various processes for generating polygon data, such as a process for painting polygons with colors and patterns, and determining the end shape of polygons. Among these processes, in particular, the edge line process for attaching edge line data for representing road edge lines to each polygon is highly useful. In this edge line processing, for example, it is possible to ensure the appearance of the map by generating edge line data so that the edge lines of the grouped polygons are continuous.

  In order to secure the appearance of the map, it may be desired to determine the shape of the end portion where the polygons are connected. When determining this shape, multiple types of determination methods, including the necessity of determination, are used properly based on at least part of the attributes, shape, and orientation of both the target road to be determined and the connected road to be connected to the target road. It is desirable. At this time, the proper use may be performed depending on whether or not the target road and the connection road are grouped, and whether or not there is a polygon grouped in the connection road. By doing so, the continuity of the shape can be ensured between the polygons to be recognized as continuous roads.

  The present invention does not necessarily have all of the above-described features, and can be configured by omitting some or combining them appropriately. The present invention can be realized not only as a map data generation device but also as a map data generation method that generates map data using a computer. Further, it can be realized as a computer program for causing a computer to generate a function for generating map data, or can be provided in the form of a recording medium on which such a computer program is recorded. In this case, as a recording medium, a flexible disk, a CD-ROM, a magneto-optical disk, an IC card, a ROM cartridge, a punch card, a printed matter on which a code such as a barcode is printed, an internal storage device of a computer (RAM, ROM, etc. Various types of computer-readable media such as a memory) and an external storage device can be used.

Embodiments of the present invention will be described in the following order.
A. Device configuration:
B. Road polygon generation processing:
C. Polygon processing:
D. Polygon grouping:
E. Polygon end processing:
E1. Processing method:
E2. When the target road and the connecting road are all the same type:
E3. When the target road and connecting road are of the same type / different types:
E4. When the connecting road is different from the target road:
E5. List of usage conditions for end processing and flowchart:
E6. Different types of end treatment (variation):
F. Edge line processing:
G. Effects and variations:

A. Device configuration:
FIG. 1 is an explanatory diagram showing a configuration of a map data generating apparatus as an embodiment. The map data generation device 10 is configured by installing a computer program for realizing each function required for generating map data in a general-purpose computer. The functional block of the map data generation device 10 is shown in the figure. In the present embodiment, these functional blocks are constructed by software as described above, but can also be constructed by ASIC or other hardware.

  The map data generation device 10 generates polygon data 50 based on the network data 40. In the present embodiment, the network data 40 and the polygon data 50 are provided and managed by a server connected to the map data generation device 10 via a network. As the network, either a limited network such as a LAN or a wide area network such as the Internet may be used. The network data 40 and the polygon data 50 may be stored and managed in the map data generation device 10.

  The network data 40 is data used for route search, and is data representing road connection states by nodes and links. In the network data, attribute information is also attached to each link and node. The attribute information includes road types such as national roads, prefectural roads, and general roads, the number of road lanes, road names, and height levels.

  The height level is data representing the height of the road as a quantized numerical value. In this embodiment, the height level data takes an integer value of “−1, 0, 1, 2”. “−1” means an underground or semi-underground road, and “0” means a road running on the ground. “1” and “2” mean elevated roads. The reason why a plurality of levels are assigned to the elevated road is to make it possible to deal with multi-layer elevated roads. The higher the value, the higher the elevated road. By using the height level data in this way, there is an advantage that the three-dimensional vertical relationship between the roads can be expressed with a small data capacity, compared with the case where the road height data is directly stored as numerical data. .

  The polygon data 50 is a database that stores and manages polygons for drawing a map. Hereinafter, the term “polygon data” may be used to represent data for drawing each polygon. The polygon data 50 stores data for drawing polygons divided into layers representing terrain, layers representing roads and railways, and layers representing features such as buildings. The map data generation device 10 according to the present embodiment creates only the road polygon for drawing the road in the polygon data 50 based on the network data 40. Polygons such as terrain, railways, and buildings are generated separately by operator operations.

  In the figure, functional blocks for automatically generating road polygons are shown. These functional blocks cooperate with each other under the control of the main control unit 12 to realize a map data generation function, particularly a road polygon automatic generation function.

  The communication unit 11 controls reading and writing of the network data 40 and the polygon data 50 via the network. The intermediate data storage unit 13 temporarily stores and manages various data generated in the road polygon generation process. The polygon data generation unit 14 generates a rectangular polygon representing a road shape based on the link data of the network data 40. Specifications for generating polygons are given by a specification table 18. In the embodiment, at this stage, once a rectangular polygon is generated, the end shape described later is determined for this polygon. On the other hand, at this stage, only polygonal line or line segment data consisting of point clouds at a fixed distance from each link included in the link data is obtained, and the format as polygon data is processing such as determining the end shape. It may be performed after completion of.

  As shown in the figure, the specification table 18 gives default values such as a polygon width, a fill color, and a priority according to the road type. Priority is control information that regulates the order of rendering. Polygons with high priority are drawn to overwrite other polygons, and are hidden or divided by other polygons on the map. Will be displayed preferentially. The specification table 18 is merely a table for giving default values. When the width or the like is given by the attribute of the network data 40, the polygon data generating unit 14 preferentially uses the value given by the attribute. Since the polygon generated by the polygon data generation unit 14 is intermediate, it is stored in the intermediate data storage unit 13.

  The grouping unit 15 groups a plurality of polygon data stored in the intermediate data storage unit 13 according to a preset rule. In this embodiment, for the sake of convenience, a series of polygons to be recognized as continuous roads are grouped. Examples of polygons that should be grouped include polygons that represent roads with road names such as “National highway * route”, roads that have one-way restrictions in the same direction, and connection angles that are shallow and almost in the same direction. For example, the road facing The grouping method will be described in detail later.

  The polygon data generation unit 14 further shapes the end of the road polygon stored in the intermediate data storage unit 13. Since the initial polygon generated based on the link data of the network data 40 has a rectangular shape, there is a possibility that the road has an irregular shape at the connection portion between the polygons. The polygon data generation unit 14 determines the end shape so as to suppress a sense of incongruity at the time of drawing with reference to attributes and connection angles of connected polygons. A method for determining the end shape will be described later.

  The edge line processing unit 17 generates an edge line on the road polygon whose end shape is determined. At this time, unnecessary edge lines are deleted in consideration of whether it is an elevated or an intersection on the ground. Further, by uniformly handling the grouped polygons, a continuous edge line is drawn on the road represented by these polygons. Specific contents of the edge line processing will be described later.

  The map data generation device 10 can automatically generate road polygons by the processing by the above functional blocks. The road polygon generated in this way is stored in the polygon data 50. Below, the concrete content is demonstrated about the whole process for producing | generating a road polygon, and each processing process.

B. Road polygon generation processing:
FIG. 2 is a flowchart of the road polygon generation process. This process is realized by the cooperation of the functional blocks shown in FIG. 1, and is a process executed by the CPU of the personal computer constituting the map data generation device 10 according to the computer program in terms of hardware.

  When the road polygon generation process is started, the CPU reads the network data 40 (step S10). The schematic configuration of the network data 40 is illustrated in the figure. The network data 40 is composed of nodes and links. A link represents a road as a line segment, and a node is an intersection or end point of a link. In the figure, links L1 to L8 and nodes N1 and N2 are illustrated. The link L4 and the link L5 intersect two-dimensionally, but no node is set at the intersection. This means that the links L4 and L5 are elevated and there is no intersection.

