JP2012150823A - Three-dimensional map drawing system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a three-dimensional map retaining a reduction scale.SOLUTION: Feature data formed by three-dimensionally drawing features such as roads, buildings, and the like is prepared, and a three-dimensional map is drawn based on the data. The feature data is created by not a perspective projection but a method for projecting actual features CST2 on a projection plane PL2 with parallel lines along the projection direction PRJ, namely, parallel projection. The feature data is given by two-dimensional raster data or polygon data for drawing a projection drawing obtained by the parallel projection. The three dimensional map can be drawn just by drawing the feature data prepared in such manner without performing a processing applying a heavy load such as rendering. Different from the perspective projection, the parallel projection can retain the positional relationship between buildings, and reduction scale of the shape so as to provide the three-dimensional map retaining the reduction scale.

Description

  The present invention relates to a three-dimensional map drawing system that draws a three-dimensional map that three-dimensionally represents a feature.

  There is a technology for three-dimensionally displaying features such as buildings and roads when displaying an electronic map on a navigation device or a computer screen. In such a three-dimensional map, the features are usually drawn by a projection method called perspective projection.

  FIG. 1 is an explanatory diagram illustrating a drawing example of a three-dimensional map by perspective projection. As shown in FIG. 1A, in perspective projection, a projection result PI1 is obtained as a collection of points where a straight line connecting the user's viewpoint PV and each part of the actual feature CST1 intersects with the projection plane PL1. According to such a projection method, as shown in FIG. 1B, the feature can be drawn three-dimensionally in a state close to the state in which the feature is actually seen. In this example, an example in which the viewpoint PV is set above the feature is shown. Compared to a two-dimensional map, a three-dimensional map has an advantage that it is easy to visually and intuitively grasp the geography of the range represented on the map.

  As prior art relating to display in a three-dimensional map, there are Patent Literature 1 and Patent Literature 2. Patent Document 1 discloses a technique for determining whether or not a traffic sign is hidden behind a building when perspectively projecting three-dimensional map information, and displaying the traffic sign in advance when it is hidden. Patent Document 2 discloses a technique for displaying a character representing a name only for a polygon having an area larger than a predetermined area when perspective projection is performed from an overhead viewpoint.

Japanese Patent No. 4070507 Japanese Patent No. 3428294

As illustrated in FIG. 1B, the perspective projection can provide an image close to the scenery that the user is actually looking at.
However, this method has a problem that the scale of the expressed map cannot be maintained. As shown in FIG. 1 (b), the distance in the depth direction (vertical direction in the figure) is drawn from the near view (near the lower side of the figure) to the far view (near the upper side of the figure) rather than the actual interval. It will be. The distance in the left-right direction is also drawn more closely in the distant view than in the close view. That is, the distance represented by the unit length on the map is drawn differently for the foreground and the background in both the left and right directions and the depth direction.

Conventionally, 3D map technology has been directed to reproducing the real world seen by the user, and the problem that the scale is lost due to perspective projection has not been considered. The fact that the scale is lost in a map is a serious problem that greatly impairs the significance of the map. The fact that the scale is not maintained means that a three-dimensional image drawn by perspective projection is not useful as a map. In order to grasp the positional relationship of features properly, the user had to refer to a flat map after all.
An object of the present application is to solve such problems and provide a three-dimensional map with a reduced scale.

A configuration of the present invention as a three-dimensional map drawing system that draws a three-dimensional map that represents a three-dimensional feature will be described.
The present invention includes a feature database, a drawing range input unit, and a drawing unit. The feature database stores feature data as two-dimensional drawing data obtained by projecting a feature onto a plane by parallel projection from an oblique direction inclined by a predetermined projection angle with respect to the vertical direction. In the present invention, the feature is drawn by parallel projection instead of perspective projection. The feature data may be provided in any format of raster data and polygon data. However, the polygon data has an advantage that the entire data amount can be suppressed and the map does not become rough even when enlarged and drawn, so that a high-quality map can be provided.

  When the drawing range input unit inputs a specification of a range in which a three-dimensional map is to be drawn, the drawing unit reads and draws feature data corresponding to the specification from the feature database. Drawing includes both map display on a display such as a computer and a navigation device, and print output of a map by a printer or the like. The range to be drawn (hereinafter referred to as the drawing range) can be selected from various methods, such as a method that directly specifies the range using latitude and longitude coordinates, a method that specifies the drawing range's representative point, scaling factor, etc. Can do. In addition to the method in which the user inputs the drawing range, a method may be employed in which the current position during route guidance is input and the drawing range input unit automatically sets the range.

  In the map drawn by the three-dimensional map drawing system of the present invention, each feature is three-dimensionally expressed by parallel projection. FIG. 2 is an explanatory diagram showing an example of drawing a three-dimensional map by parallel projection. As shown in FIG. 2A, in the parallel projection, a projection result PI2 is obtained at the intersection of a predetermined parallel line PRJ passing through each point of the actual feature CST2 and the projection plane PL2. If the direction of the parallel line PRJ is the vertical direction and the projection plane PL2 is parallel to the ground surface, the projection result is a two-dimensional plane map. In the present invention, however, the parallel projection is performed from an oblique direction different from the vertical direction. The projection result is three-dimensionally drawn.

  FIG. 2B is an example of a map drawn by parallel projection. For example, the sides of buildings BLD1, BLD2, and BLD3 are formed of parallel lines. Thus, in parallel projection, parallel sides of real features are represented in parallel on the map. This means that a building with a certain width actually is represented with a certain width on the map. The same applies not only to the width of the building but also to the road width and the space between buildings. That is, according to the parallel projection, the scales in the left-right direction and the depth direction are maintained although the feature is expressed three-dimensionally.

  The present invention can provide a three-dimensional map with a reduced scale by using parallel projection in this way. In parallel projection, drawing may be performed with a certain magnification in the depth direction in order to match the sense of depth obtained from the projection with the actual depth. Even when a constant magnification is applied in this way, as long as parallel projection is employed, the scale is relatively maintained in each of the left and right directions and the depth direction.

  The technique of parallel projection itself has already been widely used in the field of drafting, but there has been no example of applying it to a three-dimensional map in this way. As described above, the conventional three-dimensional map is directed to faithfully drawing the scenery as the user can see, so the adoption of parallel projection has not been studied at all. The inventor has changed the idea from drawing the scenery faithfully to focusing on maintaining the scale as a map, and adopted parallel projection.

By adopting parallel projection, the present invention also has the following advantages in terms of processing load when drawing a map.
In perspective projection (see FIG. 1A), it is necessary to determine a viewpoint PV as a reference for projection, whereas in parallel projection (see FIG. 2A), it is not necessary to determine a viewpoint. Therefore, in perspective projection, every time a viewpoint is designated, it is necessary to perform a projection process called rendering on the basis of a three-dimensional model representing the three-dimensional shape of a feature to obtain a projection drawing.
On the other hand, in parallel projection, since it is not necessary to specify a viewpoint, a drawing result for a predetermined projection direction can be prepared in advance. Drawing results generated independently of the viewpoint can be used in common regardless of how the map drawing range is specified. As a result, in the present invention, since rendering processing when drawing a three-dimensional map becomes unnecessary, it is possible to drastically reduce the processing load when drawing the map.

In the present invention, the feature data may be generated by parallel projecting a virtual feature obtained by enlarging the feature in the height direction by a factor multiple larger than 1.
The user usually looks up at features from the ground. In parallel projection by oblique projection on a feature, the height sensation received from the projection may be lower than the height sensation when looking up at the actual feature. If projection is performed on a virtual feature that is higher than the actual one by the above-described coefficient multiplication, the shift in height sense can be mitigated. Even if the height direction is multiplied by a factor, the horizontal and depth scales are maintained, so that the advantages of the present invention are not impaired.

