Navigation system and memorizing medium for memorizing operation programs used for the same

• US 6,169,516 B1
• Filed: 01/20/1998
• Issued: 01/02/2001
• Est. Priority Date: 01/20/1997
• Status: Expired due to Fees

• Current Assignee: Nissan Motor Co., Ltd.
• Original Assignee: Nissan Motor Co., Ltd.
• Inventors: Oizumi, Ken, Takada, Masayuki, Watanabe, Masaki, Takahashi, Toshiaki, Hirose, Satoru, Kishi, Norimasa
• Primary Examiner(s): Blum, Theodore M.
• Application Number:
  US09/009,188
• Time in Patent Office: 1,078 Days
• Field of Search: 342/357.13, 701/208, 340/995, 345/419, 345/420
• US Class Current: 342/357.51
• CPC Class Codes: G01C 21/3635 Guidance using 3D or perspective road maps
• CPC Class Codes: G01S 19/13 Receivers
• CPC Class Codes: G09B 29/106 using electronic means

Abstract

A navigation system stereoscopically displays an area based on altitude information data of the actual terrain of the area, and puts thereon map display components such as roads, place manes and the like to form a stereoscopic map on the screen, which fits the actual view of the area.

Claims

1. A navigation system comprising:

a topographical data memory storing a topographical data which provides topographical plane coordinates with altitude values of displayed components;

a map data memory storing position and attribute information on map display components which include roads and names of places;

an input unit which inputs display reference point position coordinates and viewing line directional angle by which the position and direction of displayed map are derived;

a displayed region determining block which determines a region displayed on a screen in accordance with information issued from said input unit;

a topographical geometric modeling block which reads from said topographical data memory a topographical geometric data on the displayed region determined by said displayed region determining block and carries out modeling of the topographical geometry by processing said topographical geometric data;

a display reference point altitude determining block which determines an altitude value of the display reference point by processing both the information from said input unit and the information from said topographical geometric modeling block;

a viewpoint coordinate determining block which determines a viewpoint coordinate by processing both the information from said input unit and said display reference point altitude determining block;

a map component altitude determining block which reads from said map data memory a map display component within said displayed region and determines an altitude value of said map display component with reference to information from said topographical geometry modeling block thereby to produce a display graphic data;

a coordinate transforming block which, based on both information from said viewpoint coordinate determining block and information from said input unit, applies a perspective-projection transformation to both information from said topographical geometric modeling block and information from said map component altitude determining block;

a drawing process block which produces a stereoscopic map image by processing information from said coordinate transforming block; and

an image display unit which actually displays said stereoscopic map image.

2. A navigation system as claimed in claim 1, in which said drawing process block processes the information from said coordinate transforming block while effecting a hidden surface removing process.

3. A navigation system as claimed in claim 1, in which said drawing process block draws a displayed guide route with a color and a line which are different from those for a displayed normal road.

4. A navigation system as claimed in claim 1, in which said topographical geometric modeling block forms three-dimensional sampling point groups (x, y, z) by setting suitably distributed point groups in said displayed region and reading from the topographical data memory an altitude value “

z”

corresponding to the plane coordinates of each point, and forms a polyhedral topographical geometry model by connecting the three-dimensional sampling groups with straight lines in accordance with a given rule.

5. A navigation system as claimed in claim 4, in which the sampling point groups placed near said viewpoint coordinate have a higher distribution density and the sampling points groups placed remote from said viewpoint have lower distribution density.

6. A navigation system as claimed in claim 1, in which said viewpoint coordinate determining block varies the altitude coordinate value of the viewpoint coordinate in accordance with the display reference point altitude value determined by said display reference point altitude determining block.

7. A navigation system as claimed in claim 6, in which said viewpoint coordinate determining block determines the altitude value of said viewpoint coordinate by adding a predetermined offset to said display reference point altitude value.

8. A navigation system as claimed in claim 1, in which, in case wherein the map data stored in said map data memory is of a type wherein position information on the map components is stored in the form of a two-dimensional coordinate and wherein the map components include roads and name places except altitude values therefor, said topographical geometric modeling block derives, with reference to the topographical geometric model produced by said topographical geometric modeling block, a two-dimensional coordinate altitude value corresponding to the two-dimensional coordinate possessed by said map display components and produces the display graph data in the form of a three-dimensional coordinate.

