Map display apparatus

A navigation apparatus for displaying most appropriately information such as character strings, routes, etc., when a map is displayed by bird's-eye view display. The navigation apparatus includes a portion for calculating the present position on the basis of information from sensors, a portion for executing perspective conversion operation for displaying a map by bird's-eye view display, a portion for disposing the present position or the present position and a position representing a destination at the most suitable positions, a portion for controlling so that overlap of character strings can be eliminated, a portion for controlling the same character strings, a portion for displaying most appropriately a background such as lines and planes, a portion for controlling marks to be displayed, and a portion for executing graphic plotting by using the resulting map data.

 

We claim:

1. A map display apparatus comprising:

memory means for storing map data necessary for plotting a map of a predetermined region;

character data selection means for selecting a character string having a predetermined attribute from character data read out from said memory means;

perspective conversion means for perspective converting the character data selected by said character data selection means to produce perspective-converted character data;

character data display means for displaying the perspective-converted character data produced by said perspective conversion means by a bird's-eye view display; and

vector data display means for executing perspective conversion for vector data read out from said memory means and displaying it by a bird's-eye view display;

wherein said character data selection means includes:

character overlap judgement means for judging overlap between different character strings; and

character string selection means for selecting a character string having a predetermined attribute for those character strings which are judged as overlapping by said character overlap judgement means.

2. A map display apparatus comprising:

memory means for storing map data necessary for plotting a map of a predetermined region;

character data selection means for selecting a character string having a predetermined attribute from character data read out from said memory means;

perspective conversion means for perspective converting the character data selected by said character data selection means to produce perspective-converted character data;

character data display means for displaying the perspective-converted character data produced by said perspective conversion means by a bird's-eye view display; and

vector data display means for executing perspective conversion for vector data read out from said memory means and displaying it by a bird's-eye view display;

wherein said character data selection means includes:

character overlap judgement means for judging overlap between different character strings; and

character string selection means for selecting a character string in the proximity of a visual point for those character strings which are judged as overlapping by said character overlap judgement means.

3. A map display apparatus comprising:

memory means for storing map data necessary for plotting a map of a predetermined region;

character data selection means for selecting a character string having a predetermined attribute from character data read out from said memory means;

perspective conversion means for perspective converting the character data selected by said character data selection means to produce perspective-converted character data;

character data display means for displaying the perspective-converted character data produced by said perspective conversion means by a bird's-eye view display; and

vector data display means for executing perspective conversion for vector data read out from said memory means and displaying it by a bird's-eye view display;

wherein said character data selection means includes:

character overlap judgement means for judging overlap between different character strings; and

font substitution means for a smaller font for those character strings which are judged as overlapping by said character overlap judgement means.

4. A map display apparatus according to any of claims 1 through 3, wherein said character overlap judgement means judges overlap between character strings by using a rectangular region information circumscribed with the character strings.

5. A map display apparatus according to any of claims 1 through 3, wherein said character overlap judgement means judges overlap between character strings by using a rectangular region information of a rectangle situated more inward by a predetermined distance from a rectangle circumscribed with the character strings.

6. A map display apparatus according to any of claims 1 through 3, wherein said character overlap judgement means judges overlap by using a polygonal region information of a polygon situated more inward by a predetermined distance from a polygon encompassing the character strings.

7. A map display apparatus comprising:

memory means for storing map data necessary for plotting a map of a predetermined region;

same character string selection means for selecting the same character strings from character data read out from said memory means;

character data selection means for selecting a predetermined character string from the same character strings selected by said same character string selection means;

perspective conversion means for perspective converting the character data selected by said character data selection means to produce perspective-converted character data;

character data display means for displaying the perspective-converted character data produced by said perspective conversion means by a bird's-eye view display; and

vector data display means for executing perspective conversion for vector data read out from said memory means and displaying it by a bird's-eye view display.

8. A map display apparatus according to claim 7, wherein said character data selection means selects a character string in the proximity of a visual point.

9. A map display apparatus according to claim 7, wherein said same character string selection means judges character strings as the same character strings when the distance between the character strings that are being judged is within a predetermined range.

10. A map display apparatus according to claim 7, wherein said same character string selection means judges character strings as the same character strings when the character strings that are being judged are subjected to perspective conversion and are displayed, and when the distance between them is within a predetermined range.

11. A map display apparatus comprising:

memory means for storing map data necessary for plotting a map of a predetermined region;

map display means for displaying a bird's-eye view map by using map data read out from said memory means;

driving orbit memory means for storing a car's own driving orbit; and

driving orbit display means for executing perspective conversion of a plurality of routes stored in said driving orbit memory means to produce perspective-converted routes and displaying said perspective-converted routes in such a manner that the gaps between orbit point strings become equidistant when said perspective-converted routes are displayed by a bird's-eye view display.

12. A map display apparatus according to claim 11, wherein said driving orbit display means thins out the orbit data so that orbit point strings become equidistant when a plurality of orbits stored in said driving orbit memory means are subjected to perspective conversion and are displayed by bird's-eye view display, and displays the orbit data.

13. A map display apparatus according to claim 11, wherein said driving orbit memory means calculates interpolation points of orbit data so that the orbit point strings are equidistant when a plurality of orbits stored in said driving orbit memory means are subjected to perspective conversion and are displayed, and displays them.

14. A map display apparatus comprising:

memory means for storing map data necessary for plotting a map of a predetermined region;

map data display means for executing perspective conversion of each apex when a pattern exists in the map data read out from said memory means, and displaying the map data by using a pattern used for a plan view map display; and

character data display means for executing perspective conversion for the character data read out from said memory means and displaying it by a bird's-eye view display.

15. A map display apparatus according to claim 14, wherein said map data display means includes means for executing perspective conversion of each apex of a vector when a pattern exists in the map data constituted by vector data, and displaying it by a vector display by using a pattern used for a plan view map display.

16. A map display apparatus according to claim 14, wherein said map data display means includes means for executing perspective conversion of each apex constituting a polygon when a pattern exists inside the polygon encompassed by polygonal data, and displaying the polygon by using a pattern used for a plan view map display.

17. A map display apparatus comprising:

memory means for storing map data necessary for plotting a map of a predetermined region;

map display means for selectively displaying either a bird's-eye view map or a plan view map by using the map data read out from said memory means;

mark selection means for selecting a respective mark to be displayed in superposition with the displayed bird's-eye view map and the displayed plan view map; and

mark display means for displaying the selected mark in superposition with the displayed bird's-eye view map or the displayed plan view map.

