JP2015001575A - Map data generation system and map output system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technique for further realistically drawing center lines of roadways by taking account of median strips in a map.SOLUTION: A map data generation system 100 includes: a road network database 220 that stores road network data representing roads with nodes and links; a drawing database 240 for storing map polygon data including road polygon data 242 and median strip polygon data 244; and a division line polygon data generation unit 116. The division line polygon data generation unit 116 generates division line polygon data 248 on the basis of links. In that case, the division line polygon data generation unit, besides the links, refers to the median strip polygon data 242, and specifies regions where the median strips are present to generate the division line polygon data 248 in a state of avoiding the median strips.

Description

  The present invention relates to a technique for generating lane marking data for drawing lane markings such as a lane center line, a lane outside line, and a lane boundary line drawn on a road on a map.

  In recent years, maps tend not only to represent the arrangement of features such as roads and buildings, but also to reproduce a more realistic state. As an example, various road markings such as pedestrian crossings, stop lines, zebra zones (conduction zones), and traveling direction arrows drawn on real roads, and lane markings such as roadway outer lines, roadway center lines, and lane boundaries May be required to be reproduced on a map. Thus, by reproducing a state close to reality on the map, the user of the map can easily contrast the map with the local site, and the convenience of the map can be improved. Such a demand is higher for electronic maps displayed on a display such as a computer or a navigation device than for maps as printed matter. Further, there is a strong demand for a three-dimensional map in which features and the like are three-dimensionally displayed rather than a two-dimensional map.

As a technique related to road markings and lane markings, for example, there are techniques described in Patent Documents 1 and 2 below.
In the technique described in Patent Document 1, road markings (road markings and lane markings) are extracted from road surface images taken by a video camera mounted on a vehicle, and image data of road markings is generated. However, in this technique, in order to generate road marking image data, a field survey of photographing the road surface is indispensable. For this reason, if it is attempted to draw road markings on roads nationwide, the survey load will be enormous.
Therefore, in the technique described in Patent Document 2, road marking data for drawing road markings and lane markings is generated using drawing data such as existing road polygons and road network data. According to this technique, it is possible to reduce the load while ensuring a certain degree of accuracy when generating road marking data.

JP 2010-175756 A JP 2012-133132 A

In the technique described in Patent Document 2, when determining the position of the road center line (also simply referred to as the center line) at the time of generating the road marking data, by calculating the lane width × the number of lanes, The width used for the lane is determined, and the position of the center line is determined by dividing the width by the number of lanes on the upper and lower lines.
However, on an actual road, the center line is drawn in various ways, and the technique described in Patent Document 2 described above does not always sufficiently reproduce the center line, and there is still room for improvement.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a technique for drawing a roadway center line more realistically on a map.

In order to solve at least a part of the above-described problems, the present invention employs the following configuration.
A first device of the present invention is a map data generation system for generating map data for drawing a map,
A road network database for storing road network data representing roads by nodes and links;
A drawing database for storing map polygon data including road polygon data for drawing the road and median polygon data for rendering a median strip;
A lane line drawing data generation unit that generates lane line drawing data for drawing a road center line on the road based on the road network data and the map polygon data;
The lane marking drawing data generation unit identifies an area where the median strip exists based on the median strip polygon data, avoids the area, and generates the lane marking data based on the link It is characterized by that.

The roadway center line is a lane marking that divides lanes facing each other on the road. This roadway center line is drawn on both sides of the median strip when a median strip exists on the road. In order to draw the road center line based on the road network data (link), for example, on a road with a median strip, a method of offsetting the generated road center line in the width direction by a predetermined distance is conceivable. .
In order to draw the roadway center line with a light processing load, it is preferable to refer to a smaller number of databases. Further, if the purpose of drawing the road center line on the map is to improve the reality, it is not necessary to accurately reproduce the road center line. From this point of view, it can be said that it is preferable to reproduce the roadway center line by referring only to the road network data. However, the link in the road network data is not necessarily set at the center of the road, and the shape and width of the median strip are various. Although the inventor of the present application tried various methods, there was a case where the center line of the roadway could not be drawn at a desired position by the method of referring only to the road network data. Moreover, if the roadway centerline is drawn over the median strip, or conversely, the roadway centerline is drawn at a position that is unnaturally separated from the median strip, the effect is simply that the roadway centerline is inaccurate. Not only that, but the reality of the map could be compromised.
Therefore, the map data generation system of the present invention refers to the median polygon data in addition to the road network data, and based on this, identifies the region where the median zone exists, The restriction condition to avoid is imposed, and the lane marking data of the roadway center line is generated. In this way, it is possible to transform the roadway center line generated from the link etc. so that the positional relationship with the median strip does not become unnatural by imposing restrictions when generating the road center line. It becomes. By doing so, it becomes possible to improve the reality of the roadway center line.
The lane marking data may be vector data such as polygon data or raster data.

There is a case where only one roadway center line is drawn and a case where two roadway centerlines are drawn. When there is at least a median strip, it is normal for two roadway center lines to be drawn on either side of the roadway center line. Therefore, first, the lane marking drawing data generation unit determines whether the median strip exists so as to generate lane line drawing data for two roadway center lines for a road that is determined to have a median strip. Accordingly, it is desirable to switch the number of lane marking data generated.
As a method for avoiding the region where the median strip exists, two methods are conceivable. The first method is a method of generating a roadway center line so as to avoid a region where a median strip exists in advance. The first method includes, for example, a method in which a part of the outline of the median polygon is translated to be used for generating the road centerline. The second method is a method in which a roadway center line is once generated, and then necessary movement and deformation are performed in accordance with the positional relationship between the roadway center line and the median strip. Any method may be employed in the present invention.

In the map data generation system of the present invention,
The lane marking drawing data generation unit obtains a center line of the central separator based on the central separator polygon data, and generates the lane marking drawing data based on the center line and the link. Also good.
The center line of the median strip can be obtained, for example, by thinning the median polygon.

The position and shape of the median strip are diverse and do not necessarily overlap the link. Therefore, when the road center line is generated on the basis of the link, the correction and deformation of the position becomes large, and complicated processing may be required or an appropriate result may not be obtained. On the other hand, since the center line of the median strip can be said to be a line segment that reflects the position and shape of the median strip in advance, it is relatively easy to generate a roadway center line using this. It becomes possible to obtain a simple roadway center line.
The above aspect is particularly useful when the median strip is divided and provided along the traveling direction of the vehicle, and when the centerlines of the median strip thus provided are shifted from each other. High nature.

