U.S. patent application number 09/955749 was filed with the patent office on 2002-04-25 for navigation system and method of displaying quasi-three-dimensional map information.
Invention is credited to Nakamura, Hikaru.
Application Number | 20020049532 09/955749 |
Document ID | / |
Family ID | 18776487 |
Filed Date | 2002-04-25 |
United States Patent
Application |
20020049532 |
Kind Code |
A1 |
Nakamura, Hikaru |
April 25, 2002 |
Navigation system and method of displaying quasi-three-dimensional
map information
Abstract
In displaying map information, a map drawing unit generates map
drawing data with an equal scale factor and a coordinate conversion
unit does not execute coordinate conversion to an area a including
the screen center and the lower area thereof, and writes in a VRAM
the map drawing data that maintains the scale factor as it is.
Further, the coordinate conversion unit writes in the VRAM map
drawing data reduced with a specific reduction scale factor only in
the horizontal direction as to each of the areas on the left and
right of the area a; map drawing data reduced with a specific
reduction scale factor only in the vertical direction as to the
area directly above the area a; and map drawing data reduced with
specific reduction scale factors both in the horizontal and
vertical directions as to each of the areas located obliquely left
above and obliquely right above the area a. Thus, the navigation
system of the invention lightens the burden of calculation
processing, displays detailed information of the most important
area surrounding the vehicle position, and provides a seemingly
bird's-eye view display, namely, quasi-three-dimensional map
information, that gives a user an extensive view.
Inventors: |
Nakamura, Hikaru; (Tokyo,
JP) |
Correspondence
Address: |
BRINKS HOFER GILSON & LIONE
P.O. BOX 10395
CHICAGO
IL
60610
US
|
Family ID: |
18776487 |
Appl. No.: |
09/955749 |
Filed: |
September 19, 2001 |
Current U.S.
Class: |
701/455 ;
340/995.1 |
Current CPC
Class: |
G01C 21/367
20130101 |
Class at
Publication: |
701/208 ;
701/212; 340/995 |
International
Class: |
G01C 021/32 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 27, 2000 |
JP |
2000-293752 |
Claims
What is claimed is:
1. A navigation system comprising: a map data storage medium that
stores map data having a uniform reduction scale factor for drawing
map information; a drawing memory corresponding to a display
screen; and a map drawing unit that reads map data from the map
data storage medium, draws map information in the drawing memory
with regard to a first area including a screen center and a lower
part thereunder, and draws map information in the drawing memory
with a smaller reduction scale factor than that in the first area,
with regard to a second area surrounding the first area.
2. A navigation system as claimed in claim 1, wherein: the first
area is rectangular; and the map drawing unit draws map information
in the drawing memory with a reduction scale factor only in the
horizontal direction with regard to areas on both sides relative to
the first area, with a reduction scale factor only in the vertical
direction with regard to an area above the first area, and with
reduction scale factors in both the vertical and horizontal
directions with regard to areas obliquely above the first area.
3. A navigation system as claimed in claim 2, wherein the reduction
scale factor for the areas on both sides relative to the first area
is different from the reduction scale factor for the area above the
first area.
4. A navigation system as claimed in claim 2, wherein the reduction
scale factor for the areas on both sides relative to the first area
is equal to the reduction scale factor for the area above the first
area.
5. A navigation system as claimed in claim 2, wherein the reduction
scale factor for the area to the right of the first area is
different from the reduction scale factor for the area to the left
of the first area.
6. A navigation system as claimed in claim 2, wherein the map
drawing unit divides the areas on both sides of the first area into
plural areas, and with regard to the divided areas, sets the
reduction scale factors gradually smaller as the divided areas
become more distant from the first area.
7. A navigation system as claimed in claim 2, wherein the map
drawing unit divides the area above the first area into plural
areas, and with regard to the divided areas, sets the reduction
scale factors gradually smaller as the divided areas become more
distant from the first area.
8. A navigation system as claimed in claim 2, wherein the map
drawing unit: divides the areas on both sides of the first area
into plural areas, and with regard to the divided areas, sets the
reduction scale factors gradually smaller as the divided areas
become more distant from the first area; divides the area above the
first area into plural areas, and with regard to the divided areas,
sets the reduction scale factors gradually smaller as the divided
areas become more distant from the first area; and with regard to
the areas obliquely above the first area, draws map information in
the drawing memory with gradually decreasing scale factors in both
the vertical and horizontal directions as the divided areas become
more distant from the first area.
9. A navigation system as claimed in claim 2, wherein the map
drawing unit draws map information in the drawing memory with a
head-up display that includes a vehicle position in the first area
and sets the travel direction of the vehicle upward on the image
screen.