18. A map display apparatus comprising:

memory means for storing map data necessary for plotting a map of a predetermined region;

map display means for displaying a bird's-eye view map and a plan view map by using the map data read out from said memory means;

mark selection means for selecting a mark in accordance with the map to be displayed in superposition with the map to be displayed; and

mark display means for displaying the mark selected by said mark selection means in superposition with the bird's-eye view map and the plan view map.

19. A map display apparatus according to claim 18, wherein said mark selection means selects and displays a mark representing the plan view display during display of the plan view map, and selects and displays a mark representing the bird's-eye view display during display of the bird's-eye view map.

20. A map display apparatus according to claim 18, wherein said mark selection means changes the shape of the mark representing a present position in both the bird's-eye view map and the plan view map.

21. A map display apparatus according to claim 18, wherein said mark selection means changes the shape of the mark representing a present position in accordance with the position of a visual point or a projection angle in the bird's-eye view map.

22. A map display apparatus according to claim 18, wherein said mark selection means displays a mark representing a reduced scale of a map in the plan view map and does not display the mark representing the reduced scale of the map in the bird's-eye view map.

23. A map display apparatus comprising:

a memory which stores map data necessary for plotting a map of a predetermined region;

a character data selector which selects a character string having a predetermined attribute from character data read out from said memory;

a perspective converter which perspective converts the character data selected by said character data selector to produce perspective-converted character data;

a character data display which displays the perspective-converted character data produced by said perspective converter by a bird's-eye view display; and

a vector data display which executes perspective conversion for vector data read out from said memory and displays it by a bird's-eye view display;

wherein said character data selector includes:

a character overlap judger which judges overlap between different character strings; and

a character string selector which selects a character string having a predetermined attribute for those character strings which are judged as overlapping by said character overlap judger.

24. A map display apparatus comprising:

a memory which stores map data necessary for plotting a map of a predetermined region;

a character data selector which selects a character string having a predetermined attribute from character data read out from said memory;

a perspective converter which perspective converts the character data selected by said character data selector to produce perspective-converted character data;

a character data display which displays the perspective-converted character data produced by said perspective converter by a bird's-eye view display; and

a vector data display which executes perspective conversion for vector data read out from said memory and displays it by a bird's-eye view display;

wherein said character data selector includes:

a character overlap judger which judges overlap between different character strings; and

a character string selector which selects a character string in the proximity of a visual point for those character strings which are judged as overlapping by said character overlap judger.

25. A map display apparatus comprising:

a memory which stores map data necessary for plotting a map of a predetermined region;

a character data selector which selects a character string having a predetermined attribute from character data read out from said memory;

a perspective converter which perspective converts the character data selected by said character data selector to produce perspective-converted character data;

a character data display which displays the perspective-converted character data produced by said perspective converter by a bird's-eye view display; and

a vector data display which executes perspective conversion for vector data read out from said memory and displays it by a bird's-eye view display;

wherein said character data selector includes:

a character overlap judger which judges overlap between different character strings; and

a font substituter for a smaller font for those character strings which are judged as overlapping by said character overlap judger.

26. A map display apparatus comprising:

a memory which stores map data necessary for plotting a map of a predetermined region;

a same character string selector which selects the same character strings from character data read out from said memory;

a character data selector which selects a predetermined character string from the same character strings selected by said same character string selector;

a perspective converter which perspective converts the character data selected by said character data selector to produce perspective-converted character data;

a character data display which displays the perspective-converted character data produced by said perspective converter by a bird's-eye view display; and

a vector data display which executes perspective conversion for vector data read out from said memory and displays it by a bird's-eye view display.

27. A map display apparatus comprising:

a memory which stores map data necessary for plotting a map of a predetermined region;

a map display which displays a bird's-eye view map by using map data read out from said memory;

a driving orbit memory which stores a car's own driving orbit; and

a driving orbit display which executes perspective conversion of a plurality of routes stored in said driving orbit memory to produce perspective-converted routes and displays said perspective-converted routes in such a manner that the gaps between orbit point strings become equidistant when said perspective-converted routes are displayed by a bird's-eye view display.

28. A map display apparatus comprising:

a memory which stores map data necessary for plotting a map of a predetermined region;

a map data display which executes perspective conversion of each apex when a pattern exists in the map data read out from said memory, and displays the map data by using a pattern used for a plan view map display; and

a character data display which executes perspective conversion for the character data read out from said memory and displays it by a bird's-eye view display.

29. A map display apparatus comprising:

a memory which stores map data necessary for plotting a map of a predetermined region;

a map display which selectively displays either a bird's-eye view map or a plan view map by using the map data read out from said memory;

a mark selector which selects a respective mark to be displayed in superposition with the displayed bird's-eye view map and the displayed plan view map; and

a mark display which displays the selected mark in superposition with the displayed bird's-eye view map or the displayed plan view map.

30. A map display apparatus comprising:

a memory which stores map data necessary for plotting a map of a predetermined region;

a map display which displays a bird's-eye view map and a plan view map by using the map data read out from said memory;

a mark selector which selects a mark in accordance with the map to be displayed in superposition with the map to be displayed; and

a mark display which displays the mark selected by said mark selector in superposition with the bird's-eye view map and the plan view map.

BACKGROUND OF THE INVENTION

This invention relates to a map display apparatus for use in a navigation system for measuring the position of a mobile body and reporting the present position to a user, and more specifically to a bird's-eye view map display apparatus which provides a map in a more comprehensible way to the user.

A navigation apparatus mounted to a mobile body processes information from a variety of sensors to measure the position of the mobile body and reports the position to a user. This navigation apparatus comprises position measurement means for measuring the absolute position of a mobile body, memory means for storing map data constituted by two-dimensional vector data obtained by projecting points on the ground such as roads and buildings on a plane divided into meshes by universal transverse mercator projection and character data accompanying the two-dimensional vector data, input means for receiving commands from the user, and display means for reading the necessary vector data from the map mesh stored in the memory means in accordance with the command inputted from the input means and conversion processing the data to display the map on a display Here, data conversion processing includes movement conversion for changing the display position of the map, reduced scale conversion, such as enlargement and reduction, used for displaying the map in an arbitrary reduced scale and rotation conversion for changing the displaying direction of the map. By means of these processings, a plan view map depicting the ground surface directly overhead by normal projection is displayed on the display.

