Portable or vehicular navigating apparatus and method capable of displaying bird's eye view

• US 5,793,310 A
• Filed: 02/03/1995
• Issued: 08/11/1998
• Est. Priority Date: 02/04/1994
• Status: Expired due to Term

• Current Assignee: Nissan Motor Co., Ltd.
• Original Assignee: Nissan Motor Co., Ltd.
• Inventors: Watanabe, Masaki, Kishi, Norimasa, Yatsugi, Yoshitaka, Yamada, Kiyomichi
• Primary Examiner(s): Hofsass, Jeffery A.
• Assistant Examiner(s): Lee, Benjamin C.
• Application Number:
  US08/384,715
• Time in Patent Office: 1,285 Days
• Field of Search: 340/995, 340/988, 340/990, 364/444, 364/449, 364/439, 701/201, 701/202, 701/211, 701/212, 701/213
• 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

In an apparatus and method for navigating a mobile body such as a vehicle or user, an accurate and easily grasping road map graphic data in a bird'"'"'s eye display mode are achieved with a running route on which the mobile body has traveled maintained and having a continuity to the past running information and operability of the navigating apparatus is improved. In the navigating apparatus and method, the present position information and display parameter information are previously set, a line of sight is determined on the basis of the forwarding direction information, a view point position is determined on the basis of the forwarding direction is determined. A road map data expressed with a two-dimensional X-Y plane as a reference is stored. The road map data stored receive their coordinate transformations on the basis of the determined view point position and direction of line of sight to generate the bird'"'"'s eye view. Such generated bird'"'"'s eye view image data are output to a display unit so that the bird'"'"'s eye view can be viewed from a display image screen. Furthermore, character data such as names of places are selectively superimposed on respective minor regions of the image screen without superimpositions on other character data belonging to adjacent minor regions.

Claims

1. A navigating apparatus comprising:

a) present position detecting means for detecting a present position of a mobile body and a forwarding direction toward which the mobile body moves at the present position thereof;

b) initial display parameter value setting means for previously setting the detected present position and display parameters thereinto as initial values;

c) direction of line of sight determining means for determining a direction of line of sight for a perspectively projected image on the basis of at least the detected forwarding direction;

d) view point position determining means for determining a position of a view point on which the direction of line of sight is based on the basis of at least the information of the forwarding direction detected by the present position detecting means;

e) road map data storing means for storing at least a road map data expressed with a two-dimensional X-Y plane as a reference;

f) coordinate transforming means for executing a coordinate transformation of the road map data stored in said road map data storing means on the basis of at least the determined direction of line of sight and the determined view point position into a bird'"'"'s eye view which is the perspectively projected image of the read road map data so as to generate the bird'"'"'s eye view; and

g) display means for receiving the display data of the bird'"'"'s eye view and for displaying the bird'"'"'s eye view on its image screen;

wherein said direction of line of sight determining means determines the direction of line of sight placed on a reference point (Q) on the basis of at least a past positional information of the present position before a predetermined period of time has passed or before the mobile body in which the navigating apparatus is mounted has run by a predetermined interval of distance, and

space="preserve" listing-type="equation">α

(t)=w.sub.i ×

δ

+(1-w.sub.i)×

α

(t-1), 0<

w.sub.i <

1,

α

(t);

the direction of line of sight,

δ

;

the forwarding direction, δ

=arg |P_p -P_o |,

P_p ;

a previously measured present position before the predetermined period of time has passed or before the mobile body has run by the predetermined interval of distance, and

α

(t-1);

the determined line of sight before the predetermined period of time has passed or before the mobile body has run by the predetermined interval of distance.

2. A navigating apparatus as claimed in claim 1, wherein the view point position E(X_o, Y_o, Z_o) is determined as follows:

space="preserve" listing-type="equation">x=X.sub.p +L×

cos α

(t),

space="preserve" listing-type="equation">y=Y.sub.p +L×

sin α

(t),

(x, y) denotes coordinate positions of the referring point (B) on the X-Y plane and L denotes a distance from the reference point (Q) to the referring point (B); and

space="preserve" listing-type="equation">X.sub.o =x-hx cos α

(t)/tan θ

,

space="preserve" listing-type="equation">Y.sub.o =y-hx sin α

(t)/tan θ

,

and

space="preserve" listing-type="equation">Z.sub.o =h,

wherein h denotes a height of the view point and θ

denotes an angle of depression for the view point.

3. A navigating apparatus as claimed in claim 1, wherein said present position detecting means comprises:

a GPS; and

a geomagnetic direction sensor.

4. A navigating apparatus as claimed in claim 1, wherein said direction of line of sight determining means determines a next direction of the line of sight of the perspectively projected image on the basis of a past direction of the line of sight.