In the map data generation system of the present invention,
The lane marking drawing data may be data for drawing a roadway center line parallel to a straight line portion along the link of the center separation band.

The median strip is often formed by a combination of a straight portion and a curved portion such as an arc. However, the straight line portion may appear not only in the road running direction, that is, in the direction along the link, but also in the direction intersecting the link in a place where a crosswalk that crosses the median strip is formed. . The “straight line portion along the link of the median strip” means to exclude the straight line portion that intersects the link in this way. Whether or not it is a straight line portion along the link can be, for example, a line segment whose angle with the link is less than or equal to a predetermined value (for example, less than 45 degrees) in the outline of the median strip polygon. The straight line portion along the link of the median strip, that is, the edge of the median strip polygon, can be extracted by analyzing the median polygon.
Thus, if the road center line is drawn in parallel with the edge of the median strip polygon, it is possible to easily and reliably avoid the overlap between the median strip and the road center line. In addition, because the roadway center line can be drawn along the outline of the median strip, even if the width of the median strip is changing, the roadway centerline looks good according to the shape of the median strip Can be drawn.
When a plurality of median strips are separated from each other on the same road, the lane marking drawing data generation unit connects them between the roadway median lines along the edges of the median strips. What is necessary is just to produce the plotting line drawing data which interpolates with a straight line or a curve.

In the map data generation system of the present invention,
The lane marking data generation unit may extract median zone polygon data to be considered in generating the lane marking data based on the distance from the link prior to the generation of the lane marking data. Good.

In the present invention, the median strip is taken into account when generating the roadway center line. However, not all polygon data on the target road is a median strip. This is because, on the road, a plurality of polygon data such as sidewalks may be mixed in addition to the median strip. In consideration of such a case, it is preferable to extract the median strip polygon data to be considered in the generation of the lane marking data before the lane marking data is generated.
If attribute data indicating the median strip or data that can identify the corresponding link is attached to the polygon of the median strip, it is relatively easy to refer to these data. However, if there is no such data, it is difficult to extract the median strip. According to the above aspect, the median strip is extracted based on the distance between the link and the polygon. By doing so, it is possible to extract a polygon considered to exist near the center as a median strip polygon according to the positional relationship between the link and the polygon.
The distance from the link can be, for example, the shortest distance between the link and a representative point such as a polygon center line, a part of the contour line, or the center of gravity. The distance from the link may be the shortest distance between the straight line portion along the polygonal link on the road and the link.
As the extraction method, for example, in the case of a road where only one link is set, that is, a single road, it is assumed that the link exists in the center and the distance from the link is equal to or less than a predetermined value. A polygon may be extracted. The predetermined value in this case can be set within a half width of the road. In addition, in the case of two roads with two links in the up and down directions, it is assumed that there is a median between the links, and the sum of the distance from each link to the polygon is It is good also as what is extracted on the conditions of below predetermined value. The predetermined value in this case can use the distance between the two links.
In the above extraction, as described above, instead of the condition that only the median polygon is applicable, an exclusion condition that is applicable to other than the median polygon on the road of interest such as a sidewalk polygon is used. You may do it.

In the map data generation system of the present invention,
The link is associated with the number of bidirectional lanes on the road,
The lane line drawing data generation unit further draws lane line drawing data for drawing lane lines other than the lane center line in the region from the lane center line to the road edge of the road based on the number of lanes. Is generated.

By doing this, drawing of the dividing line other than the road center line, that is, the road outside line and the lane boundary line, in consideration of the positional relationship with the median strip between the road center line and the road edge. realizable. The roadway outer line may be drawn from the road edge, for example, on the inner side of the width of the roadside belt. In addition, if the lane boundary line is drawn at a position that equally divides the roadway center line and the roadway outer line according to the number of lanes, the balance between the division lines can be maintained.
The road edge may be extracted, for example, by obtaining the intersection of the outline of the road polygon and a straight line perpendicular to the link, or the position of the road edge or the road outer line may be determined by the distance from the link. You may give prescription data. Further, when a sidewalk polygon exists on the road polygon, a boundary line along the link between the sidewalk polygon and the road polygon may be extracted, and this boundary line may be used as a road edge.

A second device of the present invention is a map output system for outputting a map,
Stores map polygon data including road polygon data for drawing a road, median polygon data for drawing a median strip, and plot line drawing data for drawing a road centerline on the road A drawing database;
The road is drawn using the road polygon data, and the median strip and the road centerline are drawn using the median polygon data and the lane marking data superimposed on the road polygon data, and the map is output A map output unit,
The lane marking data is
A map data generation system for generating map data for drawing a map,
A road network database for storing road network data representing roads by nodes and links;
A map polygon database storing map polygon data including road polygon data for drawing the road and median strip polygon data for drawing a median strip;
A lane line drawing data generation unit that generates the lane line drawing data based on the road network data and the map polygon data;
The lane marking drawing data generation unit avoids an area where the median strip exists and is specified based on the median polygon data, and generates the lane marking data based on the link.
It is data generated by a map data generation system.

  According to the map output system of the present invention, when a median strip exists on the road, a map drawn so that the roadway center line does not overlap the median strip can be output. Examples of output include various modes such as display on a display and printing by a printer.

  The present invention does not necessarily have all the various features described above, and may be configured by omitting some of them or combining them appropriately. The present invention can also be configured as an invention of a map data generation method and a map output method in addition to the above-described configuration as a map data generation system and a map output system. Further, the present invention can be realized in various modes such as a computer program that realizes these, a recording medium that records the program, and a data signal that includes the program and is embodied in a carrier wave. In addition, in each aspect, it is possible to apply the various additional elements shown above.

  When the present invention is configured as a computer program or a recording medium on which the program is recorded, it may be configured as an entire program for controlling the operation of the map data generation system and the map display system, and the functions of the present invention It is good also as what comprises only the part to fulfill. The recording medium includes a flexible disk, a CD-ROM, a DVD-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, a computer internal storage device (RAM or Various types of computer-readable media such as a memory such as a ROM and an external storage device can be used.