In navigation apparatuses, according to the prior arts plan view map display which depicts a map by normal projection directly overhead has been employed to display the map. When two points spaced apart from each other are simultaneously displayed, therefore, a reduced scale becomes unavoidably great and detailed information cannot be displayed. One of the means for solving this problem is a bird's-eye view display system which displays a map when points having a certain height from the ground surface are looked down obliquely from afar on a plane. In order to apply this bird's-eye view display to the navigation apparatuses, the following problems must be solved.

First, in the case of the bird's-eye view display which displays a broader range of regions than the plan view map, a reduced scale becomes great at points far from the start point, so that a greater quantity of information is displayed. According to the prior art systems, character strings of those regions in which the reduced scale becomes great are not displayed or the character strings in the proximity of a visual point are merely displayed at the upper part. For this reason, fall-off of characters and overlap of character strings are unavoidable, and recognizability of the characters by the user drops.

Secondly, background data and character data are constituted in the map data base so that display quality attains the highest level when the plan view map is displayed. Therefore, in the bird's-eye view map display displaying a broader range of regions, the frequency of the occurrence that the same character strings are displayed at a plurality of positions becomes higher. Since no counter-measure has been taken in the past for the same character strings the same character string is unnecessarily displayed and this unnecessary character string hides the roads and other background data. In consequence, display quality gets deteriorated.

Thirdly, though a route to the destination is displayed in superposition with the map in a different color from those of the background roads, all the route data are displayed with the same line width in the past because the concept of the road width does not exist in the vector data expressing the routes. However, because the map is expressed three-dimensionally in the bird's-eye view display, the feel of three-dimensional depth will be lost if all the routes are displayed by the same line width.

In the fourth place, in the display of a driving orbit, it has been customary in the prior art to store the position information of driving in a certain distance interval and to display the points representing the driving orbit on the basis of the position information so stored. When the driving orbit is displayed by the method of the prior art system on the bird's-eye view map, however, the gap of the point strings representing the orbit is enlarged in the proximity of the visual point at which the reduced scale becomes small, and the user cannot easily recognize which route he has taken The gap of the dot strings becomes unnecessary narrow, on the contrary, at portions away from the visual point at which the reduced scale becomes great, and the roads and the character strings as the background information are hidden. Therefore, the user cannot easily recognize the map information, either.

In the fifth place, pattern information, e.g. solid lines and dash lines, used for displaying the vector information such as roads, railways, administrative districts, etc., and pattern information, e.g. check and checkered patterns, used for displaying polygons representing water systems, green zones, etch, are registered to the map data base. When the map containing these pattern information is displayed by bird's-eye view, the prior art systems execute not only perspective conversion of each apex coordinates constituting the lines and the polygons but also perspective conversion of the patterns for displaying the map. Therefore, the processing time becomes enormously long, and the time required for bird's-eye map display gets elongated.

In the sixth place, in order to prevent dispersion of the map data displayed near an infinite remote point called a "disappearing point" in the bird's-eye map display, the display region is limited to the foreground region by a predetermined distance from the disappearing point and artificial background information such as virtual horizontal line and sky are displayed at the depth in the prior art system. However, these artificial background information in the prior art systems have fixed patterns or fixed colors and do not match the surrounding conditions.

In the seventh place, when the bird's-eye view map display and the plan view map display are switched, the user cannot easily discriminate which of them is actually displayed when the number of objects plotted is small. Moreover, the user can operate and change the position of the visual point in the bird's-eye view map display, and the map region actually displayed greatly changes depending on the position of the visual point and on the direction of the visual field. In the prior art systems, however, there is no means for providing the information of the position of the visual point, etc., even when the position of the visual point and the direction of the visual field are changed, and the systems are not easy to handle.

In the eighth place, when the bird's-eye view map is displayed, the map displaying direction is set in such a manner that the image display direction coincides with the driving direction, as described, for examples in JP-A-2-244188. When the destination is set, the driving direction and the direction of the destination are not always coincident, so that the destination disappears from the screen Accordingly, there remains the problem that the user cannot recognize the map while always confirming the direction of the destination.

In the conventional bird's-eye view map displays in the ninth place, even when a map information density is low in a certain specific direction or when a specific direction comprises only information having specific attributes, the display position of the visual point, that is, the display position of the present position, does not change on the screen. In other words, there occurs the case where a large quantity of information, which are not much significant, are displayed on the display region having a limited area, and the information cannot be provided efficiently.

SUMMARY OF THE INVENTION

To solve the first problem, the present invention uses means for judging whether or not overlap occurs between character strings or symbols, and selecting and displaying character strings or symbols having predetermined attributes when overlap exists, or selecting and displaying character strings or symbols in the proximity of the visual point, or replacing the overlapping character strings or symbols by a font size smaller than the recommended font size. The character overlap judgement means uses means for judging that the character strings overlap by using rectangular region information circumscribed with the character strings when the mutual circumscribed rectangular regions overlap, or judges that the character strings overlap by using rectangular region information of rectangles positioned more inside by a predetermined distance from the rectangles circumscribed with the character strings when mutual rectangle regions overlap.

To solve the second problem, the present invention uses means for judging whether or not the same character strings or symbols exist inside the screen displaying a certain bird's-eye view map, and selecting and displaying character strings in the proximity of the visual point when the same character string or symbol exists. It is effective to display both the character strings or symbols if the mutual distance is great even when the same character strings or symbols exist. Accordingly, the present invention uses means for selecting and displaying character strings in the proximity of the visual point when the distance between the same character strings or symbols or the distance between them in the bird's-eye view map display is judged as existing within a predetermined range, and for displaying both of the character strings or the symbols when the distance is judged as existing outside the range.

To solve the third problems the present invention uses means for displaying routes in the proximity of the visual point by thicker lines than routes apart from the visual point when the routes are displayed on the bird's-eye view map. Alternatively, the present invention uses means for dividing the bird's-eye view map into a plurality of regions and displaying routes by a line width inherent to ach region when the routes to be displayed in superposition in these regions are displayed.

To solve the fourth problem, the present invention uses means for obtaining an orbit which supplements the stored orbit information for the driving routes in the proximity of the visual point, and displaying the orbit in superposition with the bird's-eye view map. As to driving orbits away from the visual point, on the other hand, the present invention uses means for thinning out the stored orbit information and displaying the orbits so thinned out in superposition on the bird's-eye view map.

To solve the fifth problem, the present invention uses means for executing perspective conversion the lines constituting the map data and each apex coordinates constituting polygons, and displaying the polygons or the lines by using the patterns used for plan view map display by using the coordinates values after perspective conversion.

