Apparatus and method for navigating vehicle to destination using display unit

• US 5,748,109 A
• Filed: 12/23/1994
• Issued: 05/05/1998
• Est. Priority Date: 12/27/1993
• Status: Expired due to Term

• Current Assignee: Nissan Motor Co., Ltd.
• Original Assignee: Nissan Motor Co., Ltd.
• Inventors: Tsuda, Hiroshi, Kosaka, Akio, Iwasaki, Masayasu, Watanabe, Masaki, Nakayama, Okihiko, Kishi, Norimasa, Yatsugi, Yoshitaka, Yamada, Kiyomichi
• Primary Examiner(s): Hofsass, Jeffrey
• Assistant Examiner(s): Lee, Benjamin C.
• Application Number:
  US08/362,647
• Time in Patent Office: 1,229 Days
• Field of Search: 340/995, 340/990, 340/988, 340/973, 340/976, 340/975, 364/449, 364/443, 364/444, 364/444.2, 345/133, 345/139
• US Class Current: 340/995.14
• CPC Class Codes: G01C 21/3635 Guidance using 3D or perspective road maps
• CPC Class Codes: G08G 1/0969 having a display in the form of a map
• CPC Class Codes: G09B 29/106 using electronic means

Abstract

A bird'"'"'s eye view commonly used in a flight simulation is applicable to an apparatus and method for navigating a vehicle running on a set route of travel to a set destination using a (color) display unit according to the present invention. The bird'"'"'s eye view of a road map surrounding a present position of the vehicle has a viewing point placed at a predetermined position on an upper sky in a direction opposite to the set destination with the present position of the vehicle as a reference and has a line of sight looking down over the road map so that a part of the road map surrounding the present position of the vehicle can be viewed in an extended scale form and the remaining part of the road map remote from the present position and nearer to the set destination can be viewed in a gradually reduction scale form.

Claims

1. An apparatus for navigating a vehicle using a display unit, comprising:

a) road map storing means for storing a road map data related to a road map, the road map data including road network image data and character data related to the road map;

b) vehicle position detecting means for detecting a present position of the vehicle;

c) vehicle destination setting means through which a destination the vehicle is desired to reach is set on the road map;

d) start point setting means for setting a start point of location on the road map at which the vehicle is to start on the basis of the detected position of the vehicle;

e) route of travel setting means for setting a route of travel on the road map from the start point to the set destination; and

f) display control means for controlling an image of the road map surrounding the set route of travel which is displayed on the display unit in a form of a bird'"'"'s eye view such that the bird'"'"'s eye as a viewing point is referenced at a predetermined position on a raised plane from said road map and offset in a direction opposite to the set destination with respect to the present position of the vehicle being displayed to appear to a user as looking down over the road map from the bird'"'"'s eye, said road network image data being displayed on the display unit in a perspective view from the bird'"'"'s eye view image of the road map and the character data being displayed on the display unit as plane data at a constant size regardless of a position of the displayed image screen on the display unit with respect to the present position of the vehicle.

2. An apparatus for navigating a vehicle using a display unit as claimed in claim 1, which further comprises:

g) first road network image data extracting means for extracting a first part of the road network image data to be displayed on a first part of the image data to be displayed on a second part of the display image screen of the display unit, the first part of the display image screen corresponding to a display area from a lowest side of the display image screen up to a predetermined height thereof as viewed externally from the display unit;

h) second road network image data for extracting a second part of the road network display image screen of the display unit, the second part of the display image screen corresponding to another display area from the predetermined height up to a highest side of the display image screen as viewed externally from the display unit; and

i) first character data extracting means for extracting a first part of the stored character data to be displayed on the first part of the display image screen; and

j) second character data extracting means for extracting a second part of the stored character data to be displayed on the second part of the display image screen, and wherein said display image control means controls the image to be displayed on the display image screen of the display unit in the form of the bird'"'"'s eye view such that the first part of the road network image data extracting means is displayed onto the second part of the road network image data on the first part of the character data on the first part of the display image screen after the first part of the character data extracted by the first character data extracting means has been displayed on the first part of the display image screen, and the second part of the stored character data extracted by the second character data extracting means is, in turn, displayed onto the second part of the display image screen after the second part of the stored road network data extracted by the second road network data extracting means has been displayed on the second part of the display image screen.