9. A navigation system as claimed in claim 8, in which the map data stored in said map data memory includes a position information described in a two-dimensional coordinate of point groups constituting road links and a road type information indicating whether said road links indicate a high level road or a tunnel, and in which when determining the altitude value of the constituting point based on the two-dimensional position information of said road link constituting point and said topographical geometric model, said map component altitude determining block calculates the altitude value of internal constituting point of the road links in view of altitude values of two terminal points of the road links without respect to the topographical geometric model in case wherein said internal constituting point of the road links show a high level road or a tunnel.

10. A navigation system as claimed in claim 8, in which the map data stored in said map data memory includes a position information described in a two-dimensional coordinate of point groups constituting road links and a road type information indicating whether said road links indicate a high level road or a tunnel, and in which when determining the altitude value of the constituting point based on said position information and the altitude value of said topographical geometric model, said map component altitude determining block adds to said road links new constituting points which divides said road links and calculates the altitude values of said new constituting points with reference to the topographical geometric model in case wherein the road links corresponding to the constituting points do not indicate a high level road nor a tunnel and the density of said constituting points is smaller than that of the sampling points determined by said topographical geometric modeling block.

11. A navigation system as claimed in claim 1, in which when producing said display graphic data for road, railway, water system and facilities, said map component altitude determining block adds to an original altitude value of them given from external and internal information means a predetermined offset value thereby to produce a coordinate value of said road, railway, water system and said facilities in the direction of the height.

12. A navigation system as claimed in claim 11, in which the offset value of said road and said railway is greater than that of said water system and said facilities.

13. A navigation system as claimed in claim 11, in which an offset value used for defining said guide route is greater than that for the road and said railway.

14. A navigation system as claimed in claim 11, in which when determining the altitude value of a graphic data for indicating the present position of the system-mounted vehicle, said map component altitude determining block adds to the altitude value determined based on the topographical geometric model given by the topographical geometric modeling block a predetermined offset value thereby to produce a coordinate value of the present position of the system-mounted vehicle in the direction of height.

15. A navigation system as claimed in claim 14, in which the offset value used for indicating the present position of the system-mounted vehicle is greater than that for the road and said railway.

16. A navigation system as claimed in claim 11, in which when producing the display graphic data used for indicating a position where a place name is shown, said map component altitude determining block adds to an original altitude value of said position given by external and internal information means an offset value which is greater than the offset value determined for the road thereby to produce a coordinate value of the display position for the place name in the direction of the height.

17. A navigation system as claimed in claim 11, in which when producing the display graphic data used for indicating a position where a place name is shown, said map component altitude determining block adds to an original altitude value of said position given by external and internal information means a given offset value thereby to produce a coordinate value of the display position for the place name in the direction of the height, said given offset value being so determined that any character in a character train to be displayed at said position is not hidden by the topographical geometry of the display position.

18. A navigation system as claimed in claim 1, in which when, as a result of said perspective-projection transformation, a plurality of draw elements for the display map component are realized to be overlapped on the same viewing line, said drawing process block operates to display on the image display unit only a portion other than the overlapped portion in case of displaying the draw elements located remote from the viewpoint.

19. A navigation system as claimed in claim 1, in which when, as a result of said perspective-projection transformation, a plurality of draw elements for the display map component are realized to be overlapped on the same viewing line, said drawing process block operates to display on the image display unit the overlapped portion with a color different from that of the other portion in case of displaying the draw elements located remote from the viewpoint.

20. A navigation system as claimed in claim 19, in which the color for said overlapped portion is prepared by mixing the color for the other portion and the color for the overlapped portion.

21. A navigation system as claimed in claim 1, in which when, as a result of said perspective-projection transformation, a plurality of draw elements for the display map component are realized to be overlapped on the same viewing line, said drawing process block operates to display on the image display unit the overlapped portion with a dotted line.

22. A navigation system as claimed in claim 1, in which when drawing a polygon representing the topographical geometry, said drawing process block operates to draw each of planes of said polygon with a color which changes in accordance with the altitude of the topographical geometry.

23. A navigation system as claimed in claim 22, in which during the process for drawing each of the planes of said polygon with the changing color, said drawing process block operates to draw lines each extending between adjacent apexes of said polygon.

24. A navigation system as claimed in claim 23, in which each of said lines which are drawn is one of a line of longitude and a line of latitude.