In the present invention, the feature database may store feature data of a plurality of layers having different scales. By dividing the hierarchy, the narrow area can be converted into detailed data at the lower hierarchy, and the high area can be converted into the wide area while suppressing the amount of data by omitting the detailed features. Three or more layers may be provided. The drawing unit can draw a map using feature data in a hierarchy corresponding to the range to be drawn.
When multiple layers are provided in this way, the feature data of each layer is generated by parallel projection with the same projection direction and projection angle (hereinafter referred to as “parallel projection parameter”) for performing parallel projection. It is preferable. The position where a certain coordinate point is projected is determined by parallel projection parameters. Therefore, if the parallel projection parameters are unified in each layer, projection positions in each layer of the same coordinate point can be easily associated with each other. As a result, it is relatively easy to enlarge and reduce the map while fixing a specific point such as the center position of the drawing range.
It is possible to change the parallel projection parameters in each layer. In this case, when changing the layer used for drawing, it is preferable to perform drawing of the next layer after analyzing the position where a specific point such as the center position of the drawing range is projected in the next layer. .

In the present invention, the feature database may store a plurality of types of feature data having different projection directions with respect to the same region. In this case, the drawing range input unit can further input designation of the direction in which the three-dimensional map is drawn, and the drawing unit can perform drawing using the feature data of the projection direction corresponding to the designated direction. .
By doing so, it is possible to draw a three-dimensional map viewed from various directions, and to improve convenience. In a 3D map projected from one direction, a part that is hidden behind a 3D-drawn building, the so-called blind spot, is created. By providing a 3D map with a different projection orientation, this blind spot is eliminated. can do. In addition, when a 3D map is used for route guidance, a heading-up display that displays the traveling direction on the upper side can be realized smoothly by using different 3D maps with different projection directions depending on the route to be guided. Can do.
In this aspect, the drawing direction may be specified by the user, or the user's traveling direction may be used in the heading-up display.

In this invention, you may provide further the character database which stored the character data which designates the character for showing the name of a feature. When feature data from a plurality of projection directions is provided, the character database may be prepared for each projection direction individually, or one type of character database may be combined with a plurality of types of feature data having different projection directions. You may associate. When associating with multiple types of feature data, character data is provided with a flag (hereinafter referred to as the behind flag) for specifying whether to output the character on the 3D map according to the projection direction. The unit may output the character designated by this flag on the three-dimensional map. The output includes display on a display or the like and printing with a printer or the like.
In the three-dimensional map, since the feature can be visually recognized depending on the projection direction or hidden in the blind spot, it is preferable to control whether or not the character representing the feature is also output. According to the above-described aspect, since whether or not to display characters is stored in advance as a behind flag, it is possible to appropriately control output of characters without performing complicated calculation / analysis processing.

In the character data, the position where the character should be output may be specified in three dimensions including height information. The rendering unit can display the information reflecting the height information by outputting characters to the specified position at the position where the same parallel projection as the parallel projection when generating the feature data is performed. .
By doing this, not only the grounding part of the feature expressed in three dimensions, but also the character can be expressed near the wall of the upper floor or above the feature, and an easy-to-read 3D map can be output. . The height information can be specified in various forms such as actually measured values such as meters and the number of floors of the feature, and may be changed for each feature. Also, different heights may be designated according to the drawing direction.

In the present invention, the feature database may store the feature data by dividing it into a mesh composed of a predetermined two-dimensional area. In this case, it is preferable to allow each mesh to store feature data for features that do not exist on the mesh.
In a conventional flat electronic map, data of features that exist across meshes are stored as polygons divided into meshes. In a three-dimensional electronic map, the data of features that exist across the mesh are stored separately for each mesh if it can be divided, and stored in any mesh for those that cannot be divided. As described above, in the conventional electronic map data, the feature data of each mesh is usually stored as the data of a feature that is partly or entirely present in the mesh.
However, in parallel projection, as a new problem that could not occur in the past, even if a feature exists in one of the meshes, the upper part may be drawn on another mesh. In the present invention, as a countermeasure in such a case, each mesh is allowed to store data of a feature not on the mesh. By doing this, it is possible to draw a three-dimensional map by parallel projection without requiring complicated processing even for a feature to be drawn across the mesh.

In the present invention, the road data included in the feature data may be parallel projected in consideration of the height of each point on the road, so-called undulation. When drawing route guidance information such as a route or a current position on a three-dimensional map using such feature data, it is preferable to use the following configuration.
The route guidance information input unit inputs the route guidance information to be drawn, that is, at least one of the route position and the current position as information specified in three dimensions including the height. The drawing unit draws a path by applying the same parallel projection as the parallel projection used when generating the feature data to the specified information.
When only one of the road data or the route guidance information has the height information, the route guidance information and the road are drawn with being shifted in parallel projection. On the other hand, in the above-described configuration, the same parallel projection as the road is applied to the route guidance information, so that the above-described deviation can be eliminated and the route guidance information can be drawn.
However, when road data is prepared based on two-dimensional data that does not take into account undulation, the route guidance information may be drawn using the two-dimensional data without performing parallel projection. In this case, it is desirable to prepare features other than roads such as buildings as data that does not consider undulation.

The present invention is not limited to the three-dimensional map drawing system described above, and can be configured in various ways.
For example, the present invention may be configured as a feature data generation method for generating feature data used for drawing a three-dimensional map by a computer.
In this feature data generation method, a three-dimensional map database in which a three-dimensional model representing a three-dimensional shape of a feature is stored in advance is prepared. This three-dimensional map database can be prepared by a method provided in a computer for generating feature data, a method provided by a medium such as a DVD, or a method stored in a server accessible by a computer via a network.
The computer inputs designation of a target area for which feature data is to be generated, and inputs a three-dimensional model existing in the target area and a predetermined area adjacent to the memory from the three-dimensional map database. Then, for the 3D model in the memory, 2D drawing data in which the features are projected onto the plane by parallel projection is generated, stored in the memory, and specified as the target area from the 2D drawing data. Extract the data in the area, and generate and output the feature data.

As described above, in the present invention, parallel projection is performed after reading not only the target region but also a three-dimensional model existing in a predetermined range adjacent thereto. In parallel projection, there is a possibility that a projection of a feature existing in a mesh is drawn out of the mesh. On the contrary, even if the feature does not exist in the target area, a part of the projection may be drawn in the target area as a result of the parallel projection. Considering these, in the present invention, parallel projection is performed including a predetermined range adjacent to the target region. By doing so, it is possible to obtain a projection of a feature that does not exist in the target region without omission.
The predetermined range may be set according to the mesh size and parallel projection parameters. As the projection angle approaches vertical, the predetermined range can be narrowed, and as the projection angle approaches horizontal, it is necessary to widen the predetermined range.
Further, the predetermined range does not necessarily have to be set so that the target area is at the center. For example, when projected from the east, the projected view extends to the west, so that a projected view of the feature existing in the mesh on the west side of the target region is not drawn in the target region. In this way, in consideration of the projection direction, only a mesh having an orientation in which a feature may be drawn in the target region, that is, a mesh adjacent to the target region on the projection direction side may be set as the predetermined range. .

  In addition, the present invention may be configured as a 3D map drawing method for drawing a 3D map by a computer, or may be configured as a computer program for causing a computer to execute such drawing. Moreover, you may comprise as a computer-readable recording medium which recorded such a computer program. Recording media include flexible disks, CD-ROMs, magneto-optical disks, IC cards, ROM cartridges, punch cards, printed matter on which codes such as bar codes are printed, computer internal storage devices (memory such as RAM and ROM), and A variety of computer-readable media such as an external storage device can be used.