3. The apparatus of claim 1, further comprising:

g) first road network image data extracting means for extracting a first part of the road network image data to be displayed on a first part of the display image screen of the display unit, the first part of the display image screen corresponding to a display area from a lowest side of the display image screen up to a predetermined height thereof as viewed externally from the display unit;

h) second road network image data extracting means for extracting a second part of the road network display image screen of the display unit, the second part of the display image screen corresponding to another display area from the predetermined height up to a highest side of the display image screen as viewed externally from the display unit; and

i) first character data extracting means for extracting a first part of the stored character data to be displayed on the first part of the display image screen; and

j) second character data extracting means for extracting a second part of the stored character data to be displayed on the second part of the display image screen, and wherein said display image control means controls the image to be displayed on the display image screen of the display unit in the form of the bird'"'"'s eye view such that the first part of the road network image data extracted by the first road network image data extracting means is displayed onto the first part of the character data on the first part of the display image screen after the first part of the character data extracted by the first character data extracting means has been displayed on the first part of the display image screen, and the second part of the stored character data extracted by the second character data extracting means is, in turn, displayed onto the second part of the display image screen after the second part of the stored road network data extracted by the second road network data extracting means has been displayed on the second part of the display image screen;

wherein the first part of the display image screen corresponds to a part of the road map ranging from the present position of the vehicle to a predetermined distance away from the set destination and the second part of the display image screen corresponds to the remaining part of the road map ranging from the predetermined distance to the set destination and wherein said character data includes names of places.

4. The apparatus of claim 1, wherein said road map storing means stores the road map including road network image data and character data related to the road map, which further comprises:

g) first road network image data extracting means for extracting a first part of the road network image data to be displayed on a first part of the display image screen of the display unit, the first part of the display image screen corresponding to a first range of the road map within which a part of the road network ranging from the present position of the vehicle to a predetermined distance away from the set destination;

h) second road network image data extracting means for extracting a second part of the road network image data to be displayed on a second part of the display image screen of the display unit, the second part of the display image screen corresponding to a second range of the road map within which the remaining part of the road network ranging from the predetermined distance to the set destination falls;

i) first character data extracting means for extracting a first part of the stored character data to be displayed on the first part of the display image screen of the display unit; and

j) second character data extracting means for extracting a second part of the stored character data to be displayed on the second part of the display image screen of the display unit, and wherein said display image control means controls the image to be displayed on the display image screen in the form of the bird'"'"'s eye view such that the first part of the road network image data extracted by the first road network image data extracting means is displayed onto the first part of the character data on the first part of the display image screen, the first part thereof corresponding to a predetermined display area from a lowest side of the display image screen to a predetermined height thereof as viewed externally from the display unit, after said first part of the stored character data extracted by the first character data extracting means has been displayed on the first part of the display image screen of the display unit, and the second part of the stored character data extracted by the second character data extracting means is displayed onto the second part of the road network data on the second part of the display image screen, the second part of the display image screen corresponding to the remaining display area from a highest side of the display image screen to the predetermined height as viewed externally from the display unit, after the second part of the stored road network data extracted by the second road network data extracting means has been displayed on the second part of the display image screen of the display unit;

k) bird'"'"'s eye view generating means for generating a plurality of bird'"'"'s eye views each achieved when the bird'"'"'s eye as a viewing point is placed on an upper sky offset in the direction opposite to the set destination with the present position of the vehicle as the reference and the road map surrounding the set route of travel is being looked down over from the viewing point and each bird'"'"'s eye view having either of a different line of sight toward the set destination or a different height from the earth; and

l) bird'"'"'s eye view selecting means for selecting one of the bird'"'"'s eye views which is to be displayed on the display image screen by said display image control means according to on which the bird'"'"'s eye view a longest distance of the set route of travel is to be displayed.