25. A navigation system as claimed in claim 1, further comprising:

a first block which issues information on seasons;

a second block which memorizes color information corresponding to said seasons;

a third block which displays color determined by said image display unit;

a fourth block which makes a color correction to the displayed color on the third block by reading, from said second block, the color information in accordance with the seasonal information from said first block.

26. A navigation system as claimed in claim 1, further comprising:

a first block which issues the present time;

a second block which memories color information corresponding to the present time;

a third block which displays color determined by said image display unit;

a fourth block which makes a color collection to the displayed color on the third block by reading, from said second block, the color information in accordance with the time information from said first block.

27. A navigation system as claimed in claim 1, further comprising:

a first block which issues the present weather;

a second block which memorizes color information corresponding to the present weather;

a third block which displays color determined by said image display unit;

a fourth block which makes a color collection to the displayed color on the third block by reading, from said second block, the color information in accordance with the weather information from said first block.

28. A navigation system comprising:

a topographical data memory storing a topographical data which provides topographical plane coordinates with altitude values of displayed components;

a map data memory storing position and attribute information on map display components which include roads and names of places;

an input unit which inputs display reference point position coordinates and viewing line directional angle by which the position and direction of displayed map are derived;

a displayed region determining block which determines a region displayed on a screen in accordance with information issued from said input unit;

a topographical geometric modeling block which reads from said topographical data memory a topographical geometric data on the displayed region determined by said displayed region determining block and carries out modeling of the topographical geometry by processing said topographical geometric data, said modeling block forming three-dimensional sampling point groups (x, y, z) by setting suitably distributed point groups in said displayed region and reading from the topographical data memory an altitude value “

z”

corresponding to the plane coordinates of each point, and forming a polyhedral topographical geometry model by connecting the three-dimensional sampling groups with straight lines in accordance with a given rule;

a display reference point altitude determining block which determines an altitude value of the display reference point by processing both the information from said input unit and the information from said topographical geometric modeling block;

a viewpoint coordinate determining block which determines a viewpoint coordinate by processing both the information from said input unit and said display reference point altitude determining block;

a map component altitude determining block which reads from said map data memory a map display component within said displayed region and determines an altitude value of said map display component with reference to information from said topographical geometry modeling block thereby to produce a display graphic data;

a coordinate transforming block which, based on both information from said viewpoint coordinate determining block and information from said input unit, applies a perspective-projection transformation to both information from said topographical geometric modeling block and information from said map component altitude determining block;

a topographical geometry drawing process block which draws said polyhedral topographical geometry, which has been subjected- to said perspective-projection transformation by said coordinate transforming block, in order from the depth in an overwriting manner thereby to output a stereoscopic map image;

a map component altitude comparing block which compares the altitude value of the display position of each map display component determined by the map component altitude determining block with the altitude value of a corresponding portion of the topographical geometry;

a map component drawing process block which, based on the result of the comparison by said map component altitude comparing block, overwrites on said topographical geometry the map display component whose altitude value is equal to and greater than the altitude value of the corresponding portion of the topographical geometry; and

an image display unit which couples the stereoscopic map image produced by said topographical geometry drawing process block and the map component image produced by said map component drawing process block and displays the coupled image.

29. A navigation system as claimed in claim 28, in which, based on the color drawn on the topography, said map component altitude comparing block compares the altitude value of the display position of each map display component with the altitude value of the corresponding portion of the topographical geometry.

30. A navigation system as claimed in claim 28, in which when the map display component to be displayed is a guide route, said map component drawing process block draws said guide route with color or line which is different from that drawn for a normal road.

31. A navigation system as claimed in claim 28, in which when said map display component is of a line-figured map component, said map component altitude comparing block instructs said map component drawing process block to carry out overwriting of links of the line-figured map component when the altitude values of both ends of said links are equal to or greater than the altitude values of the corresponding portions of the topographical geometry, and in which when said map display component is of a flat map component, said map component altitude comparing block instructs said map component drawing process block to carry out overwriting of the surface map component when the altitude values of all apexes of said surface map component are equal to or greater than the altitude values of the corresponding portions of the topographical geometry.

32. A navigation system as claimed in claim 28, in which when said map display component is of a line-figured map component, such as road, river or railroad, said map component altitude comparing block instructs said map component drawing process block to draw the line-figured map component with a color or line different from that of the other portion when one of the altitude values of ends of said links is smaller than the altitude value of the corresponding portion of the topographical geometry.