It is explanatory drawing which shows the example of a drawing of the three-dimensional map by perspective projection. It is explanatory drawing which shows the example of a drawing of the three-dimensional map by parallel projection. It is explanatory drawing which shows the structure of a three-dimensional map display system. It is explanatory drawing which shows the content of feature data. It is explanatory drawing which shows the data structure of feature data. It is explanatory drawing which shows the relationship between a projection angle and a drawing result. It is explanatory drawing which shows the projection direction of parallel projection. It is explanatory drawing which shows the hierarchical structure of feature data. It is explanatory drawing which shows the modification of the hierarchical structure of feature data. It is explanatory drawing which shows the production | generation method of feature data. It is a flowchart of the production | generation process of feature data. It is explanatory drawing which shows the link of feature data and character data. It is explanatory drawing which shows the content of a behind flag. It is a flowchart of a map display process. It is explanatory drawing which illustrates the three-dimensional map by an Example. It is a flowchart of a route guidance process. It is a flowchart of a display range determination process. It is explanatory drawing which shows the influence by undulation. It is explanatory drawing which shows the coordinate transformation method in consideration of the undulation. It is a flowchart of a coordinate transformation process. It is explanatory drawing which shows a route guidance example.

Embodiments of the present invention will be described in the following order.
A. Device configuration:
B. Feature data structure:
B1. Parallel projection data:
B2. Multiple projection orientations:
B3. Hierarchical structure:
C. Feature data generation method:
D. Character data structure:
E. Map display processing:
F. Route guidance process:
F1. Overall processing:
F2. Coordinate transformation:

A. Device configuration:
FIG. 3 is an explanatory diagram showing the configuration of the three-dimensional map display system in the embodiment. A configuration example is shown in which a map is displayed on the mobile phone 300 based on map data provided from the server 200 via the network NE2 or the like. As a terminal for displaying the map, a personal computer, a navigation device, or the like may be used. Further, the 3D map display system may be configured as a system that operates in a stand-alone manner, in addition to a system that includes a terminal such as the mobile phone 300 and the server 200.
In the figure, a data generation device 100 that generates three-dimensional map data is also shown.

The mobile phone 300 includes various functional blocks that operate under the main control unit 304. In the present embodiment, the main control unit 304 and each functional block are configured by installing software that realizes the respective functions, but a part or all of them may be configured by hardware.
The transmission / reception unit 301 communicates with the server 200 via the network NE2. In the present embodiment, transmission / reception of map data and commands for displaying a three-dimensional map is mainly performed.
The command input unit 302 inputs an instruction from the user through operation of the keyboard 300k or the like. Examples of instructions in the present embodiment include a display range of a three-dimensional map, designation of enlargement / reduction, setting of a starting point and a destination for route guidance, and the like.
The GPS input unit 303 obtains latitude and longitude coordinate values based on a GPS (Global Positioning System) signal. In route guidance, the traveling direction is calculated based on changes in latitude and longitude.
The map information storage unit 305 is a buffer that temporarily stores map data provided from the server 200. When a map to be displayed moves from moment to moment as in route guidance, the map information storage unit 305 receives map data in an insufficient range from the server 200 and displays the map.
When performing route guidance, the map matching conversion unit 307 displays the searched route and the current position on the road on the parallel-projected three-dimensional map without deviation, so that the coordinate value of the route position and the current position is displayed. Necessary coordinate transformations are applied to it. A method of coordinate conversion will be described later.
The display control unit 306 displays a three-dimensional map on the display 300 d of the mobile phone 300 based on the data provided from the map information storage unit 305 and the map matching conversion unit 307.

The server 200 includes functional blocks shown in the figure. In this embodiment, these functional blocks are configured by installing software that realizes the respective functions, but a part or all of the functional blocks may be configured by hardware.
The map database 210 is a database for displaying a three-dimensional map. In this embodiment, map data including feature data 211, character data 212, and network data 213 is stored. The feature data 211 is data for three-dimensionally displaying features such as roads and buildings, and is two-dimensional polygon data obtained by parallel projection of a three-dimensional model of the feature. The character data 212 is data such as characters to be displayed on the map, for example, feature names and place names. The network data 213 is data representing a road as a collection of nodes and links. A node is data corresponding to an intersection of roads or an end point of a road. A link is a line segment connecting nodes, and is data corresponding to a road. In this embodiment, the positions of nodes and links constituting the network data 213 are determined by three-dimensional data of latitude / longitude and height.
The transmission / reception unit 201 transmits / receives data to / from the mobile phone 300 via the network NE2. In the present embodiment, transmission / reception of map data and commands for displaying a three-dimensional map is mainly performed. The transmission / reception unit 201 also communicates with the data generation device 100 via the network NE1. In the present embodiment, the generated map data is mainly exchanged.
The database management unit 202 controls reading and writing of data from the map database 210.
The route search unit 203 performs route search using the network data 213 in the map database 210. Dijkstra method or the like can be used for route search.

The data generation apparatus 100 includes functional blocks shown in the figure. In this embodiment, these functional blocks are configured by installing software that realizes the respective functions in a personal computer, but a part or all of the functional blocks may be configured by hardware.
The transmission / reception unit 105 exchanges data with the server 200 via the network NE1.
The command input unit 101 inputs an operator instruction via a keyboard or the like. In the present embodiment, designation of an area where map data is to be generated, designation of parallel projection parameters, and the like are included.
The 3D map database 104 is a database that stores a three-dimensional model used for generating map data. For features such as roads and buildings, electronic data representing a three-dimensional shape is stored. Conventionally, the 3D map database 104 can use a 3D model provided for displaying a 3D map by perspective projection.
The parallel projection unit 102 performs drawing by parallel projection based on the 3D map database 104 to generate feature data. The drawn projection map is stored in the parallel projection data 103 and stored in the feature data 211 of the map database 210 of the server 200 via the transmission / reception unit 105. The parallel projection unit 102 determines whether or not each feature becomes a blind spot of another feature during the parallel projection process, and passes the determination result to the behind flag setting unit 106.
The behind flag setting unit 106 inputs character data representing the name of each feature from the 3D map database 104, and determines whether or not each character should be displayed on the map based on the determination result received from the parallel projection unit 102. Set the behind flag to specify. The behind flag is set to a value indicating non-display of a character when a certain feature becomes a blind spot of another feature, and is set to a value indicating display when the feature does not become a blind spot. In this embodiment, the feature data 211 is prepared for a plurality of projection azimuths, and the dead angle changes according to the projection azimuth, so the behind flag is set for each projection azimuth.

B. Feature data structure:
B1. Parallel projection data:
FIG. 4 is an explanatory diagram showing the contents of the feature data. It shows a state in which data D1 and D2 are obtained from the three-dimensional data D3 by parallel projection. The three-dimensional data D3 is data representing the shape of the building M3 on the plane P3 with three-dimensional coordinates of x, y, and z.
When this building M3 is projected in parallel on the plane P1 in the vertical direction (arrow A1 direction in the figure), the building M3 becomes data D1 expressed two-dimensionally like a rectangle M1. This corresponds to conventional two-dimensional map data.
On the other hand, in this embodiment, parallel projection is performed on a plane P2 in an oblique direction (in the direction of arrow A2 in the figure) inclined by a predetermined projection angle with respect to the vertical direction. As a result, on the data D2, a building is drawn three-dimensionally like a building M2. Although the building M2 is expressed three-dimensionally, the data D2 is only projected two-dimensional drawing data. In this embodiment, polygon data for drawing the building M2 is defined by a sequence of points such as coordinate values (u1, v1) and (u2, v2) in the uv coordinates in the projection plane. Individual polygon data may be used for the side wall and roof portion of the building M2, or the whole may be used as one polygon data. The window W may be prepared as a texture to be pasted on the wall surface of the building, that is, raster data, or the window may be prepared as individual polygon data.
The feature data of the present embodiment is constituted by two-dimensional data obtained by projecting each feature by oblique parallel projection as described above.