10. A navigation system as claimed in claim 2, wherein the map
drawing unit draws the map information in the drawing memory with a
north-up display that includes a vehicle position in the first area
and sets the northern direction upward on the image screen.
11. A navigation system as claimed in claim 2, wherein the first
area is drawn with an equal scale factor that is set by a user.
12. A method of displaying quasi-three-dimensional map information,
comprising: reading map data corresponding to an area wider than an
area required for displaying the map information with an equal
scale factor; drawing the map information, as to a horizontal
reduction scale factor for a display screen, by setting a reduction
scale factor for a first area to a first reference value, setting a
reduction scale factor for areas on the sides of the first area to
a first value smaller than the first reference value, and as to a
vertical reduction scale factor for the display screen, by setting
a reduction scale factor for a lower area to a second reference
value, setting a reduction scale factor for an area above the lower
area to a second value smaller than the second reference value; and
displaying the drawn map information on the display screen.
13. A method of displaying quasi-three-dimensional map information,
as claimed in claim 12, wherein the first value and the second
value are set to the same value.
14. A method of displaying quasi-three-dimensional map information,
as claimed in claim 12, wherein the first value and the second
value are set to different values.
15. A method of displaying quasi-three-dimensional map information,
as claimed in claim 12, the method further comprising: dividing the
areas on the sides of the first area into plural areas, and with
regard to the divided areas, setting the horizontal reduction scale
factors gradually smaller as the divided areas become more distant
from the first area; and dividing the area above the lower area
into plural areas, and with regard to the divided areas, setting
the vertical reduction scale factors gradually smaller as the
divided areas become more distant from the lower area.
16. A method of displaying quasi-three-dimensional map information,
as claimed in claim 12, wherein the first area and the lower area
are drawn with equal scale factors that are set by a user.
17. A method of displaying map information, comprising: reading map
data for an area to be displayed, where the map data are defined
with respect to an X, Y coordinate system; identifying a first area
within the area to be displayed; drawing map information based on
the map data, where map information for the first area is drawn in
accordance with a first scale factor in at least one of the
coordinate directions, and map information for at least part of a
second area within the area to be displayed that is outside the
first area is drawn with a scale factor smaller than the first
scale factor in the at least one coordinate direction; and
displaying the drawn map information for the area to be
displayed.
18. A method as claimed in claim 17, wherein the first scale factor
is set by a user.
19. A method as claimed in claim 17, wherein the drawn map
information is displayed in one of a head-up display, in which a
vehicle position is included in the first area and a travel
direction of the vehicle is upward, and a north-up display, in
which a vehicle position is included in the first area and the
northern direction in the displayed map information is upward.
20. A method as claimed in claim 17, wherein the first area is
substantially centrally located with respect to at least one
coordinate direction within the area to be displayed.
21. A method as claimed in claim 20, wherein the first area is
substantially centrally located with respect to the X coordinate
direction.
22. A method as claimed in claim 21, wherein the first area is
located in the lower part of the area to be displayed.
23. A method as claimed in claim 17, wherein the second area is
drawn, with respect to a first coordinate direction, with one or
more scale factors smaller than a scale factor for the first area,
and the second area is drawn, with respect to a second coordinate
direction, with one or more scale factors smaller than a scale
factor for the first area.
24. A method as claimed in claim 23, wherein the scale factors in
the second area for each coordinate direction are set to be
gradually smaller for areas within the second area that become more
distant from the first area.
25. A method as claimed in claim 17, wherein the first scale factor
is set to one.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a navigation system that
displays map information and a method of displaying map information
in a quasi-three-dimensional manner.
[0003] 2. Related Art
[0004] In general, a vehicle navigation system detects a present
position of the vehicle, reads out map data corresponding to an
area surrounding the present vehicle position from an information
storage medium such as a CD, DVD, etc., and displays the map
information surrounding the vehicle position on a display screen.
Further, the system displays a vehicle position mark that indicates
the present position of the vehicle at a specific position on the
screen, and scrolls the map information of the area surrounding the
vehicle putting the vehicle position mark in the center, in
accordance with the travel of the vehicle, whereby a driver is able
to comprehend the map information surrounding the vehicle position
at any time.
[0005] Further, a recent navigation system sets an observing point
with a specific position high above the vehicle position, and uses
a known technique that displays the map information along the
vehicle travel direction from a bird's-eye view. Thus, by providing
a bird's-eye view display, the system is able to present seemingly
three-dimensional map information that gives a user an extensive
view. Accordingly, the system allows the user to receive more
information than presenting the map information on a plane
(two-dimensionally), and it becomes easier for the user to confirm
the travel direction of the vehicle, which is advantageous.
[0006] In the bird's-eye view display, the map information near the
lower part of the display screen is expanded to a maximum degree,
and the most important map information surrounding the vehicle
position, which is placed at or slightly under the screen center,
reduced accordingly and becomes difficult to see, which is a
problem.