  The CPU polygonizes each link included in the network data 40 (step S20). In the drawing, polygons P1, P4, and P8 generated based on the links L1, L4, and L8 are illustrated. Since details of the processing will be described later, only the outline will be described here. In the polygonizing process, the CPU generates a rectangular polygon so that each link is an axis of symmetry. The width of the polygon is determined by the road type. In this example, the ratio of the width of the national road, prefectural road, and general road was set to 3: 2: 1. In the case of adding “highway” as another type, for example, a method of setting the ratio of the width of an expressway, a national road, a prefectural road, and a general road to 5: 4: 3: 2 can be adopted. Each polygon is connected by a node, for example, as polygons P1 and P4 (shown with hatching in the figure) are connected by a node N1. In a node to which three or more links are connected, such as nodes N1 and N2, a plurality of polygons are overlapped and generated. The road width may be set individually for each road regardless of the type.

  The CPU groups the polygons thus generated according to a certain rule (step S30). In the network data, since the link is divided for each node installed at an intersection or the like, the polygon generated based on this is also divided between the nodes. As a result, for example, a single continuous road is represented by a set of a plurality of polygons, such as the national highway *. Grouping is a process for collecting a plurality of polygons that should be recognized as constituting a continuous road in consideration of such actual conditions. Specific processing contents will be described later.

  Next, the CPU executes polygon end processing (step S40). Since the polygon generated in step S20 has a rectangular shape, there is a possibility that a gap or an extra protruding portion may occur at the connection portion depending on the connection state between the polygons. End processing refers to processing for shaping this end shape according to the connection state between polygons. Since the polygon is a closed figure, strictly speaking, there is no “end”. In this specification, the end of the polygon means a side including the end of the link or road in the traveling direction.

  A typical processing example of the terminal processing is shown in the figure. Consider a case where two polygons Po1 and Po2 intersect at a shallow connection angle as shown in the figure. The shapes of the polygons Po1 and Po2 are rectangular as shown by hatching before the end processing is performed. In the end processing, the intersection points M1 and M2 of the side lines L11 and L12 of the polygon Po1 and the side lines L21 and L22 of Po2 are obtained, and the end shape of the polygon Po1 is shaped so that the line segment connecting the two ends. In the terminal processing, a plurality of processing methods including the method illustrated here are used properly in consideration of the road type and the like. Specific contents of the end treatment will be described later.

  When the end processing is thus completed, the CPU performs edge line generation processing (step S50). An example of processing is shown in the figure. As shown on the left side of the figure, the polygon POL has no edge line in the state before processing. By performing the edge line generation process, the edge line EL is generated so as to surround the entire circumference of the polygon POL.

  When the edge line is generated as described above, an unnecessary edge line is generated at the connection portion between the roads, and the appearance is as if the roads are divided. Therefore, the CPU erases unnecessary edge lines among the generated edge lines (step S60). Specific contents of the processing will be described later.

  The CPU outputs the road polygon thus generated to the polygon data 50 (step S70), and the road polygon generation processing is completed. In the present embodiment, it is assumed that all processes are automatically performed, but an instruction from an operator may be appropriately interposed. For example, when each processing in FIG. 2 is completed, the processing result is displayed and the operator confirms whether or not appropriate processing has been performed. A decision may be made. In this embodiment, the polygon processing (step S20), grouping (step S30), end processing (step S40), edge line generation processing (step S50), and unnecessary edge line deletion (step S60) are performed. Execute for all links for each process. On the other hand, as another processing method, the above-described series of processing (steps S20 to S60) may be executed for each link. In this case, polygon data corresponding to all links can be generated by repeatedly executing a series of processes while changing the link to be processed. Hereinafter, specific contents will be sequentially described for various processes in which only the outline is shown in the above description.

C. Polygon processing:
FIG. 3 is a flowchart of the polygonizing process. This process is a process of generating a rectangular polygon by giving a width to the link, and is a process corresponding to step S20 of the road polygon generation process (FIG. 2).

  When processing is started, the CPU first selects a link to be processed based on a predetermined order (step S31) and inputs its attributes (step S32). Attributes include road type, number of lanes, road width, and the like. However, it is not always necessary to set all these attributes.

  The CPU determines the width of the polygon to be generated next (step S33). If an attribute related to the road width is read in step S32, that value is used. For example, when the road width itself is given as an attribute, the width of the polygon can be determined based on the value. When the number of lanes is given, the width of the polygon can be determined using a standard value preset as the width per lane. When these attributes are not obtained, default values given in the specification table (see FIG. 1) are used.

  Next, the CPU sets the color of the polygon based on the specification table (step S34). In the present embodiment, the colors are divided according to the road type. When the attribute is input (step S32), if the road type is not obtained, the CPU treats it as a general road and determines the color. The color of the road may be further subdivided in consideration of not only the road type but also the number of lanes and other conditions. Conversely, it may be determined only by the number of lanes and other conditions without depending on the road type.

  The CPU generates a rectangular polygon by obtaining a set of points having a width W for each point on the link with each link as the axis of symmetry (step S35). In the figure, an example of the polygon P4 for the link L4 is shown. The polygon is a rectangle having the same length Len as the link L4 and a set width W. Here, the case where the link L4 is linear is illustrated, but the same processing is performed when the link is defined as a polygonal line. That is, by obtaining a set of points having a width W for each point on the link, the side line becomes a broken line state, and a polygon having a rectangular end shape is generated.

  Until the CPU completes the above processing for all links (step S36), the polygonization processing is completed. The generated polygon is stored in the intermediate data storage unit (see FIG. 1) and is used for the subsequent processing. In this embodiment, rectangular temporary polygon data is generated by the above processing. On the other hand, in the polygonization process, the data format as a polygon is not adjusted, but only a polygonal line or a line segment group that defines the outer shape of the polygon may be obtained. In this case, the data format as the polygon may be adjusted after completion of the end processing described later, for example.

D. Polygon grouping:
FIG. 4 is an explanatory diagram showing an example of the grouping process. An example in which six roads from R1 to R6 intersect at one intersection is shown. The hatching partially attached to the road represents the road type. In the illustrated example, polygons R1, R3, and R6 are national roads, polygon R4 is a prefectural road, and R2 and R5 are general roads. The polygon R5 has a one-way restriction in the direction toward the intersection, and the polygon R2 has a one-way restriction in a direction away from the intersection.

  Grouping is a process of associating a plurality of polygons recognized to form a continuous road. In the present embodiment, first, roads with continuous one-way restrictions are grouped. In the example shown in the figure, a one-way restriction continuous to the polygons R2 and R5 is attached. Therefore, these two roads are grouped. In the figure, this group is shown with a label Gr2. In addition to traffic restrictions, when a road is given a name, such as a national highway *, polygons having the same name as an attribute may be grouped.

  Next, consider a case where the polygon R1 is grouped. The polygon R1 is not restricted in traffic. In this embodiment, in such a case, roads having the same road type are selected and grouped. In the example shown in the figure, the polygons R1, R3, and R6 are of the same type, and therefore there are two polygons R3 and R6 as targets for grouping the polygon R1. Although it is possible to group these two roads together, in this embodiment, the grouping is performed so that the road does not branch. This is because including a branch complicates the edge line processing described later. In this embodiment, the side having a smaller connection angle with the polygon R1 among the polygons R3 and R6 is selected as a grouping target so as not to include a branch. The connection angle refers to an angle formed by the symmetry axis of each road or an angle formed by the traveling direction of the polygon R1. In the illustrated example, the connection angle Ang3 between the polygon R1 and the polygon R3 is smaller than the connection angle with the polygon R6. Therefore, the polygon R1 and the polygon R3 are grouped. In the figure, this group is represented with a label Gr1.

  According to the above-described processing, the polygons R4 and R6 have no road to be grouped at this intersection. Accordingly, the polygons R4 and R6 form a group independently at this point. In the figure, this group is represented with labels Gr3 and Gr4.