FIG. 5 is an explanatory diagram showing the data structure of the feature data. The data structure will be described by taking one building BL01 as an example.
On the left side of the figure, the positional relationship of this building BL01 is shown two-dimensionally. Map data is maintained by being divided into meshes M01 and M02. The rectangle in the mesh M01 in which the lower left latitude and longitude are represented by P01 (LAT01, LON01) is the building BL01. The latitude and longitude of the building BL01 is represented by coordinates G (LATb, L0Nb). Here, the case where the building BL01 does not protrude from the mesh M01 is illustrated.

When parallel projection is performed on the building BL01 existing at this position (arrow CH01), the building BL01 is drawn three-dimensionally as shown by the meshes M03 and M04. In the present embodiment, the lower left latitude / longitude P02 (LAT02, LON02) of the mesh M03 coincides with P01 of the mesh M01. In the present embodiment, the meshes M03 and M04 are defined so that the latitude and longitude of each vertex coincide with the latitude and longitude of the vertexes of the meshes M01 and M02 on the plane. However, the meshes M03 and M04 on the projection plane can be set independently of the meshes M01 and M02 on the plane.
As a result of the parallel projection, the building BL01 is drawn not only by the part BL03 in the mesh M03 but also by the part BL04 in the mesh M04. In the present embodiment, as indicated by arrows CH03 and CH04, among the polygons for drawing one building BL01, the part BL03 belonging to the mesh M03 and the part BL04 belonging to the mesh M04 are separated, and each is obtained as separate polygon data. to manage.

The structure of each polygon data is illustrated on the right side of the figure. The name, position, shape, type, character, attribute, etc. are stored in the data for each polygon.
In this embodiment, the name BL01 of the building is used as the name. Since a common name is assigned to the part BL03 belonging to the mesh M03 and the part BL04 belonging to M04, it is possible to determine that both are polygons for the same building. A name unique to the polygon can also be used as the name. In this case, it is preferable to separately prepare information for associating polygons for the same building.

  The position is the latitude and longitude coordinates (LATBL0Nb) where the building BL01 exists. The shape is data defining a sequence of points forming a polygon with relative two-dimensional coordinates uv defined in each mesh. Data such as Pb1 (u1, v1) and Pb2 (u2, v2) of the shape data for the part BL03 are values representing the positions of the vertices Pb1 and Pb2 by uv coordinates in the mesh M03. Data such as Pb3 (u3, v3) and Pb4 (u4, v4) of the shape data for the portion BL04 is a value representing the positions of the vertices Pb3 and Pb4 with uv coordinates in the mesh M04.

The type stores the type of the feature represented by the polygon. The character is data indicating the name of the feature. However, in this embodiment, since the character data is prepared separately from the feature data, the feature data includes data indicating the storage location of the character data (in the figure). LINK) is stored. As data representing the storage destination, a path, address, URL (Uniform Resource Locator), etc. for character data for the building BL01 can be used.
The attribute is additional information for the feature. For example, the height, number of floors for buildings, and the type of lane width, national road, etc. for roads can be used.

FIG. 6 is an explanatory diagram showing the relationship between the projection angle and the drawing result. As described above, in this embodiment, data for drawing a projection map obtained by parallel projection of a feature is used as the feature data. The projection angle and projection direction, which are parallel projection parameters, can be arbitrarily set. As shown on the left side of the figure, the projection angle Ang is defined so that the projection from the vertical direction (PA0 in the figure) is 0 degree and becomes larger as it approaches the horizontal. That is, the projection angle Ang is PA0 <PA1 <PA2 <PA3.
The drawing IMG1 in the upper right of the drawing is a parallel projection view at the projection angle PA1. The lower right drawing IMG2 is a parallel projection view at the projection angle PA2. If the projection angle Ang is small, it is easy to grasp the positional relationship between buildings with a feeling close to a planar map as shown in the drawing IMG1. If the projection angle Ang is large, it becomes easy to intuitively grasp the shape of the building as shown in the drawing IMG2. The projection angle may be set in consideration of these visual effects. Also, a plurality of feature data having different projection angles may be prepared and selectable by the user.

In this embodiment, an actual building is not projected in parallel as it is, but is projected in parallel after multiplying a coefficient larger than 1 only in the height direction. As shown on the left side of the figure, a virtual building having a height C · h obtained by multiplying the actual height h of the building BLD by a coefficient C is obtained, and parallel projection is performed on the virtual building. IMG1 and IMG2 are obtained.
Users often look up at buildings from below. Therefore, when parallel projection is performed as viewed from above, the height sensation of the building obtained from the projection may not match the height sensation when actually looking up. On the other hand, as described above, by multiplying the virtual building expanded only in the height direction by multiplying by the coefficient C, the uncomfortable feeling of height can be alleviated.
The coefficient C can be arbitrarily set in consideration of visual effects. As apparent from comparison between the drawings IMG1 and IMG2, the height sensation of the building also changes depending on the projection angle Ang. Therefore, when performing parallel projection at a plurality of projection angles Ang, the coefficient C depends on the projection angle Ang. May be changed. However, if such a sense of incongruity is not a problem, parallel projection may be performed without multiplying by a coefficient.

B2. Multiple projection orientations:
Parallel projection parameters are a projection angle and a projection direction. The projection angle is a parameter representing how much the projection angle is projected from the vertical as shown in FIG. The projection azimuth is a parameter that indicates which azimuth to incline. The feature data can be prepared for a single projection direction, but in this embodiment, it is prepared for a plurality of directions.

FIG. 7 is an explanatory diagram showing the projection direction of parallel projection. As shown in the figure, in this embodiment, the azimuth is shifted by 45 degrees with respect to one area AR, and parallel projection is performed for each of eight azimuths from azimuth 1 to azimuth 8 to generate feature data. For example, in azimuth 1, a projection projected in parallel as viewed from the north side is obtained, and in azimuth 5, a projection projected in parallel from the south side is obtained. Even a building that had a blind spot in azimuth 1 will be drawn without a blind spot in azimuth 5 in the reverse direction. If feature data is prepared in multiple directions, even if a blind spot occurs in this way, the geographic location of the blind spot can be confirmed on a map of another orientation. It is possible to alleviate the trouble caused by the occurrence.
In this embodiment, feature data of 8 directions is prepared, but it may be 4 directions, 16 directions or more. According to the result of the study by the present inventor, if feature data is prepared in 16 directions and the projection maps of each direction are sequentially switched, it is as if the area AR is seen while circling around the area AR. It has been found that such a display can be realized without a sense of incongruity. From this point of view, it can be said that it is preferable to prepare the feature data for 16 directions.

B3. Hierarchical structure:
FIG. 8 is an explanatory diagram showing a hierarchical structure of feature data. In the present embodiment, both the feature data and the character data are divided into a plurality of hierarchies. The hierarchy LV1 is data for displaying a narrow area in detail. The hierarchy LV3 is data for efficiently displaying a wide area by thinning out features to be drawn. The hierarchy LV2 is data for drawing an intermediate area between the hierarchies LV1 and LV3. These hierarchies are used properly according to the enlargement / reduction of the map to be displayed. Not only three layers, but two layers or four or more layers may be used.
In this embodiment, parallel projection is performed with the same parallel projection parameters in all of the layers LV1 to LV3. That is, as shown in the drawing, a specific region (hatched portion in the drawing) on the ground surface GL is projected in the same manner in any of the hierarchies LV1 to LV3. Therefore, even when the hierarchy is switched in accordance with the enlarged / reduced display of the map, the area corresponding to the display area in the previous hierarchy can be easily identified in the next hierarchy, and smooth display can be achieved with relatively simple processing. Can be realized.