To solve the sixth problem, the present invention uses means for limiting display of the map in the foreground regions by a predetermined distance from the disappearing point and changing the colors and patterns of the artificial background such as the horizontal line and the sky to be displayed at the depth. More concretely, the present invention uses means for changing the colors and the patterns of the artificial background information by a blue color representing the sky when lamps are not lit and by a black or grey color when the lamps are lit, by using signals representing the condition of the car, that is, light turn ON/OFF signal of the car.

To solve the seventh problem the present invention uses means for causing a map display control portion to switch the bird's-eye view map and the plan view map in accordance with a user's request, and causing a menu display portion, which displays a mark in superposition with the map, to receive the change of the display state of the map and to display the mark representing the plan view map in superposition with the map when the map is switched from the bird's-eye view map to the plan view map. When the map is switched from the plan view map to the bird's-eye view maps the mark representing the bird's-eye view map is displayed in superposition with the map. When the user changes the position of the visual point during the display of the bird's-eye view map, the shape of the mark representing the present position is changed and is displayed in superposition with the map.

To solve the eighth problem, the present invention promotes the user to set the destination. After setting of the destination is completed, the direction of the visual point is brought into conformity with the direction of the destination from the position of the visual point, and the position/direction of the visual point and the projection angle are calculated so that the map of predetermined regions is displayed by the bird's-eye view map. Even when the present position is updated, the processing described above is always executed repeatedly to bring the position of the visual point into conformity with the present position and to display the bird's-eye view map.

To solve the ninth problem, a region inside the bird's-eye view map, which has a low map information density, and a region constituted by information having only specific attributes are retrieved. When these regions are retrieved, the position of the visual point is changed so that the region having a low map information density and the region comprising only the information of the specific attributes do not occupy a large area on the display screen. The bird's-eye view map is displayed by using the information of the position of the visual point and the projection angle so obtained.

When overlap exists between the character strings in the bird's-eye view map display, the first means displays one of them, or displays the overlapping character strings by changing their size to the smaller fonts.

When the same character strings or symbols exist in the bird's-eye view map display, the second means selects and displays the character strings closer to the visual point.

In the bird's-eye view map display, the third means so functions as to display the guiding route near the visual point by a greater line width than the guide routes existing away from the visual point.

In the bird's-eye view map display, the fourth means so functions as to display the dot strings representing the driving orbit with suitable gaps between the region near the visual point and the region far from the visual point.

In the bird's-eye view map display, the fifth means so functions as to speed up the display of pattern lines and polygons in which patterns exist.

In the bird's-eye view map display, the sixth means so functions as to display the artificial background in different colors and different patterns in accordance with the condition of the car.

In the bird's-eye view map display, when the bird's-eye view map and the plan view map are mutually switched, the seventh means so functions as to change the shape of the mark to be displayed in superposition with the map in the direction of the position of the visual point and the visual field.

In the bird's-eye view map display, the ninth means so functions as to reduce the occupying area of the regions having a low map information density or comprising only information of specific attributes.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a bird's-eye view map display according to an embodiment of the present invention;

FIG. 2 is an explanatory view showing a perspective conversion processing of a map;

FIGS. 3A, 3B, 3C and 3D are explanatory views showing a perspective conversion process of a map;

FIG. 4 is a structural view of a navigation apparatus according to an embodiment of the present invention;

FIG. 5 is a hardware structural view of an arithmetic processing portion of the embodiment of the present invention;

FIG. 6 is an explanatory view showing appearance of a navigation apparatus according to an embodiment of the present invention;

FIG. 7 is a functional structural view of an arithmetic processing portion for accomplishing bird's-eye view map display;

FIG. 8 is a flowchart of map plotting means for accomplishing bird's-eye view map display;

FIG. 9 is a flowchart of coordinates conversion means for accomplishing bird's-eye view map display;

FIG. 10 is a flowchart of perspective conversion computation for accomplishing bird's-eye view map display;

FIG. 11 is a flowchart of display position computation for accomplishing bird's-eye view map display;

FIG. 12 is a flowchart of plotting judgement means for accomplishing bird's-eye view map display;

FIGS. 13A and 13B are flowcharts of polygonal and linear pattern displays in bird's-eye view map display;

FIG. 14 is a flowchart of character string display in bird's-eye view map display;

FIG. 15 is a flowchart of character plotting means;

FIGS. 16A, 16B, 16C and 16D show an embodiment for character fringing display for representing one character by a plurality of characters;

FIGS. 17A and 17B show an embodiment for character clipping processing;

FIGS. 18A to 18J show an embodiment for display means of a fringed character;

FIG. 19 is a flowchart of a route display in bird's-eye view map display;

FIG. 20 is a flowchart of orbit display in bird's-eye view map display;

FIG. 21 is a flowchart of artificial background display in bird's-eye view map display;

FIG. 22 is a flowchart of mark display in bird's-eye view map display;

FIGS. 23A, 23B and 23C are explanatory views useful for explaining a setting method of a visual point and a projection plane in bird's-eye view map display;

FIGS. 24A, 24B and 24C are explanatory views useful for explaining a setting method of a visual point and a projection plane in bird's-eye view map display;

FIGS. 25A and 25B show an embodiment for optimization display of the present position in bird's-eye view map display;

FIGS. 26A, 26B, 27A, 27B, 28A, 28B, 29A and 29B show an embodiment for character string overlap judgement in bird's-eye view map display;

FIGS. 30A, 30B, 31A, 31B, 32A, 32B, 33A and 33B show an embodiment for character string overlap judgement in bird's-eye view map display;

FIGS. 34A, 34B, 35A, 35B, 36A, 36B, 37A and 37B show an embodiment for character string overlap judgement in bird's-eye view map display;

FIGS. 38A, 38B and 38C show an embodiment for avoiding character string overlap display in bird's-eye view map display;

FIGS. 39A and 39B show an embodiment for avoiding character string overlap display in bird's-eye view map display;

FIGS. 40A, 40B and 40C show an embodiment for displaying the same character string in bird's-eye view map display;

FIGS. 41A, 41B and 41C show an embodiment for polygonal and linear pattern display in bird's-eye view map display;

FIGS. 42A and 42B show an embodiment for route display in bird's-eye view map display;

FIGS. 43A and 43B show an embodiment for orbit display in bird's-eye view map display;

FIGS. 44A and 44B show an embodiment for artificial background display in bird's-eye view map display;

FIGS. 45A and 45B show an embodiment for mark display in bird's-eye view map display; and

FIGS. 46A and 46B show an embodiment for present position mark display in bird's-eye view map display.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows an example of the bird's-eye view map displayed by a bird's-eye view map display device mounted to a navigation system according to an embodiment of the invention. The bird's-eye view map display device according to this embodiment generates a bird's-eye view 102 showing a bird's-eye view from a specific position as a projection chart of two-dimensional map data (indicated by reference numeral 101 in FIG. 1), and displays it on a display screen of a display 2. Incidentally, in the bird's-eye view 102 shown in FIG. 1, a folded line 103 is provided with a thick line and is highlighted in order to represent a guiding route. An artificial background 104 represents the sky, a mark 105 represents the present position and an orbit mark 106 represents the orbit of a car so far driven. Further, arrows in FIG. 1 represent the relationship of projection from the two-dimensional map data 101 to the bird's-eye view 102.