5. A navigating apparatus as claimed in claim 1, wherein said road map data stored in said road map data storing means includes traffic intersection data and route road point data, which further comprises predictive route road point calculating means for calculating a route road point present in the forwarding direction of the mobile body from another route point which corresponds to the present position of the mobile body as a predicted route point to which the mobile body moves on the basis of the present position detected by said present position detecting means and forwarding direction at the present position detected by said present position detecting means and on the basis of the road map data stored in said road map memory, and wherein said direction of line of sight determining means determines the direction of line of sight and determines a reference point of the perspectively projected view on the basis of the present position of the mobile body detected by said present position detecting means, the forwarding direction at the detected present position, and the predicted route road point, and said coordinate transforming means executes the coordinate transformation of the road map data on the basis of the determined information from the direction of line of sight determining means.

6. A navigating apparatus as claimed in claim 5, which further comprises turn signal detecting means for detecting an information on a turn signal of the mobile body and wherein said predictive route road point calculating means calculates the predicted route road point on the basis of the present position detected by said present position detecting means, the forwarding direction at the present position detected by said present position detecting means, the road map data stored in said road map data storing means, and the information on the turn signal of the mobile body detected by said turn signal detecting means.

7. A navigating apparatus as claimed in claim 6, wherein said mobile body is an automotive vehicle having a combination lamp to indicate right and left turns and no turn when no combination lamp is turned on.

8. A navigating apparatus as claimed in claim 1, wherein said road map storing means stores character data constituting names of places to be superimposed on the road map data and wherein said initial display parameter value setting means, said direction of line of sight determining means and coordinate transforming means are constituted by display reference point determining unit which is so constructed as to determine a display reference point on the road map data to be displayed on the basis of at least the present position detected by said present position detecting means and a calculation processing unit which is so constructed as to fetch the road map data required to be displayed on the image screen of said display means and to determine contents of displays on the display image screen of said display means, said display image screen being previously divided into a plurality of minor display regions and said calculation processing unit selecting one of character data constituting one of the names of places which is displayed within the same minor region in accordance with the division of the image screen into the minor regions.

9. A navigating apparatus as claimed in claim 8, wherein said calculation processing unit further comprises first means for determining whether a superimposition of the character data constituting the name of place belonging to one of the divided minor regions on either of the character data constituting names of places belonging to adjacent left and right minor regions occurs for each of the divided minor regions, for each predetermined one of the character data constituting the names of places which are display candidates and wherein said calculation processing unit executes such a decimination that parts of the character data which are superimposed mutually are erased and not displayed when a plurality of the character data are determined to be superimposed.

10. A navigating apparatus as claimed in claim 9, wherein said calculation processing unit further comprises second means for determining whether a superimposition of the character data constituting the name of place belonging to one of the divided minor regions on any one of the character data belonging to adjacent upper or lower minor regions or belonging to a left or right minor region adjacent to the adjacent upper or lower region thereof occurs for each of the divided minor regions, for each predetermined one of the character data constituting the names of places which are display candidates and wherein said calculation processing unit executes such a decimination that parts of the character data which are superimposed mutually are erased and not displayed when a plurality of the character data are determined to be superimposed.

11. A navigating apparatus as claimed in claim 9, wherein said calculation processing unit further comprises third means for determining whether a lateral superimposition of the character data constituting the name of place belonging to one of the divided minor regions on any one of the character data belonging to a laterally adjacent minor region in a lateral direction of the image screen and determined whether a longitudinal superimposition of the character data constituting the name of place belonging to one of the divided minor regions on any one of the character data belonging to a longitudinally adjacent minor region, for each predetermined one of the character data constituting the names of places which are display candidates and wherein said calculation processing unit executes such a decimination that parts of the character data which are superimposed mutually are erased and not displayed when a plurality of the character data are determined to be laterally and longitudinally superimposed.

12. A navigating apparatus as claimed in claim 11, wherein the divided minor regions that said calculation processing unit handles include virtually imaged minor regions extended outside the display image screen and wherein said calculation processing unit executes the calculation processing such that at least one of the character data constituting the names of places which is adjacent to an outside periphery of the image screen is partially displayed.

13. A navigating apparatus as claimed in claim 12, wherein said character data constituting the names of places have degrees of display importance as their attributes and wherein said calculation processing unit selects the character data constituting the names of places to be displayed on the basis of their degrees of the display importance.