FIG. 9 is an explanatory diagram showing a modification of the hierarchical structure of the feature data. Here, an example is shown in which the parallel projection parameters are different between the lower hierarchy LV1 and the middle hierarchy LV2. The lower layer LV1 projects with a large projection angle (close to horizontal), while the middle layer LV2 projects with a small projection angle (close to vertical).
As a result, the coordinate systems u1 and v1 of the lower hierarchy LV1 and the coordinate systems u2 and v2 of the intermediate hierarchy LV2 are different from each other, and therefore, in each hierarchy, a range corresponding to the hatched area of the ground surface GL is obtained. It becomes difficult to specify. When switching the display from the low hierarchy LV1 to the middle hierarchy LV2 in such a state, a range on the ground surface GL corresponding to the display range in the low hierarchy LV1 is obtained, and then the range on the middle hierarchy LV2 corresponding to this range Will be processed.
If such a processing load is acceptable, the parallel projection parameters may be changed for each layer as shown in FIG. For example, a map to be drawn can be brought closer to a planar map by making the projection angle smaller (closer to the vertical) in a wider hierarchy. In other words, there is an advantage that by changing the hierarchy, it is possible to selectively use the advantage of the planar map and the advantage of the three-dimensional map.

C. Feature data generation method:
FIG. 10 is an explanatory diagram illustrating a feature data generation method. In this embodiment, the feature data is generated by parallel projection of the three-dimensional feature data included in the 3D map database. However, when map data is generated and managed by dividing it into meshes, there is a problem that appropriate feature data cannot be generated if parallel projection is performed in units of meshes.
Consider the case of generating feature data corresponding to the hatched mesh MP in FIG. In the 3D map database, meshes M11 to M55 exist around the mesh MP as shown in the figure, and various features exist in each mesh. Here, consider the case of parallel projection of the feature B34 existing in the mesh M34 adjacent to the mesh MP. If parallel projection is performed in the direction indicated by Vpj34 in the figure, the upper part of the feature B34 is projected into the mesh MP. As described above, when the feature data is generated by parallel projection, a part of the feature that does not exist in the mesh may be projected onto the mesh MP to be processed. Therefore, if parallel projection is simply performed for each mesh, projections of features existing in other meshes are lacking, and appropriate feature data cannot be obtained.

  Therefore, in this embodiment, the mesh MP to be processed is adjacent to the mesh (M22, M23, M24, M25, M32, M34, M42, M43, M44), and the mesh ( M11 to M15, M21, M25, M31, M35, M41, M45, M51 to M55) are read, and parallel projection is applied to the entire meshes M11 to M55, and then the mesh MP is supported. The feature data was generated by cutting out the polygon of the part. By doing this, parallel projection is also performed on the feature B34 existing in the adjacent mesh M34 during processing of the mesh MP, so that the upper part thereof can be converted into feature data without omission.

In the present embodiment, as described above, the meshes at positions from the mesh MP to be processed to two sections are used, but the range used for generating the feature data can be arbitrarily set. If the size of each mesh is sufficiently large compared to the size of the feature, and there is no possibility that a feature that is two blocks away is projected onto the mesh to be processed, then one Parallel projection may be performed using only a mesh directly adjacent to the mesh. Conversely, when the mesh size is smaller than the feature size, parallel projection may be performed using a range of three or more sections.
Furthermore, the range used for parallel projection need not be evenly arranged around the mesh MP to be processed, and may be biased in consideration of the projection direction. For example, consider the case of parallel projection in the direction of the arrow Vpj34 as shown in FIG. At this time, as a result of the feature B32 existing in the mesh M32 adjacent to the left side of the mesh MP being projected in the direction of the arrow Vpj32, the projection view is drawn on the left side of the feature B32. That is, the feature B32 is not projected onto the mesh MP in this projection direction. Therefore, when the mesh MP is processed, it is not necessary to use the mesh M32 for parallel projection.
Similarly, in the case of performing parallel projection with the projection direction indicated by the arrow Vp in FIG.
As described above, the range used for parallel projection may be set so as to be biased toward the projection direction with respect to the mesh MP to be processed.

FIG. 11 is a flowchart of the feature data generation process. This is a process performed by the parallel projection unit 102 (see FIG. 3) of the data generation apparatus 100, and is a process executed by a CPU of a personal computer constituting the data generation apparatus 100 in terms of hardware.
When the process is started, the CPU inputs designation of a mesh to be processed (step S100). This process corresponds to the designation of the mesh MP in FIG. As a specification method, a mesh-specific index, mesh coordinates, or the like can be used. A method may be used in which the data generation device 100 analyzes a mesh including the coordinate value of a point designated by the operator on the map and sets this as a mesh to be processed.

  Further, the CPU inputs parallel projection parameters, that is, a projection direction and a projection angle (step S101). The parallel projection parameters may be specified by the operator every time the feature data is generated, or a method of setting default parallel projection parameters in the data generation apparatus 100 in advance may be used.

  Next, the CPU reads the 3D map database for the target mesh and the meshes in a predetermined range around the target mesh (step S102). In this embodiment, as shown in FIG. 10, 3D map data belonging to meshes within two sections from the target mesh MP is read. As described with reference to FIG. 10, the range can be arbitrarily set. The read 3D map data is temporarily stored in the memory of the data generation device 100.

  The CPU performs parallel projection on the read 3D feature data based on the parallel projection parameters specified in step S101 (step S103). By this processing, a projection diagram in which each feature is three-dimensionally expressed by parallel projection is drawn. In the present embodiment, these drawing results are temporarily stored in the memory of the data generation device 100 as two-dimensional polygon data. The drawing result may be stored as raster data.

  When the parallel projection is completed, the CPU cuts out a region corresponding to the target mesh from the generated polygon data (step S104). For polygons drawn across a plurality of meshes, as shown in FIG. 5, only the part in the target mesh is extracted and set as new polygon data. Further, at the time of cutting out, various data shown in FIG. 5 such as name, position, and shape are prepared for each polygon.

Then, the CPU stores it as feature data (step S105). In this embodiment, the data is transmitted to the server 200 (see FIG. 3) together with an instruction to store the feature data 211.
By executing the above processing for all meshes, the feature data 211 of this embodiment can be maintained.

D. Character data structure:
FIG. 12 is an explanatory diagram showing a link between feature data and character data. The structure of the feature data 211 is schematically shown on the left side of the figure. As shown in FIG. 8, the feature data is divided and prepared in levels LV1 to LV3, and is divided and prepared in directions 1 to 8 as shown in FIG. As shown in the figure, the feature data from the azimuth 1 to the azimuth 8 in the hierarchy LV1 include records corresponding to the feature named BL03 in common. A record for this feature also exists in the feature data in the hierarchies LV2 and LV3. As described above, in this embodiment, records for the same feature are duplicated with respect to various layers and orientations.

The character data 212 stores a plurality of character records in which character information representing the names of the features is recorded. In this embodiment, character records are also arranged for each hierarchy.
In each record of the feature data, information LINK indicating the storage location of the character record indicating the name of the feature is recorded. In this embodiment, since one character record is commonly used for feature data in a plurality of directions in each hierarchy, the contents of the information LINK stored in the feature BL03 in the hierarchy LV1 are the same. is there. In the figure, arrows indicate how one character record is associated with multiple feature records.