[0007] Further, a precise execution of the bird's-eye view display
will require calculations of the trigonometric function using the
angle along the visual field direction. Because the calculations
need to be executed for each display pixel, a display corresponding
to the vehicle position that varies every moment will impose a very
heavy burden on the calculations, which is also a problem. Also,
the display positions of various mark images and character
information, etc., which are superimposed on the map data, need to
be calculated before executing the bird's-eye view display, which
also requires the calculations of the trigonometric function,
imposing a still heavier burden.
[0008] The present invention has been made in view of these
circumstances, and it is an object of the invention to provide a
navigation system that lightens the burden of the calculation
processing and also achieves a display of the detailed information
of the most important area surrounding the vehicle position.
SUMMARY OF THE INVENTION
[0009] In order to accomplish the foregoing object, the navigation
system of the present invention stores in a map data storage means
map data having a uniform reduction scale factor, necessary for
drawing map information. On the basis of the map data read from the
map data storage means, a map drawing means draws the map
information in a drawing memory with regard to a first area
including a screen center, and, with regard to a second area
surrounding the first area, draws the map information in the
drawing memory with a smaller reduction scale factor than that in
the first area.
[0010] Generally, the navigation system lays out the vehicle
position on the center area of the display screen or slightly
lower. Therefore, by drawing the map information of the second area
surrounding the first area with a smaller reduction scale factor
than that for the first area including the screen center, the
navigation system of the invention makes it possible to display
detailed map information in the most important area surrounding the
vehicle position. In the second area remote from the vehicle
position, the system makes it possible to display map information
including more remote information.
[0011] Since the system draws the map information corresponding to
the second area by very simple calculations that reduce the map
information on the basis of the specific reduction scale factors,
the system does not require complicated calculation processing
using the trigonometric function as in case of the bird's-eye view
display, and thereby reduces the burden of the processing to a
great extent. Further, the system uses map data having a uniform
reduction scale factor, which is the same as the map data that a
general navigation system uses. Therefore, it does not need to
create new map data for drawing the map information, and is able to
use the existing map data as it is, which is advantageous.
[0012] It is preferable that the first area is rectangular,
including the screen center and the lower area thereof. The map
drawing means draws the map information in the drawing memory with
a reduction scale factor only in the horizontal direction as to
areas on both sides of the first area, with a reduction scale
factor only in the vertical direction as to an area directly above
the first area, and with reduction scale factors in both the
vertical and horizontal directions as to the slant upper areas
relative to the first area. Since the system reduces the map
information in this manner, it is able to display
quasi-three-dimensional map information having a feeling of depth,
resembling the bird's-eye view display.
[0013] According to the method of displaying
quasi-three-dimensional map information of the present invention,
map data corresponding to an area wider than an area required for
displaying the map information with an equal scale factor is read.
Next, the map information is drawn, setting a horizontal reduction
scale factor for areas on both sides of a center area to a first
value smaller than a first reference value, while bringing the
horizontal reduction scale factor for the center area into
correspondence with the first reference value and bringing a
vertical reduction scale factor for an area lower than the center
area into correspondence with a second reference value, and setting
the vertical reduction scale factor for an area above the lower
area to a second value smaller than the second reference value.
Finally, the drawn map information drawn is displayed on the
display screen.
[0014] Thus, with regard to the specific area lower than the center
area of the display screen, since the map information can be drawn
with the equal scale factor, setting the vehicle position in this
specific area achieves a display of detailed map information in the
area surrounding the vehicle position. In setting the area where
the map information is drawn with the equal scale factor in the
center, as to the areas on both sides of this area, the map data
are reduced in the horizontal direction. As to the area above this
center area, the map data are reduced in the vertical direction. As
to the areas located obliquely above this center area, the map data
are reduced in both the horizontal and vertical directions.
Therefore, map information that allows a user to view remote
places, that is, the quasi-three-dimensional map information, can
be expressed through simple calculation processing.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] Preferred embodiments of the present invention will be
described in detail based on the followings, wherein:
[0016] FIG. 1 is a block diagram illustrating the general
construction of a navigation system relating to one embodiment;
[0017] FIG. 2 is a chart explaining an aspect of coordinate
conversion processing by a coordinate conversion unit;
[0018] FIG. 3 is a chart explaining an aspect of coordinate
conversion processing by the coordinate conversion unit;
[0019] FIG. 4 is a chart explaining an aspect of coordinate
conversion processing by the coordinate conversion unit;
[0020] FIG. 5 is a chart explaining the reduction scale of the map
drawing data that are written in a VRAM after a specific coordinate
conversion processing;
[0021] FIG. 6 is a flow chart illustrating an operating procedure
while displaying map information;
[0022] FIG. 7 is a chart illustrating a display example of map
information;
[0023] FIG. 8 is a chart illustrating a display example of map
information by a conventional navigation system;
[0024] FIG. 9 is a chart explaining the contents of the coordinate
conversion processing in a modified example, in which the division
number of the peripheral area surrounding the screen center is
increased; and
[0025] FIG. 10 is a chart explaining the reduction scale of the map
drawing data that are written in a VRAM after a specific coordinate
conversion processing, in the modified example shown in FIG. 9.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0026] One embodiment of a navigation system to which the present
invention is applied will be described with reference to the
accompanying drawings.