It is explanatory drawing which shows schematic structure of the map output system 10 as one Example of this invention. It is explanatory drawing which shows schematic structure of the map data generation system 100 as one Example of this invention. It is explanatory drawing which illustrates some road network data stored in the road network database. It is explanatory drawing which shows typically the outline | summary of the production | generation method of the lane marking polygon data 248 using road network data. It is explanatory drawing which shows the example of an output of a roadway outer side line polygon and a roadway center line polygon. It is explanatory drawing which shows typically the outline | summary of the production | generation method of the roadway centerline polygon data using road network data and map polygon data. It is a flowchart which shows the flow of a division line drawing data generation process. It is a flowchart which shows the flow of a roadway outside line production | generation process. It is a flowchart which shows the flow of a roadway centerline production | generation process. It is a flowchart which shows the flow of a roadway centerline production | generation process. It is a flowchart which shows the flow of a lane boundary line production | generation process. It is a flowchart which shows the flow of a map output process. It is explanatory drawing which shows the road network data as a modification. It is explanatory drawing which shows the road network data as a modification. It is a flowchart which shows the flow of the roadway centerline production | generation process as a modification. It is a flowchart which shows the flow of the roadway centerline production | generation process as a modification. It is a flowchart which shows the flow of the roadway centerline production | generation process as a modification.

Hereinafter, embodiments of the present invention will be described based on examples.
A. Map output system configuration:
FIG. 1 is an explanatory diagram showing a schematic configuration of a map output system 10 as an embodiment of the present invention. The map output system 10 is a system that displays and outputs a map in response to a display instruction from a user. In order to improve the convenience of the map, the map output system 10 of the present embodiment has various road markings such as a pedestrian crossing, a stop line, a zebra zone (conduction zone), a traveling direction arrow on the road in the map, Draw lines such as roadway outer lines, roadway center lines, and lane boundary lines, and median strips.

  The map output system 10 is configured by installing software for executing map output processing, which will be described later, in a computer including a CPU, RAM, and ROM (not shown). In this embodiment, an example of a system configuration that operates in a stand-alone manner is shown, but each element shown in the figure may be realized by distributed processing using a plurality of computers connected via a network.

The map output system 10 includes a drawing database 20 as a database used for map output processing. The drawing database 20 stores various map polygon data for drawing a map. Map polygon data includes, for example, building polygon data for drawing buildings, water polygon data for drawing seas, rivers, lakes, etc., road polygon data for drawing roads, and median strips. Includes median strip polygon data for drawing, sidewalk polygon data for drawing sidewalks, road marking polygon data for drawing road markings, lane marking polygon data for drawing lane markings, etc. It is. The drawing database 20 also stores marks and character data for drawing marks and characters displayed on the map.
Of the various map polygon data described above, the lane marking polygon data is generated by the map data generation system 100. The map data generation system 100 will be described in detail later.
The drawing database 20 may be stored in a hard disk or the like in the map output system 10, or may be provided from a server connected via a network. Moreover, you may provide from storage media, such as DVD.

The map output system 10 is provided with various functional blocks for executing map output processing with reference to the drawing database 20 described above. The map output system 10 includes a main control unit 12, a command input unit 14, a transmission / reception unit 16, and a map output unit 18 as these functional blocks. In this embodiment, these functional blocks are configured by software by installing a computer program for realizing each function, but may be configured by hardware.
Hereinafter, the contents of each functional block will be described.

The main control unit 12 performs a function of integrally controlling the entire functional blocks and realizing map output by the map output system 10.
The command input unit 14 inputs various commands related to map output based on user operations. Examples of the input command include designation of a map display area and designation of a map display mode (for example, a two-dimensional display mode and a three-dimensional mode). The input command includes an instruction to acquire map polygon data from other systems such as the map data generation system 100.
For example, when the drawing database 20 is upgraded, the transmission / reception unit 16 transmits a download request for map polygon data or the like to another system such as the map data generation system 100, and downloads various data as a response. To do. The downloaded map polygon data and the like are stored in the drawing database 20.
The map output unit 18 reads necessary data according to the display area and display mode designated by the user, reads the necessary data, draws the map, and outputs it. The map output unit 18 displays the drawn map on the display 30 or prints it with a printer (not shown).

B. Configuration of map data generation system:
FIG. 2 is an explanatory diagram showing a schematic configuration of the map data generation system 100 as an embodiment of the present invention. The map data generation system 100 generates lane marking polygon data 248 for drawing a lane marking in accordance with an instruction from an operator.

  The map data generation system 100 is configured by installing software for causing each process to be described later to be installed in a computer including a CPU, RAM, and ROM (not shown). In this embodiment, an example of a system configuration that operates in a stand-alone manner is shown, but each element shown in the figure may be realized by distributed processing using a plurality of computers connected via a network.

The map data generation system 100 includes a map database 200 as a database used for lane marking drawing data generation processing. The map database 200 includes a road network database 220 and a drawing database 240.
The road network database 220 stores road network data in which roads are represented by nodes and links. In the road network data, attribute data indicating a road type, a road name, the number of lanes, and the like are also set for each link and node. The road network data will be described in detail later.
The drawing database 240 includes road polygon data 242 for drawing a road, center divider polygon data 244 for drawing a center divider, and sidewalk polygon data 246 for drawing a trail as map polygon data. Storing.
The drawing database 240 also stores lane marking polygon data 248 generated by lane marking drawing data generation processing described later. In the present embodiment, the drawing database 240 stores roadway outer line polygon data, roadway centerline polygon data, and lane boundary line polygon data as the division line polygon data 248. As will be described later, the lane marking polygon data 248 includes road network data stored in the road network database 220, road polygon data 242 stored in the drawing database 240, median strip polygon data 244, sidewalk polygon data. 246.
The road network database 220 and the road polygon data 242, the median strip polygon data 244, and the sidewalk polygon data 246 in the drawing database 20 may be stored in a hard disk or the like in the map data generation system 100, or on the network. You may provide from the connected server. Moreover, you may provide from storage media, such as DVD.

The map data generation system 100 is provided with various functional blocks for executing the lane marking drawing data generation processing with reference to the road network database 220 and the drawing database 240 described above. The map data generation system 100 includes a main control unit 112, a command input unit 114, a lane marking polygon data generation unit 116, and a transmission / reception unit 118 as these functional blocks. In this embodiment, these functional blocks are configured by software by installing a computer program for realizing each function, but may be configured by hardware.
Hereinafter, the contents of each functional block will be described.

The main control unit 112 performs a function of integrating and controlling the entire functional blocks and realizing the generation of the lane marking polygon data 248 by the map data generation system 100.
The command input unit 114 inputs various commands related to generation of the lane marking polygon data 248 based on the operation of the operator. Examples of the command to be input include designation of an area in which the lane marking polygon data 248 is to be generated. The input command includes notification of update of the lane marking polygon data 248 to the map output system 10.
The lane marking polygon data generation unit 116 refers to the map database 200 for the area specified by the operator, reads necessary data, and generates the lane marking polygon data 248. The generated lane marking polygon data 248 is stored in the drawing database 240.
For example, when the lane marking polygon data 248 is upgraded, the transmission / reception unit 118 receives a download request from the map data generation system 100 and transmits the lane marking polygon data 248 as a response.

