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Description  |
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BACKGROUND OF THE INVENTION
This invention relates to a navigation system for a motor vehicle by which
a route to be taken is displayed by a cathode ray tube CRT screen, a
liquid crystal display, or another display means to navigate the vehicle.
More particularly, this invention relates to such a navigation system
provided with a route determination process by which a desired route can
be determined readily and correctly.
A known navigation system is provided with a screen on which a road map is
displayed. In one type of such a system, a route is determined by
pinpointing and thereby inputting, with a cursor on the screen or by means
of a light pen, desired intersections on the displayed road map
consecutively from a starting point to a destination. In another type of
system, once a starting point and destination are input, a shortest route
from the starting point to the destination is automatically determined,
according to map data previously stored, and indicated on the road map
displayed by the screen.
These types of navigation systems, however, have the following
shortcomings.
During route determination using the former type of navigation system, if
there lies ahead, in the direction designated by the cursor or light pen,
an intersection of roads that form a small angle with regard to each other
or an intersection of a plurality of roads, an undesired route may be
determined. In this case, the user has to return the cursor or other
designating means to the previous location, and again instruct the system
to determine a route.
On the other hand, the latter type of system also falls short, in spite of
its operation facility, because it uses previously stored and not up-dated
program data in determining a route. When unexpected repair work is
underway at the automatically selected route, or when the route the user
preferred is not selected, the user has to correct the route, after
completion of the automatic route determination, in the same laborious
manner as in the former type of navigation system.
SUMMARY OF THE INVENTION
Wherefore, an object of the present invention is to provide a navigation
system for vehicles where and by which a desired route can be readily and
quickly determined.
In order to attain the stated object, the navigation system of the present
invention includes, as shown in FIG. 1, display means M1, map data storage
means M2, display control means M3, intersection numbering means M4,
number indication control means M5, intersection number input means M6,
and route determination means M7.
The display means M1 displays a road map thereon.
The map data storage means M2 stores map data for providing a road map to
be displayed by the display means M1.
The display control means M3 controls the display means M1 to display a
road map according to the map data stored in the map data storage means
M2.
The intersection numbering means M4 prepares intersection numbers by
numbering each intersection included in the road map displayed by the
display means M1.
The number indication control means M5 controls the display means M1 to
indicate the intersection number in the vicinity of the respective
intersection on the road map displayed by the display means M1.
The intersection number input means M6 inputs a given intersection number
from among the intersection numbers indicated on the display means M1.
The route determination means M7 stores as a route each road between the
intersections corresponding to the intersection numbers input by the
intersection number input means M6, and cognizably indicates each road as
a route on the road map displayed by the display means M1.
In operation, the display control means M3 first displays on the display
means M1 a road map according to the map data stored in the map data
storage means M2. The intersection numbering means M4 then prepares
intersection numbers with respect to each intersection on the road map
displayed on the display means M1. Next, the number indication control
means M5 causes the display means M1 to indicate the intersection numbers
prepared by the intersection numbering means M4 on the road map in the
vicinity of their respective intersection.
Subsequently, intersections on a desired route are consecutively designated
by inputting, via the intersection number input means M6, the
corresponding intersection numbers from among those indicated by the
number indication control means M5 on the display means M1. Consequently,
the route determination means M7 stores as a route each road located
between the designated intersections identified by the intersection
numbers, and cognizably indicates each road as a route on the road map
displayed on the display means M1.
BRIEF DESCRIPTION OF THE DRAWINGS
The present invention will now be described, by way of example, with
reference to the drawings, in which:
FIG. 1 is a block diagram schematically showing the navigation system of
the present invention;
FIG. 2 is a block diagram schematically showing a navigation system of the
preferred embodiment as a whole;
FIG. 3 is table illustrating intersection data used in route determination;
FIGS. 4A and 4B are flow diagrams which together show the route
determination process of the present invention;
FIG. 5 is an illustration showing how the route determined at the route
determination process is indicated on the road map displayed by the
display.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
An embodiment of the present navigation system is explained hereunder
referring to the drawings although it is understood that other embodiments
are within the scope of the present invention.
As shown in FIG. 2, a navigation system 1 according to the present
embodiment includes an antenna 2a and a known receiver 2 for receiving
signals transmitted from an artificial satellite that is part of the
Global Positioning System GPS. Diffusion conversion is performed on the
received signals to obtain longitude data, latitude data, and altitude
data indicative of the location where the signal is received, i.e. current
position of the vehicle, and velocity data indicative of the traveling
velocity of the received location, i.e. driving velocity of the vehicle.