The outline of bird's-eye view map display as the characterizing feature of the present invention will be explained with reference to FIG. 2.

In printed map charts or in the navigation systems according to the prior art, a map is represented by a plan map display obtained when a given area is viewed from an infinitely remote point above this area. Because this plan map display has the advantage that a reduced scale is constant irrespective of points inside the same display screen, the feel of distance is easy to grasp. When an area between certain two points is represented on the same screen, however, the operation for adjusting and optimizing the reduced scale of the map display becomes necessary, and if the distance between these two points is great, only limited information can be displayed because the quantity of information that can be displayed at one time is restricted by the size of the display used and the level of its precision. Bird's-eye view display is employed as means for solving this problem When this bird's-eye view display is used, the information of those portions which are close to the visual point is enlarged while the information of those remote from the visual point is reduced, as is obvious from FIG. 2. Therefore, when the area between certain two points is displayed on the same screen, the point for which more detailed information is required is situated close to the visual point with the other being remote from the visual point, and their mutual positional relationship is represented in an easily comprehensible form by displaying the two points on the same screen Further, a greater quantity of information can be provided to the user on the information near the visual point. This bird's-eye view display can be accomplished by effecting perspective conversion which projects two- or three-dimensional map information of a plane A to a plane B describing a certain angle .THETA. with the plane A. Since two-dimensional map data can be used as the map information used, bird's-eye view display is feasible by adding the perspective conversion function to existing navigation systems without adding new map data, but various contrivances must be made when the bird's-eye view display is put into practical use.

FIG. 4 shows a structural example of a navigation apparatus for a mobile body to which the present invention is applied.

Hereinafter, each structural unit of this navigation apparatus will be explained. A processor unit 1 detects the present position on the basis of the information outputted from various sensors 6 to 9, reads the map information necessary for display from a map memory unit 3 on the basis of the present position information so detected, graphically expands the map data, displays this data on a display 2 by superposing a present position mark, selects an optimum route connecting the destination indicated by the user to the present position and guides the user by using a speech input/output device 4 or the display 2. In other words, it is a central unit for executing various processings. The display 2 is the unit which displays the graphic information generated by the processor unit 1, and comprises a CRT (Cathode-Ray Tube) or a liquid crystal display. A signal S1 between the processor unit and the display is generally connected by RBG signals or NTSC (National Television System Committee) signals. The map memory device 3 comprises a large capacity memory medium such as a CD-ROM or an IC card and executes read/write processing of the required map data The speech input/output device 4 converts the message to the user generated by the processor unit 1 to the speech signals, outputs theme recognizes the user's voice and transfers it to the processing unit 1. An input device 5 is the unit that accepts the user's instructions and comprises hard switches such as scroll keys 41, reduced scale keys 42 and angle changing keys 43 shown in FIG. 6, for examples a joystick, touch panels bonded on the displays or the like. The sensor used for detecting the position in the navigation system for a mobile body comprises a wheel speed sensor 6 for measuring the distance from the product of the circumference of a wheel and the number of revolution of the wheel and measuring a turning angle of the mobile body from the difference of the numbers of revolution of the wheels forming a pair, a terrestrial magnetic sensor 7 for detecting the magnetic field of the earth and detecting the moving direction of the mobile body, a gyro sensor 8 for detecting the turning angle of the mobile body such as an optical fiber gyro or an oscillation gyro, and a GPS receiver 9 for receiving signals from a GPS satellite, measuring the distance between the mobile body and the GPS satellite and the change ratio of this distance for at least three satellites and thus measuring the present position of the mobile body, its travelling direction and its course. The input device 5 further includes a traffic information receiver 10 for receiving signals from beacon transmitters that transmit traffic information such as road jamming information, closed-to-traffic information, parking lot information, etc., and from FM multiplex broadcasting. Furthermore, an internal LAN device 11 is provided so as to receive various information of the car such as door open/close information, the information on the kind and condition of lamps turned ON, the information of the engine condition, the information on the result of trouble-shooting, and so forth.

FIG. 5 is an explanatory view showing the hardware construction of the processor unit.

Hereinafter, each constituent element will be explained. The processor unit 1 employs the construction wherein devices are connected by a bus. The devices include a CPU 21 for executing computation of numerical values and controlling each devices an RAM 22 for storing the map and the operation data, an ROM 23 for storing the program and the data, a DMA (Direct Memory Access) 24 for executing data transfer at a high speed between the memory and the memory and between the memory and each devices a plotting controller 25 for executing at a high speed graphic plotting such as expansion of vector data to pixel information, etc. and for executing display control, a VRAM 26 for storing graphic image data, a color palette 27 for converting the image data to the RGB signals, an A/D convertor 28 for converting analog signals to digital signals, an SCI 29 for converting serial signals to parallel signals in synchronism with the bus, a PIO 30 for establishing synchronism with the parallel signal and putting it on the buss and a counter 31 for integrating pulse signals.

FIG. 7 is a explanatory view useful for explaining the functional construction of the processor unit 1.