C. Road network data:
FIG. 3 is an explanatory diagram illustrating a part of the road network data stored in the road network database 220. In the road network data, “link”, “node / composition point”, “number of lanes”, and “passing point defining data” are associated with each other. In this embodiment, the link is set to pass through the center of the road.
“Link” indicates link identification information.
The “node / composition point” indicates identification information of nodes at both ends of the link and identification information of a configuration point representing a point through which the link passes. The node and the component point are given coordinate values indicating their positions (not shown).
“Number of lanes” indicates the number of lanes in a bidirectional lane (up lane, down lane) on the road corresponding to the link.
“Passing point defining data” is data for defining a passing point through which a lane marking passes. In FIG. 3, the lane marking is assumed to be the roadway outer line. The passing point defining data includes “road width” and “roadside width”. Since the roadway outer line is drawn on the center side from the left and right road edges of the road by the width of the roadside belt, the “road width” and the “roadband width” can be used as passing point defining data.

In the illustrated example, nodes at both ends of the link LK1 are nodes ND1 and ND2. Further, the link LK1 includes constituent points P1 to P4 as constituent points representing points through which the link LK1 passes. Further, the link LK1 is a one-lane road on one side where an opposite lane exists from the node ND1 to the node ND2, as shown in the “number of lanes” column.
In addition, the nodes ND1, ND2, and the configuration points P1 to P4 respectively include road widths Wn1, Wp1, Wp2, roads at each node and the configuration points, as passage point definition data that defines the passage points through which the lane markings pass. Wp3, Wp4, Wn2, and roadside belt widths Wr1, Wr2 are associated with each other. The width Wr1 of the roadside band is the width of the roadside band of the lane (for example, the upward lane) whose traveling direction is from the node ND1 to the node ND2, and the width Wr2 of the roadside band is the width of the roadside band ND1 It is the width of the roadside zone of the lane (for example, descending lane) that is the direction toward the road. If the roadway outer line is drawn only on one side of the road, the width of any roadside belt may be omitted. Further, the width of the roadside belt may be given for each node or component point.
As shown in the figure, the passing point defining data may be stored in the road network database 220 as a part of the road network data, or stored in another database in association with the nodes and the configuration points. You may do it.
Hereinafter, a method for generating the lane marking polygon data 248 using the above-described road network data will be described.

D. How to generate lane marking polygon data:
FIG. 4 is an explanatory diagram schematically showing an outline of a method for generating lane marking polygon data 248 using road network data. Here, a method of generating lane marking polygon data 248 (roadway outer line polygon data, roadway centerline polygon data) for drawing the roadway outer line and the roadway centerline using the road network data shown in FIG. 3 will be described. To do.
In the illustrated example, it is assumed that the link LK1 is set to pass through the center of the road polygon PGr1. Further, it is assumed that neither the median strip polygon representing the median strip nor the sidewalk polygon representing the sidewalk exists on the road polygon PGr1.

First, the passing point of the roadway outer line is obtained based on the node, composing point, and passing point defining data in the road network data.
In the present embodiment, the passing point defining data is the width of the road in the directions of the normals L1 to L6 of the nodes and the component points, and the width of the road in the roadside zone. Therefore, assuming that the link is in the center of the road, the distance from the link to the vehicle outer line is the difference between 1/2 of the road width and the width of the roadside belt. In this embodiment, as shown in FIG. 3, the width of the road is given for each node and each component point, and the width of the roadside band is common. However, the width of the roadside belt is given separately in the upward direction and the downward direction. Using such passing point defining data, for example, in the node ND1, the distance to the passing point PL1 in the upstream direction (node ND1 → ND2 direction) is obtained as (Wn1) / 2−Wr1, and the downstream direction (node ND2 → ND1). (Direction) to the passing point PL2 is obtained as (Wn1) / 2−Wr2. The positions of the other passing points PL3 to PL12 can also be obtained using the width values shown in the figure.

Next, as indicated by the alternate long and short dash line in the figure, the curve C1 smoothly connecting the passing points PL1, PL3, PL5, PL7, PL9, and PL11 of one roadway outer line, and the passing point of the other roadway outer line Curves C2 that smoothly connect PL2, PL4, PL6, PL8, PL10, and PL12 are obtained. As the curves C1 and C2, a Bezier curve or a spline curve can be used.
Then, by giving the curves C1 and C2 the widths of the predetermined division lines, the roadway outer line polygons SL1a and SL1b (see FIG. 5) representing the roadway outer line are generated on the curves C1 and C2. By doing so, the roadway outer line drawn on the road can be drawn in accordance with the shape of the road.
The roadway outer line polygons SL1a and SL1b are given attribute information indicating that they are roadway outer line polygons so as to be distinguished from other polygons later.

Further, since the link LK1 is a one-lane road with an opposite lane, a roadway centerline polygon CL1 (see FIG. 5) representing the roadway centerline is generated at the center of the roadway outer line polygons SL1a and SL1b. The roadway centerline polygon CL1 is given attribute information indicating that it is a roadway centerline polygon in order to be distinguished from other polygons later.
For example, when the link LK1 has two lanes in the up lane and three lanes in the down lane, the road center line polygon CL1 is generated at a position that internally divides the road outer line polygon SL1a, SL1b into 2: 3. To do. As for the up lane on one side of the two lanes, the road lane outer line polygon SL1a and the center of the road center line polygon CL1 are divided into two halves. Lane boundary polygons for drawing lane boundary lines are respectively generated at positions that divide the line polygon CL1 into three equal parts. By doing so, the roadway center line and the lane boundary line can be drawn with good balance between the pair of roadway outer lines.
The lane boundary line polygon is given attribute information indicating that it is a lane boundary line polygon in order to be distinguished from other polygons later.