  FIG. 5 is a flowchart of the grouping process. FIG. 5 is a flowchart for realizing the processing described in FIG. 4, and corresponds to step S <b> 30 of the road polygon generation processing (FIG. 2). The CPU first selects a road to be processed (hereinafter referred to as a target road) (step S31), and extracts a road (hereinafter referred to as a connected road) connected to the polygon (step S32). In the example of FIG. 4, when the polygon R1 is selected as the target road, the polygons R2 to R6 are selected as connection roads.

  The CPU reads the attributes of the target road and the connected road (step S33), and searches for a road having the same name as the target road (step S34). If there is a road with the same name (step S34), the target road and this road are grouped (step S39). For example, as shown in FIG. 4, a method of attaching a common label as an attribute of each road forming a group can be adopted for grouping.

  When there is no road with the same name (step S34), the CPU searches for a connection road with one-way traffic continuous with the target road (step S35). If there is a road satisfying such conditions, the road and the target road are grouped (step S39).

  If there is no road that satisfies the above-mentioned conditions, or if the target road is not restricted to one-way traffic (step S35), the CPU then uses the same type of road as the target road as a candidate for grouping. (Step S36). And a candidate is narrowed down to the selected road from which the connection angle becomes below predetermined value Ang (step S37). The predetermined value Ang can be arbitrarily set, but is set to 90 ° in this embodiment. By this processing, roads connected so as to be bent at an acute angle are excluded from grouping candidates.

  The CPU selects the narrowest road from the narrowed roads (step S38), and groups this road and the target road (step S39). If no candidate roads remain after narrowing down to step S37, a group is formed with only the target roads. The CPU repeatedly executes the above processing until all the roads are completed.

  The conditions for grouping and the priority thereof are not limited to the above example, and various settings are possible. For example, regarding the conditions for traffic restrictions, not only one-way traffic but also restrictions such as prohibition of turning left and right may be considered. It is also possible to omit the condition related to the connection angle (step S37). The condition related to the type (step S36) and the condition related to the connection angle (step S37) may be arranged in parallel, and roads satisfying either one may be set as grouping candidates.

  FIG. 6 is a flowchart of a grouping process as a modification. The priority of the conditions for grouping is different from the grouping processing of the embodiment (FIG. 5). First, the CPU selects a road to be processed (hereinafter referred to as a target road) (step S31), and extracts a road connected to the road (hereinafter referred to as a connected road) (step S32).

  The CPU reads the attributes of the target road and the connected road (step S33), and extracts the same type of road as the target road (step S34A). Further, the CPU extracts a road having a connection angle equal to or smaller than Ang, that is, a road connected at a shallow angle (step S35A).

  Next, the CPU searches for a connection road with one-way traffic that is continuous with the target road (step S36A). If there is a road satisfying such conditions, the road and the target road are grouped (step S39). When there is no road satisfying the above-described conditions, or when the one-way restriction is not attached to the target road (step S35), the CPU searches for a road having the same name as the target road (step S37A).

  If such a road exists, the road and the target road are grouped (step S39). If no such road exists, a road with the smallest connection angle is selected from the roads selected in the above processing ( In step S38A), the road and the target road are grouped (step S39). The predetermined value Ang can be arbitrarily set, but is set to 90 ° in this embodiment. By this processing, roads connected so as to be bent at an acute angle are excluded from grouping candidates. The CPU repeatedly executes the above processing until all the roads are completed.

  The process of the modified example is useful when it is not possible to specify a group without including a branch only by the road name, such as when there is a possibility that a road with the same name may branch into a plurality of roads. The grouping can be performed under various conditions and priorities in addition to the modified example.

E. Polygon end processing:
Polygon end processing is processing for shaping the end shape of a polygon according to the connection state between polygons in order to improve the appearance of the map. In this embodiment, the terminal processing is performed by properly using a plurality of processing methods depending on conditions. In the following, first, a plurality of processing methods are shown in FIGS. 7 to 10, and then a specific processing method according to road connection conditions is described based on FIGS. 11 to 15, and then a flowchart in FIG. Show.

E1. Processing method:
In this embodiment, in addition to the process of generating a simple rectangular polygon by widening the link, there are four types of polygon end shape shaping processes: connection processing, fillet processing, convex polygon processing, and M-shaped processing. Use. Hereinafter, the processing contents of these four types of processing will be sequentially described.

(1) Connection process:
FIG. 7 is a flowchart of the connection process. In the connection process, first, the direction of each link is defined radially about the node where the links to be processed intersect (step S100). The link data is composed of point sequence data consisting of the via points. The process of step S100 is a process of arranging this point sequence data starting from the node. This process is a preprocess for defining the positional relationship between links, as will be described later. Therefore, when the positional relationship between the links is defined by another method, the process of step S100 may be omitted.

  Next, the CPU selects one link as a target link [1] to be processed from a plurality of links intersecting at the node (step S101). Then, a link adjacent in the counterclockwise direction from the target link [1] is searched, and this link is selected as the target link [2] (step S102). The search direction does not necessarily need to be counterclockwise, and may be clockwise.

  An example of processing is shown on the right side of the figure. The upper diagram shows a case where two roads intersect at node N, and the lower diagram shows three examples. In the upper diagram, it is assumed that two links L [1] and L [2] intersect at the node N, and the link L [1] is selected as the target link [1]. When searching from here counterclockwise (arrow direction in the figure), the link L [2] is selected as the target link [2].

  When the target links [1] and [2] are thus selected, the CPU calculates the intersection of the left line of the rectangular polygon [1] and the right line of the rectangular polygon [2] (step S103). The left side and the right side are defined with reference to the link direction defined in step S100. Rectangular polygons [1] and [2] mean rectangular polygons formed by widening the target links [1] and [2], respectively. At this stage, the format as polygon data may not be prepared. In a rectangular polygon, it is sufficient if the left and right side lines that define the sides parallel to the links [1] and [2] are defined.

  In the processing example on the right side, the left line corresponding to the link L [1] is RL [1], and the right line is RR [1]. The left line corresponding to the link L [2] is RL [2], and the right line is RR [2]. In the process of step S103, an intersection C [1] between the left line RL [1] and the right line RR [2] is obtained.

  The CPU repeats the above processing for all links while replacing the target link [2] with the target link [1] (steps S104 and S105). In the processing example on the right side, when the process of setting the link L [1] as the target link [1] is completed, the same process is executed with the link L [2] as the target link [1]. At this time, the link L [1] is selected as the target link [2], and the intersection C [2] of the left line RL [2] and the right line RR [1] is obtained.

  When the processing is completed for all the links, the CPU generates a polygon having the intersections and nodes obtained by these processing as vertices (step S106). In the processing example on the right side, the end shape of the polygon corresponding to the link L [1] is defined by a line connecting the intersection C [1], the node N, and the intersection C [2] as shown by a thick line in the figure. .

  The same applies when three or more links intersect. Processing in the case where the three links L [1] to L [3] intersect will be described according to an example shown below the processing example. When the link L [1] is selected as the target link [1], the link L [2] is selected as the target link [2], and the intersection C [1] is obtained. Hereinafter, the intersections C [2] and [3] are obtained by sequentially setting the links L [2] and [3] as the target link [1]. As a result, the end shapes of the polygons corresponding to the links L [1] to [3] are defined as indicated by thick lines in the drawing.

(2) Fillet processing:
FIG. 8 is a flowchart of fillet processing. This process is executed as a post process following the connection process (step S110). The CPU calculates a connection angle AC for the link to be processed (step S111). In this embodiment, the connection angle AC is an angle corresponding to the course change angle when entering from one of the links to be processed and exiting from the other. In the figure, a state in which connection processing is performed on two links is shown. Two polygons POL [1] and [2] are generated by the connection process. As the connection angle AC increases, an acute corner CO appears at the connection portion of the polygons POL [1] and [2].