Hereinafter, each constituent element will be explained Present position calculation means 66 integrates on the time axis the distance data and the angle data obtained by integrating the distance pulse data S5 measured by the wheel speed sensor 6 and the angular velocity data S7 measured by the gyro 8, respectively, and calculates the position (X', Y') after driving of the mobile body from the initial position (X, Y). In order to bring the rotating angle of the mobile body into conformity with the azimuth of driving, the azimuth data S6 obtained from the terrestrial magnetic sensor 7 and the angle data obtained by integrating the angular velocity data from the gyro 8 are mapped on the 1:1 basis, and the absolute azimuth of the driving direction of the mobile body is corrected. When the data obtained from the sensors described above are integrated on the time axis, the sensor errors accumulate. Therefore, a processing for canceling the errors so accumulated is executed in a certain time interval on the basis of the position data S8 obtained from the GPS receiver 9, and the present position information is outputted. Since the present position information acquired in this way contains the sensor errors, map-match processing 67 is executed so as to further improve positional accuracy. This is the processing which collates the road data contained in the map in the proximity of the present position read by the data read processing means 68 with the driving orbit obtained from the present position calculation means 66, and brings the present position to the road having the highest similarity of shape. When this map-match processing is executed, the present position coincides in most cases with the driving road, and the present position information can be accurately outputted. The present position information calculated in this way is stored in orbit memory means 69 whenever the mobile body drives in a predetermined distance. The orbit data is used for plotting an orbit mark on the road on the corresponding map for the road through which the mobile body has run so far.

On the other hand, user operation analysis means 61 accepts the request from the user by the input device 5, analyzes the content of the request and controls each unit so that a processing corresponding to the request can be executed When the user requests to guide the route to the destination, for example, it requires the map plotting means 65 to execute processing for displaying the map for setting the destination and further requests route calculation means 62 to execute processing for calculating the route from the present position to the destination The route calculation means 62 retrieves a node connecting between two designated points from the map data by a Dichistler method, etc., and stores the route so obtained in route memory means 63. At this time, it is possible to determine the route in which the distance between the two points is the shortest, the route through which the destination can be reached within the shortest time or the route through which the driving cost is the lowest. Route guiding means 64 compares the link information of the guide route stored in the route memory means 63 with the present position information obtained by the present position calculation means 66 and the map match processing means 67 and notifies to the user whether or not to drive straight or whether or not to turn right or left before passing by a crossing, etc., by the speech input/output device 4, displays the travelling direction on the map displayed on the display, and teaches the route to the user. Data read processing means 68 so operates as to prepare for reading the map data of the requested region from the map memory device 3. Map plotting means 65 receives the map data around the point for which display is requested from the data read processing means 68 and transfers the command for plotting the designated object in the reduced scale, the plotting direction and the plotting system that are designated, respectively, to graphic plotting means 71. On the other hand, menu plotting means 70 receives a command outputted from the user operation analysis means 61 and transfers a command for plotting various kinds of requested menus and marks to be displayed in overlap with the map to graphic processing means 71. The graphic processing means 71 receives the plotting commands generated by the map plotting means 65 and the menu plotting means 70, and expands the image on the VRAM 26.

FIG. 8 is an explanatory view useful for explaining the functions of the map plotting means 65.

Hereinafter, each constituent element will be explained. Display region judgement means 81 decides the display reduced scale of the map and decides also which region should be displayed with which point of the map data as the center. Initial data clip means 82 selects, by clip processing, the data necessary for display from the line data, the plan data and the character data representing objects such as roads, buildings, etc., necessary for subsequent processings from each mesh of the map data read out by the data read processing means 68 from the map memory device 3, the line data comprising recommended routes and stored in the route memory means 63 and the point data comprising driving orbits and stored in the orbit memory means 69, on the basis of the information set by the display region judgement means 81. The clip processing algorithms hereby used include a Cohen-Sutherland line clip algorithm for the line and point data and a Sutherland-Hogman polygon clip algorithm for the plan and character data (Foley, van dam, Feiner, Hughes: Computer Graphics: Addison-Wesley Publishing Company, pp. 111-127). This processing can reduce the data quantity which should be subsequently subjected to coordinates conversion and plotting processing and can improve a processing speed.

Coordinates conversion means 83 enlarges or reduces the map data obtained by the clip processing to the target size and when an object must be displayed by rotating it, this means 83 so functions as to effect affin conversion of each coordinates value of the map data. Plotting judgement means 84 so functions as to select those data which are practically necessary for plotting by using the map data obtained by the coordinates conversion means 83. When the reduced scale is great, for example, the data quantity to be plotted substantially increases. Therefore, this means 84 so functions as to omit small roads and the names of places which may be omitted, and to eliminate character strings that are displayed in superposition with one another. Data clip means 85 so functions as to select the map data relating to the plotting area from the map data obtained from the plotting judgement means 84, by clip processing. The clip processing algorithm hereby used may be the same algorithm used by the initial data clip means. Further, this processing may be omitted. Artificial background setting means 86 provides the function which is necessary for bird's-eye view map display and displays the artificial background such as the horizontal line, the sky, etc., in order to reduce the plotting data quantity and to improve the screen recognition property Plotting command generation means 87 generates commands for plotting lines, polygons, characters, etc., so as to plot the resulting point, line and plane data as well as the character data by the designated colors and patterns, and the command for setting the colors and the patterns and outputs them to the graphic processing means 71.

Next, the fundamental display system of the bird's-eye view map display will be explained with reference to FIGS. 3A, B, C, D and FIG. 8.

At first, the region for bird's-eye view display is decided by the display region judgement means 81 from the position of the visual point and the direction of the visual field and from the angle .THETA. (projection angle) described between the plane A and the plane B in FIG. 2 (step 1 in FIG. 3A). When a bird's-eye view is displayed on a rectangular displays map data of a narrow region is necessary for the area near the visual point and map data of a broad region is necessary for the area remote from the visual point. Therefore, the map data of a trapezoidal mesh regions in the drawings is plotted finally. Next, the necessary map data is extracted by the initial data clip means 82 from the map mesh data inclusive of the region for bird's-eye view display by using the rectangular regions which are circumscribed with the trapezoidal region to be practically plotted (step 2 in FIG. 3B). Next, the coordinates conversion means 83 enlarges or reduces the extracted data and then executes affin conversion so that the trapezoid stands upright. Further, perspective conversion is executed so as to convert each coordinates value of the map data to the data which is represented three-dimensionally (step 3 in FIG. 3C). In this instance, perspective conversion is expressed by the following equations (1) and (2) where the position coordinates of the visual point are (Tx, Ty, Tz), the angle between the plane A and the plane B is .THETA., the map data coordinates values before conversion are (x, y) and the map data coordinates values after conversion are (x', y'): ##EQU1##

The trapezoid represented at the step 2 in FIG. 3B is subjected to coordinates conversion into the rectangular region represented at the step 3 in FIG. 3C whereas the rectangle circumscribed with the trapezoid represented at the step 2 in FIG. 3B is subjected to coordinates conversion into a deformed rectangle circumscribed with the rectangle represented at the step 3 in FIG. 3C, by perspective conversions respectively Because the portions other than the rectangular region need not be plotted, these portions other than the rectangular region are clipped by the data clip means 85 (step 4 in FIG. 3D). The plotting command generation means 87 generates the plotting command by using the map data so obtained, and the graphic processing means 71 conducts plotting to the VRAM 26 so that the bird's-eye view map shown in FIG. 1 can be displayed.