FIG. 5 is an explanatory diagram showing an output example of the roadway outer line polygon and the roadway centerline polygon. The roadway outer side line polygon SL1a is drawn on the curve C1 shown in FIG. Further, the roadway outer side line polygon SL1b is drawn on the curve C2 shown in FIG. A roadway centerline polygon CL1 is drawn at the center between the roadway outer line polygon SL1a and the roadway outer line polygon SL1b.
In the present embodiment, as described above, the shapes of the roadway outer line polygons SL1a and SL1b and the roadway centerline polygon CL1 can be flexibly specified using the plurality of passing points PL1 to PL12. Therefore, the curved roadway outer line polygons SL1a and SL1b and the roadway centerline polygon CL1 can be drawn in accordance with the shape of the road polygon PGr1. In addition, even when the lane width changes along the link LK1, the roadway outer line polygon can be drawn at a position corresponding to the lane width.

E. Other methods for generating roadway centerline polygon data:
In the example shown in FIGS. 4 and 5, lane marking polygon data 248 (roadway outer line polygon data, roadway centerline polygon data, lane boundary line polygons) when no median polygon or sidewalk polygon exists on the road polygon. (Data) generation method was explained. Hereinafter, a method for generating roadway centerline polygon data when a median polygon and a sidewalk polygon exist on the road polygon will be described. In this case, lane marking polygon data 248 is generated using map polygon data in addition to road network data. When the median polygon is generated on the road polygon, if the median line polygon data is generated without using the map polygon data, the median line polygon is generated in the area where the median polygon exists. This is also because the roadway centerline polygon cannot be generated on both sides of the median polygon where the roadway centerline polygon should be generated.
The method for generating the roadway outer side line polygon data is the same as the method described above with reference to FIGS.

  FIG. 6 is an explanatory diagram schematically showing an outline of a method for generating roadway centerline polygon data using road network data and map polygon data. Here, it is assumed that the median polygon and the sidewalk polygon are indistinguishable from the attribute information.

  FIG. 6A shows a state in which the median strip polygons PGa and PGb, the sidewalk polygon PGc, and the roadway outer line polygons SLna and SLnb exist on the road polygon PGn. The roadway outside line polygons SLna and SLnb have already been generated by the generation method described above, and it can be distinguished from the attribute information that they are roadway outside line polygons.

First, prior to generating the lane marking polygon data 248, a median strip polygon to be considered when generating a roadway centerline polygon is extracted from the polygons PGa, PGb, and PGc existing on the road polygon PGn. In this embodiment, the median polygon is extracted based on the distance from the link LKn.
Specifically, as shown in FIG. 6B, center lines LCa, LCb, and LCc along the link LKn are obtained for the polygons PGa, PGb, and PGc, respectively. Here, the center line along the link is a center line (line segment) at which the angle formed with the link is less than 45 degrees. The center line along the polygon link can be obtained, for example, by thinning the polygon.
Next, the shortest distances Lpga, Lpgb, and Lpgc from the link LKn to the center lines LCa, LCb, and LCc are obtained, respectively. In FIG. 6, the center lines LCa, LCb, and LCc are drawn in parallel with the link LKn. However, when the link and the polygon center line intersect, the shortest distance from the link to the polygon center line is 0 ( Zero). Then, a polygon whose shortest distance from the link LKn to the center line is equal to or less than the threshold value Lth is extracted as a median strip polygon. The threshold value Lth is determined within a range in which the distance from the link is relatively short and away from the road end toward the center, and the polygon can be regarded as a median polygon. The threshold value Lth can be set, for example, as a ratio to the width of the road. In the illustrated example, since the distances Lpga and Lpgb from the link LKn to the center lines LCa and LCb are equal to or less than the threshold value Lth, the polygons PGa and PGb are extracted as the median strip polygon.
The extracted polygons PGa and PGb are assigned attribute information indicating that the polygons are median strips so that they can be distinguished later from other polygons. On the other hand, since the distance Lpgc from the link LKn to the center line LCc is larger than the threshold value Lth, the polygon PG3 is determined not to be a median strip polygon but to a sidewalk polygon. Then, attribute information indicating a sidewalk polygon is assigned to the polygon PGc so that it can be distinguished from other polygons later.
The process of extracting the median strip polygons PGa and PGb can be omitted if attribute information indicating whether the median strip polygon or the sidewalk polygon is previously assigned to the polygons PGa, PGb, and PGc. .

Next, based on the center band polygon data for drawing the center band polygons PGa and PGb, the area where the center band polygons PGa and PGb exist is specified. Then, as shown in FIG. 6 (c), the road centerline polygons CLna and CLnb are generated while avoiding the region where the median strip polygons PG1 and PG2 exist.
In the illustrated example, first, the shape of the median strip polygons PGa and PGb is analyzed to extract a straight line portion along the link LKn of the median strip polygons PGa and PGb. The straight line portion along the link is a line segment whose angle with the link is less than 45 degrees in the outline of the median strip polygon. Then, the roadway centerline polygons CLna and PGCLnb are generated at a predetermined interval in parallel with the straight portions of the median strip polygons PGa and PGb. In the illustrated example, since a plurality of median strip polygons PGa and PGb are spaced apart on the road polygon PGn, the road centerline polygons CLna and CLnb are also spaced apart. In such a case, as shown by surrounding the separated portions with broken lines in the figure, the road center line polygons CLna and CLnb formed separately are complemented by connecting them with linear polygons. . By doing so, the roadway center line can be drawn parallel to the straight line portion along the link LKn of the median strip polygons PGa and PGb, so that the appearance of the roadway center line can be improved. Further, even when the position or width of the central separation band is changed as in the central separation band polygon PGb, a good-looking roadway center line can be drawn according to the shape of the central separation band.
After generating the roadway centerline polygons CLna and CLnb, the roadway centerline polygon CLna and the roadway outer side line polygon SLna, and the roadway according to the number of road lanes, as in the example shown in FIGS. Lane boundary line polygons BLna and BLnb are generated between the center line polygon CLnb and the roadway outer line polygon SLnb, respectively.
Hereinafter, a flow of lane line drawing data generation processing to which the above-described lane line polygon data generation method is applied will be described.

F. Parcel line drawing data generation processing:
FIG. 7 is a flowchart showing the flow of the lane marking drawing data generation process. This process is a process executed by the CPU (partition line polygon data generation unit 116) of the map data system 100 when an instruction to generate the lane line drawing data is input by the operator of the map data generation system 100. In the present embodiment, the lane line drawing data generation process generates lane line polygon data 248, that is, roadway outside line polygon data, roadway centerline polygon data, and lane boundary line polygon data.
The phrase “generates polygon data” is synonymous with the phrase “generates polygons”.

  When this process is started, the map data generation system 100 refers to the road network database 220 and the drawing database 240 (step S100). Then, the map data generation system 100 executes a road outer line generation process for generating road outer line polygon data based on the road network data (step S200). The roadway outer line generation process will be described later.