  The fillet process is performed only when the connection angle AC is larger than the predetermined value Th (step S112). In this embodiment, the predetermined value Th is 90 °, but this value can be set arbitrarily. When the connection angle AC is larger than the predetermined value Th, the CPU deletes the acute corner CO in a curved line with the arc FLT (step S113). The radius of the arc FLT may be a predetermined fixed value, or may be set by a method such as multiplying the width of the polygon by a predetermined coefficient.

(3) Convex polygon processing:
FIG. 9 is a flowchart of the convex polygon processing. The CPU converts the end shape of the rectangular polygon to be processed into a convex polygon in the following procedure (step S120). Convex polygonization refers to a shaping method that connects polygon side lines with a polygonal line so as to form a convex shape. That is, the polygonal line is limited to a convex polygon, that is, one that forms a shape that does not protrude any diagonal from the polygon. In this embodiment, the end shape is shaped into an isosceles trapezoid.

  In the figure, the processing contents of convex polygon conversion are illustrated. It is assumed that rectangular polygon side lines RR and RL are defined for the link L having the node N as an end point. The CPU obtains a point Ap2 by which the node N is moved Wh along the link and moved Wh in the direction parallel to the link. This may be described as a process in which a square of one side Wh having a node N as a vertex and a side parallel to the link is obtained, and the vertex at the diagonal of the node N is Ap2. Similarly, a point Ap3 that is line-symmetric with respect to the point Ap2 and the link L is obtained. Then, the end shape of the polygon is defined by the polygonal lines connecting the end points Ap1 and Ap4 of the side lines RR and RL and the points Ap2 and Ap3.

  Although Wh used in the above-described processing can be arbitrarily set, in this embodiment, a road half width of a road type that is two or more steps lower than the road type to be processed is used. In this embodiment, the road types are ranked in the order of highway, national road, prefectural road, and general road. For example, when the target road PP is a national road, the length of Wh is the road half width of the prefectural road. It becomes. The value of Wh may be obtained by multiplying the half width W1 of the target road by a certain ratio. The processing in the next step S120A is used in the modification and is omitted in the embodiment, so the content will be described later.

  Next, the CPU calculates the width W1 and priority P1 of the target road, and the width W2 and priority P2 of the road (connection road) intersecting with the target road (step S121). Then, when the width W1 is larger than W2 or when the priority P1 is higher than P2 (step S122), a process of deleting an extra portion from the convex polygonal portion is executed (step S123). The superiority or inferiority of the priority is as set in the specification table (see FIG. 1). In this embodiment, for example, “National road” has a higher priority than “Prefectural road”. Therefore, when the target road is a “national road” and the connection road is a “prefectural road”, the process of step S123 is executed regardless of the width. When the priority of the target road is low, for example, when the target road is “prefectural road” and the connection road is “national road”, the road width W1 of the target road is larger than the road width W2 of the connection road. If it is wide, the process of step S123 is executed.

  An example of processing in step S123 is shown in the figure. Here, it is assumed that the polygon POL [1] having the width W1 is subjected to the convex polygon processing. The polygon POL [1] is wider than the width W2 of the intersecting polygon POL [2]. In such a situation, as illustrated, there is a possibility that the polygon POL [1] protrudes from the polygon POL [2]. Therefore, with respect to the polygon POL [1], the hatched area A in the figure is deleted.

  Due to the rounding error of the calculation at the time of deletion, there may be a gap between the polygon POL [1] and the polygon POL [2] after the deletion, as indicated by a dashed ellipse in the figure. Since this gap is very fine, it is left as it is in this embodiment. However, by adding a point that coincides with the vertex of the polygon POL [1] on the side line of the polygon POL [2], The gap may be eliminated.

  In this embodiment, when the width W1 of the polygon POL [1] is equal to or smaller than the width W2 of the polygon POL [2] of the connection road (step S122), the process of deleting the extra part is skipped. In such a case, the polygon POL [1] is unlikely to protrude from the polygon POL [2]. Moreover, it is because it dislikes that the clearance gap mentioned above arises by performing the process which deletes an excess part. This skip is not indispensable, and it is possible to perform a process (step S123) of deleting an extra portion regardless of the widths of the polygons POL [1] and [2].

  In the convex polygon processing, an arcuate end shape may be adopted instead of the isosceles trapezoidal end shape. For example, the end shape may be shaped with a semicircle having diameters at both ends of the target road PP.

(4) M character processing:
FIG. 10 is an explanatory diagram showing a method of M-character processing. The M-shaped process is a process for shaping the end shape of the target road PP into an M-shaped shape including points CP1, CP2, N, CP3, and CP4. Points CP1 and CP4 are vertices when the target road PP is formed in a rectangular shape. Point N is a node where the target road PP and the connection road PC are connected. The intersection points CP2 and CP3 are intersection points between the line segment obtained by translating the end side LCe of the connection road PC by the distance Wh and the measurement lines LCi and LCo. The distance Wh is a half width of the connection road PC. The method of determining the points CP2 and CP3 of the M-shaped process is not limited to the illustrated case, and various settings can be made.

E2. When the target road and the connecting road are all the same type:
Next, a method for selectively using each of the above-described processes will be described by taking as an example a case where any two roads are selected from a plurality of intersecting roads and the end shape is shaped between the two roads. FIG. 11 is an explanatory view showing a terminal processing method (1). This process is applied under the condition that the target road and the connecting road are all of the same type. In the figure, i) when the width of the target road and the connecting road are the same, ii) when the width of the connecting road is narrower than the target road and 30 ° <connection angle ≦ 90 °, iii) the width of the connecting road In the case where the connection road is narrower than the target road and the connection angle ≦ 30 °, iv) The four processing examples are shown separately for the connection angle> 90 °. Under the conditions corresponding to FIG. 11, connection processing, M-shaped processing, and fillet processing are applied.

  A process example in the case shown in the uppermost stage, that is, a case where the road width is the same and the connection angle is 90 ° or less will be described. In this example, the target road PP and the connection road PC are connected at a connection angle AC of 90 ° or less. Polygons formed when connection processing is not performed are polygons PP and PC having a rectangular end shape as shown in the left figure.

  In this state, connection processing (see FIG. 7) is performed. That is, the intersection points CPi and CPo of the side lines LPi and LPo of the target road PP and the side lines LCi and LCo of the connection road PC are obtained. Then, the end shape of the target road PP is shaped so that the line segment CPi-node-CPo connecting the two becomes a side. Here, for convenience of explanation, it is shown that the target road PP is once formed as a rectangular polygon, and then the end shape is corrected by the connection process. On the other hand, the side lines LPi and LPo and the intersection points CPi and CPo may be obtained based on the link, and the shape of the target road PP may be determined without going through a rectangular polygon. The same applies to each process described below.

  In the second row from the top, a processing example is shown for a case where the width of the target road and the connection road are different and 30 ° <connection angle ≦ 90 °. In the example of the figure, the width of the connecting road PC is narrower than the target road PP. In this state, when connection processing is performed, the intersection points CPi and CPo of the respective side lines are obtained at positions where the side lines LPi are extended and the side lines LPo are shortened as shown in the right figure.

  In the connection process described above, as the connection angle becomes shallower, the position of the intersection point CPi is farther away from the end of the target road PP before the process. Therefore, when the connection angle is shallow, the target road PP may have an irregular shape. In this embodiment, in order to avoid such an adverse effect, when the connection angle ≦ 30 °, an M-shaped process obtained by modifying the connection process is performed. In the third row from the top, the case where the width of the connection road is narrower than the target road and the connection angle ≦ 30 ° is shown as an example of performing the M-shaped process. The range of the connection angle to which the M-shaped process is applied is not limited to the illustrated case, and various settings can be made.