14. A navigating apparatus comprising:

a) present position detecting means for detecting a present position of a mobile body and a forwarding direction toward which the mobile body moves at the present position thereof;

b) initial display parameter value setting means for previously setting the detected present position and display parameters thereinto as initial values;

c) direction of line of sight determining means for determining a direction of line of sight for a perspectively projected image on the basis of at least the detected forwarding direction;

d) view point position determining means for determining a position of a view point on which the direction of line of sight is based on the basis of at least the information of the forwarding direction detected by the present position detecting means;

e) road map data storing means for storing at least a road map data expressed with a two-dimensional X-Y plane as a reference;

f) coordinate transforming means for executing a coordinate transformation of the road map data stored in said road map data storing means on the basis of at least the determined direction of line of sight and the determined view point position into a bird'"'"'s eye view which is the perspectively projected image of the read road map data so as to generate the bird'"'"'s eye view; and

g) display means for receiving the display data of the bird'"'"'s eye view and for displaying the bird'"'"'s eye view on its image screen,

wherein said direction of line of sight determining means determines the direction of line of sight placed on a reference point (O) on the basis of at least a past positional information of the present position before a predetermined period of time has passed or before the mobile body in which the navigating apparatus is mounted has run by a predetermined interval of distance, and wherein

space="preserve" listing-type="equation">α

(t)=wO·

δ

.sub.o +w1·

δ

.sub.1 + - - - +w.sub.i ·

δ

.sub.i,

wherein w0+w1+w2+ - - - W_I =1 and δ

_i denotes the direction of line of sight or the forwarding direction of the mobile body, δ

_i being calculated before the predetermined period of time has passed by an i-th number of times or before the predetermined interval of distance through which the mobile body has run by the i-th number of times.

15. A navigating apparatus comprising:

a present position detecting means for detecting a present position of a mobile body and a forwarding direction toward which the mobile body moves at the present position thereof;

b) initial display parameter value setting means for previously setting the detected present position and display parameters thereinto as initial values;

c) direction of line of sight determining means for determining a direction of line of sight for a perspectively projected image on the basis of at least the detected forwarding direction;

d) view point position determining means for determining a position of a view point on which the direction of line of sight is based on the basis of at least the information of the forwarding direction detected by the present position detecting means;

e) road map data storing means for storing at least a road map data expressed with a two-dimensional X-Y plane as a reference;

f) coordinate transforming means for executing a coordinate transformation of the road map data stored in said road map data storing means on the basis of at least the determined direction of line of sight and the determined view point position into a bird'"'"'s eye view which is the perspectively projected image of the read road map data so as to generate the bird'"'"'s eye view; and

g) display means for receiving the display data of the bird'"'"'s eye view and for displaying the bird'"'"'s eye view on its image screen,

wherein said direction of line of sight determining means determines the direction of line of sight placed on a reference point (O) on the basis of at least a past positional information of the present position before a predetermined period of time has passed or before the mobile body in which the navigating apparatus is mounted has run by a predetermined interval of distance, and wherein

space="preserve" listing-type="equation">α

(t)=β

.sub.p -arg|P.sub.r -P.sub.o |,

wherein β

_p denotes an angle formed between the positional information of a position P_r of a road through which the mobile body has passed and which is remote by R from the present position and the present position P_o.

16. A navigating apparatus comprising:

a) external storing means for storing road map data which are divided into a plurality of square-shaped land-partitioned regions defined as meshes;

b) display reference point determining means for determining a display reference point on the road map data;

c) calculation processing means for executing a calculation processing required to display a bird'"'"'s eye view on the basis of the mesh data from said external storing means and the determination information of said display reference point determining means; and

d) image displaying means for displaying the road map data as the result of calculation processing by said calculation processing means on its display screen;

wherein said direction of line of sight determining means determines the direction of line of sight placed on a reference point (O) on the basis of at least a past positional information of the present position before a predetermined period of time has passed or before the mobile body in which the navigating apparatus is mounted has run by a predetermined interval of distance, and

space="preserve" listing-type="equation">α

(t)=w.sub.i ×

δ

+(1-w.sub.i)×

α

(t-1), 0<

w.sub.i <

1,

α

(t);

the direction of line of sight.

δ

;

the forwarding direction, δ

=arg|P_p -P_o |,

P_p ;

a previously measured present position before the predetermined period of time has passed or before the mobile body has run by the predetermined interval of distance, and

α

(t-1);

the determined line of sight before the predetermined period of time has passed or before the mobile body has run by the predetermined interval of distance.