5. The apparatus of claim 1, further comprising:

g) first road network image data extracting means for extracting a first part of the road network image data to be displayed on a first part of the display image screen of the display unit, the first part of the display image screen corresponding to a display area from a lowest side of the display image screen up to a predetermined height thereof as viewed externally from the display unit;

h) second road network image data extracting means for extracting a second part of the road network image data to be displayed on a second Part of the display image screen of the display unit, the second part of the display image screen corresponding to another display area from the predetermined height up to a highest side of the display image screen as viewed externally from the display unit; and

i) first character data extracting means for extracting a first part of the stored character data to be displayed on the first part of the display image screen; and

j) second character data extracting means for extracting a second part of the stored character data to be displayed on the second part of the display image screen of the display unit, and wherein said display image control means controls the image to be displayed on the display image screen in the form of the bird'"'"'s eye view such that the first part of the road network image data extracted by the first road network image data extracting means is displayed onto the first part of the character data on the first part of the display image screen, after said first part of the stored character data extracted by the first character data extracting means has been displayed on the first part of the display image screen of the display unit, and the second part of the stored character data extracted by the second character data extracting means is displayed onto the second part of the road network image data on after the second part of the stored road network image data extracted by the second road network image data extracting means has been displayed on the second part of the display image screen of the display unit;

in which the first part of the display image screen corresponds to a part of the road map ranging from the present position of the vehicle to a predetermined distance away from the set destination and the second part of the display image screen corresponds to the remaining part of the road map ranging from the predetermined distance to the set destination and wherein said character data include names of places; and

further comprising

k) bird'"'"'s eye view generating means for generating a plurality of bird'"'"'s eye views each achieved when the bird'"'"'s eye as a viewing point is placed on an upper sky offset in the direction opposite to the set destination with the present position of the vehicle as the reference and the road map surrounding the set route of travel is being looked down over from the viewing point and each bird'"'"'s eye view having either of a different line of sight toward the set destination or a different height from the earth; and

l) bird'"'"'s eye view selecting means for selecting one of the bird'"'"'s eye views which is to be displayed on the display image screen by said display image control means according to on which the bird'"'"'s eye view a longest distance of the set route of travel is to be displayed;

wherein said bird'"'"'s eye view selecting means selects one of the respective bird'"'"'s eye views as being one of the lines of sight in the direction through which the sum of the length of each route link between nodes on the set route of travel displayed on the respective bird'"'"'s eve view is a maximum; and

wherein the display unit is a full color display unit, and wherein said display image control means controls the image to be displayed on the display image screen in the form of the desired bird'"'"'s eye view such that the roads transformed into the bird'"'"'s eye view are displayed on the display image screen in different display colors according to ranks of roads on the road map.

6. The apparatus of claim 1, wherein said road map storing means stores the road map including road network image data and character data related to the road map, which further comprises:

g) first road network image data extracting means for extracting a first part of the road network image data to be displayed on a first part of the display image screen of the display unit, the first part of the display image screen corresponding to a first range of the road map within which a part of the road network ranging from the present position of the vehicle to a predetermined distance away from the set destination;

h) second road network image data extracting means for extracting a second part of the road network image data to be displayed on a second part of the display image screen of the display unit, the second part of the display image screen corresponding to a second range of the road map within which the remaining part of the road network ranging from the predetermined distance to the set destination falls;

i) first character data extracting means for extracting a first part of the stored character data to be displayed on the first part of the display image screen of the display unit; and

j) second character data extracting means for extracting a second part of the stored character data to be displayed on the second part of the display image screen of the display unit, and wherein said display image control means controls the image to be displayed on the display image screen in the form of the bird'"'"'s eye view such that the first part of the road network image data extracted by the first road network image data extracting means is displayed onto the first part of the character data on the first part of the display image screen, the first part thereof corresponding to a predetermined display area from a lowest side of the display image screen to a predetermined height thereof as viewed externally from the display unit, after said first part of the stored character data extracted by the first character data extracting means has been displayed on the first part of the display image screen of the display unit, and the second part of the stored character data extracted by the second character data extracting means is displayed onto the second part of the road network data on the second part of the display image screen, the second part of the display image screen corresponding to the remaining display area from a highest side of the display image screen to the predetermined height as viewed externally from the display unit, after the second part of the stored road network data extracted by the second road network data extracting means has been displayed on the second part of the display image screen of the display unit.