[0027] FIG. 1 is a block diagram illustrating the general
construction of the navigation system relating to one embodiment.
The navigation system includes a navigation controller 1, a DVD 2,
a disk reader 3, a remote control unit 4, a vehicle position
detection unit 5, and a display unit 6.
[0028] The navigation controller 1 controls the overall operation
of the navigation system. Generally, the navigation controller I
comprises a CPU, ROM, RAM, etc., and executes a specified program
stored in the ROM or the like to achieve the function thereof. The
detailed construction of the navigation controller 1 will be
described later. Here, the program to achieve the function of the
navigation controller 1 may be stored in the DVD 2, so that the
program can be read out each time the navigation system is
started.
[0029] The DVD 2 is an information storage medium that houses map
data necessary for displaying maps, searching routes, etc.
Specifically, the DVD 2 stores the map data of a rectangular sheet
drawing divided by predetermined longitude and latitude as the
unit, and the map data of each sheet drawing can be specified and
read out by designating the number of the sheet drawing.
[0030] Further, the map data of each sheet drawing contains (1) a
"drawing unit" composed of various data for displaying map
information, (2) a "road unit" composed of various data for
processing map matching, route searching, route guiding, etc., and
(3) an "intersection unit" composed of various data for presenting
detailed information of intersections, and so forth.
[0031] The map data contained in the drawing unit generally are
made up with an equal scale factor, that is, the vertical and
horizontal reduction scale factors are set to one and the same
value. This embodiment applies a specified coordinate conversion
processing (detailed later) to the map data having the same scale
factor, and thereby draws the map information of the peripheral
area with a further reduced scale factor when compared to that in
drawing the area including the screen center.
[0032] The disk reader 3 has one or more sheets of the DVD 2 loaded
and reads out map data from the DVD 2 under the control of the
navigation controller 1. Here, the disk loaded may not necessarily
be a DVD; it may be a CD. The disk reader 3 also may be configured
so that a DVD and a CD can selectively be loaded thereon.
[0033] The remote control unit 4 is furnished with various
operating keys, such as a vertically/horizontally moving cursor key
and keys for setting items at the cursor positions on the display
screen, etc., and it transmits an infrared signal according to a
key operation toward the navigation controller 1. For example, the
remote control unit 4 is able to set the reduction scale factor of
the map information presented on the screen of the display unit
6.
[0034] The vehicle position detection unit 5 is furnished with a
GPS receiver, an azimuth sensor, a distance sensor, etc., and
detects a vehicle position (longitude, latitude) at a specific
timing and outputs the detected result.
[0035] The display unit 6 displays various images of the map
information and the like of the area surrounding the vehicle
position, on the basis of the drawing data provided from the
navigation controller 1.
[0036] Next, the detailed construction of the navigation controller
1 will be described. The navigation controller I shown in FIG. 1
includes a map buffer 10, a map reading control unit 12, a map
drawing unit 14, a coordinate conversion unit 17, a VRAM 18, an
image synthesizing unit 20, a vehicle-position calculating unit 30,
a route-search processing unit 32, a guidance route memory 34, a
guidance-route drawing unit 36, a mark-image drawing unit 38, and
an input processing unit 40.
[0037] The map buffer 10 temporarily stores the map data read out
from the DVD 2 by the disk reader 3. The map reading control unit
12 outputs to the disk reader 3 a readout request for the map data
in a specific area, in correspondence with the vehicle position
calculated by the vehicle-position calculating unit 30 and the
request from the input processing unit 40 and so forth.
[0038] The map drawing unit 14 generates map drawing data required
for the display of map information on the basis of the map data
stored in the map buffer 10, and includes a geographical drawing
unit 15 and an additional information drawing unit 16. The
geographical drawing unit 15 generates geographical drawing data
for illustrating geographical features such as roads, rivers and
the like, appearing on the map. The additional information drawing
unit 16 generates additional information drawing data for
displaying various kinds of additional information on the map, for
example, marks indicating various kinds of facilities such as
public facilities and convenience stores, character strings
indicating the names of the facilities and the place names thereof,
and so forth.