The character record stores information such as name, display contents, font, color, size, behind flag, position, and height.
The name is the name of the feature to which the character record corresponds. You may use the name of the polygon which comprises a feature. As shown in FIG. 5, since one feature may be drawn with a plurality of polygons, when using the names of polygons, a plurality of names are stored.
The display content is a character string representing the name of the feature. The font, color, and size are information that defines the display mode of the character string.
The behind flag is a flag that controls whether or not characters can be displayed, and is set in association with the direction of the feature data. In the example in the figure, since “1, 1, 1, 1, 0, 0, 1, 1” is set, characters are displayed in the directions 1 to 4 and the directions 7 and 8 (setting = 1). , Directions 5 and 6 mean that they are not displayed (setting = 0). A method for setting the behind flag will be described later.
The position is the coordinate at which the character is displayed. The coordinates of the representative point of the corresponding feature, that is, the same value as the “position” information in the feature data can be used.
Height is the height at which characters are displayed. The height may be expressed in units of meters or the like, or may be expressed using pixels at the time of display, the number of floors of features, and the like.
By specifying the height information, it is possible to display the character at a position higher than the ground contact surface of the feature, and it is possible to realize a display that makes it easy to grasp the relationship between the character and the feature. In this embodiment, the height is a value common to all directions, but it may be set for each direction as in the behind flag.

  In the present embodiment, character data is prepared for each layer, but character data may be common to all layers. In this case, a flag for controlling the display / non-display of the character data may be set according to the hierarchy. For this flag, a format conforming to the behind flag can be adopted.

FIG. 13 is an explanatory diagram showing the contents of the behind flag. The center figure shows the two-dimensional arrangement of the two features of the buildings BL03 and BL04. Moreover, the set value of the behind flag (BF) for the building BL01 in each direction is shown.
When the buildings BL01 and BL04 are projected in parallel from the direction 1, the building BL01 is visible without being a blind spot of the building BL04. In direction 1, since there is no problem even if the character representing the name of the building BL01 is displayed on the map, the behind flag BF is set to “1” meaning character display. The same applies to the orientations 2, 3, 7, and 8.
The lower right projection PIC4 is a parallel projection from azimuth 4. As shown in the drawing, in the parallel projection from the azimuth 4, the building BL01 does not become a blind spot of the building BL04. Therefore, the behind flag BF is set to “1”.
The lower projection PIC5 is a parallel projection from the azimuth 5. In this state, the building BL01 is a blind spot of the building BL04. When the name of the building BL01 is displayed in such a state, the user does not know which building name is displayed. Therefore, in this state, since the character of the building BL01 should be hidden, the behind flag BF is set to “0” meaning non-display.
A projection PIC6 in the lower left is a parallel projection from the azimuth 6. In this state, as shown in the drawing, the upper part of the building BL01 is slightly visible. In such a case, the behind flag can be set to either display / non-display. In the figure, an example in which the behind flag BF is set to non-display “0” in consideration of the point that it is only slightly visible. Although it is a part, the behind flag BF may be set to “1” in consideration of the point where the building BL03 is visible.

  Although the setting of the behind flag for the building BL01 has been described with reference to FIG. 13, it can be similarly set for the building BL04. In the state shown in FIG. 13, it is appropriate that the behind flag of the building BL04 is set to display “1” for all directions.

Whether or not it becomes a blind spot depends not only on the planar positional relationship of the building but also on the height of the building, so it is preferable to set the behind flag according to the result of parallel projection. Also in the example of FIG. 13, if the height of the building BL01 is sufficiently higher than the building BL04, the behind flag BF may be “1” in all directions.
The behind flag may be set manually by the operator, or in the feature data generation process (see FIG. 11), when performing parallel projection of each feature, it is determined whether or not it becomes a blind spot of another feature. Thus, it may be set automatically. A feature that partially looks like the building BL03 in the azimuth 6 in FIG. 13 can be handled as follows, for example.
(1) Display when the area of the drawn portion is a predetermined value or more;
(2) Display when the area of the drawn portion is equal to or greater than a predetermined ratio of the building BL01;
(3) Display when a part or all of the ground contact portion of the building BL01 is drawn;
(4) Display when the portion to be drawn is a predetermined number of floors or more;

E. Map display processing:
FIG. 14 is a flowchart of the map display process. In the present embodiment, the process is executed by the main control unit 304 and the display control unit 306 of the mobile phone 300, and the process executed by the CPU of the mobile phone 300 in terms of hardware.

In this process, the CPU first inputs designation of the display position, orientation, and range (step S300). The user may specify these with a keyboard or the like, or the current position obtained by GPS may be used as the display position.
The CPU extracts map information corresponding to the designation from the map information already acquired in the previous map display process and stored in the mobile phone 300 (step S301). Map information is a generic name for various data necessary for displaying a map, such as feature data, character data, and network data.
The state of extraction is shown in the figure. Of the map information ME divided by the mesh, the hatched part is the map information already held in the mobile phone 300. An area IA represents a range corresponding to a designation from the user. In this example, a portion that overlaps the region IA in the held map information, that is, a portion excluding the meshes ME3 and ME4 is extracted.
The meshes ME3 and ME4 that do not overlap with the area IA may be deleted as unnecessary information, or may be left as long as the memory of the mobile phone 300 allows.

  If the extracted map information is insufficient to display a map (step S302), the CPU acquires the map information of the insufficient part from the server 200 (step S303). In the above example, since the meshes ME1 and ME2 are insufficient to display the area IA, these pieces of map information are acquired.

When the map information is thus acquired, the CPU draws the feature (step S304). In the present embodiment, the feature data is only two-dimensional polygon data that has already been projected in parallel. Therefore, if a polygon is drawn according to the acquired feature data, a three-dimensional map can be displayed.
In the prior art, a processing called rendering was performed using a three-dimensional model to create a perspective projection drawing and a three-dimensional map was drawn. Therefore, the processing load required for rendering was very large. In the example, there is a great advantage that a three-dimensional map can be drawn with a very light load.

The CPU displays the characters for which the behind flag is set to 1 on the map (step S305). The character display may be performed together with the drawing of the feature (step S304).
The display position of characters in the displayed map can be set by the following procedure.
First, since the latitude and longitude of the vertices of each mesh constituting the feature data are known, the point corresponding to the position information (latitude and longitude) attached to the character record in the mesh is specified. Based on the latitude and longitude of the character record, the latitude and longitude of the vertices of each mesh may be interpolated to obtain the uv coordinate value defined in the mesh.
Next, the character display position is moved in the u-axis direction according to the height information. If the height information is specified by the pixel value at the time of display, the specified value can be used. If the height information is given in meters, floors, etc., it can be converted into pixel values by multiplying by a coefficient corresponding to the projection angle.

In this embodiment, by using the behind flag, it is possible to display characters only for features that are not blind spots. Since the behind flag is set for each direction, display / non-display of characters can be switched according to the designated direction.
When rendering a 3D model, it was necessary to control whether to display or not display characters because it was necessary to determine whether or not the feature had a blind spot during the rendering process. While the processing load required for display control is very large, this embodiment has a great advantage that control is possible with a very light load.

  FIG. 15 is an explanatory diagram illustrating a three-dimensional map according to the embodiment. The output example of the area corresponding to the photograph of Fig.15 (a) was shown. Conventional three-dimensional map output by perspective projection is also as shown in FIG. In the display of FIG. 15A, it is easy to grasp the shapes of the buildings BL1 and BL2, and there is an advantage that a user standing at this point can intuitively identify the buildings BL1 and BL2. However, in FIG. 15A, it is difficult to grasp the positional relationship between the two, and it is impossible to grasp the distance to other buildings that are visible in the distance.