7. The apparatus of claim 6, further comprising:

k) bird'"'"'s eye view generating means for generating a plurality of bird'"'"'s eye views each achieved when the bird'"'"'s eye as a viewing point is placed on an upper sky located in the direction opposite to the set destination with the present position of the vehicle as the reference and the road map surrounding the set route of travel is being looked down over from the viewing point and each bird'"'"'s eye view having either of a different line of sight toward the set destination or a different height of the earth; and

l) bird'"'"'s eye view selecting means for selecting one of the prepared bird'"'"'s eye views which is to be displayed on the display image screen by said display image control means according to on which the bird'"'"'s eye view a longest distance of the set route of travel is to be displayed;

wherein said bird'"'"'s eye view selecting means derives a total value (Lθ

), equal to the sum of the length of each route link between nodes on the set route of travel displayed on the respective bird'"'"'s eye view, for each different line of sight and said bird'"'"'s eye view selecting means selects one of the respective bird'"'"'s eye views as being one of the lines of sight in the direction through which the total value (Lθ

) is the maximum.

8. The apparatus of claim 7,

wherein the display unit is a full color display unit, and wherein said display image control means controls the image to be displayed on the display image screen in the form of the desired bird'"'"'s eye view such that the roads transformed into the bird'"'"'s eye view are displayed on the display image screen in different display colors according to ranks of roads on the road map;

and which further comprises;

m) grid line painting means for painting grid lines having any one of the same class of colors as that to which the display color of at least one rank of the roads on the road map to be displayed on the display image screen of the display unit in the form of the bird'"'"'s eye view belongs and for painting grid lines on the road map so that each crossing point of the grid lines has any one of the same class of colors as that to which the display color of at least one rank of the roads belongs.

9. The apparatus of claim 7, wherein the display unit is a full color display unit, and wherein said display image control means controls the image to be displayed on the display image screen in the form of the desired bird'"'"'s eye view such that the roads transformed into the bird'"'"'s eye view are displayed on the display image screen in different display colors according to ranks of roads on the road map;

and which further comprises;

m) grid line painting means for painting grid lines having any one of the same class of colors as that to which the display color of at least one rank of the roads on the road map to be displayed on the display image screen of the display unit in the form of the bird'"'"'s eye view belongs.

10. The apparatus of claim 9, further comprising grid line painting means for painting grid lines on the road map so that each crossing point of the grid lines as any one of the same class of colors as that to which the display color of at least one rank of the road belongs;

and wherein

said display image control means displays the roads in the bird'"'"'s eye view according to a predetermined display priority order on each rank of the roads including the set route of travel, and said grid line painting means paints the grid lines with any one of the same class of colors as that to which the display order of one of the roads having a lowest priority order of the predetermined display priority order belongs.

11. An apparatus for navigating a vehicle using a display unit, comprising:

a) road map storing means for storing road map data related to a road map;

b) vehicle position detecting means for detecting a present position of the vehicle;

c) vehicle destination setting means through which a destination the vehicle is desired to reach is set on the road map;

d) start point setting means for setting a starting point location on the road map at which the vehicle is to start based on the detected present position of the vehicle;

e) route of travel setting means for setting a route of travel on the road map from the starting point to the destination set;

(f) display control means for controlling an image of the road map surrounding the route of travel set which is displayed on the display unit in a form of a bird'"'"'s eye view such that the bird'"'"'s eye as a viewing point is referenced at a predetermined position on a raised plane from said road map and offset in a direction opposite to the set destination with respect to the present position of the vehicle, and the road map surrounding the set route of travel is being displayed to appear to a user as looking down over the road map from the bird'"'"'s eye; and

g) hairpin curve detecting means for detecting whether at least one hairpin curve is present in the set route of travel at a location which is in a direction opposite to the set destination with respect to the present position of the vehicle as the reference, and informing said display control means of the presence of the hairpin curve when it is detected,

wherein said display control means, responsive to the information from the hairpin curve detecting means that the hairpin curve is present, controls the image of the set route of travel to be displayed on the display image screen of the display unit in the form of the bird'"'"'s eye view so that the point of view of the bird'"'"'s eye view is moved from the predetermined position toward a direction opposite to the present position of the vehicle offset with respect to the detected hairpin curve so that the road map surrounding the set route of travel is viewed including the detected hairpin curve.

12. An apparatus for navigating a vehicle using a display unit as claimed in claim 11, which further comprises:

h) position area determining means for determining a position of a region and an area of the region, the region being enclosed by a line segment orthogonal to another line segment connecting the present position of the vehicle to the set destination and being enclosed by the hairpin curve detected by said hairpin curve detecting means, and wherein said display control means controls the image of the road map surrounding the set route of travel including a part of the road map corresponding to the region in the form of the bird'"'"'s eye view.