17. A navigating apparatus comprising:

a) present position detecting means for detecting a present position of a mobile body and for detecting a forwarding direction at the present position toward which the mobile body moves;

b) road map data storing means for storing a road map information including a road map data previously expressed with a two-dimensional X-Y plane as a reference and traffic intersection data and route road point data on the road map data;

c) predicted route road point calculating means for calculating a route road point present in a forward direction of the mobile body toward which the mobile body moves from a route road point at which the mobile body is present as the present position on the basis of the present position detected by the present position detecting means, the forwarding direction at the present position detected by the present position detecting means, and the road map information;

d) view point position/reference point position determining means for determining a reference point position and a direction of a view point on a road map display on the basis of the present position and forwarding direction at the present position detected by said present position detecting means;

e) display information generating means for carrying out a coordinate transformation of the road map information on the basis of the data of the view point position and reference point position data from the view point position/reference point position determining means so as to generate a display information; and

f) display means for displaying the generated display information on its image screen;

wherein said direction of line of sight determining means determines the direction of line of sight placed on a reference point (O) on the basis of at least a past positional information of the present position before a predetermined period of time has passed or before the mobile body in which the navigating apparatus is mounted has run by a predetermined interval of distance, and

space="preserve" listing-type="equation">α

(t)=w.sub.i ×

δ

+(1-w.sub.i)×

α

(t-1), 0<

w.sub.i <

1,

α

(t);

the direction of line of sight,

δ

;

the forwarding direction, δ

=arg|P_p -P_o |,

P_p ;

a previously measured present position before the predetermined period of time has passed or before the mobile body has run by the predetermined interval of distance, and

α

(t-1);

the determined line of sight before the predetermined period of time has passed or before the mobile body has run by the predetermined interval of distance.

18. A navigating apparatus comprising:

a) external memory means for storing road map information having a road map graphic data and character data constituting names of places to be superimposed on the road graphic data;

b) display reference point determining means for determining a display reference point on the road map according to a position of a vehicle;

c) a calculation processing unit which is so constructed as to fetch the road map information required to be displayed from said eternal memory means and so as to determine contents of displays, on the basis of the determined display reference point; and

d) image display unit which is so constructed as to display an output from said calculation processing unit in a form of a road map image on its screen, wherein the image screen of the image display unit is divided into a plurality of image minor regions and said calculation processing unit selects and displays one of the character data constituting the names of places to be displayed within one of the same minor regions in accordance with the division of the image screen into the plurality of minor regions;

wherein said direction of line of sight determining means determines the direction of line of sight placed on a reference point (O) on the basis of at least a past positional information of the present position before a predetermined period of time has passed or before the mobile body in which the navigating apparatus is mounted has run by a predetermined interval of distance, and

space="preserve" listing-type="equation">α

(t)=w.sub.i ×

δ

+(1-w.sub.i)×

α

(t-1), 0<

w.sub.i <

1,

α

(t);

the direction of line of sight,

δ

;

the forwarding direction, δ

=arg|P_p -P_o |,

P_p ;

a previously measured present position before the predetermined period of time has passed or before the mobile body has run by the predetermined interval of distance, and

α

(t-1);

the determined line of sight before the predetermined period of time has passed or before the mobile body has run by the predetermined interval of distance.

19. A method for navigating a mobile body, comprising the steps of:

a) detecting a present position of the mobile body and a forwarding direction toward which the mobile body moves at the present position thereof;

b) previously setting the detected present position and display parameters values;

c) determining a direction of line of sight for a perspectively projected image on the basis of at least the information of the detected forwarding direction;

d) determining a position of a view point on which the direction of line of sight is based on the basis of at least the information of the detected forwarding direction;

e) storing at least a road map data expressed with a two-dimensional X-Y plane as a reference;

f) executing a coordinate transformation of the road map data stored in said road map data storing means on the basis of at least the determined direction of line of sight and the determined view point position into a bird'"'"'s eye view which is the perspectively projected image of the read road map data so as to generate the bird'"'"'s eye view; and

g) receiving the data of the bird'"'"'s eye view and displaying the bird'"'"'s eye view on an image screen;

wherein said direction of line of sight determining means determines the direction of line of sight placed on a reference point (O) on the basis of at least a past positional information of the present position before a predetermined period of time has passed or before the mobile body in which the navigating apparatus is mounted has run by a predetermined interval of distance, and

space="preserve" listing-type="equation">α

(t)=w.sub.i ×

δ

+(1-w.sub.i)×

α

(t-1), 0<

w.sub.i <

1,

α

(t);

the direction of line of sight,

δ

;

the forwarding direction, δ

=arg|P_p -P_o |,

P_p ;

a previously measured present position before the predetermined period of time has passed or before the mobile body has run by the predetermined interval of distance, and

α

(t-1);

the determined line of sight before the predetermined period of time has passed or before the mobile body has run by the predetermined interval of distance.