The navigation system 1 also includes an input device 4, as intersection
number input means M6, for externally inputting the intersection numbers,
a base point from which to start the navigation, and other instructions
such as cancellation of the determined route.
The navigation system 1 also includes an external storage device 6, a
display drive device 34, and a display 14. The external storage device 6
may be an optical disc or magnetic disc and serves as a map data storage
means M2. The display 14 may include a cathode ray tube CRT, a liquid
crystal screen, or other display means and displays a road map and other
necessary information.
The navigation system 1 further includes a main controller 20. The main
controller 20 retrieves data from the receiver 2, the input device 4, the
external storage device 6, and other parts of the navigation system 1, and
controls the display 14 to indicate a road map and a determined route
based on the data retrieved.
As shown by chain lines in FIG. 5, the map data stored in the external
storage device 6 takes the form of n.times.m units of map data M11, M12, .
. . Mnm, each unit of map data corresponding to the size of the map that
the screen of the display 14 can show at one time. The external storage
device 6 also stores intersection data prepared with respect to each
intersection included in the map data for providing data to be used in the
route determination and the route indication.
The intersection data, as shown in FIG. 3, includes an intersection address
Ci (i: integer value from 1 to n) for each intersection in the map data,
longitude (x-coordinate) data and latitude (y-coordinate) data indicative
of the location of the intersections, intersection addresses Ci of next
intersections, a node list indicative of inflection point(s) between each
intersection and corresponding next intersections.
As a result of the route determination process described later in detail,
each intersection address included in the intersection data is provided
with a respective intersection number and thereby identified. Further, the
intersection address Ci corresponding to the intersection on a determined
route is consecutively stored as a registered route intersection Pi.
The main controller 20 is a known microcomputer including a CPU 22, a ROM
24, a RAM 26, an input/output port 28, and a bus line 30 connecting these
components. The main controller 20 is provided with a display drive device
34 which sends out drive signals to and thereby activates the display 14.
In response to a command input by a user at the input device 4, the main
controller 20 executes a corresponding process of either route
determination or navigation.
During the navigation process, the current position of a moving vehicle is
continually detected and indicated on a road map displayed by the display
14, and the route determined at the route determination process is
indicated, referring to the intersection address Ci registered as a route
intersection, on the road map to guide a driver. Further details of the
navigation process are irrelevant to the present invention and are
therefore omitted for simplification
As shown in FIGS. 4A and 4B, in response to a command to start the route
determination process, a road map is displayed by the display 14 according
to the map data currently stored in the RAM 26, step 110. Therefore, if
the navigation process has been performed prior to the instant process,
the same road map as that displayed by the display 14 during the prior
navigation process is again displayed by the display 14.
At the following step 120, it is determined whether any information
concerning the area from which to start route determination has been
input. If "YES" is determined, the flow proceeds to step 130.
In order to designate the base point, a wide area map may be first
displayed, which is next gradually zoomed by pointing with a cursor to
obtain a more detailed map on which the user locates and inputs a base
point. Alternatively, the information input may be in the form of, for
example, longitude and latitude value data of the base point, or
x-coordinate and y-coordinate data of any landmark building nearby the
base point.
At step 130, map data, including the base point input at step 120, is
retrieved from the external storage device 6 to the RAM 26. During data
retrieval, a unit of map data including the base point, which is referred
to as the central unit map hereinafter, is first retrieved from among all
the units of map data M11-Mnm, and subsequently, three units of map data
are retrieved. The three units of map data, which are referred to as
peripheral unit maps hereinafter, correspond to the areas which are
adjacent to the central unit map and lie in the driving direction. The
four unit maps, including the central unit map and the three adjacent
peripheral unit maps, are then stored in the RAM 26. At the next step 140,
display data is prepared and a road map is thereby displayed by the
display 14. The road map that is displayed by the display 14 at step 110
is also prepared from the four unit maps stored in the RAM 26 at that
time.
Thus, the process at steps 110, 130, and 140 serve as the display control
means M3.
For instance, if the information for point A in FIG. 5 is input as
information designating the base area, a central unit map M85 including
the point A and the three peripheral unit maps M75, M76, and M86 are
retrieved. The three peripheral unit maps M75, M76, and M86, which are
respectively situated above, above and to the right, and to the right of
the central unit map M85, are selected based on the location of point A
relative to the center of the central unit map M85. At the next step 140,
the display data is prepared from the four unit maps with the point A at
its center, thereby displaying a road map of range B1 shown by dashed
lines in FIG. 5.