  Next, the map data generation system 100 determines whether or not the road to be processed is a road in which an opposite lane exists based on the road network data (step S300). When the road to be processed is a road where an oncoming lane exists (step S300: YES), the map data generation system 100 executes a road centerline generation process for generating roadway centerline polygon data (step S400). ). The roadway center line generation process will be described later. When the road to be processed is a road in which no opposite lane exists, that is, a one-way road (step S300: NO), the road center line is not drawn on the road. Proceed to the next step without executing the roadway center line generation process.

  Next, the map data generation system 100 determines whether the road to be processed is a plurality of lanes based on the road network data (step S500). When the road to be processed is a plurality of lanes (step S500: YES), the map data generation system 100 executes a lane boundary generation process for generating lane boundary polygon data (step S600). The lane boundary line generation process will be described later. If the road to be processed is not a plurality of lanes (step S500: NO), no lane boundary line is drawn on the road, so the map data generation system 100 executes the following lane boundary line generation process without executing the lane boundary line generation process. Proceed to step.

  Then, the map data generation system 100 stores the various lane marking polygon data 248 generated by the above processing in the drawing database 240 (step S700), and ends the lane marking drawing data generation processing. The lane marking polygon data 248 is transmitted in response to a request from the map output system 10.

G. Roadway outside line generation processing:
FIG. 8 is a flowchart showing the flow of the roadway outer line generation process. This process corresponds to step S200 in FIG.
When this process is started, the map data generation system 100 obtains the passing point of the roadway outer line based on the node, the configuration point, and the passing point defining data (step S210). The map data generation system 100 obtains, for example, the passing points PL1, PL3, PL5, PL7, PL9, PL11 and the passing points PL2, PL4, PL6, PL8, PL10, PL12 shown in FIG.
Then, the map data generation system 100 obtains a curve that smoothly connects the passing points of the roadway outer line (step S220), and gives the curve a predetermined dividing line width so that the roadway outer line on the curve. A polygon is generated (step S220). Then, the map data generation system 100 assigns attribute information indicating that it is a roadway outer line polygon to the roadway outer line polygon so that it can be distinguished from other polygons later, and ends the roadway outer line generation process.

H. Roadway Chuo Line generation process:
9 and 10 are flowcharts showing the flow of the roadway center line generation process. This process corresponds to step S400 in FIG.
When this processing is started, first, the map data generation system 100 executes the following processing for extracting a median strip polygon to be considered when generating a roadway centerline polygon. That is, the map data generation system 100 determines whether there is another polygon to which no attribute information indicating the type of polygon exists on the road polygon (step S410). If another polygon exists on the road polygon (step S410: YES), the map data generation system 100 obtains a center line along the link of the other polygon (step S420). Here, the center line along the link is a center line (line segment) at which the angle formed with the link is less than 45 degrees. The center line along the polygon link can be obtained, for example, by thinning the polygon. The map data generation system 100 obtains center lines Lc1, Lc2, Lc3 of the polygons PG1, PG2, PG3 shown in FIG. Then, the map data generation system 100 calculates the shortest distance between the center line of the other polygon and the link (step S430). For example, the map data generation system 100 obtains Lpga, Lpgb, and Lpgc shown in FIG. When the link and the polygon center line intersect, the shortest distance between the polygon center line and the link is 0 (zero). Then, the map data generation system 100 extracts a polygon whose distance from the link is equal to or less than the threshold Lth as a median polygon (step S440). In the example illustrated in FIG. 6, the map data generation system 100 extracts polygons PG1 and PG2 whose distance from the link LKn is equal to or less than a threshold value Lth as a median strip polygon. Then, the map data generation system 100 assigns attribute information indicating the median strip polygon to the median strip polygon extracted so that other polygons can be distinguished later. Further, the map data generation system 100 assigns attribute information indicating a sidewalk polygon to a polygon that is not a median polygon so that it can be distinguished from other polygons later. In the drawing database 240, when attribute information indicating the respective types is assigned in advance to the median strip polygon and the sidewalk polygon, the processing in steps S410 to S440 can be omitted.

  Next, the map data generation system 100 determines whether or not a median polygon has been extracted (step S450). When the median polygon is extracted (step S450: YES), the map data generation system 100 analyzes the median polygon and extracts a straight line portion along the link of the median polygon (step). S460). The straight line portion along the link is a line segment whose angle with the link is less than 45 degrees in the outline of the median strip polygon. Then, the map data generation system 100 generates a roadway centerline polygon parallel to the straight line portion (step S462). The distance between the straight line portion along the link of the median polygon and the roadway centerline polygon is set in advance. In addition, as shown in FIG. 6, when a plurality of median strip polygons are separated from each other on the road polygon, the map data generation system 100 follows the straight line portion of the adjacent median strip polygons. Each roadway centerline polygon is connected by a linear polygon to complement the roadway centerline polygon formed separately (step S464). Then, the map data generation system 100 assigns attribute information indicating that it is a roadway centerline polygon to the roadway centerline polygon so that it can be distinguished from other polygons later, and ends the roadway centerline generation process.

If no other polygon exists on the road polygon in Step S410 (Step S410: NO), and if no median polygon is extracted in Step S450 (Step S450: NO), the map data generation system 100 Reads the roadway outside line polygon data generated by the roadway outside line generation process described above (step S470). The figure shows a pair of roadway centerline polygons drawn on both sides of the road.
Then, the map data generation system 100 refers to the road network data, and obtains the passing point of the road center line for each node and component point according to the number of lanes of each road facing each other (step S472). In the illustrated example, the number of lanes of the up lane R1 is three lanes, and the number of lanes of the down lane R2 facing the up lane R1 is two lanes. In this case, for each node and component point, as indicated by a cross in the figure, the position that internally divides the width WR between the vehicle outer side line polygons into 3: 2 is set as the passing point of the roadway center line.
Then, the map data generation system 100 obtains a curve that smoothly connects a plurality of passing points (step S474), and gives the road centerline polygon on the curve by giving this curve the width of a predetermined division line. Generate (step S476). Then, the map data generation system 100 assigns attribute information indicating that it is a roadway centerline polygon to the roadway centerline polygon so that it can be distinguished from other polygons later, and ends the roadway centerline generation process.