33. A navigation system as claimed in claim 28, further comprising:

a first block which issues information on seasons;

a second block which memorizes color information corresponding to said seasons;

a third block which displays color determined by said image display unit;

a fourth block which makes a color collection to the displayed color on the third block by reading, from second block, the color information in accordance with the seasonal information from said first block.

34. A navigation system as claimed in claim 28, further comprising:

a first block which issues the present time;

a second block which memorizes color information corresponding to the present time;

a third block which displays color determined by said image display unit;

a fourth block which make a color correction to the displayed color on the third block by reading, from said second block, the color information in accordance with the time information from said first block.

35. A navigation system as claimed in claim 28, further comprising:

a first block which issues the present weather;

a second block which memorizes color information corresponding to the present weather;

a third block which displays color determined by said image display unit;

a fourth block which makes a color correction to the displayed color on the third block by reading, from said second block, the color information in accordance with the weather information from said first block.

36. A navigation system comprising:

a topographical data memory storing a topographical data which provides topographical plane coordinates with altitude values of displayed components;

a line-figured data memory storing position and attribute information on map display components which include roads, rivers and railway;

a place name and background data memory storing position and attribute information on map display components which include name places and icons;

an input unit which inputs display reference point position coordinates and viewing line directional angle by which the position and direction of displayed map are derived;

a displayed region determining block which determines a region displayed on a screen in accordance with information issued from said input unit;

a topographical geometric modeling block which reads from said topographical data memory a topographical geometric data on the displayed region determined by said displayed region determining block and carries out modeling of the topographical geometry by processing said topographical geometric data, said modeling block forming three-dimensional sampling point groups (x, y, z) by setting suitably distributed point groups in said displayed region and reading from the topographical data memory an altitude value “

z”

corresponding to the plane coordinates of each point, and forming a polyhedral topographical geometry model by connecting the three-dimensional sampling groups with straight lines in accordance with a given rule;

a display reference point altitude determining block which determines an altitude value of the display reference point by processing both the information from said input unit and the information from said topographical geometric modeling block;

a viewpoint coordinate determining block which determines a viewpoint coordinate by processing both the information from said input unit and said display reference point altitude determining block;

a map component altitude determining block which reads from said line-figured data memory a line-figured data within said displayed region, reads from said place name and background data memory said place name and background data and determines an altitude value of each of said line-figured map component and the positions of said place name and said icon with reference to information from said topographical geometry modeling block thereby to produce a display graphic data;

a coordinate transforming block which, based on both the viewpoint coordinate determined by said viewpoint coordinate determining block and the viewing line directional angle input from said input unit, applies a perspective-projection transformation to both said topographical geometry model and said display graphic data, such as the line-figured map component, the place name and the icon whose altitude values have been determined;

a drawing process block which effects drawing and outputs a stereoscopic map image signal while carrying out a hidden surface removing process applied to the data to which said transparent-projection transformation has been applied by said coordinate transforming block;

a line-figured data altitude comparing block which compares the altitude value of an end of each link of the line-figured data determined by said map component altitude determining block with the altitude value of a corresponding portion of the topographical geometry;

a line-figured data drawing process block which, based on a result of the comparison by said line-figured data altitude comparing block, overwrites on the topographical geometry the line-figured map component when the altitude value of the end of the link of the line-figured component is equal to or greater than the altitude value of the corresponding portion of the topographical geometry; and

an image display unit which couples the stereoscopic map image from said drawing process block and the line-figured image from said line-figured data drawing process block and displays the coupled image.

37. A navigation system as claimed in claim 36, in which when said line-figured component to be displayed is a guide route, said line-figured data drawing process block draws said guide route with color or line which is different from that drawn for a normal road.

38. A navigation system as claimed in claim 37, in which when the altitude values of each link of the line-figured map component are equal to or greater than the altitude values of the corresponding portions of the topographical geometry, said line-figured data altitude comparing block instructs said line-figured data drawing process block to carry out overwriting of the links of the line-figured map component.

39. A navigation system as claimed in claim 36, in which when the altitude value of at least one of ends of each link of said line-figured map component is smaller than the altitude value of a corresponding portion of the topographical geometry, said line-figured data altitude comparing block instructs said line-figured data drawing process block to carry out overwriting of the line-figured map component with a color or line which is different from that drawn for other portion.