  FIG. 15B is an output example of a two-dimensional map. Also in FIG. 15B, the buildings corresponding to the buildings BL1 and BL2 in FIG. Although it is easy to grasp the positional relationship between the buildings BL1 and BL2 on the two-dimensional map, when viewed from a user who actually stands in this area, these illustrated features correspond to the buildings BL1 and BL2 in FIG. This is difficult to grasp intuitively.

FIG. 15C shows an output example in this embodiment. Also in FIG. 15C, the buildings BL1 and BL2 are indicated by a dashed box. It is drawn in parallel projection, and the map scale is maintained. Therefore, the positional relationship between the buildings BL1 and BL2 and the distance to the buildings located farther than these buildings can be grasped to the same extent as the two-dimensional map (FIG. 15B).
In FIG. 15C, since the features are displayed three-dimensionally, the shapes of the buildings BL1 and BL2 can be intuitively recognized. While FIG. 15 (c) is drawn as if looking down from above, the user who actually stands at this point looks at the buildings BL1 and BL2 as if looking up downward as shown in FIG. 15 (a). Still, it is possible to intuitively identify the buildings BL1 and BL2 based on the display of FIG.
As described above, the 3D map display in this embodiment uses the parallel projection to maintain the scale of the 2D map and the 3D map to easily grasp the shape of the feature intuitively. You can combine the advantages.

In FIG. 15C, the characters “XX building” and “second ** building” are illustrated. The names of other features are not shown in order to avoid complications.
In this embodiment, since the display position of the character including the height information is designated, as shown in the figure, the character is displayed on the upper part instead of the grounded part of the building. In a 3D map, displaying characters on top of features in this way prevents the characters from becoming blind spots of other features, and makes it easy to recognize the correspondence between characters and features. Can be realized.
In this example, the character is arranged on the roof of each building by specifying the height of the building as the height information of the character. The height information can be arbitrarily set, and characters may be displayed on the side wall portion of the building.

F. Route guidance process:
F1. Overall processing:
FIG. 16 is a flowchart of route guidance processing. The processing of the mobile phone 300 is shown on the left side, and the processing of the server 200 is shown on the right side. These are processes executed by the various functional blocks shown in FIG. 3 in cooperation, and are executed by the CPU of the mobile phone 300 and the server 200 in terms of hardware.

First, the user of the mobile phone 300 designates a starting point and a destination for route search (step S210). As the departure point, the current position acquired by GPS may be used. The destination can be set by various methods such as feature names, addresses, and latitude and longitude coordinate values. The mobile phone 300 transmits these designation results to the server 200.
When the server 200 receives the designation of the departure point and destination (step S200), the server 200 searches for a route using the network data 213 (see FIG. 3) (step S201). For the route search, for example, the Dijkstra method or the like can be used. The server 200 outputs the search result, that is, the network data to be a route to the mobile phone 300 (step S202).

When receiving the search result (step S211), the mobile phone 300 performs route guidance according to the following procedure.
First, the mobile phone 300 inputs the current position and traveling direction of the user (step S220). The current position can be specified by GPS. The traveling direction can be obtained based on the change from the previous position to the current position.
Next, the mobile phone 300 performs display range determination processing (step S220). This process is a process for determining the display range of the map based on the current position and the traveling direction (step S220).

FIG. 17 is a flowchart of the display range determination process. The mobile phone 300 first determines the orientation of the map based on the traveling direction (step S221). As described with reference to FIG. 7, since feature data is prepared for eight directions in this embodiment, the direction to be used is selected according to the traveling direction.
The method for determining the orientation of the map is shown in the figure. The central square area represents an area to be displayed, and eight directions corresponding to FIG. 7 are shown around it. Each azimuth is assigned an angle region of 45 degrees, as indicated by a broken line. The mobile phone 300 selects the one including the traveling direction from these eight angular regions. For example, when traveling in the direction indicated by the arrow HD, the azimuth 5 is selected.
The angle region can be determined according to the number of directions in which the feature data is prepared. When feature data of 16 azimuths are prepared, the angle may be set to 22.5 degrees.

In addition, as illustrated in the azimuth 1 and the azimuth 8 in the drawing, the angle range assigned to each azimuth may be set to be larger than 45 degrees, and an overlapping area may be provided between the azimuths. The range indicated by the alternate long and short dash line in the figure represents an angle region wider than 45 degrees. When such a wide angle region is assigned to the azimuth 1 and the azimuth 8, an overlapping region is generated between the two as in the hatched region HA.
With this setting, this region can be used as a hysteresis region when determining the direction. For example, when the traveling direction changes from azimuth 8 to azimuth 1, the azimuth 8 is used even when the traveling direction enters the overlapping area HA, and conversely, when the traveling direction changes from azimuth 1 to azimuth 8. The direction 1 is used even if the traveling direction enters the overlapping area HA. Providing hysteresis in this way has the advantage of avoiding frequent switching of the displayed map when the traveling direction changes in the vicinity of the boundary between azimuth 1 and azimuth 8.
Although an example in which the overlap area HA is provided between the azimuth 1 and the azimuth 8 is shown in the drawing, it is possible to similarly provide an overlap area between other azimuths.
When the display orientation is thus determined, the mobile phone 300 can determine the display range based on the current position and orientation (step S222).

An example of determining the display range during route guidance is shown on the right side of the figure.
Consider a case where the vehicle moves to positions POS1, POS2, and POS3 along a path PS indicated by a broken line. At the position POS1, the traveling direction DR1 corresponds to directly above in the drawing, that is, the azimuth 5 (see the drawing in step S221). Therefore, the cellular phone 300 sets the range of the width XAr and the vertical YAr as the display range Ar1 using the feature data of the azimuth 5. The width and the vertical size may be determined by an instruction from the user, or may be automatically set according to the progress speed of the user. The traveling speed can be calculated based on the temporal change of the current position.

  Next, when moving to the position POS2, the traveling direction DR2 changes slightly to the right. However, since the traveling direction DR2 still belongs to the angle region of the azimuth 5, the mobile phone 300 selects the azimuth 5 at the position POS2 and determines the display range AR2. As a result, while moving from the position POS1 to the position POS2, the direction of travel changes to the right, but the map is displayed in the form of parallel movement with the azimuth 5 being maintained.

  Next, when moving to the position POS3, the traveling direction DR3 further changes to the right. This traveling direction DR3 deviates from the angular region of azimuth 5 and belongs to the angular region of azimuth 6. Therefore, the mobile phone 300 selects the orientation 6 at the position POS3 and determines the display range AR3. At the time of route guidance, the display switches from the azimuth 5 to the azimuth 6 on the way from the position POS2 to the position POS3.

Returning to FIG. 16, the route guidance process will be described.
In this embodiment, the network data representing the route and the current position are defined by three-dimensional position coordinates including the height. The road is also generated by parallel projection of 3D data having height information in order to reflect the so-called undulation, that is, the height change of the ground surface. Therefore, if the network data is projected by the same method as the parallel projection and is not displayed on the map, the route is displayed shifted from the road.
Therefore, in this embodiment, in order to appropriately display the route on the road, a process for obtaining a display position by performing parallel projection on the current position and the network data is performed. This is the coordinate conversion process (step S230). A processing method for coordinate transformation will be described later.

When the above processing is completed, the mobile phone 300 executes map display processing according to the designated display range (step S300). The contents of this process are the same as those shown in FIG.
Next, the mobile phone 300 displays the route and the current position (step S310). The route may be indicated by a color, line, or the like different from the road, or an arrow or the like may be displayed in a direction to travel or a corner.

  The mobile phone 300 performs the route guidance by repeatedly executing the processes after step S220 until the user arrives at the destination (step S311).