I. Lane boundary generation processing:
FIG. 11 is a flowchart showing the flow of lane boundary line generation processing. This process corresponds to step S600 in FIG.
When this process is started, the map data generation system 100 generates the roadway outside line polygon data generated by the roadway outside line generation process described above and the roadway centerline polygon data generated by the roadway centerline generation process. Is read (step S610). A pair of roadway outer side line polygons and a roadway centerline polygon are shown in the figure. In the illustrated example, on one road, the number of lanes of the up lane R1 is 3 lanes, and the number of lanes of the down lane R2 facing the up lane road R1 is 2 lanes.
Then, the map data generation system 100 refers to the road network data, determines the passing point of the lane boundary line for each node and composing point according to the number of lanes of each facing lane, and groups them (step S620). . In the illustrated example, the number of lanes of the up lane R1 is three lanes, and therefore, as shown by the crosses in the drawing, each node and component point are defined as the road lane R1 side road lane line and the lane center line. A position that divides the space into three equal parts is set as a passing point of the lane boundary line in the upward lane R1, and is grouped as shown by being surrounded by a broken line in the drawing. In addition, since the number of lanes in the down lane R2 is two lanes, each node and component point is 2 between the road outer line on the side of the down lane R2 and the road center line as indicated by a cross in the figure. The equally dividing position is set as a passing point of the lane boundary line in the down lane R2, and is grouped as shown by being surrounded by a broken line in the drawing.
And the map data generation system 100 calculates | requires the curve which connects a several passage point smoothly about each group of a passage point (step S630), and gives the width of the division line set beforehand to these curves, A lane boundary line polygon is generated on each curve (step S640). Then, the map data generation system 100 assigns attribute information indicating that it is a lane boundary line polygon to the lane boundary line polygon so that it can be distinguished from other polygons later, and ends the lane boundary line generation process.

According to the map data generation device 100 of the present embodiment described above, a plurality of passing points of lane markings are obtained based on the passing point defining data associated with each node and component point, and the plurality of passing points are determined. It is possible to generate the lane marking polygon data 248 by flexibly specifying the shape of the lane marking polygon. Therefore, it is possible to generate lane marking data for drawing lane markings according to the shape of the road with a relatively light load.
Further, according to the map data generation device 100 of the present embodiment, when a median strip exists on the road, the roadway center line is drawn according to the shape of the median strip so as not to overlap the median strip. The lane marking data can be generated.

J. et al. Map output processing:
FIG. 12 is a flowchart showing the flow of the map output process. This process is a process executed by the CPU (map output unit 18) of the map output system 10 when a map display instruction is input by the map user.
The map output system 10 refers to the drawing database 20 for the area specified by the user (step S800).
Then, the map output system 10 reads the road polygon data and draws a road on the map (step S810).
Next, the map output system 10 reads the median strip polygon data, the sidewalk polygon data, the road marking polygon data, and the lane marking polygon data, and superimposes them on the road drawn in step S810, so that the median strip, the sidewalk, the road marking, A partition line is drawn (step S820).
Next, the map output system 10 reads the building polygon data and the water portion polygon data, and draws the building, the sea, the lake, and the river on the map (step S830).
Next, the map output system 10 reads the mark and character data, and draws the mark and character on the map (step S840).
Then, the map output system 10 outputs the map drawn in steps S800 to S850 (step S850).

According to the map output system 10 of the present embodiment described above, it is possible to output a map in which the lane markings drawn on the road are drawn according to the shape of the road.
Further, according to the map output system 10 of the present embodiment, even if a median strip exists on the road, a map drawn so that the roadway center line does not overlap the median strip can be output. it can.

K. Variations:
As mentioned above, although several embodiment of this invention was described, this invention is not limited to such embodiment at all, and implementation in various aspects is possible within the range which does not deviate from the summary. It is. For example, the following modifications are possible.

K1. Modification 1:
In the map data generation system 100 of the above embodiment, the road network data uses the width of the road and the width of the roadside band as the passing point defining data for defining the passing point of the roadway outer line. Is not limited to this. As the passing point defining data, a relative coordinate value from the passing point link may be used.
FIG. 13 is an explanatory diagram showing road network data as a modified example. As shown in the figure, this road network data uses the coordinate value of the passing point of the road outer line as the passing point defining data. By using such passing point defining data, it is possible to obtain the passing point of the roadway outer line without performing calculation using the width of the road and the width of the roadside zone.

Moreover, in the map data generation system 100 of the said Example, although the road network data shall contain the passage point prescription | regulation data which prescribes | regulates the passage point of a roadway outer side line, this invention is not limited to this. It may include passing point defining data that defines passing points of other lane markings such as a roadway center line and a lane boundary line.
FIG. 14 is an explanatory diagram showing road network data as a modified example. As shown in the figure, this road network data includes relative coordinate values from the link of the passing point of the road outer line, the coordinate value of the passing point of the road center line, and the coordinate value of the passing point of the lane boundary line. . By using such passing point regulation data, a process for determining the passing point of the roadway outer line in the roadway outer line generation process, a process for determining the passing point of the roadway centerline in the roadway centerline generation process, and a lane boundary line generation process The process of obtaining the passing point of the lane boundary line at can be omitted.
You may make it set a color (white, yellow) and a form (a solid line, a broken line, a double line etc.) for every division line. By doing so, the reality of the map can be improved.

K2. Modification 2:
In the map data generation system 100 of the above embodiment, the road centerline polygon data is generated by the processing shown in FIGS. 6 and 9 when the median strip exists on the road. It is not limited to this.

  FIGS. 15-17 is a flowchart which shows the flow of the roadway centerline production | generation process as a modification. Here, in the drawing database 240, it is assumed that attribute information indicating that the median polygon is a median polygon is assigned to the median polygon. Therefore, the map data generation system 100 does not perform the processing of steps S410 to S450 in FIG.

As shown in FIG. 15, when this process is started, the map data generation system 100 reads road polygon data 242, median strip polygon data 244, and sidewalk polygon data 246 from the drawing database 240 (step S900).
The map data generation system 100 determines whether the median strip polygon data 244 has been read (step S910). When the median strip polygon data 244 is not read (step S910: NO), the map data generation system 100 advances the processing to step S470 shown in FIG.
On the other hand, when the median polygon data 244 is read (step S910: YES), the map data generation system 100 obtains the center line along the road polygon link (step S920). In the illustrated example, a center line CL indicated by a one-dot chain line is obtained for the road polygon PGn corresponding to the link LKn.