[0039] The coordinate conversion unit 17 applies a specified
coordinate conversion processing to the map drawing data generated
by the map drawing unit 14, generates map drawing data that
artificially expresses the three-dimensional map information, and
writes the data in the VRAM 18. Specifically, the coordinate
conversion unit 17 executes the specified coordinate conversion
processing on the geographical drawing data generated by the
geographical drawing unit 15, and writes in the VRAM 18
geographical drawing data after the coordinate conversion
processing. Further, the coordinate conversion unit 17 executes a
specified coordinate conversion processing on the drawing position
of the additional information drawing data generated by the
additional information drawing unit 16, and overwrites the result
in the VRAM 18. The coordinate conversion processing executed by
the coordinate conversion unit 17 will be detailed later.
[0040] The VRAM 18 temporarily stores the map drawing data after
the specified coordinate conversion processing executed by the
coordinate conversion unit 17 and guidance route drawing data
generated by the guidance-route drawing unit 36.
[0041] The image synthesizing unit 20 superimposes the drawing data
provided from the mark-image drawing unit 38 on the map drawing
data read from the VRAM 18 in correspondence with the vehicle
position to thereby synthesize the images, and outputs the
synthesized drawing data to the display unit 6.
[0042] The vehicle-position calculating unit 30 calculates the
vehicle position and azimuth on the basis of the data provided from
the vehicle position detection unit 5. If the calculated vehicle
position does not exist on a road in the map data, the
vehicle-position calculating unit 30 will execute the map matching
processing to correct the vehicle position.
[0043] The route-search processing unit 32 searches for a travel
route that connects the start point and the destination point
designated by the user under a specific condition. As the guidance
route, it sets a travel route that minimizes the cost under various
kinds of conditions, for example, under the condition of the
shortest distance and/or the shortest time. The guidance route
memory 34 stores the data representing the contents of the guidance
route (guidance route data) set by the route-search processing unit
32.
[0044] The guidance-route drawing unit 36 selects data for the map
information written in the VRAM 18 at that moment out of the
guidance route data that are set by the route-search processing
unit 32 and stored by the guidance route memory 34, and generates
the guidance route drawing data to superimpose the guidance route
on the map information for display.
[0045] The mark-image drawing unit 38 generates drawing data for
displaying a specific vehicle position mark at the vehicle position
after the map matching processing, and for displaying a specific
cursor mark at the cursor position.
[0046] The input processing unit 40 provides commands to the
relevant units inside the navigation controller 1 for executing the
operations corresponding to various operational instructions
transmitted from the remote control unit 4.
[0047] The map buffer 10 corresponds to a map data storage means,
the map drawing unit 14 and coordinate conversion unit 17
correspond to a map drawing means, and the VRAM 18 corresponds to a
drawing memory.
[0048] The navigation system in this embodiment possesses the
configuration as described above. Next, the contents of the
coordinate conversion processing performed by the coordinate
conversion unit 17 will be described in detail.
[0049] FIG. 2 through FIG. 4 explain the coordinate conversion
processing performed by the coordinate conversion unit 17. First,
the geographical drawing unit 15 in the map drawing unit 14
generates the geographical drawing data. As a premise, the
geographical drawing data are drawn in a specific area wider than a
rectangular display area P corresponding to the display screen of
the display unit 6.
[0050] The X-axis and the Y-axis are set in the geographical
drawing data. Further, the lengths of each side of the display area
P on the display unit 6 are normalized, and on the XY coordinate
system, the left lower vertex of the display area P is brought in
correspondence with the coordinate position (0, 0), and the right
upper vertex is brought in correspondence with the coordinate
position (1, 1). In general, the X-axis and the Y-axis are
expressed to intersect at the position (X, Y)=(0, 0). However, in
FIG. 2 through FIG. 4, the intersection of the X-axis and the
Y-axis are displaced to clarify explanation.
[0051] As shown in FIG. 3, (1) the area 0.ltoreq.Y<1/2 is
defined as "area 1", and (2) the area 1/2.ltoreq.Y.ltoreq.1 is
defined as "area 2". As shown in FIG. 3, the geographical drawing
data in the area 2 are converted by the coordinate conversion
processing along the Y-axis direction with a specific reduction
scale factor .alpha. (0<.alpha.<1). Specifically, the
coordinate value (X', Y') after the coordinate conversion
processing along the Y-axis direction can be attained by the
following expression.
(X', Y')=(X, 1/2+.alpha.(Y-1/2))
[0052] FIG. 3 illustrates the state of the coordinate conversion
processing of the geographical drawing data in setting the
reduction scale factor a to "1/2". For example, the geographical
drawing data of the original coordinate points (0, 1) and (0, 3/2)
are converted into the coordinate points (0, 3/4) and (0, 1),
respectively. With regard to the geographical drawing data of the
other coordinate points, the coordinate conversion processing is
carried out in the same manner. As the result, the geographical
drawing data having the coordinate data in the Y-axis direction
reduced to 1/2 are to be drawn within the area 2.