40. A memorizing medium memorizing a navigation program including the steps of:

(a) determining a displayed region based on a position coordinate of a display reference point and a viewing line directional angle data;

(b) reading a topographical geometric data within said displayed region and effecting modeling of the topographical geometry;

(c) determining an altitude value of said display reference point with reference to both said position coordinate of said display reference point and said topographical geometric model;

(d) determining a viewpoint coordinate for a perspective-projection transformation with reference to the position coordinate of said display reference point, said viewing line directional angle and the altitude value of said display reference point;

(e) reading map display component data within said displayed region and determining an altitude value of the map display component based on, if needed, said topographical geometric model thereby to provide a display graphic data;

(f) applying a transparent-projection transformation to both said topographical geometry model and said map display component whose altitude value has been determined, with reference to both said viewpoint coordinate and said viewing line directional angle; and

(g) producing a stereoscopic map image signal from the data to which said transparent-projection transformation has been applied.

41. A memorizing medium memorizing a navigation program including the steps of:

(a) determining a displayed region based on a position coordinate of a display reference point and a viewing line direction angle data;

(b) forming three-dimensional sampling point groups (x, y, z) by setting suitably distributed point groups in said displayed region and reading an altitude value “

z”

corresponding to plane coordinates (x, y) of each point, and forming a polyhedral topographical geometry model by connecting the three-dimensional sampling groups with straight lines in accordance with a given rule;

(c) determining an altitude value of said display reference point with reference to the position coordinate of said display reference point and said topographical geometric model;

(d) determining a viewpoint coordinate for a perspective-projection transformation with reference to the position coordinate of said display reference point, said viewing line direction angle and the altitude value of said display reference point;

(e) reading map display component data within said displayed region and determining an altitude value of the map display component based on, if needed, said topographical geometric model thereby to provide a display graphic data;

(f) applying a transparent-projection transformation to both said topographical geometric model and said map display component whose altitude value has been determined, with reference to both said viewpoint coordinate and said viewing line directional angle;

(g) producing an image signal for drawing a polygon which shows the transformed topographical geometry, said polygon being drawn in order from the depth in overwriting manner;

(h) comparing the altitude value of the display position of each map display component with the altitude value of a corresponding portion of the topographical geometric model; and

(i) producing in accordance with the result of the comparison an image signal by which only the map display component whose altitude value is greater than that of the corresponding portion of said topographical geometry is overwritten on the topographical geometric model.

42. A memorizing medium memorizing a navigation program including the steps of:

(a) determining a displayed region based on a position coordinate of a display reference point and a viewing line direction angle data;

(b) forming three-dimensional sampling point groups (x, y, z) by setting suitably distributed point groups in said displayed region and reading an altitude value “

z”

corresponding to plane coordinates (x, y) of each point, and forming a polyhedral topographical geometry model by connecting the three-dimensional sampling groups with straight lines in accordance with a given rule;

(c) determining an altitude value of said display reference point with reference to the position coordinate of said display reference point and said topographical geometric model;

(d) determining a viewpoint coordinate for a perspective-projection transformation with reference to the position coordinate of said display reference point, said viewing line direction angle and the altitude value of said display reference point;

(f) reading a line-figured map display component data within said displayed region, reading a place name and background data and determining an altitude value of each of said line-figured map component and the positions of said place name and said icon with reference to said topographical geometric model thereby to produce a display graphic data;

(g) based on the viewpoint coordinate and the viewing line directional angle, applying a transparent-projection transformation to both said topographical geometry model and said display graphic data, such as the line-figured map component, the place name and the icon whose altitude values have been determined;

(h) effecting drawing and outputting a stereoscopic map image signal while carrying out a hidden surface removing process applied to the data to which the transparent-projection transformation has been applied; and

(i) comparing the altitude value of an end of each line of the line-figured map component with the altitude value of a corresponding portion of the topographical geometry, and based on a result of the comparison, overwriting on the topographical geometry the line-figured map component when the altitude value of the end of the link of the line-figured component is greater than the altitude value of the corresponding portion of the topographical geometry.