20. A navigating apparatus comprising:

a) present position detecting means for detecting a present position of a mobile body and a forwarding direction toward which the mobile body moves at the present position thereof;

b) initial display parameter value setting means for previously setting the detected present position and display parameters thereinto as initial values;

c) direction of line of sight determining means for determining a direction of line of sight for a bird'"'"'s eye view including the present position of the mobile body on the basis of at least the detected forwarding direction;

d) view point position determining means for determining a position of a view point on the basis of at least the direction of line of sight;

e) road map data storing means for storing at least a road map data expressed with a two-dimensional X-Y plane as a reference;

f) coordinate transforming means for executing a coordinate transformation of the road map data stored in said road map data storing means on the basis of at least the determined direction of line of sight and the determined view point position into the bird'"'"'s eye view so as to generate the bird'"'"'s eye view including the present position of the mobile body; and

g) display means for receiving the display data of the bird'"'"'s eye view and for displaying on its image screen the bird'"'"'s eye view including the present position of the mobile body;

wherein said direction of line of sight determining means determines the direction of line of sight placed on a reference point (O) on the basis of at least a past positional information of the present position before a predetermined period of time has gassed or before the mobile body in which the navigating apparatus is mounted has run by a predetermined interval of distance, and

space="preserve" listing-type="equation">α

(t)=w.sub.i ×

δ

+(1-w.sub.i)×

α

(t-1), 0<

w.sub.i <

1,

α

(t);

the direction of line of sight,

δ

;

the forwarding direction, δ

=arg|P_p -P_o |,

P_p ;

a previously measured present position before the predetermined period of time has passed or before the mobile body has run by the predetermined interval of distance, and

α

(t-1) the determined line of sight before the predetermined period of time has passed or before the mobile body has run by the predetermined interval of distance.

21. A navigation apparatus comprising:

present position detecting means for detecting a present position of a mobile body and a forwarding direction toward which the mobile body moves at the present position thereof;

initial display parameter value setting means for previously setting the detected present position and display parameters thereinto as initial values;

direction of line of sight determining means for determining a direction of line of sight for a perspective projected image on the basis of at least the detected forwarding direction;

view point position determining means for determining a position of a viewpoint on which the direction of line of sight is based on the basis of at least the information of the forwarding direction detected by the present position detecting means;

road map data storing means for storing at least a road map data expressed with a two-dimensional X-Y plane as a reference;

coordinate transforming means for executing a coordinate transformation of the road map data stored in said road map data storing means on the basis of at least the determined direction of line of sight and the determined viewpoint position into a bird'"'"'s eye view which is the perspectively projected image of the road map data so as to generate the bird'"'"'s eye view; and

display means for receiving the display data of the bird'"'"'s eye view and for displaying the bird'"'"'s eye view on its image screen, wherein said initial display parameter setting means sets an initial referring point (B(Xb, Yb, O)), an initial viewpoint position (Xo, Yo, Zo), an initial viewpoint position height h, and a degression angle (θ

) of the viewpoint position E and said direction of line of sight determining means determines the line of sight so that the present position of the mobile body is placed on a straight line connecting a position (E(Xo, Yo, O)) of the viewpoint on the X-Y plane of the road map data to the initial referring point (B), the present position of the mobile body is placed on a display reference point (Q) placed on the straight line between the viewpoint position (E(Xo, Yo, O)) and the initial referring point (B), and determines the line of sight on the basis of the following equation;

space="preserve" listing-type="equation">α

(t)=wiδ

+(1-wi)α

(t-1),

wherein 0<

wi<

1, δ

denotes the forwarding direction of the mobile body at the present position and δ

=arg|P_p -P_o |, wherein P_p denotes a previously detected present position before a present period of time has passed or before the mobile body has run by a predetermined interval of distance, and α

(t-1) denotes a predetermined line of sight before the predetermined period of time has passed or before the mobile body has run by the predetermined interval of distance.

22. A navigating apparatus comprising:

a) present position detecting means for detecting a present position of a mobile body and a forwarding direction toward which the mobile body moves at the present position thereof;

b) initial display parameter value setting means for previously setting the detected present position and display parameters thereinto as initial values;

c) direction of line of sight determining means for determining a direction of line of sight for a perspectively projected image on the basis of at least the detected forwarding direction;

d) view point position determining means for determining a position of a view point on which the direction of line of sight is based on the basis of at least the information of the forwarding direction detected by the present position detecting means;

e) road map data storing means for storing at least a road map data expressed with a two-dimensional X-Y plane as a reference;

f) coordinate transforming means for executing a coordinate transformation of the road map data stored in said road map data storing means on the basis of at least the determined direction of line of sight and the determined view point position into a bird'"'"'s eye view which is the perspectively projected image of the read road map data so as to generate the bird'"'"'s eye view; and

g) display means for receiving the display data of the bird'"'"'s eye view and for displaying the bird'"'"'s eye view on its image screen, which further comprises;

recommended route storing means for storing a recommended route data, wherein said direction of line of sight determining means determines the direction of line of sight on the basis of the forwarding direction and recommended route data stored in said recommended route data storing means and wherein said coordinate transforming means executes the coordinate transformation on the basis of the determined direction of line of sight, the determined view point position, and the recommended route data; and

wherein said direction of line of sight determining means determines the direction of line of sight α

(t) as follows;

α

(t)=β

_r =arg|N-P_o |, wherein N (X_n, Y_n, Z_n) denotes a recommended position (X_n, Y_n, Z_n) corresponding to a recommended route position on a recommended route to be traveled which is remote from the present position P_o by a road distance R and β

_r denotes a direction of the recommended position N viewed from the present position P_o.