[0053] Next, as shown in FIG. 4, (1) the area 0.ltoreq.X.ltoreq.1/3
is defined as "area 3", (2) the area 1/3<X<2/3 is defined as
"area 4", and (3) the area 2/3.ltoreq.X.ltoreq.1 is defined as
"area 5". As shown in FIG. 4, the geographical drawing data in area
3 are converted by the coordinate conversion processing along the
X-axis direction with a specific reduction scale factor
.beta.(0<.beta.<1). In the same manner, the geographical data
in area 5 are converted by the coordinate conversion processing
along the X-axis direction with a specific reduction scale factor
.gamma.(0<.gamma.<1).
[0054] Specifically, the coordinate value (X", Y") after the
coordinate conversion processing along the X-axis direction can be
obtained by the following expressions.
(X", Y")=(.beta.(X-1/3)+1/3, Y) (area 3)
(X", Y")=(2/3+.gamma.(X-2/3), Y) (area 5)
[0055] FIG. 4 illustrates the state of the coordinate conversion
processing of the geographical drawing data in setting the
reduction scale factors .beta. and .gamma. each to "1/2". For
example, in area 3, the geographical drawing data of the original
coordinate points (-1/3, 0) and (0, 0) are converted into the
coordinate points (0, 0) and (1/6, 0), respectively. With regard to
the geographical drawing data of the other coordinate points, the
coordinate conversion processing is carried out in the same manner.
As the result, the geographical drawing data having the coordinate
data in the X-axis direction reduced to 1/2 are to be drawn within
area 3.
[0056] In the same manner, in area 5, the geographical drawing data
of the original coordinate points (1, 0) and (4/3, 0) are converted
into the coordinate points (5/6, 0) and (1, 0), respectively. With
regard to the geographical drawing data of the other coordinate
points, the coordinate conversion processing is carried out in the
same manner. As the result, the geographical drawing data having
the coordinate data in the X-axis direction reduced to 1/2 are to
be drawn within area 5.
[0057] Further, the coordinate conversion unit 17 carries out the
same coordinate conversion processing to thereby acquire the
displayed position of the additional information drawing data drawn
by the additional information drawing unit 16 in the map drawing
unit 14, and superimposes the additional information drawing data
on the geographical drawing data after the coordinate conversion
processing. Therefore, the VRAM 18 is in the state that the
geographical drawing data and the additional information drawing
data are superimposed, that is, the map drawing data are written
in.
[0058] FIG. 5 explains the reduction scale of the map drawing data
that are written in the VRAM 18 after the specific coordinate
conversion processing. The area a shown in the drawing includes the
screen center and the area underneath. The map drawing data in this
area a are drawn with a specific equal scale factor 6 that is
voluntarily set by the user through the remote control unit 4. With
regard to the area d directly above the area a, the data are drawn
with the specific reduction scale factor .alpha. only in the
vertical direction. With regard to the area b and the area c
located on both sides of the area a, the data are drawn with the
specific reduction scale factor .beta. or .gamma. only in the
horizontal direction. With regard to the area e and the area f
located obliquely above the area a, the data are drawn with the
specific reduction scale factors .alpha. (in the vertical
direction), and .beta., .gamma. (in the horizontal direction).
[0059] Here, the area a shown in FIG. 5 corresponds to "a first
area", and the area b through the area f correspond to "a second
area". The equal scale factor 6 set by the user corresponds to "a
first reference value" and "a second reference value", the
reduction scale factors .beta. and .gamma. correspond to "a first
value", and the reduction scale factor .alpha. corresponds to "a
second value".
[0060] Next, the operation of the navigation system in displaying
the map information for the area surrounding the vehicle position
will be described in detail. FIG. 6 is a flow chart illustrating
the operating procedure in displaying the map information.
[0061] The map reading control unit 12 sends a readout request for
the map data in a specific area to the disk reader 3, in
correspondence with the vehicle position calculated by the
vehicle-position calculating unit 30. In response, the disk reader
3 reads the map data for the specific area from the DVD 2, and
stores the data in the map buffer 10 (Step 100). Specifically, Step
100 reads out the map data required for displaying a specific area
wider than the display area P (see FIG. 2) that covers the display
screen of the display unit 6, when the map data are displayed with
the equal scale factor.