43. A navigation system comprising:

a topographical data memory storing a topographical data which provides topographical plane coordinates with altitude values of displayed components;

a map data memory storing position and attribute information on map display components which include roads and names of places;

an input unit which inputs display reference point position coordinates and viewing line directional angle by which the position and direction of displayed map are derived;

a displayed region determining block which determines a region which is to be displayed on a screen in accordance with information issued from said input unit;

an altitude changing region determining block which determines a changing region in the displayed region in accordance with a certain rule which is determined with reference to the display reference point and the viewing line directional angle;

a topographical geometric modeling block which reads from said topographical data memory a topographical geometric data of sampling points within the displayed region determined by said displayed-region determining block and carries out modeling of the topographical geometry by processing said topographical geometric data;

a display reference point altitude determining block which determines an altitude value of the display reference point by processing both the information from said input unit and the information from said topographical geometric modeling block;

a topographical geometry altitude changing block which changes the altitude values of the sampling points to values similar to the altitude value of the display reference point, thereby to remodel the topographical geometry model;

a viewpoint coordinate determining block which determines a viewpoint coordinate by processing both the information from said input unit and the information from said display reference point altitude determining block;

a map component altitude determining block which reads from said map data memory a map display component within said displayed region and determines an altitude value of said map display component with reference to the remodeled topographical geometry derived by said topographical geometry altitude changing block, thereby to produce a display graphic data;

a coordinate transforming block which, based on both information from said viewpoint coordinate determining block and information from said input unit, applies a perspective-projection transformation to both information from said topographical geometric modeling block and information from said map component altitude determining block;

a drawing process block which produces a stereoscopic map image of the area within said displayed region by processing information from said coordinate transforming block; and

an image display unit which actually displays said stereoscopic map image.

44. A navigation system comprising:

a topographical data memory storing a topographical data which provides topographical plane coordinates with altitude values of displayed components;

a map data memory storing position and attribute information on map display components which include roads and names of places;

an input unit which inputs display reference point position coordinates and viewing line directional angle by which the position and direction of displayed map are derived;

a displayed region determining block which determines a region displayed on a screen in accordance with information issued from said input unit;

an altitude changing region determining block which determines a changing region in the displayed region in accordance with a certain rule which is determined with reference to the display reference point and the viewing line directional angle;

a topographical geometric modeling block which reads from said topographical data memory a topographical geometric data on the displayed region determined by said displayed region determining block and carries out modeling of the topographical geometry by processing said topographical geometric data, said modeling block forming three-dimensional sampling point groups (x, y, z) by setting suitably distributed point groups in said displayed region and reading from the topographical data memory an altitude value “

z”

corresponding to a plane coordinate (x, y) of each point, and forming a polyhedral topographical geometry model by connecting the three-dimensional sampling groups with straight lines in accordance with a given rule;

a display reference point altitude determining block which determines an altitude value of the display reference point by processing both the information from said input unit and the information from said topographical geometric modeling block;

a viewpoint coordinate determining block which determines a viewpoint coordinate by processing both the information from said input unit and information from said display reference point altitude determining block;

a topographical geometry altitude changing block which changes the altitude values of the sampling points to values similar to the altitude value of the display reference point, thereby to remodel the topographical geometry model;

a map component altitude determining block which reads from said map data memory a map display component within said displayed region and determines an altitude value of said map display component with reference to the remodeled topographical geometry derived by said topographical geometry altitude changing block, thereby to produce a display graphic data;

a coordinate transforming block which, based on both information from said viewpoint coordinate determining block and information from said input unit, applies a perspective-projection transformation to both information from said topographical geometric modeling block and information from said map component altitude determining block;

a topographical geometry drawing process block which draws the polyhedral topographical geometry, which has been subjected to said perspective-projection transformation by said coordinate transforming block, in order from the depth in an overwriting manner thereby to output a stereoscopic map image;

a map component altitude comparing block which compares the altitude value of the display position of each map display component determined by the map component altitude determining block with the altitude value of a corresponding portion of the topographical geometry;

a map component drawing process block which, based on the result of the comparison by said map component altitude comparing block, overwrites on said topographical geometry the map display component whose altitude value is equal to and greater than the altitude value of the corresponding portion of the topographical geometry; and

an image display unit which couples the stereoscopic map image produced by said topographical geometry drawing process block and the map component image produced by said map component drawing process block and displays the coupled image.