Next, the perspective conversion parameters in bird's-eye view map displays that is, the angle .THETA. between the map and the projection plane (projection angle) and the coordinates (Tx, Ty, Tz) of the origin of the visual point coordinates system containing the projection plane, which is viewed from the object coordinates system containing in turn the map plane, or in other words, the method of calculating the position of the projection plane, will be explained with reference to FIGS. 23A, B and C. It is desired for the navigation apparatus to display in detail the point at which the user is now driving, that is, the region around the present position Therefore, the explanation will be given on the case where the present position is displayed at the lower center portion of the screen as shown in FIG. 23C. To accomplish bird's-eye view display, it is judged whether rotation of map is necessary at step 1002, and in the event the rotation is considered necessary then the angle .phi. between the driving direction vector and the base of the map mesh is first determined at the step 1004 in FIG. 9, and affin conversion for rotating the map data to be plotted by the angle .phi. is executed for each data constituting the map (step 1005). Since bird's-eye view display is judged as being made at the step 1006, the flow proceeds to the processing for calculating the projection angle .THETA. and the position of the visual point (steps 1008 and 1009). The projection angle .THETA. is set to an angle near 0 when it is desired to make display so that the difference of the reduced scale becomes small between the portions near the visual point and the portions away from the visual point, and is set to near 90.degree. when it is desired to make display so that the difference of the reduced scale becomes great between the portions near the visual point and the portions away from the visual point. Normally, the projection angle .THETA. is set to the range of about 30 to about 45.degree.. Since the user desires to arbitrarily set the map region to be displayed by bird's-eye view map display, the projection angle .THETA. can be set by the projection angle change key 43 provided to the navigation apparatus shown in FIG. 6. When this key 43 is so operated as to increase the projection angle, the projection angle increases, so that the map of remote regions is displayed. When the key 43 is so operated as to decrease the projection angle, the projection angle .THETA. decreases, so that the map near the present position is displayed.

Next, as to the position (Tx, Ty, Tz) of the projection plane, calculation is executed at the step 1009 so that the difference (.DELTA.x, .DELTA.y, .DELTA.z) obtained by subtracting the position (Tx, Ty, Tz) of the position of the projection plane from the present position (x, y, z) is always a constant value. As the absolute values, further, .DELTA.x is set to 0, .DELTA.z is set to a small value when display is made by a small reduced scale in match with the reduced scale of the map display and to a large reduced scale when display is made by a large reduced scale. Normally, .DELTA.z is decided preferably so that the reduced scale of the plane view is coincident with the reduced scale of a certain point near the center of bird's-eye view display. Since the reduced scale of the map is preferably changeable in accordance with the user's request, the step 1009 operates in such a manner as to set .DELTA.z to a small value when the user designates a small reduced scale by the reduced scale key 42 provided to the navigation apparatus shown in FIG. 6 and to a large value when a large reduced scale is designated. The .DELTA.y value may be either a positive value or a negative value but this embodiment uses the negative value and sets it so that the present position is displayed at a lower 1/3 position of the screen. Step 1010 executes perspective conversion of each coordinates value of the map data by using the projection angle .THETA. and the position (Tx, Ty, Tz) of the projection plane that are obtained in the manner described above.

The detail of this perspective conversion operation will be explained with reference to FIG. 10. First, whether or not the plane data constituted by polygons such as water systems, green zones, etc., exist is judged (step 1020). When the result proves YES, perspective conversion is executed for each node constituting the polygon (step 1021). This operation is executed for all the polygons (step 1022). Next, when the line data constituting the map such as the roads, the railways, the administrative districts, etc., and the optimum route from the present position to the destination are calculated, whether or not the line data representing the route exist is judged (step 1023). When the result proves YES, perspective conversion is executed for each node that constitutes the line (step 1024). Further, when the character data constituting the map such as the area names, symbols, etc., and the orbit are displayed, whether or not the point data representing the orbit exist is judged (step 1026). As to the character strings such as the area names, symbols, etc., it is advisable to handle one point representing a given character string such as the upper left end point of the character string as the point data. When these point data are judged as existing, perspective conversion is executed for each node constituting the point (step 1027) and is then executed for all the points (step 1028). The graphic processing means 71 executes plotting processing by using the map data so obtained. In consequence, in bird's-eye view map display shown in FIG. 23C, the driving direction is always displayed in the UP direction on the screen and the present position is always displayed at the same point on the screen.

Next, the explanation will be given on the display method of the bird's-eye view map, which can be easily recognized by the driver, when a certain destination is designated by the input device 5 from the map or the retrieved screen, will be explained with reference to FIG. 9 and FIGS. 24A, B and C. It is desired for the navigation apparatus to display in detail the point at which the user is driving at present, that is, the area near the present position. Therefore, the present position is displayed at the center lower portion of the screen, more concretely at the lower 1/3 region of the transverse center of the screen, as shown in FIG. 24C. To accomplish bird's-eye view display shown in FIG. 24C, the angle .phi. between the line perpendicular to the line connecting the present position to the destination shown in FIG. 24A and the base of the map mesh is first determined at the step 1004 in FIG. 9 and affin conversion is executed by the angle .phi. for each coordinates value of the map data to be plotted (step 1005). Since this bird's-eye view display is judged as being made at the step 1006, the flow then proceeds to the processings for calculating the projection angle .THETA. and the position of the visual point (steps 1008 and 1009). The projection angle .THETA. is set to an angle near 0 when it is desired to make display so that the difference of the reduced scale between small between the portions near the visual point and the portions away from the visual point, and is set to an angle near 90.degree. when it is desired to make display so that the difference of the reduced scale becomes great between the portions near the visual point and the portions away from the visual point. Normally, the projection angle is set to the range of about 30 to about 45.degree.. Since the user desires to arbitrarily set the map region to be displayed by bird's-eye view map displays the projection angle .THETA. can be set by the projection angle change key 43 provided to the navigation apparatus shown in FIG. 6. When this key 43 is so operated as to increase the angle, the projection angle .THETA. increases, so that the map of remote portions is displayed. When the key 43 is so operated as to decrease the projection angle, the projection angle .THETA. decreases, so that the map near the present position is displayed.