[0062] Next, the map drawing unit 14, using the map data read from
the map buffer 10, generates the map drawing data corresponding to
the area surrounding the vehicle position (Step 101). As the map
drawing unit 14 generates the map drawing data, the coordinate
conversion unit 17 executes the specified coordinate conversion
processing to the generated map drawing data (Step 102), and the
VRAM 18 stores the map drawing data after the coordinate conversion
processing (Step 103). The specific operation of the coordinate
conversion processing performed at Step 102 is as explained
above.
[0063] Next, the image synthesizing unit 20 reads the map drawing
data of the area corresponding to one screen from the VRAM 18,
synthesizes the map drawing data read from the VRAM 18 with the
drawing data generated by the mark-image drawing unit 38, and
provides the synthesized image to the display unit 6. As a result,
the map information is displayed on the image screen of the display
unit 6 (Step 104). After that, the system returns to Step 100,
reads map data corresponding to a new vehicle position, and repeats
the same processing thereafter.
[0064] FIG. 7 illustrates an example of the display of map
information by the navigation system of this embodiment. FIG. 8
illustrates an example of the display of map information by a
conventional navigation system, where the vehicle position is set
at the same position as in FIG. 7 for comparison, and the map
information corresponding to the area surrounding the vehicle
position is drawn in a plane (two-dimensionally) as an example.
Further, in FIG. 8, some parts of the roads lying outside the
display area of the display unit 6 are illustrated by the dotted
lines, in order to clarify the difference from FIG. 7.
[0065] As shown in FIG. 7, in the area a corresponding to the area
surrounding the vehicle position G, the map information is not
reduced in the vertical and horizontal directions. Accordingly, the
map information in the area surrounding the vehicle position can be
displayed in detail in the same manner as in the case of the map
information displayed two-dimensionally in FIG. 8. Map information
reduced in the horizontal direction is displayed in the areas b, c;
map information reduced in the vertical direction is displayed in
the area d; and map information reduced in both the vertical and
horizontal directions is displayed in the areas e, f. Therefore, in
comparison with the map information displayed two-dimensionally as
shown in FIG. 8, the system of this embodiment is able to display
map information including still more remote information. When
viewing the map information as a whole, in comparison with the map
information corresponding to the vehicle position G, the map
information of the surrounding areas is reduced in the display,
thereby presenting artificial three-dimensional map information
having a feeling of depth, which resembles a bird's-eye view
display.
[0066] Thus, the navigation system of this embodiment executes the
specific coordinate conversion processing on the map drawing data,
and thereby draws the map information of the area b through the
area f surrounding the area a with diminished reduction scale
factors, compared to the scale factor for the area a including the
screen center. Therefore, the system is able to display detailed
map information with regard to the most important area a
surrounding the vehicle position, and with regard to the area b
through the area f remote from the vehicle position, it is also
able to display map information including information of still more
remote areas. Further, since the system reduces the map drawing
data through simple calculations using the specific reduction scale
factors .alpha., .beta., .gamma., the system is able to display
artificial three-dimensional map information without a complicated
calculation processing using the trigonometric function as in case
of the bird's-eye view display, which relieves the burden of
calculation processing to a great extent.
[0067] Naturally, the invention is not limited to the
aforementioned embodiment, and various changes and modifications
are possible within the spirit and scope of the invention. For
example, the reduction scale factors .alpha., .beta., .gamma. are
set to 1/2 in this embodiment, however the setting values may be
otherwise. Although the setting values for the reduction scale
factors .alpha., .beta., .gamma. are made uniform in this
embodiment, it is not necessarily required to make the setting
values uniform for the reduction scale factors, and they may be set
to values different from each other.
[0068] Further, in the described embodiment, the peripheral area
surrounding the area a corresponding to the vehicle position (the
area including the screen center) is divided into five areas of the
area b through the area f. However, the system may be designed to
have an increased number of divisions of the peripheral area
surrounding the screen center, and display the map information with
different reduction scale factors in correspondence with each of
the divided areas.
[0069] FIG. 9 explains the coordinate conversion processing in a
modified embodiment, in which the number of divisions of the
peripheral area surrounding the screen center is increased. With
regard to the vertical direction, this modified embodiment sets
three areas, defining (1) the area 0.ltoreq.Y<1/2 as "area 6",
(2) the area 1/2.ltoreq.Y<3/4 as "area 7", and (3) the area
3/4.ltoreq.Y.ltoreq.1 as "area 8". The geographical drawing data in
the area 7 are attained by the coordinate conversion processing
having the reduction scale factor .alpha. set to 1/2 along the
Y-axis direction, and the geographical drawing data in the area 8
are attained by the coordinate conversion processing having the
reduction scale factor .alpha. set to 1/3 along the Y-axis
direction.