13. An apparatus for navigating a vehicle using a display unit as claimed in claim 11, wherein said hairpin curve detecting means includes hairpin curve length and direction determining means for determining a length and direction of the detected hairpin curve and wherein said display control means includes changing means for changing at least either of the predetermined position of the viewing point or a direction of a line of sight of the bird'"'"'s eye view according to the determined length and direction of the detected hairpin curve.

14. An apparatus for navigating a vehicle using a display unit as claimed in claim 11, wherein said road map storing means stores the road map including road network image data and character data related to the road map, which further comprises:

g) first road network image data extracting means for extracting a first part of the road network image data to be displayed on a first part of the display image screen of the display unit, the first part of the display image screen corresponding to a first range of the road map within which a part of the road network ranging from the present position of the vehicle to a predetermined distance away from the set destination;

h) second road network image data extracting means for extracting a second part of the road network image data to be displayed on a second part of the display image screen of the display unit, the second part of the display image screen corresponding to a second range of the road map within which the remaining part of the road network ranging from the predetermined distance to the set destination fails;

i) first character data extracting means for extracting a first part of the second character data to be displayed on the first part of the display image screen of the display unit; and

j) second character data extracting means for extracting a second part of the stored character data to be displayed on the second part of the display image screen of the display unit, and wherein said display image control means controls the image to be displayed on the display image screen in the for of the bird'"'"'s eye view such that the first part of the road network image data extracted by the first road network image data extracting means is displayed onto the first Dart of the character data on the first part of the display image screen, the first part thereof corresponding to a predetermined display area from a lowest side of the display image screen to a predetermined height thereof as viewed externally from the display unit, after said first part of the stored image character data extracted by the first character data extracting means has been displayed on the first part of the display image screen of the display unit, and the second part of the stored character data extracted by the second character data extracting means is displayed onto the second part of the road network data on the second part of the display image screen, the second part of the display image screen corresponding to the remaining display area from a highest side of the display image screen to the predetermined height as viewed externally from the display unit, after the second part of the stored road network data extracted by the second road network data extracting means has been displayed on the second part of the display image screen of the display unit.

15. An apparatus for navigating a vehicle using a display unit as claimed in claim 11, wherein said road map storing means stores the road map data including road network image data and character data related to the road map, which further comprises:

g) first road network image data extracting means for extracting a first part of the road network image data to be displayed on a first part of the display image screen of the display unit, the first part of the display image screen corresponding to a display area from a lowest side of the display image screen up to a predetermined height thereof as viewed externally from the display unit;

h) second road network image data extracting means for extracting a second part of the road network image data to be displayed on a second part of the display image screen of the display unit, the second part of the display image screen corresponding to another display area from the predetermined height up to a highest side of the display image screen as viewed externally form the display unit;

i) first character data extracting means for extracting a first part of the stored character data to be displayed on the first part of the display image screen; and

j) second character data extracting means for extracting a second part of the stored character data to be displayed on the second part of the display image screen; and

wherein said display image control means controls the image to be displayed on the display image screen of the display unit in the form of the bird'"'"'s eye view such that the first part of the road network image data extracted by the first road network image data extracting means is displayed onto the first part of the character data on the first part of the display image screen after the first part of the character data extracted by the first character data extracting means has been displayed on the first part of the character data extracted by the first character data extracting means has been displayed on the first part of the display image screen, and the second part of the stored character data extracted by the second character data extracting means is, in turn, displayed onto the second part of the road network data on the second part of the display image screen after the second part of the stored road network data extracted by the second road network data extracting means has been displayed on the second part of the display image screen.

16. An apparatus for navigating a vehicle using a display unit as claimed in claim 15, wherein the first part of the display image screen corresponds to a part of the road map ranging from the present position of the vehicle to a predetermined distance away from the set destination and the second part of the display image screen corresponds to the remaining part of the road map ranging from the predetermined distance to the set destination and wherein said character data include names of places.