  The fourth row shows the case where the widths of the target road and the connection road are different and the connection angle is larger than 90 °. Also in these cases, the end shape can be shaped as illustrated by performing connection processing, extending or shortening the side lines of the target road and the connection road, and obtaining intersection points. However, when the connection angle is larger than 90 °, the intersection of the side lines forms an acute corner CO in the figure. In this embodiment, in order to improve the appearance of the corner, a fillet process is performed in such a case. In this embodiment, the shaping by the arc FLT is applied when the angle CO is smaller than 90 °. However, the angle used as a criterion for determining whether to apply the shaping is not limited to 90 ° and is arbitrarily set. Is possible. The shaping by the arc FLT may not be applied.

  In this embodiment, as described above, the M-shaped process is applied when the width of the connection road is narrower than the target road and the connection angle ≦ 30 °. At this time, for the connecting road (PC at the third level in FIG. 11), the first step from the top is performed. This is because, when the connection road PC in the third stage is processed, although the connection angle ≦ 30 °, the width of the partner road (in this case, the target road PP in the third stage) is wider. In this state, in the third-stage case, the end shapes of the connection road PC and the target road PP are inconsistent. However, in reality, the target road PP that has been subjected to the M-shaped process in the third stage is drawn after the connection road PC, so that the end of the connection road PC is covered by the target road PP. There is no unnaturalness on the display.

  However, as a modification of the present embodiment, the shaping process may be properly used so that the end shape is matched in the above-described case. First, the first case in FIG. 11 is limited to the case where the widths of the target road and the connecting road are “same”. The second level is applied to the case where the width of the target road and the connection road is “difference”, including the case where the connection road is wider than the target road, and 30 ° <connection angle ≦ 90 °. Further, when the width of the connection road is “wider” than the target road and the connection angle ≦ 30 °, a process of shaping the end into the shape of the third-stage connection road PC (referred to as “pencil process”) Apply. Since the method of setting the intersection points CP2 and CP3 that define the shape of the pencil process is the same as that of the M-shaped process, description thereof is omitted. By doing so, it becomes possible to avoid unnaturalness of the connected portion regardless of the drawing order of the target road and the connected road.

E3. When the target road and connecting road are of the same type / different types:
FIG. 12 is an explanatory view showing a terminal processing method (2). This process is applied under the condition that roads that are the same and different from the target road are mixed on the connection road. This is an example of processing for a case where two or more roads are connected to the target road.

  In the figure, similar to FIG. 11, four kinds of processing examples are shown. The uppermost row shows an example in which the width of the target road and the connection road are the same and the connection angle is 90 ° or less. The second row from the top shows an example in which the width of the connection road is narrower than the target road and 30 ° <connection angle ≦ 90 °. The third row from the top shows an example in which the connecting road is narrower than the target road and the connecting angle ≦ 30 °. In these three cases, the connection process or the M-shaped process is performed as described with reference to FIG.

The fourth row from the top shows a case where the connection angle between the target road and the connection road is larger than 90 °. In this embodiment, in this case, the end shape is shaped by the convex polygon processing.
As shown in the fourth example from the top, in the convex polygon conversion process, the intersection (node) of the link of the target road PP and the link of the connection road PC is set as the apex, and on the end side LPe of the target road. One side is arranged, a square SQ (a hatched portion in the figure) is arranged in the direction of extending the link, and a vertex CP2 diagonal to the node is obtained.

  FIG. 13 is an explanatory diagram showing the effect of the convex polygon processing. The results of determining the end shape for the target roads POL1 to POL3 by three methods are shown. In this example, a type of road POL4 that is narrower than the target road further intersects.

  The target road POL1 represents a rectangular polygon. In this state, although the target road POL1 does not protrude from the road POL4, as shown in the area IS1 in the figure, if the connection road used in the connection process with the target road POL1 is included, it is painted separately in the intersection The state becomes unnatural.

  The target road POL2 represents the result when the connection process is filled (fourth row from the top in FIG. 11). When the fillet is applied, there is a possibility that the end of the target road POL2 protrudes from the road POL4 as shown in a region IS2 in the figure. Such a shape is unnatural and unrealistic.

  The target road POL3 is an example in a case where a convex polygon process is performed. As shown in the drawing, the end shape of the target road POL3 is also in a natural state and does not protrude from the road POL4. As described above, the length (one side of the square SQ in FIG. 12) in which the target road POL3 is extended by the convex polygon processing is suppressed by the half width of the lower road type than the target road. It is. As described above, the convex polygon processing of the present embodiment has an effect that the end shape of the target road can be shaped without protruding from the road intersecting the target road.

E4. When the connecting road is different from the target road:
FIG. 14 is an explanatory view showing a terminal processing method (3). This process is applied when any of the connecting roads is a different type of road from the target road. In such a case, there are cases where the same type of road exists between the connected roads, and cases where the same type of road does not exist between the connected roads, which are all different types of roads.

  In the figure, four examples of processing are shown. In the top row, an example in which the width Wpc of the connection road PC is wider than the width Wpp of the target road PP is shown. In the present embodiment, in such a case, the terminal shape is not shaped and left in a rectangular shape. The reason will be described later.

  The second row from the top shows an example in which the width of the target road and the connection road are the same and the connection angle is 90 ° or less. In this case, similarly to the case described with reference to FIG. 11, the end shape is shaped by cutting at a line segment connecting the intersections of the polygon side lines.

  The third row from the top shows a case where the connecting road is narrower than the target road and the connecting angle is 90 ° or less. In this case, convex polygon processing is performed. A specific processing method is as described above with reference to FIG. The length of one side of the square SQ in the convex polygon processing may be determined by the half width Wh of the connecting road PC.

  The fourth row from the top shows a case where the width of the connection road is equal to or less than the width of the target road and the connection angle is larger than 90 °. Also in this case, the end shape of the target road PP is shaped by the convex polygon processing described with reference to FIG.

  As described above, in this embodiment, when the width of the connecting road is wider than the width of the target road, the end shape is not shaped. However, with respect to the connecting road, the convex polygon processing is applied as the end shape shaping processing in order to meet the third or fourth level condition from the top. If the connected road processed in this way is drawn after the target road, the end of the target road is covered with the connected road, and display unnaturalness does not occur. In this embodiment, for this reason, when the width of the connecting road is wider than the width of the target road, the end shape of the target road is not shaped. However, even in such a case, the end shape may be shaped. In this case, for example, it is possible to perform processing for shaping so as to conform to the end shape of the connection road after the convex polygon processing is performed. By doing so, there is an advantage that unnaturalness in display can be avoided regardless of the drawing order of the connection road and the target road.

E5. List of usage conditions for end processing and flowchart:
FIG. 15 is an explanatory diagram showing a list of terminal processing methods. The application conditions of each process shown in FIGS. 11 to 14 are shown in a list form. The type column indicates the relationship between the type of the target road and the connection road and each case. The next column is a connection road to be processed. In this embodiment, when there are a plurality of connection roads, one of them is selected, and the shape determination process for the target road is performed based on the relationship between the target road and the connection road. The connection road to be processed represents a rule for performing the above selection. The “connection state” in the next column indicates a condition for properly using the processing method of the end shape of the target road using the width and the connection angle between the target road and the connection road.

  Cases 1 to 3 correspond to FIG. 11, that is, when all of the target road and the connection road are of the same type. For this case, a road belonging to the same group as the target road is selected from the connected roads and used for shaping the end shape of the target road. The shaping of the end shape is performed by one of “connection process”, “M-shaped process”, and “connection process & fillet” (see FIG. 11) according to the conditions shown in the figure.

  Cases 4 to 6 are cases where roads of the same type and different types as the target road exist in the connected roads (see FIG. 12). In these cases, the end processing is applied with the road of the same type as the target road having the smallest connection angle as the connection road. When a road of the same group as the target road exists, the road can be used as a connection road. In cases 4 to 6, the end shape is shaped by any one of “connection process”, “M-shaped process”, and “convex polygonalization process” according to the conditions shown in the figure.