23. A navigating apparatus as claimed in claim 22, wherein ##EQU20## wherein θ

denotes an angle of depression of the line of sight, h denotes a height of the line of sight, F denotes a tangent of an angle of field of view in a lateral direction, u denotes an aspect ratio of the display image screen, D_c denotes a distance from a position corresponding to a lowest end of the display image screen to a display reference point Q, and ω

denotes a curve angle of a traffic intersection having a steepest corner.

24. A navigating apparatus comprising:

a) present position detecting means for detecting a present position of a mobile body and a forwarding direction toward which the mobile body moves at the present position thereof;

b) initial display parameter value setting means for previously setting the detected present position and display parameters thereinto as initial values;

c) direction of line of sight determining means for determining a direction of line of sight for a perspectively projected image on the basis of at least the detected forwarding direction;

d) view point position determining means for determining a position of a view point on which the direction of line of sight is based on the basis of at least the information of the forwarding direction detected by the present position detecting means;

e) road map data storing means for storing at least a road map data expressed with a two-dimensional X-Y plane as a reference;

f) coordinate transforming means for executing a coordinate transformation of the road map data stored in said road map data storing means on the basis of at least the determined direction of line of sight and the determined view point position into a bird'"'"'s eye view which is the perspectively projected image of the read road map data so as to generate the bird'"'"'s eye view; and

g) display means for receiving the display data of the bird'"'"'s eye view and for displaying the bird'"'"'s eye view on its image screen, which further comprises;

recommended route storing means for storing a recommended route data, wherein said direction of line of sight determining means determines the direction of line of sight on the basis of the forwarding direction and recommended route data stored in said recommended route data storing means and wherein said coordinate transforming means executes the coordinate transformation on the basis of the determined direction of line of sight, the determined view point position, and the recommended route data; and

wherein said direction of line of sight determining means determines the direction of line of sight α

(t) as follows;

space="preserve" listing-type="equation">α

(t)=wδ

+(1-w)α

(t-1),

wherein δ

=β

_r, 0<

w<

1, β

_r =arg|N-P_o | and denotes a direction of a recommended position which corresponds to a recommended route position viewed from the present position P_o.

25. A navigating apparatus comprising:

a) present position detecting means for detecting a present position of a mobile body and a forwarding direction toward which the mobile body moves at the present position thereof;

b) initial display parameter value setting means for previously setting the detected present position and display parameters thereinto as initial values;

c) direction of line of sight determining means for determining a direction of line of sight for a perspectively projected image on the basis of at least the detected forwarding direction;

d) view point position determining means for determining a position of a view point on which the direction of line of sight is based on the basis of at least the information of the forwarding direction detected by the present position detecting means;

e) road map data storing means for storing at least a road map data expressed with a two-dimensional X-Y plane as a reference;

f) coordinate transforming means for executing a coordinate transformation of the road map data stored in said road map data storing means on the basis of at least the determined direction of line of sight and the determined view point position into a bird'"'"'s eye view which is the perspectively projected image of the read road map data so as to generate the bird'"'"'s eye view; and

g) display means for receiving the display data of the bird'"'"'s eye view and for displaying the bird'"'"'s eye view on its image screen, which further comprises;

recommended route storing means for storing a recommended route data, wherein said direction of line of sight determining means determines the direction of line of sight on the basis of the forwarding direction and recommended route data stored in said recommended route data storing means and wherein said coordinate transforming means executes the coordinate transformation on the basis of the determined direction of line of sight, the determined view point position, and the recommended route data; and

wherein the direction of line of sight determining means determines the direction of line of sight α

(t) as follows;

space="preserve" listing-type="equation">α

(t)=wi×

arg|N.sub.1 -P.sub.o |+w2×

arg|N.sub.2 -P.sub.o |+ - - - +wi×

arg|N.sub.i -P.sub.o |,

wherein w1+w2+ - - - +wi=1 and N₁ through N_i denote a plurality of recommended positions of 1 through i which correspond to recommended route positions, and P_o denotes the present position of the mobile body.