45. A navigation system comprising:

a topographical data memory storing a topographical data which provides topographical plane coordinates with altitude values of displayed components;

a line-figured data memory storing position and attribute information on map display components which include roads, rivers and railways;

a place name and background data memory which stores position and attribute information on map display components which include a character train such as place name and position and attribute information on map display components which include a background which can be represented in image by a polygon or surface graphic;

an input unit which inputs display reference point position coordinates and viewing line directional angle by which the position and direction of displayed map are derived;

a displayed region determining block which determines a region displayed on a screen in accordance with information issued from said input unit;

an altitude changing region determining block which determines a changing region in the displayed region in accordance with a certain rule which is determined with reference to the display reference point and the viewing line directional angle;

a topographical geometric modeling block which reads from said topographical data memory a topographical geometric data on the displayed region determined by said displayed region determining block and carries out modeling of the topographical geometry by processing said topographical geometric data, said modeling block forming three-dimensional sampling point groups (x, y, z) by setting suitably distributed point groups in said displayed region and reading from the topographical data memory an altitude value “

z”

corresponding to a plane coordinate (x, y) of each point, and forming a polyhedral topographical geometry model by connecting the three-dimensional sampling groups with straight lines in accordance with a given rule;

a display reference point altitude determining block which determines an altitude value of the display reference point by processing both the information from said input unit and the information from said topographical geometric modeling block;

a topographical geometry altitude changing block which changes the altitude values of the sampling points to values similar to the altitude value of the display reference point, thereby to remodel the topographical geometry model;

a viewpoint coordinate determining block which determines a viewpoint coordinate by processing both the information from said input unit and information from said display reference point altitude determining block;

a map component altitude determining block which reads from said line-figured data memory a line-figured data within said displayed region, and reads from said place name and background data memory said place name and background data and determines an altitude value of each of said line-figured map component and the position of said place name with reference to the remodeled topographical geometry derived by said topographical geometry altitude changing block, thereby to produce a display graphic data;

a coordinate transforming block which, based on both information from said viewpoint coordinate determining block and information from said input unit, applies a perspective-projection transformation to both information from said topographical geometric modeling block and information from said map component altitude determining block;

a hidden surface removing drawing block which carries out a drawing for the topographical geometry data and the place name and background data while effecting a hidden surface removing processing, said topographical geometry data and the place name and background data having been subjected to the perceptive-projection transformation;

a line-figured data altitude comparing block which compares the altitude value of an end of each link of the line-figured data determined by said map component altitude determining block with the altitude value of a corresponding portion of the topographical geometry;

a line-figured data drawing process block which, based on a result of the comparison by said line-figured data altitude comparing block, overwrites on the topographical geometry the line-figured map component when the altitude value of the end of the link of the line-figured component is equal to or greater than the altitude value of the corresponding portion of the topographical geometry; and

an image display unit which couples the stereoscopic map image from said drawing process block and the line-figured image from said line-figured data drawing process block and displays the coupled image.

46. A navigation system comprising:

a topographical data memory storing a topographical data which provides topographical plane coordinates with altitude values of displayed components;

a map data memory storing position and attribute information on map display components which include roads and names of places;

an input unit which inputs display reference point position coordinates and viewing line directional angle by which the position and direction of displayed map are derived;

a displayed region determining block which determines a region which is to be displayed on a screen in accordance with information issued from said input unit;

a plane/stereoscopic display part determining block which determines in the displayed region a first part which is to be displayed in a plane manner and a second part which is to be displayed in a stereoscopic manner, the determination being made in accordance with a given rule determined with reference to the display reference point and the viewing line directional angle;

a topographical geometric modeling block which reads from said topographical data memory a topographical geometric data of sampling points within the displayed region determined by said displayed region determining block and carries out modeling of the topographical geometry by processing said topographical geometric data;

a display reference point altitude determining block which determines an altitude value of the display reference point by processing both the information from said input unit and the information from said topographical geometric modeling block;

a viewpoint coordinate determining block which determines a viewpoint coordinate by processing both the information from said input unit and the information from said display reference point altitude determining block;

a map component altitude determining block which reads from said map data memory a map display component which is to be displayed in said second part and determines an altitude value of the map display component with reference to said topographical geometric model derived by said topographical geometric modeling block, thereby to produce a stereoscopic display graphic data;

an altitude setting block which reads from said map data memory a map display component which is to be displayed in said first part and determines the altitude value of the map display component to a value substantially equal to the display reference point altitude value determined by said display reference point altitude determining block, thereby to produce a plane display graphic data;

a coordinate transforming block which, based on both information from said viewpoint coordinate determining block and information from said input unit, applies a perspective-projection transformation to both said topographical geometric model and said stereoscopic display graphic data;

a stereoscopic map drawing process block which, based on the data subjected to the perspective-projection transformation by said coordinate transforming block, draws a stereoscopic map image within the displayed region;

a plane perspective-projection drawing process block which, based on said plane display graphic data, draws a plane perspective-projection image which is to overwritten on the image drawn by said stereoscopic map drawing process block; and

an image display unit which displays both said stereoscopic map image drawn by said stereoscopic map drawing process block and the plane perspective-projection image drawn by said plane perspective-projection drawing process block.