  Cases 7 to 10 are processing when there is no road of the same type as the target road on the connection road (see FIG. 14). Both cases where the same type of road exists between connected roads and cases of different types are included. In this processing, the end processing is performed with the connection road having the smallest connection angle among the roads of the same type that do not exist in the connection road. In cases 7 to 10, one of “no correction”, “connection processing”, and “convex polygon processing” is performed according to the conditions shown in the drawing. “No correction” means that the shape of the target road is rectangular.

  FIG. 16 is a flowchart of polygon end processing. This is a process of shaping the terminal shape of the polygon by performing proper use as shown in FIG. 15, and is a process corresponding to step S40 of the road polygon generation process (FIG. 2).

  When the process is started, the CPU selects a road polygon to be processed as a target road (step S41), and selects a connection road for the target road. If there is no connection road (step S42), the process is restarted from step S41, and another road polygon is selected as the target road (step S46).

  If there is a connected road (step S42), the attributes of the target road and the connected road are input (step S43). The attribute to be input is information required for proper use of end processing, and includes road type, road width, or number of lanes. The CPU uses the attribute thus obtained to determine a terminal shape determination method in light of the conditions shown in FIG. 15, and determines the terminal shape (steps S44 and S45). Of the information necessary for determining the determination method, the connection angle can be calculated by the angle formed by the links. The CPU repeatedly executes the above processing until the processing of all roads is completed.

E6. Different types of end treatment (variation):
The end treatment is not limited to FIGS. 11 to 16 and can be properly used in various ways. FIG. 17 illustrates the proper use as a modification. In the embodiment, an example is shown in which any one of a plurality of roads existing at an intersection is selected in addition to the target road, and the end shape is shaped. However, in the modified example, processing is performed on three or more roads. Here is an example that allows this.

  In the modification, the process is executed by dividing into nine cases shown in the figure. Case 1 is a case where there is no connection road. In this case, the end shape is rectangular.

  Case 2 is a case where all the roads existing at the intersection are of the same type. In this case, connection processing is performed for all roads. For example, when there are three roads at the intersection, the state shown in the processing example of FIG.

  Case 3 is a case where both the same type / different types of roads are mixed at the intersection and the roads have connectivity. In this case, connection processing is performed on all roads of the same type as the target road.

  The determination method of the presence or absence of connectivity is illustrated on the lower side of the figure. In a variation, connectivity is determined based on the angle between links. For example, consider a case where links L1 to L3 intersect at a node as shown in the figure. The angles between the links are determined as A12, A23, and A31. In the modified example, it is defined that “with connectivity” when the maximum angle is larger than the predetermined value 30 °, and “without connectivity” when the maximum angle is 30 ° or less. The predetermined value serving as a criterion for determining the presence / absence of connectivity is not limited to 30 ° and can be arbitrarily set.

  A state where connectivity is present when three links intersect is illustrated on the right side. As shown in the figure, when the links L4 to L6 intersect, the angle A46 formed by the links L4 and L6 is the maximum angle. When the angle A46 is 30 ° or less, it is determined that “no connectivity”.

  Case 4 is a case where both of the same type / different types of roads are mixed at the intersection and the roads have no connectivity. In this case, the convex polygon processing is performed for each road individually.

  Since the modified example is different from the example in that the process is performed on three or more lines, the convex polygon processing (FIG. 9) also differs from the example. Returning to FIG. 9, the convex polygon processing in the modified example will be described. As described above, in the convex polygon processing, the end shape of the target road is converted to a convex polygon (step S120). In the modification, thereafter, the presence or absence of connectivity between the connecting roads is determined (step S120A). In Case 4 (FIG. 17), the connectivity between the target road and the connecting road is determined, whereas in Step S120A, the connectivity between the connecting roads is determined. However, there is no difference in the method for determining connectivity, and “connectivity is present” when the connection angle between roads is greater than 30 °.

  In the modified example, when there is no connectivity between the connecting roads, the convex polygon process is terminated. In this case, regardless of the width and priority of the target road and the connecting road, the extra portion is not deleted (step S123), and the end shape of the target road is in the form of a convex polygon (step (S120 is completed). When there is connectivity between connected roads, the same processing as in the embodiment (steps S121 to S123) is executed. The reason why the processing is switched in this manner depending on the presence / absence of connectivity between the connecting roads is that, when there is no connectivity, the appearance is impaired when the unnecessary portion is deleted (step S123).

  Case 5 is a case where the same type of road as the target road does not exist in the intersection. However, it is assumed that the same type of road exists in the connection road, that is, another road in the intersection. In such a case, a convex polygon process is performed on the target road.

  Cases 6 and 7 are cases in which the roads present at the intersection are all different, but a road having the same width as the target road exists in the connection road. Case 6 is a case where there is connectivity for these roads. In such a case, connection processing is performed for all roads of the same width. Case 7 is a case where there is no connectivity. In such a case, a convex polygon process is performed on the target road.

  Cases 8 and 9 are cases where the roads present at the intersection are all different types and no road having the same width as the target road exists in the connection road. Case 8 is a case where there is even one road having a width wider than the target road. In such a case, the end shape is rectangular. Case 9 is a case where all the connected roads are smaller than the target road. In such a case, the target polygon is subjected to a convex polygon process.

  FIG. 18 is a flowchart of terminal processing in a modified example. In the order of cases 1 to 9 shown in FIG. Whether it corresponds to each case of FIG. 17 can be determined in an arbitrary determination order such as the order of cases 9 to 1. The flowchart of the end processing differs depending on this determination order. Therefore, FIG. 18 is only an example of a process for realizing proper use of the case of FIG.

  In this process, the CPU selects a road (target road) to be processed (step S61). Next, the CPU determines the condition of case 1, that is, the presence / absence of a connected road (step S62). When there is no connection road, it corresponds to case 1 and therefore the CPU sets the end shape to a rectangle (step S63).

  When there is a connected road (step S62), the CPU determines the relationship between the target road and the type of the connected road (step S64). If the target road and the connection road are all the same, it corresponds to case 2 and the CPU executes a connection process (step S65).

  In the case where the same / different types are mixed in the target road and the connection road (step S64), if there is connectivity (step S66), it corresponds to case 3, so the CPU executes a connection process (step S65). If there is no connectivity, it corresponds to Case 4 and the CPU performs convex polygon processing (step S67).

  If there is no road of the same type as the target road in the connected road (step S64), and if there is the same type of the connected road (step S68), since it corresponds to case 5, the CPU performs the convex polygon processing. This is performed (step S67).

  If there is no same type between the connected roads (step S68), it is determined whether there is a road with the same width between the connected roads (step S69). If there is a road with the same width and there is connectivity (step S70), since it corresponds to case 6, the CPU performs a connection process (step S71). When there is no connectivity (step S70), since it corresponds to case 7, the CPU performs a convex polygon processing (step S73).

  When there is no road having the same width between the connecting roads (step S69), when there is a connecting road wider than the target road (step S72), since the case corresponds to case 8, the CPU sets the end shape to a rectangle. (Step S74). If there is no wide connecting road (step S72), since it corresponds to case 9, the CPU performs a convex polygon processing (step S73).

  FIG. 19 is an explanatory diagram showing an example of end processing in a modification. In the figure, roads R11 to R17 are national roads, roads R21 to R24 are prefectural roads, and roads R31 to R33 are general roads.

  The intersection IC3 corresponds to the case 3 in FIG. 17 because the national roads R12 and R13 and the prefectural roads R22 and R23 are mixed and have connectivity. Accordingly, connection processing is performed between the national roads R12 and R13, and connection processing is performed between the prefectural roads R22 and R23. In the figure, the result of applying the connection process to the national road R13 is shown with bold lines and hatching.