26. A navigating apparatus comprising:

a) present position detecting means for detecting a present position of a mobile body and a forwarding direction toward which the mobile body moves at the present position thereof;

b) initial display parameter value setting means for previously setting the detected present position and display parameters thereinto as initial values;

c) direction of line of sight determining means for determining a direction of line of sight for a perspectively projected image on the basis of at least the detected forwarding direction;

d) view point position determining means for determining a position of a view point on which the direction of line of sight is based on the basis of at least the information of the forwarding direction detected by the present position detecting means;

e) road map data storing means for storing at least a road map data expressed with a two-dimensional X-Y plane as a reference;

f) coordinate transforming means for executing a coordinate transformation of the road map data stored in said road map data storing means on the basis of at least the determined direction of line of sight and the determined view point position into a bird'"'"'s eye view which is the perspectively projected image of the read road map data so as to generate the bird'"'"'s eye view; and

g) display means for receiving the display data of the bird'"'"'s eye view and for displaying the bird'"'"'s eye view on its image screen, which further comprises;

recommended route storing means for storing a recommended route data, wherein said direction of line of sight determining means determines the direction of line of sight on the basis of the forwarding direction and recommended route data stored in said recommended route data storing means and wherein said coordinate transforming means executes the coordinate transformation on the basis of the determined direction of line of sight, the determined view point position, and the recommended route data; and

wherein the direction of line of sight determining means determines the direction of line of sight α

(t) as follows;

space="preserve" listing-type="equation">α

(t)=w1×

arg|N.sub.1 -P.sub.o |+w2×

arg|N.sub.2 -P.sub.o |+ - - - +wi×

arg|N.sub.i -P.sub.o |+u×

δ

+v1×

arg|P.sub.o -L.sub.1 |+v2×

arg|P.sub.o -L.sub.2 |+ - - - +v.sub.j ×

arg|P.sub.o -L.sub.j |,

wherein w1+w2+ - - - +w_i +w_i +u+v1+v2+ - - - +V_j =1, N₁ through N_i denote a plurality of recommended positions of 1 through i which correspond to recommended route positions, P_o denotes the present position of the mobile body, L₁ through L_j denotes a plurality of past position information of the mobile body calculated before a predetermined period of time has passed by an j-th number of times or before predetermined interval of distance through which the mobile body has run by the j-th number of times, u denotes an aspect ratio of the display image screen, and δ

=β

_r =arg|N_i -P_o.

27. A navigating apparatus comprising:

a) present position detecting means for detecting a present position of a mobile body and a forwarding direction toward which the mobile body moves at the present position thereof;

b) initial display parameter value setting means for previously setting the detected present position and display parameters thereinto as initial values;

c) direction of line of sight determining means for determining a direction of line of sight for a perspectively projected image on the basis of at least the detected forwarding direction;

d) view point position determining means for determining a position of a view point on which the direction of line of sight is based on the basis of at least the information of the forwarding direction detected by the present position detecting means;

e) road map data storing means for storing at least a road map data expressed with a two-dimensional X-Y plane as a reference;

f) coordinate transforming means for executing a coordinate transformation of the road map data stored in said road map data storing means on the basis of at least the determined direction of line of sight and the determined view point position into a bird'"'"'s eye view which is the perspectively projected image of the read road map data so as to generate the bird'"'"'s eye view; and

g) display means for receiving the display data of the bird'"'"'s eye view and for displaying the bird'"'"'s eye view on its image screen, which further comprises;

recommended route storing means for storing a recommended route data, wherein said direction of line of sight determining means determines the direction of line of sight on the basis of the forwarding direction and recommended route data stored in said recommended route data storing means and wherein said coordinate transforming means executes the coordinate transformation on the basis of the determined direction of line of sight, the determined view point position, and the recommended route data; and

wherein said coordinate transforming means executes the coordinate transformation of the road map data to generate the bird'"'"'s eye view, with a reference point (Q) of the bird'"'"'s eye view set to be equal to a recommended position N (X_n, Y_n, O) on a recommended route which is remote from the present position P_o (X_o, Y_o, Z_o) by a road distance R, wherein

space="preserve" listing-type="equation">x=X.sub.n +L·

cos α

(t),

space="preserve" listing-type="equation">y=Y.sub.n +L·

sin α

(t),

wherein x and y denote coordinate values in x axis and y axis in a two-dimensional X-Y plane of a referring point B (x, y, O), L denotes a distance from the reference point position Q (X_n, Y_n, O) to the referring point position B (x, y, O), wherein the point position of the view point E (X_o, Y_o, Z_o) is expressed as;

space="preserve" listing-type="equation">X.sub.o =x-h·

cos α

(t)/tan θ

,

space="preserve" listing-type="equation">Y.sub.o =y-h·

sin α

(t)/tan θ

,

and

space="preserve" listing-type="equation">Z.sub.o =h,

wherein h denotes a height of the view point position E, α

(t) denotes the direction of line of sight at a time of t, and θ

denotes an angle of depression at the view point position E, and wherein the road distance R is defined as follows;