17. An apparatus for navigating a vehicle using a display unit as claimed in claim 11, which further comprises:

g) bird'"'"'s eye view generating means for generating a plurality of bird'"'"'s eye views each achieved when the bird'"'"'s eye as a viewing point is placed on an upper sky located in the direction opposite to the set destination with the present position of the vehicle as the reference and the road map surrounding the set route of travel is being looked down over from the viewing point and each bird'"'"'s eye view having either of a different line of sight toward the set destination or a different height to the earth; and

h) bird'"'"'s eye view selecting means for selecting one of the prepared bird'"'"'s eye views which is to be displayed on the display image screen by said display image control means according to on which the bird'"'"'s eye view a longest distance of the set route of travel is to be displayed.

18. An apparatus for navigating a vehicle using a display unit as claimed in claim 17, wherein said bird'"'"'s eye view generating means generates a plurality of bird'"'"'s eye views having a respectively different line of sight, said bird'"'"'s eve view selecting means derives a total value (Lθ

), equal to the sum of the length of each route link between nodes on the set route of travel displayed on the respective bird'"'"'s eye view, for each different line of sight and said bird'"'"'s eye view selecting means selects one of the respective bird'"'"'s eye views as being one of the lines of sight in the direction through which the total value (Lθ

) is a maximum.

19. An apparatus for navigating a vehicle using a display unit as claimed in claim 11, wherein the display unit is a full color display unit, and wherein said display image control means controls the image to be displayed on the display image screen in the form of the desired bird'"'"'s eye view such that the roads transformed into the bird'"'"'s eye view are displayed on the display image screen in different display colors according to ranks of roads on the road map.

20. An apparatus for navigating a vehicle using a display unit as claimed in claim 19, which further comprises:

g) grid line painting means for painting grid lines having any one of the same class of colors as that to which the display color of at least one rank of the roads on the road map to be displayed on the display image screen of the display unit in the form of the bird'"'"'s eye view belongs.

21. An apparatus for navigating a vehicle using a display unit as claimed in claim 20, wherein said display image control means displays the roads in the bird'"'"'s eye view according to a predetermined display priority order on each rank of the roads including the set route of travel and said grid line painting means paints the grid lines with any one of the same class of colors as that to which the display of one of the roads having a lowest priority order of the predetermined display priority order belongs.

22. An apparatus for navigating a vehicle using a display unit as claimed in claim 19, which further comprises:

g) grid line painting means for painting grid lines on the road map so that each crossing point of the grid lines has any one of the same class of colors as that to which the display color of at least one rank of the roads belongs.

23. An apparatus for navigating a vehicle using a display unit as claimed in claim 22, wherein said display image control means displays the roads in the bird'"'"'s eye view according to a predetermined display priority order on each rank of the roads including the set route of travel, and said grid line painting means paints the grid lines with any one of the same class of colors as that to which the display order of one of the roads having a lowest priority order of the predetermined display priority order belongs.

24. An apparatus for navigating a vehicle using a display unit as claimed in claim 19, which further comprise:

g) background painting means for painting a background of the road map in any one of the same class of colors as that to which the display color of at least one rank of the roads belongs.

25. An apparatus for navigating a vehicle using a display unit as claimed in claim 24, wherein said display image control means displays the roads according to a predetermined display priority order for each rank of the roads, and said background painting means paints the background in any one of the classes of colors as that to which the display order of one of the roads having a lowest priority order for each rank of the roads belongs.

26. An apparatus for navigating a vehicle using a display unit as claimed in claim 19, which further comprises:

g) background painting means for painting a background of the road map displayed on the display image screen by changing the display colors incrementally in a stepwise manner as the part of the road map image displayed becomes nearer to the destination so that a background color of a part of the road map which is remote from the present position of the vehicle belongs to the same class of colors as the display color to which at least one rank of the roads belongs.

27. An apparatus for navigating a vehicle using a display unit as claimed in claim 26, wherein said display image control means displays the roads according to a predetermined display priority order for each rank of the roads, and said background painting means paints the background with any one of the same class of colors as that to which the display of the predetermined display priority order for each rank of the roads belongs.

28. An apparatus for navigating a vehicle using a display unit as claimed in claim 19, which further comprises:

g) dots painting means for painting a plurality of background dots having at least one of the same classes of colors as those to which the display color of at least one rank of the roads belongs so that the dots which are present on a part of the road map, the part surrounding the present position of the vehicle, becomes coarse and those on another part of the road map which is remote from the present position of the vehicle becomes fine.