Next, as to the position (Tx, Ty, Tz) of the projection plane, calculation is made at the step 1009 so that the difference (.DELTA.x, .DELTA.y, .DELTA.z) obtained by subtracting the position (Tx, Ty, Tz) of the projection plane from the present position (x, y, z) becomes always a constant value. As the absolute values, .DELTA.x is set to 0, and .DELTA.z is set to a small value when display is made by a small reduced scale in match with the reduced scale of the map displayed, and to a great value when display is made by a large reduced scale. Normally, .DELTA.z is preferably set so that the reduced scale of the plan view is coincident with the reduced scale of a certain point near the center of bird's-eye view display Since the desires to change the reduced scale of the map, the step 1009 so operates as to set a small value to .DELTA.z when the user designates a small reduced scale by the reduced scale key 42 provided to the navigation apparatus shown in FIG. 6 and to set a large value to .DELTA.z when the user designates a large reduced scale. The .DELTA.y value may be either a positive value or a negative value, but this embodiment uses the negative value and determines the value so that the present position can be displayed at the lower 1/3 position of the screen The step 1010 executes perspective conversion of each coordinates value of the map data by using the projection angle .THETA. and the position (Tx, Ty, Tz) of the projection plane so obtained, and the graphic processing means 71 executes the plotting processing by using the resulting map data. Consequently, in bird's-eye view display shown in FIG. 24C, the destination is always displayed in the UP direction and the present position is always displayed at the same position on the screen. The navigation apparatus becomes easier to operate by switching the operation mode to the mode in which the destination and the present position are fixed always at certain two points on the screen when the car moves to the position where the destination can be displayed on the screen.

Incidentally, the polygon representing the Imperial Palace, the green zones and the water systems such as sea and lakes are not much useful as the information for the driver driving the car having the navigation apparatus, as shown in FIG. 24A. Rather, a greater quantity of information which is directly necessary for driving such as the road information, are displayed preferably on the limited screen. Means for solving this problem will be explained with reference to FIG. 11. The information of the roads and the background are represented by the nodes, and the node density of the polygons representing the green zones and the water systems such as sea and lakes tends to be lower than the node density of the lines such as the roads. Therefore, the greatest quantity of information of the roads, etc., are displayed by optimizing the display region in the transverse direction of the screen, for the region displayed in the longitudinal direction, in accordance with the initial value. This processing is executed by the display position calculation routine at the step 1011 in FIG. 9. First, whether the mode is for executing optimization of the display position is judged (step 1040). When optimization is judged as to be executed, the nodes that are practically displayed on the screen are extracted from the nodes constituting the lines and the polygons subjected to perspective conversion at the step 1041 by clip calculation (step 1041). Further, the difference .DELTA.x between the x coordinates arithmetic mean value obtained at the step 1042 and the x-coordinates value x2 at the center of the screen is calculated (step 1043). At the next step 1044, the difference .DELTA.x obtained by the step 1043 is added to the x-coordinates value of the nodes constituting the line and the polygon. The graphic processing means 71 executes the plotting processing by using the map data obtained in this manner In consequence, bird's-eye view map display capable of displaying a greater quantity of those information which are directly necessary for driving, such as the roads, can be displayed on the screen as shown in FIG. 25B.

Next, the method of the plotting processing of the objects constituting the bird's-eye view map will be explained more concretely The plotting judgement means 84 shown in FIG. 12 operates in such a manner as to optimally display the plan data, the line data and the character data constituting the map, the route data calculated in accordance with the request from the user and the orbit data representing the route so far driven, respectively.

First, whether or not the plane data exists in the plotting data is judged (step 1060). When the plane data is judged as existing, the flow proceeds to the plane data plotting processing (step 1061) shown in FIG. 13A. The plane data plotting processing judges whether the plane pattern exists inside the polygon to be practically plotted or whether the full plane should be smeared away (step 1080). When the plane pattern is not judged as existing, pattern setting is so effected as to smear away the entire portion inside the polygon and the processing is completed (step 1081). When the plane pattern is judged as existing, whether or not perspective conversion is to be executed for the plane pattern is judged (step 1082). When the plane pattern is subjected to perspective conversion and is displayed, the pattern has the feel of depth as depicted in FIG. 41A and can be therefore displayed more three-dimensionally However, the plotting time gets elongated because the processing quantity becomes greater When the plane pattern used for plan view map display is displayed, on the other hand, the display becomes planar as depicted in FIG. 41B, but the processing can be made at a higher speed because the plane pattern can be handled two-dimensionally Therefore, when a higher processing speed is required, perspective conversion of the pattern is judged as unnecessary at the step 1082 and the designated pattern itself is set as the pattern data (step 1083). When display quality has higher priority, on the other hand, perspective conversion of the pattern is judged as necessary at the step 1082. Therefore, the pattern is subjected to perspective conversion and the conversion result is set as the pattern data (step 1084). The method shown in FIG. 41C may be employed as means for improving this processing speed. This method divides a polygon into a plurality of regions (four regions shown in the drawing) in the direction of depth and smearing away each region by using the mean pattern obtained by subjecting the plane pattern to perspective conversion in each of the region. Since the pattern becomes a two-dimensional pattern inside the region according to this methods the processing speed can be improved.

Next, whether or not the line data exists in the plotting data is judged (step 1062). When the line data is judged as existing, the processing shifts to the line data plotting processing (step 1063) in FIG. 13B. In this line data plotting processing, whether the line pattern exists in the lines practically plotted or is smeared by solid lines is judged (step 1085). When the line pattern is not judged as existing, pattern setting is effected so as to draw the solid lines and the processing is completed (step 1087). When the line pattern is judged as existing, whether or not perspective conversion is to be effected for the line pattern is judged (step 1087). When the line pattern is subjected to perspective conversion and is displayed, the feel of depth develops as shown in FIG. 41A and representation can be made more three-dimensionally However, the plotting time gets elongated in this case because the processing quantity increases. When display is made by the line pattern used for plan view map display, display becomes planar as shown in FIG. 41B, but high speed processing can be made because the line pattern can be handled unidimensionally. Therefore, when a higher processing speed is required, perspective conversion of the pattern is not judged as necessary at the step 1087 and the designated pattern itself is set as the pattern data (step 1088). On the other hand, when higher priority is put to display quality, perspe