[0070] Similarly, with regard to the horizontal direction, this
modified embodiment sets five areas, defining (1) the area
0.ltoreq.X<1/5 as "area 9", (2) the area 1/5.ltoreq.X<2/5 as
"area 10", (3) the area 2/5.ltoreq.X<3/5 as "area 11", (4) the
area 3/5.ltoreq.X<4/5 as "area 12", (5) the area
4/5.ltoreq.X.ltoreq.1 as "area 13". Thus, the geographical drawing
data in the area 10 and the area 12 are attained by the coordinate
conversion processing having the reduction scale factors .beta. and
.gamma. set to 1/2 along the X-axis direction, and the geographical
drawing data in the area 9 and the area 13 are attained by the
coordinate conversion processing having the reduction scale factors
.beta. and .gamma. set to 1/3 along the X-axis direction.
[0071] FIG. 10 explains the reduction scale of the map drawing data
that are written in the VRAM 18 after the specific coordinate
conversion processing in the embodiment example shown in FIG. 9.
The area h shown in FIG. 10 includes the screen center and the area
underneath. The map drawing data in this area h, in the same manner
as for the area a in the foregoing embodiment, are drawn with a
specific equal scale factor 6 that is voluntarily set by the user
through the remote control unit 4.
[0072] With regard to the area i directly above the area h, the
data are drawn with the reduction scale factor 1/2 only in the
vertical direction. With regard to the area j directly above the
area i, the data are drawn with the reduction scale factor 1/3 only
in the vertical direction. With regard to the area k and the area m
on both sides of the area h, the data are drawn with the reduction
scale factor 1/2 only in the horizontal direction. With regard to
the area r on the left of the area k and the area s on the right of
the area m, the data are drawn with the reduction scale factor 1/3
only in the horizontal direction.
[0073] With regard to the area n and the area o located obliquely
above area h, the data are drawn with the reduction scale factor
1/2 in both the vertical and horizontal directions. With regard to
the area p directly above the area n and the area q directly above
the area o, the data are drawn with the reduction scale factor 1/3
in the vertical direction and the reduction scale factor 1/2 in the
horizontal direction. With regard to the area t on the left of the
area n and the area u on the right of the area o, the data are
drawn with the reduction scale factor 1/2 in the vertical direction
and the reduction scale factor 1/3 in the horizontal direction.
With regard to the area v directly above the area t and the area w
directly above the area u, the data are drawn with the reduction
scale factor 1/3 in both the vertical and horizontal
directions.
[0074] Thus, the number of divisions of the peripheral area
surrounding the area h including the screen center is increased in
this example, and the map information is displayed with a gradual
reduction in accordance with the distance from the screen center.
Therefore, this modified embodiment is able to present artificial
three-dimensional map information having a feeling of depth, which
is similar to the bird's-eye view display. Also in this case, since
the coordinate conversions in these areas can be carried out by
simple calculations using the specific reduction scale factors, the
map information can be displayed with an enhanced feeling of
presence without much increase in the amount of calculations.
[0075] The aforementioned embodiments utilize the head-up display
method of map information that shows the travel direction of the
vehicle always upward. However, the invention is not limited to
this, and the north-up display method wherein the map information
is displayed with the northern direction always upward may be
adopted as the display method.
[0076] Further, the aforementioned embodiments are examples wherein
the present invention is applied to a navigation system. However,
the invention is not limited to this, and it may be applied to a
personal computer that executes a specific map information display
program to which the invention is applied, whereby the same
function can be achieved.
[0077] As mentioned above, the navigation system of the invention
is able to display detailed map information of the most important
area surrounding the vehicle position, and with regard to the
second area corresponding to an area remote from the vehicle
position, it is able to display map information including more
remote map information. Further, since the system draws the map
information corresponding to the second area by very simple
calculations that reduce the map information on the basis of the
specific reduction scale factors, it does not require a complicated
calculation processing as in case of the bird's-eye view display,
and thereby reduces the burden of the processing to a great
extent.
[0078] Further, in the method of displaying the
quasi-three-dimensional map information according to the invention,
as to a specific area on the display screen, which is located near
the center in the horizontal direction and in the lower area in the
vertical direction, the map information is drawn with an equal
scale factor. Accordingly, it is possible to display detailed map
information for the area surrounding the vehicle position by
bringing the specific area or the area adjacent to that into
correspondence with the vehicle position.
[0079] Further, with regard to the areas on the sides of the area
wherein the map information is displayed with the equal scale
factor, the map data are drawn with a specific reduction scale
factor in the horizontal direction. With regard to the area above
that area, the map data are drawn with a specific reduction scale
factor in the vertical direction. With regard to the areas
obliquely above that area, the map data are drawn with specific
reduction scale factors in both the vertical and horizontal
directions. Therefore, map information that allows a user to look
out over remote places, that is, the quasi-three-dimensional map
information, can be expressed through simple calculation
processing.
* * * * *