Then, as shown in FIG. 16, the map data generation system 100 deforms the center line CL of the road polygon PGn so as to pass the center of the median polygon PGn (step S930).
Next, the map data generation system 100 sets the width of the median strip polygon (step S940). In the illustrated example, the width of the center band polygon PGa is constant except for the arc portion at the end in the link direction, and the width Wpga is set for the center band polygon PGa. Further, the width of the median strip polygon PGb in the link direction changes continuously, and the widths Wpgb1 and Wpgb2 are set for both ends of the median strip polygon PG2b. When the width of the median strip polygon changes in multiple stages, the width of the median strip polygon is set for each point.

And as shown in FIG. 17, the map data generation system 100 sets the passing point of the road center line based on the width of the median strip polygon (step S950). In the example shown in the drawing, as indicated by the crosses in the figure, the center zone polygons PGa and PGb are set to the center line CL from the center zone polygons PGa and PGb at the points where the widths Wpga, Wpgb1 and Wpgb2 of the center zone polygons PGa and PGb are set. A plurality of passing points are set at positions spaced by a predetermined interval α in the vertical direction.
Then, the map data generation system 100 generates a roadway centerline polygon on a straight line connecting a plurality of passing points (step S960). In the illustrated example, roadway centerline polygons CLna and CLnb are respectively generated.
As in the case of the roadway center line generation process in the embodiment, the roadway centerline generation process according to the modified example described above also avoids overlapping with the center separation band when the center separation band exists on the road. The plot line drawing data for drawing the road center line can be generated in accordance with the shape of the road.

K3. Modification 3:
In the above embodiment, in the road outer line generation processing shown in FIG. 8, the road outer line passing point is obtained based on the node, component point, and passing point defining data, and the road outer line polygon is determined using this passing point. However, the present invention is not limited to this. The roadway outer line may be drawn from the road edge, for example, on the inner side of the width of the roadside belt.
The road edge may be extracted, for example, by obtaining the intersection of the outline of the road polygon and a straight line perpendicular to the link, or the position of the road edge or the road outer line may be determined by the distance from the link. You may give prescription data. Further, when a sidewalk polygon exists on the road polygon, a boundary line along the link between the sidewalk polygon and the road polygon may be extracted, and this boundary line may be used as a road edge.

K4. Modification 4:
You may make it apply the map output system 10 and the map data generation system 100 in the said Example to the navigation system which performs route guidance. In this case, the navigation system may store the lane marking polygon data 248 in advance in a database, or may dynamically generate it in response to a map display request.

K5. Modification 5:
The various processes described in the above embodiments and modifications are not necessarily all provided, and some of them may be omitted or replaced with other processes. Further, in the above-described embodiment, the processing executed in software may be executed in hardware and vice versa.

  INDUSTRIAL APPLICABILITY The present invention can be used in a technique for generating lane line drawing data for drawing lane lines such as a roadway outer line, a roadway center line, and a lane boundary line drawn on a road on a map.

DESCRIPTION OF SYMBOLS 10 ... Map output system 12 ... Main control part 14 ... Command input part 16 ... Transmission / reception part 18 ... Map output part 20 ... Drawing database 30 ... Display 100 ... Map data generation system 112 ... Main control part 114 ... Command input part 116 ... Section Line polygon data generation unit 118 ... transmission / reception unit 200 ... map database 220 ... road network database 240 ... drawing database 242 ... road polygon data 244 ... median strip polygon data 246 ... sidewalk polygon data 248 ... division line polygon data

Claims (7)

A map data generation system for generating map data for drawing a map,
A road network database for storing road network data representing roads by nodes and links;
A drawing database for storing map polygon data including road polygon data for drawing the road and median polygon data for rendering a median strip;
A lane line drawing data generation unit that generates lane line drawing data for drawing a road center line on the road based on the road network data and the map polygon data;
The lane marking drawing data generation unit identifies an area where the median strip exists based on the median strip polygon data, avoids the area, and generates the lane marking data based on the link ,
Map data generation system. The map data generation system according to claim 1,
The lane marking drawing data generation unit obtains a center line of the central separator based on the central separator polygon data, and generates the lane marking drawing data based on the center line and the link.
Map data generation system. The map data generation system according to claim 1 or 2,
The lane marking data generation unit extracts median polygon data to be considered in generating the lane marking data based on the distance from the link prior to the generation of the lane marking data.
Map data generation system. The map data generation system according to any one of claims 1 to 3,
The link is associated with the number of bidirectional lanes on the road,
The lane line drawing data generation unit further draws lane line drawing data for drawing lane lines other than the lane center line in the region from the lane center line to the road edge of the road based on the number of lanes. Generate
Map data generation system. A map output system for outputting a map,
Stores map polygon data including road polygon data for drawing a road, median polygon data for drawing a median strip, and plot line drawing data for drawing a road centerline on the road A drawing database;
The road is drawn using the road polygon data, and the median strip and the road centerline are drawn using the median polygon data and the lane marking data superimposed on the road polygon data, and the map is output A map output unit,
The lane marking data is
A map data generation system for generating map data for drawing a map,
A road network database for storing road network data representing roads by nodes and links;
A map polygon database storing map polygon data including road polygon data for drawing the road and median strip polygon data for drawing a median strip;
A lane line drawing data generation unit that generates the lane line drawing data based on the road network data and the map polygon data;
The lane marking drawing data generation unit identifies an area where the median strip exists based on the median strip polygon data, avoids the area, and generates the lane marking data based on the link ,
Data generated by the map data generation system,
Map output system. A map data generation method for generating map data for drawing a map by a computer,
The computer
A road network database for storing road network data representing roads by nodes and links;
A drawing database for storing map polygon data including road polygon data for drawing the road and median strip polygon data for drawing a median strip;
The map data generation method includes:
A database reference step in which the computer refers to the road network database and the drawing database;
The computer comprises a lane line drawing data generating step for generating lane line drawing data for drawing a road center line on the road based on the road network data and the map polygon data,
The lane marking drawing data generation step specifies an area where the central separator is present based on the central separator polygon data, avoids the area, and generates the lane marking data based on the link. Including steps,
Map data generation method. A computer program for generating map data for drawing a map by a computer,
The computer
A road network database for storing road network data representing roads by nodes and links;
A drawing database for storing map polygon data including road polygon data for drawing the road and median strip polygon data for drawing a median strip;
The computer program is
A database reference function for referring to the road network database and the drawing database;
A lane line drawing data generation function for generating lane line drawing data for drawing a road center line on the road based on the road network data and the map polygon data;
Is a computer program for causing a computer to realize
The lane marking drawing data generation function identifies an area where the median strip exists based on the median polygon data, avoids the area, and generates the lane marking data based on the link Including functions,
Computer program.

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