  The intersection IC4 corresponds to the case 4 in FIG. 17 because the national roads R14 and R15 and the prefectural road R21 are mixed and the national roads have no connectivity. Accordingly, the convex polygon processing is performed on the national roads R14 and R15. In the figure, the processing results for the national road R14 are shown with bold lines and hatching.

  A national road R11 and prefectural roads R21 and R22 are mixed at the intersection IC5. When the national road R11 is the target road, the connecting roads R21 and R22 are of the same type, but are of a different type from the target road. Therefore, the intersection IC5 corresponds to the case 5 in FIG. 17, and the national road R11 is subjected to the convex polygon processing. In this example, the target road R11 has a higher priority than the connection roads R12 and R22, and therefore, unnecessary portions are deleted. In the figure, the processing results for the national road R11 are indicated by bold lines and hatching. When the target road R11 is a general road having a lower priority than the connecting roads R12 and R22, and the width of the target road R11 is narrower than the width of the connecting road, the end of the target road R11 is As shown by the broken line in the figure, it is converted into a convex polygon.

  The intersection IC5 corresponds to the case 3 for the prefectural roads R21 and R22. Accordingly, connection processing is applied to the prefectural roads R21 and R22. However, in order to avoid complication of the figure, illustration of the processing result is omitted.

  At the intersection IC6, a national road R16, a prefectural road R21, and a general road R31 are mixed. However, it is assumed that the national road R16 and the prefectural road R21 have the same width, and that both have connectivity. In this case, the intersection IC6 corresponds to the case 6 in FIG. 17, and a connection process is performed on the national road R16 and the prefectural road R21. In the figure, the processing results for the national road R16 are indicated by bold lines and hatching.

  At the intersection IC7, a national road R17, a prefectural road R24, and a general road R33 are mixed. The national road R17 and the prefectural road R24 have the same width, but there is no connectivity between the two. In this case, the intersection IC7 corresponds to Case 7 in FIG. 17, and the convex polygon processing is performed on the national road R17 and the prefectural road R24. In the figure, the processing results for the national road R17 and the prefectural road R24 are indicated by bold lines and hatching.

  At the intersection IC9, a national road R13, a prefectural road R24, and a general road R32 are mixed. When the national road R13 is the target road, all of the connecting roads are narrower than the target road. Since the intersection IC9 corresponds to the case 9 in FIG. 17 for the national road R13, the convex polygon processing is applied to the national road R13. In the figure, the processing results for the national road R13 are indicated by bold lines and hatching.

  In the intersection IC9, when the prefectural road R24 and the general road R32 are the target roads, a national road R13 having a width wider than the target road exists in the connection road. Therefore, since the intersection IC9 corresponds to the case 8, the end shapes of the prefectural road R24 and the general road R32 are kept rectangular. The proper use shown in the modification is merely an example, and the proper use of the end treatment can be further used under various conditions.

F. Edge line processing:
FIG. 20 is an explanatory diagram showing a specific example of edge line processing. The edge line process is a process for erasing unnecessary portions of the edge line in accordance with the connection state or overlapping state with other polygons for the target road. FIG. 20 shows an example of processing when there are polygons G11 to G13, G20, G30, G41 to G42, G50, G61 to G62, and G71 to G72. G11 to G13, G41 to G42, G61 to G62, and G71 to G72 are grouped, respectively. In the figure, the polygon shape before the edge line processing is shown by a solid line or a broken line. The thick line in the figure represents the state of the edge line after the edge line processing.

  A case of processing the polygon G30 will be described. At the time before processing, an edge line is generated on the entire circumference of the polygon G30 including the portion indicated by the broken line in the drawing. In this example, the polygon G30 is connected to the polygons G13 and G12. Whether or not both are connected can be determined by whether or not there is a node at the intersection of the polygons G30, G12, and G13. When the polygons G30, G12, and G13 are connected, the edge line is cut at the intersection of the side lines of each polygon, and unnecessary portions are deleted.

  A case of processing the polygon G71 will be described. The polygon G71 is assumed to be a general road with a height level of zero. On the other hand, it is assumed that the polygon G13 intersecting the polygon G71 is a national road with a height level of 2. That is, the polygon G13 at the height level 2 is an elevated road that passes over the polygon G71 at the height level 0. In such a case, the elevated road can be expressed by giving priority to the edge line of the polygon G13 positioned above and deleting the portion existing inside the polygon G13 from the edge line of the polygon G71 positioned below. it can.

  However, in the present embodiment, a technique for expressing the elevated road without actually deleting the edge line by controlling the drawing order of the polygons is adopted. That is, when the map is expressed, after the polygon G71 positioned at the lower level is drawn, the polygon G13 positioned at the higher level is overwritten. By doing so, even if the edge line remains at the time when the lower polygon G71 is drawn, the state shown in the figure can be realized by overwriting the upper polygon G13.

  Next, processing of the polygons G11 and G12 and the polygons G41 and G42 will be described. Polygons G11 and G12 are grouped (hereinafter referred to as “group 1”) and represent one continuous road. Polygons G41 and G42 are similarly grouped (hereinafter referred to as “group 4”) and represent one continuous road. These two roads run relatively close together.

  In such a state, the polygons of groups 1 and 4 may partially overlap. In the drawing, the polygons G41 and G42 are partially hatched so that the overlapping state of the polygons can be easily recognized. In some cases, these roads actually overlap with each other, such as overpasses. Depending on the setting value of the width when generating road polygons from links (see Fig. 3), roads that do not actually overlap may be represented as overlapping. There is also a possibility.

  In this embodiment, when two groups are compared, edge line processing is executed so that the superiority or inferiority of the polygons included in each group is always constant. For example, in the example shown in the figure, the edge line processing is executed so that group 1 has priority over group 4. As a result, in the portion where the polygons of groups 1 and 4 overlap, the edge line of the polygon of group 4 is always erased. This processing can also be realized by controlling the drawing order so that group 1 is overwritten on group 4.

  An example of processing when the superiority or inferiority of polygons is not uniform among groups is shown in the upper right of the figure. In this example, the polygon G12 is superior to the polygon G42, but the polygon G11 is inferior to the polygon G41. As a result, the edge line E2 bends discontinuously at the boundary between the polygons G41 and G42 as shown in the figure, resulting in an uncomfortable feeling during display.

  On the other hand, according to the process of the present embodiment, the edge line E1 for the group 1 can be drawn continuously, and a sense of discomfort on the display can be avoided. The processing of this embodiment can be realized by reflecting the superiority or inferiority set for the polygons grouped with the target road in the edge line processing of the target road. In the example shown in the figure, when the polygon G11 is processed, the grouped polygons G12 and G13 are referred to. When the drawing order is set so that the polygon G13 is superior to the polygon G42, the drawing order may be reflected in the polygon G11.

  The edge line process of the present embodiment is realized by a combination of the processes described above. In the example in the figure, the description of the processes of the polygons G20, G40, and G61 to G62 is omitted, but any of the processes described above may be applied according to the connection status with other polygons.

  FIG. 21 is a flowchart of edge line processing. FIG. 20 shows the contents of the edge line processing described with reference to FIG. 20 and corresponds to step S50 of the road polygon generation processing (FIG. 2).

  When processing is started, the CPU selects a processing target road (step S51), and determines whether or not there is a polygon that overlaps the processing target road (hereinafter referred to as "OL polygon"), that is, a polygon that partially overlaps the target road (step S51). S52). If there is no OL polygon, it is not necessary to consider the degree of overlap with other polygons, so the drawing order is simply set according to the road type (step S58).

  The smaller the value of the drawing order, the higher the priority, indicating that the drawing order is overwritten after other polygons. When there is no OL polygon, the lowest drawing order is set for each road type. For example, in the case of a national highway, the drawing order “20 to 29” is set to “29”.