47. A memorizing medium memorizing a navigation program Including the steps of:

(a) determining a displayed region based on a position coordinate of a display reference point and a viewing line directional angle data;

(b) determining an altitude changing region in said displayed region in accordance with a given rule determined with reference to said position coordinate of the display reference point and said viewing line direction angle data;

(c) reading a topographical geometric data within said displayed region to carry out modeling of the topographical geometry;

(d) determining an altitude value with reference to the position coordinate of the display reference point and said topographical geometric model;

(e) determining a viewpoint coordinate for a transparent-projection transformation with reference to the position coordinate of said display reference point, said viewing line directional angle and the altitude value of said display reference point;

(f) determining sampling points within the altitude changing region and changing the altitude values of the sampling points to values similar to the altitude value of the display reference point, thereby to remodel the topographical geometry model;

(g) reading a map display component within said displayed region and determining an altitude value of said map display component with reference to the remodeled topographical geometry, thereby to produce a display graphic data;

(h) applying the perspective-projection transformation to both said remodeled topographical geometry model and the map display component whose altitude value has been determined; and

(i) producing a stereoscopic map image from the data to which said transparent-projection transformation has been applied.

48. A memorizing medium memorizing a navigation program including the steps of:

(a) determining a displayed region based on a position coordinate of a display reference point and a viewing line directional angle data;

(b) setting in said displayed region a group of sampling points having a given density, producing a group of three-dimensional sampling points (x, y, z) by deriving an altitude value (z) corresponding to a plane coordinate (x, y) of each sampling point, and producing a polyhedral topographical geometry model by connecting the three-dimensional sampling points with straight lines in accordance with a given rule;

(c) determining an altitude value of the display reference point with reference to said position coordinate of the display reference point and said topographical geometry model;

(d) determining a viewpoint coordinate for a perspective-projection transformation, with reference to the position coordinate of the display reference point, said viewing line directional angle and the altitude value of said display reference point;

(e) determining in said displayed region an altitude changing region, in accordance with a given rule determined with reference to the position coordinate of the display reference point and said viewing angle directional angle;

(f) changing the altitude values of said sampling points to values similar to the altitude value of the display reference point, thereby to remodel the topographical geometry model;

(g) reading a map display component within said displayed region and determining an altitude value of said map display component with reference to the remodeled topographical geometry, thereby to produce a display graphic data;

(h) applying the perspective-projection transformation to both said remodeled topographical geometry model and the map display component whose altitude value has been determined; and

(i) comparing the altitude value of the display position of each map display component with the altitude value of a corresponding portion of the topographical geometry, and based on the result of the comparison, overwriting on said topographical geometry the map display component whose altitude value is equal to and greater than the altitude value of the corresponding portion of the topographical geometry.

49. A memorizing medium memorizing a navigation program Including the steps of:

(a) determining a displayed region based on a position coordinate of a display reference point and a viewing line directional angle data;

(b) determining in the displayed region a first part which is to be displayed in a plane manner and second part which is to be displayed in a stereoscopic manner, the determination being made in accordance with a given rule determined with reference to the display reference point and the viewing line directional angle;

(c) reading a topographical geometric data of sampling points within said displayed region and carrying out modeling of the topographical geometry by using said geometric data;

(d) determining a viewpoint coordinate for a perspective-projection transformation, with reference to the position coordinate of the display reference point, the viewing line directional angle and the altitude value of the display reference point;

(e) reading a map display component which is to be displayed in said second part and determining an altitude value of the map display component with reference to topographical geometric model, thereby to produce a stereoscopic display graphic data;

(f) reading a map display component which is to be displayed in said first part and determining an altitude of the map display component to a value substantially equal to the display reference point altitude value, thereby to produce a plane display graphic data;

(g) based on the viewpoint coordinate and the viewing line directional angle, applying the perspective-projection transformation to both said topographical geometric model and said stereoscopic display graphic data;

(h) based on the data which has been subjected to the perspective-projection transformation, drawing a stereoscopic map image with said displayed region; and

(i) based on said plane display graphic data, drawing a plane perspective-projection image and overwriting said image on the stereoscopic map image.