##EQU21## wherein F denotes a tangent of an angle of field of view in a lateral direction, u denotes an aspect ratio of the display image screen, D_c denotes a distance form a position corresponding to a lowest end of the display image screen to the display reference point Q, and wherein such a requirement of R<

D_c that the mobile body is not hidden below the lower end of a view plane G under the equation of R is added so that the value of D_c is defined so as to fall in the following condition;

##EQU22##

28. A navigating apparatus comprising:

a) present position detecting means for detecting a present position of a mobile body and a forwarding direction toward which the mobile body moves at the present position thereof;

b) initial display parameter value setting means for previously setting the detected present position and display parameters thereinto as initial values;

c) direction of line of sight determining means for determining a direction of line of sight for a perspectively projected image on the basis of at least the detected forwarding direction;

d) view point position determining means for determining a position of a view point on which the direction of line of sight is based on the basis of at least the information of the forwarding direction detected by the present position detecting means;

e) road map data storing means for storing at least a road map data expressed with a two-dimensional X-Y plane as a reference;

f) coordinate transforming means for executing a coordinate transformation of the road map data stored in said road map data storing means on the basis of at least the determined direction of line of sight and the determined view point position into a bird'"'"'s eye view which is the perspectively projected image of the read road map data so as to generate the bird'"'"'s eye view; and

g) display means for receiving the display data of the bird'"'"'s eye view and for displaying the bird'"'"'s eye view on its image screen, which further comprises;

display reference point determining means for determining a display reference point on the road map and wherein the road map data storing means stores the road map data, the road map data being divided into a plurality of constant meshes and said coordinate transforming means is constituted by calculation processing means for executing required calculation processings on the basis of required number of meshes fetched from the road map storing means and on the basis of information derived from said display reference point determining means, which further comprises;

display parameter inputting means for receiving the display parameters from said initial display parameter value setting means and for setting and varying arbitrarily the values of the display parameters, wherein said calculation processing means calculates the required calculation processings on the basis of the required number of meshes fetched from said road map storing means, the information derived from said display reference point determining means, and display parameters input from said display parameter input means, and wherein said display means displays the road map data in the bird'"'"'s eye view on its display image screen as results of calculations executed by said calculation processing means;

wherein said road map data storing means comprises an external memory block and wherein said calculation processing means includes;

a view point position/a road map region to be displayed determining means for determining the view point position and a road map region to be displayed on the basis of he information derived from said display reference point determining means;

data access means for providing data access to the road map data stored in the external memory block;

internal data storing means, having a predetermined memory capacity, for storing data accessed by said data access means therein;

graphic data coordinate transforming means for executing the coordinate transformation the road map data stored in said internal data storing means on the basis of the information determined by the view point position/the road map region to be displayed determining means so as to generate the bird'"'"'s eye view; and

image data outputting means for outputting the image data of the bird'"'"'s eye view generated by said graphic data coordinate transforming means; and

wherein a value of integer times as long as a length of a side of each mesh is made equal to a diameter (2 R) of a circumscribed circle covering the road map region to be displayed.

29. A navigating apparatus as claimed in claim 28, wherein said calculation processing means executes the road map displays in a stepwise manner according to a degree of details previously set on the road map data and a distance from the view point to the road map data.

30. A navigating apparatus as claimed in claim 28, wherein a value of the integer multiple (N) is previously set according to the memory capacity of said internal data storing means.

31. A navigating apparatus as claimed in claim 30, wherein said calculation processing means determines each of the meshes in the external memory block which corresponds to the determined region to be displayed by the view point position/the road map region to be displayed on the basis of a center coordinate (RX, RY) of the circumscribed circle, when said calculation processing means updates the displayed image of the display means in accordance with a movement of the display reference point.

32. A navigating apparatus as claimed in claim 28, wherein said calculating processing means executes the calculation processings so that the road map data in the bird'"'"'s eye view on a limited range of the display image screen of said display means and an information other than the road map data is displayed on a range outside the road map display range.

33. A navigating apparatus as claimed in claim 32, wherein said calculation processing means sets a boundary line on the display image screen of the display image as a pseudo horizon above which a present clock is displayed.

34. A navigating apparatus as claimed in claim 32, wherein said calculation processing means sets a boundary line on the display image screen of the display image as a pseudo horizon above which a destination at which the mobile body is finally to arrive is displayed.