  If an OL polygon exists (step S52), it is determined whether or not the polygon is elevated (step S53). This determination can be made by comparing the height levels of the target road and the OL polygon.

  If it is elevated, the drawing order is determined according to the height level (step S54). As described in the processing of the polygon G71 in FIG. 20, the drawing order is set so that the polygon having a higher value has priority over the polygon having the lower height level.

  If the road is not an elevated road (step S53), the grouped polygons are extracted for the target road and the OL polygon (step S55). In the example shown in FIG. 4, if the target road is G11, the polygons G12 and G13 grouped with the polygon G11 and the polygons G41 and G42 overlapping the polygon G11 are extracted.

  The CPU determines whether or not the drawing order has been set for any polygon between the groups thus extracted (step S56). If the drawing order is set, the preset value is also applied to the drawing order of the target road (step S57), and if not set, the drawing order is set according to the road type of the target road (step S57). S58). Accordingly, as described with reference to FIG. 20, the superiority and inferiority relationship with the polygons belonging to other groups can be unified for each group, and the appearance can be ensured. The CPU repeatedly executes the above processing for all the polygons (step S59). Although not shown in the flowchart, the CPU erases unnecessary edge lines in the above process. For example, this is the process described for the polygon G30 in FIG.

G. Effects and variations:
According to the map data generation apparatus of the present embodiment described above, polygons are grouped and reflected in processing such as edge line processing. In addition, the terminal shape determination method can be properly used in consideration of the road type of the target road and the connection road. Based on such characteristics, the map data generation device can generate road polygon data that does not impair the appearance with a relatively light load.

  Needless to say, the present invention is not limited to the above-described embodiments, and various configurations can be adopted without departing from the spirit of the present invention. For example, the various processes described in the embodiments are not necessarily all provided, and some of them may be omitted as appropriate. Further, a processing method different from the processing method shown in the embodiment may be applicable to the terminal shape determination processing, the edge line processing, and the like. In this case, other processing methods may be added to the processing of the embodiment, or may be used separately from the processing described in the embodiment. In addition, in the embodiment, the process realized by software can be realized by hardware.

It is explanatory drawing which shows the structure of the map data generation apparatus as an Example. It is a flowchart of a road polygon generation process. It is a flowchart of a polygonization process. It is explanatory drawing which shows the example of a grouping process. It is a flowchart of a grouping process. It is a flowchart of the grouping process as a modification. It is a flowchart of a connection process. It is a flowchart of a fillet process. It is a flowchart of a convex polygon-ized process. It is explanatory drawing which shows the method of M character processing. It is explanatory drawing which shows the terminal process method (1). It is explanatory drawing which shows a terminal process method (2). It is explanatory drawing which shows the effect of a convex polygon-ized process. It is explanatory drawing which shows the terminal process method (3). It is explanatory drawing which shows the list of the method of a terminal process. It is a flowchart of the terminal process of a polygon. It is explanatory drawing which shows the list of the method of the terminal process in a modification. It is a flowchart of the terminal process in a modification. It is explanatory drawing which shows the example of the terminal process in a modification. It is explanatory drawing which shows the specific example of an edge line process. It is a flowchart of an edge line process.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Map data generation apparatus 11 ... Communication part 12 ... Main control part 13 ... Intermediate data storage part 14 ... Polygon data generation part 15 ... Grouping part 17 ... Edge line processing part 18 ... Specification table 40 ... Network data 50 ... Polygon data

Claims (16)

A map data generation device for generating map data for drawing a map,
A basic data input unit for inputting geometric data and attributes used to determine the shapes of a plurality of polygons used for drawing a road included in the map data;
To determine the end shape of the road polygon based on the attributes of both the target road to be processed and the connected road to be connected to the target road, the shape determined based on the geometric data, and at least part of the direction Select which of the multiple types of determination methods prepared in advance should be applied,
A map data generation device, comprising: a polygon data generation unit that determines a terminal shape of each polygon according to the geometric data according to the selected determination method and generates polygon data for drawing a road polygon. The map data generation device according to claim 1,
The geometric data is network data representing a connection state of roads by nodes and links,
The polygon data generation unit is a map data generation device that determines a shape of the polygon based on a side line composed of a point group located at a predetermined distance from the link and the end shape. The map data generating device according to claim 1 or 2,
The said polygon data generation part is the map data generation apparatus which performs the said selection based on the difference in the road classification of the said object road and connection road. The map data generation device according to claim 3,
The polygon data generation unit selects the selection in the case where all the road types of the target road and the plurality of connection roads are the same and in other cases when there are a plurality of the connection roads with respect to the target road. Map data generating device for switching the conditions for. The map data generating device according to claim 3 or 4,
The polygon data generation unit, when there are a plurality of connected roads with respect to the target road, a map for switching the selection condition depending on whether or not there is a connected road having the same type as the target road Data generator. The map data generation device according to claim 1,
The said polygon data generation part is a map data generation apparatus which performs the said selection based on at least one of the difference in the width | variety of the said object road and connection road, and the connection angle between both. The map data generation device according to any one of claims 1 to 6,
The terminal shape determining method is a map data generation device including a method of defining the terminal shape by a line segment connecting the intersections of the side lines of the target road and the connecting road. The map data generation device according to claim 1,
The method for determining the end shape includes a method for defining the end shape by a polygonal line connecting side lines of the target road so that the target road becomes a convex polygon. A computer program for generating map data for drawing a map,
A subprogram for inputting geometric data and attributes used to determine the shapes of a plurality of polygons used for drawing a road included in the map data;
To determine the end shape of the road polygon based on the attributes of both the target road to be processed and the connected road to be connected to the target road, the shape determined based on the geometric data, and at least part of the direction A subprogram for selecting which of a plurality of types of determination methods prepared in advance is to be applied;
A computer program comprising: a subprogram for obtaining polygonal data for drawing a polygon of a road by obtaining an end shape of each polygon according to the geometric data in accordance with the selected determination method. A map data generation device for generating map data for drawing a map,
A basic data input unit for inputting geometric data and attributes used to determine the shapes of a plurality of polygons used for drawing a road included in the map data;
A grouping unit that groups at least some of the plurality of polygons based on a predetermined rule;
A map data generation apparatus comprising: a polygon data generation unit configured to generate polygon data for drawing the polygon using the geometric data based on the group. The map data generation device according to claim 10,
The geometric data is network data representing a connection state of roads by nodes and links,
The polygon data generation unit is a map data generation device that determines a shape of the polygon based on a side line composed of a point group located at a predetermined distance from the link and the end shape. The map data generation device according to claim 10 or 11,
The said grouping part is a map data generation apparatus which performs said grouping using at least one of the name of the road which the said polygon represents, and the traffic regulation attached | subjected to this road. The map data generation device according to any one of claims 10 to 12,
The attribute includes the road type of the road represented by the polygon,
The grouping unit is a map data generation device that performs the grouping between polygons having the same road type. The map data generation device according to any one of claims 10 to 13,
The grouping unit is a map data generation device that performs the grouping based on a connection angle between the plurality of polygons. The map data generation device according to any one of claims 10 to 14,
The polygon data generation unit includes an edge line processing unit for attaching edge line data for representing an edge line of the road to each polygon.
The said edge line process part is a map data generation apparatus which produces | generates the said edge line data so that the edge line of the said grouped polygon becomes continuous. A computer program for generating map data for drawing a map,
A subprogram for inputting geometric data and attributes used to determine the shapes of a plurality of polygons used for drawing a road included in the map data;
A grouping subprogram for grouping at least some of the plurality of polygons based on a predetermined rule;
A computer program comprising: a polygon data generation subprogram for generating polygon data for drawing the polygon based on the geometric data based on the group.