F2. Coordinate transformation:
FIG. 18 is an explanatory diagram showing the influence of undulation.
A plane A2D in the figure represents the ground surface in the two-dimensional map, and a plane A3D represents the ground surface in the three-dimensional map. As shown on the right side, the network data 213 and the 3D map database 104 used for generating the feature data in this embodiment are data having three-dimensional information corresponding to the plane A3D. The range corresponding to the mesh M2D in the two-dimensional plane A2D corresponds to the undulating mesh M3D.
A plane Ap shows a projection view by parallel projection. Since the projection is performed in the direction indicated by the arrow Vpj, the range corresponding to the mesh M2D in the two-dimensional plane A2D is the mesh MP2 at a slightly shifted position.
A plane Ag shown at the bottom is a coordinate plane of latitude and longitude obtained by GPS.

In the present embodiment, the current position is given by three-dimensional position coordinates such as a point P3D (x, y, z). The coordinates correspond to the position Cpg (latitude, longitude) two-dimensionally and correspond to the point P2D (X, Y) in the mesh M2D on the plane A2D on which the two-dimensional map is drawn.
If the point P3D is projected in parallel, it is drawn at the point Pp2 in the mesh Mp2 on the surface Ap. On the other hand, assuming that the two-dimensional element (X, Y) of the three-dimensional coordinates of the point P3D is a coordinate value subjected to parallel projection, it is different from the original mesh Mp2 in the plane Ap. Drawing is performed at the point Pp1 in the mesh Mp1. An error Vc from the original point Pp2 occurs.
Therefore, in the present embodiment, rendering is performed in a state in which the point P3D is projected in parallel by performing coordinate transformation corresponding to the movement by the error Vc on the point P3D within the surface Ap.

FIG. 19 is an explanatory diagram showing a coordinate conversion method in consideration of undulation. A vector corresponding to the error Vc shown in FIG. 18 is obtained, and coordinate conversion is performed using this as a correction amount. In this sense, hereinafter, the error Vc is also referred to as a correction vector Vc.
An arrow Vpj in the figure indicates the direction of parallel projection. The point P3D is assumed to be projected onto the point Pp2 by this parallel projection.
Since the result of projection using only the X and Y coordinates of the point P3D is the point Pp1, the error Vc is a vector from the point Pp1 to the point Pp2, and is equal to the vector Vc in the figure.

The correction vector Vc can be obtained by an affine transformation matrix that combines rotation and translation.
A transformation matrix corresponding to the vector Vc0 that translates in the −X direction is obtained while maintaining the height of the point P3D. If the projection angle Ap is used, the magnitude of the vector Vc0 is represented by the product of the height z of the point P3D and tan (Ap), and thus the vector Vc0 (Vc0x, Vc0y, Vc0z) is represented as follows. .
Vc0x = −z × tan (Ap);
Vc0y = 0;
Vc0z = 0;

The correction vector Vc only needs to be rotated by the projection azimuth (−Ay) around the z axis. Therefore, the correction vector Vc (Vcx, Vcy, Vcz) is expressed as follows.
Vcx = −z × tan (Ap) × cos (Ay);
Vcy = z × tan (Ap) × sin (Ay);
Vcz = 0;
Therefore, the point Pp2 can be obtained by applying the correction vector Vc described above to the point Pp1 obtained by vertically projecting P3D. Since the correction vector Vc is substantially a two-dimensional vector of (Vcx, Vcy), it can be corrected within the projection plane of parallel projection.

  The above correction vector Vc defines the y-axis as the north, the x-axis as the east, and the z-axis as the height direction, and represents the projection azimuth at angles of the east, south, west, and north directions with 0 degrees as the north. This is the value when In accordance with the definitions of x, y, z and projection direction, it is necessary to use suitable conversion formulas.

FIG. 20 is a flowchart of the coordinate conversion process. This process corresponds to step S230 in FIG. 17 and is executed by the map matching conversion unit 307 (see FIG. 3) of the mobile phone 300.
When the process is started, the mobile phone 300 inputs parallel projection parameters Ap (projection angle) and Ay (projection direction) (step S301). Then, a coordinate transformation matrix is generated based on the parallel projection parameters (step S302). The contents of the matrix are as described in FIG.

Next, the mobile phone 300 inputs the current position and the network data within the display range (step S303), and performs coordinate conversion of the current position (step S304). Also, coordinate conversion of network data is executed for all networks (steps S305 and S306). The network coordinate conversion may be performed prior to the current position coordinate conversion, or both may be performed in parallel.
When the coordinate conversion of the current position and the network data is thus completed, the mobile phone 300 ends the coordinate conversion process. A map is displayed using this conversion result (see step S310 in FIG. 16).

FIG. 21 is an explanatory diagram showing an example of route guidance. 21 shows how the guidance display changes as the route progresses in order from FIG. 21 (a) to FIG. 21 (c).
In FIG. 21A, the current position is shown in a circle on the practice route. Roads and buildings are drawn using parallel projected feature data. Since the coordinate transformation described above is performed, both the route and the current position are drawn on an appropriate road.
From FIG. 21A, it can be seen that if this route is followed for a while, a right turn is made.

FIG. 21B shows a display in a right-turned state. A map is drawn using feature data having a projection direction different from that in FIG.
As described with reference to FIG. 17, the map is switched according to the traveling direction. In this example, the map is switched from the azimuth in FIG. 21 (a) to the azimuth in FIG. 21 (b) when the traveling direction changes to the right or more during the right turn. In this way, by displaying the map using the feature data of the direction corresponding to the traveling direction, it is possible to guide the route while avoiding the blind spot due to the feature.
From FIG. 21 (b), it can be seen that if this route is followed for a while, a further right turn is made.

FIG. 21C is a display in a state where the route is turned to the right. The map is drawn using feature data having a different projection direction from that in FIG. In this example, the map is switched from the azimuth in FIG. 21 (b) to the azimuth in FIG. 21 (c) when the traveling direction changes to the right or more during the right turn.
In the example of FIG. 21, an example in which the orientation of the map changes when turning right is shown, but the orientation is not always changed only when turning right or left. When traveling on a curved road, the direction of travel may change and the direction may change. Further, the map orientation may be switched in accordance with a user instruction during route guidance.

The embodiments of the present invention have been described above. The three-dimensional map display system does not necessarily have all the functions of the above-described embodiments, and only a part may be realized. Moreover, you may provide an additional function in the content mentioned above.
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, a portion configured in hardware in the embodiment can be configured in software and vice versa.

  The present invention can be used to draw a three-dimensional map that represents a three-dimensional feature.

DESCRIPTION OF SYMBOLS 100 ... Data generation apparatus 101 ... Command input part 102 ... Parallel projection part 103 ... Parallel projection data 104 ... 3D map database 105 ... Transmission / reception part 106 ... Behind flag setting part 200 ... Server 201 ... Transmission / reception part 202 ... Database management part 203 ... Path | route Search unit 210 ... Map database 211 ... Feature data 212 ... Character data 213 ... Network data 300 ... Mobile phone 300d ... Display 300k ... Keyboard 301 ... Transmitter / receiver 302 ... Command input unit 303 ... GPS input unit 304 ... Main control unit 305 ... Map information storage unit 306 ... display control unit 307 ... map matching conversion unit

Claims (1)

A three-dimensional map drawing system for drawing a three-dimensional map representing a three-dimensional feature,
A feature database for storing feature data as two-dimensional drawing data obtained by projecting a feature onto a plane by parallel projection from an oblique direction inclined by a predetermined projection angle with respect to the vertical direction;
A drawing range input unit for inputting a designation of a range in which a three-dimensional map is to be drawn;
A drawing unit that reads and draws feature data corresponding to the designation from the feature database;
The feature database stores the feature data divided into a mesh composed of a predetermined two-dimensional region,
A three-dimensional map drawing system in which each mesh is allowed to store feature data for features that do not exist on the mesh.