29. An apparatus for navigating a vehicle using a display unit as claimed in claim 26, wherein said display image control means displays the roads according to a predetermined display priority order for each rank of the roads, and said dots painting means paints the dots in any one of the same classes of colors as those to which the display order of one of the roads having a lowest priority order of the predetermined display priority order for each rank of the roads belongs.

30. An apparatus for navigating a vehicle using a display unit as claimed in claim 29, wherein the predetermined display priority order is the order of freeways, national highways, regional principle roads, principle roads, and street roads.

31. A method for navigating a vehicle using a display unit, comprising the steps of:

a) storing a road map data related to a road map in a predetermined storing means;

b) detecting a present position of the vehicle;

c) setting a destination the vehicle is desired to reach on the road map;

d) setting a start point of location on the road map at which the vehicle is to start on the basis of the detected present position of the vehicle;

e) setting a route of travel on the road map from the start point to the destination set; and

f) displaying on a display image screen of the display unit the image of the road map surrounding the set route of travel; and

g) operatively transforming a coordinate system of the road map surrounding the set route of travel into a form of a bird'"'"'s eye view such that the bird'"'"'s eye as a viewing point is referenced at a predetermined position on a raised plane from said road map and offset in a direction opposite to the set destination with respect to the present position of the vehicle, and the road map surrounding the set route of travel being displayed to appear to a user as looking down over the road map from the bird'"'"'s eye;

h) detecting whether at least one hairpin curve is present preceding the current position in the set route of travel at a location which is in a direction opposite to the set destination with respect to the present position of the vehicle as the reference; and

wherein, at said step g), the image of the set route of travel to be displayed on the display image screen of the display unit is controlled in the form of the bird'"'"'s eye view so that the viewing point of the bird'"'"'s eye view is moved from the predetermined position toward a direction opposite to the present position of the vehicle with respect to the detected hairpin curve so that the road map surrounding the set route of travel is viewed including the detected hairpin curve.

32. A method for navigating a vehicle using a display unit, comprising the steps of:

a) storing a road map data related to a road map, the road map data including road network image data and character data related to the road map;

b) detecting a present position of the vehicle;

c) setting a destination of the vehicle is desired to reach is set on the road map;

d) setting a start point of location on the road map at which the vehicle is to start on the basis of the detected present position of the vehicle;

e) setting a route of travel on the road map from the start point to the set destination; and

f) displaying on a display image screen of the display unit the image of the road map and the character data surrounding the set route of travel; and

g) operatively transforming a coordinate system of only the road map image data surrounding the set route of travel into a form of a bird'"'"'s eye view such that the bird'"'"'s eye as a viewing point is referenced at a predetermined position on a raised plane from said road map and offset in a direction opposite to the set destination with respect to the present position of the vehicle, and the road map image data only surrounding the set route of travel being displayed in a perspective view to appear to a user as looking down over the road map from the bird'"'"'s eye and the character data being displayed as plane data without the coordinate transformation to the bird'"'"'s eye view and being displayed at a constant size regardless of a position of the display image screen with respect to the present position of the vehicle.

33. An apparatus for navigating a vehicle using a display unit, comprising:

a) road map storing means for storing road map data related to a road map, the road map data including road network image data and character data related to the road map;

b) vehicle position detecting means for detecting a present position of the vehicle;

c) vehicle destination setting means through which a destination the vehicle is desired to reach is set on the road map;

d) start point setting means for setting a starting point location on the road map at which the vehicle is to start based on the detected present position of the vehicle;

e) route of travel setting means for setting a route of travel on the road map from the starting point to the destination set; and

f) display control means for controlling an image of the road map surrounding the route of travel set which is displayed on the display unit in a form of a bird'"'"'s eye view such that the bird'"'"'s eye as a viewing point is referenced at a predetermined position on a raised plane from said road map and offset in a direction opposite to the set destination with respect to the present position of the vehicle, and the road map surrounding the set route of travel is being displayed to appear to a user as looking down over the road map from the bird'"'"'s eye, said character data being overwritten on the road network data displayed on the display unit in the bird'"'"'s eye view, the superposition of the character data on the road map or the superposition of the road map on the character data being changed depending on a height position of the road map image on an image screen of the display unit with respect to a lowest position of the display unit.