If the information concerning the base area was not input at step 120, or
after displaying a road map of the base area by the display 14 at step
140, the process goes to step 150 where intersection data corresponding to
the four units of map currently stored in the RAM 26 is retrieved. At the
next step 160, an intersection number j is prepared with respect to each
intersection address Ci. The process at step 160 thus serves as
intersection numbering means M4.
The intersection number j is a sequential number from 1 to 99 and is
temporarily given to each intersection address Ci retrieved. When the four
unit maps stored in the RAM 26 are repeatedly changed by a process which
will be later explained and as a result the intersection number reaches
99, further intersection numbers again start from 1.
Subsequently, step 170 serves as number indication control means M5 so as
to indicate the prepared intersection numbers adjacent their corresponding
intersections on the road map displayed by the display 14.
For instance, when the RAM 26 currently stores unit maps M85, M75, M76, and
M86 shown in FIG. 5 with the display 14 displaying a road map of range B1,
intersection numbers j from 1 to 10 are temporarily registered for the
corresponding ten intersections included in the four unit maps M85, M75,
M76, and M86. From among the ten intersection numbers j now registered,
the intersection numbers j of 1, 3, 4, 7, and 9 are displayed adjacent the
corresponding intersections on the road map displayed by the display 14.
Encircled points in FIG. 5 do not represent intersections, but represent
inflection points Ni on a road between intersections.
Upon indication of intersection numbers, the process step goes to step 180
where it is examined if an instruction to scroll the road map shown on the
display 14 has been input via arrow keys K, shown also in FIG. 5, provided
on the input device 4. If "NO" is determined, the flow goes to step 190.
At step 190, it is examined if an intersection number j has been input and
designated by numeral keys provided on the input device 4. If it is
determined that an intersection number j has been input, the intersection
corresponding to the designated intersection number j is registered, step
200, as an intersection on the route, which is hereinafter referred to as
a "route intersection". This registration of a route intersection is
performed by storing each registered route intersection number Pi for the
intersection address Ci corresponding to the designated intersection
number j.
At the next step 210, the road between the intersection previously
designated and the intersection designated this time is indicated as a
route on the road map displayed by the display 14. The route indication is
performed by accentuating the route with different color, boldness of
line, type of line or other appropriate variation.
The process at steps 200 and 210 thus serves as route determination means
M7.
When the route indication is completed, it is next examined at step 220 if
the map data stored in the RAM 26 is to be changed. Determination at step
220 is made according to whether the route intersection registered this
time is within the area S shown by double-dashed lines in FIG. 5. The area
S is concentric with the combined area defined by the four units of map
now stored in the RAM 26, and corresponds to the size of the road map that
the screen of the display 14 can show at one time. When it is determined
that the route intersection registered this-time is beyond the area S, the
map data is changed and the process goes to step 130. At step 130, a
central unit map including the route intersection registered this time and
three peripheral unit maps are retrieved. At the subsequent step 140, a
road map, with the route intersection registered this time at its center,
is displayed. At the following steps 150-170, intersection data
corresponding to the four units of map data newly retrieved by the RAM 26
are retrieved, intersection number j is prepared for each intersection
address Ci, and the intersection numbers thus prepared are indicated on
the road map displayed by the display 14.
On the other hand, if it is determined at step 220 that the route
intersection registered this time is within the area S, the map data is
not changed, the flow proceeds directly to step 230, and the current road
map is scrolled, without changing the map data, so as to situate the route
intersection registered this time at the center of the screen of the
display 14.
For instance, when a road map of the range B1 shown in FIG. 5 is currently
displayed and an intersection number j of 1 is input, the intersection
identified by the intersection number 1 is within the area S. Therefore,
the map data now stored in the RAM 26 is not required to be changed, and a
road map of range B2 is displayed by the display 14 with the intersection
corresponding to the intersection number 1 situated at its center.
Responsively, the intersection numbers 1-5, 7, and 8, from among all the
registered intersection numbers, are indicated adjacent their respective
intersections displayed by the display 14.
On the other hand, when the intersection corresponding to the intersection
number 1 is registered as a route intersection and the intersection number
2 is next input, the intersection corresponding to the intersection number
2 is beyond the area S. Therefore, the process goes back to step 130.
At step 130, peripheral unit maps M66, M67, and M77 are retrieved,
recognizing as a central unit map the unit map M76 including the
intersection corresponding to the intersection number 2, from the external
storage device 6 to the RAM 26, thereby displaying on the display 14 a
road map of range B3 shown by dashed lines in FIG. 5 with the intersection
corresponding to the intersection number 2 at its center. Further,
intersection numbers 11-13 are registered for the three additional
intersections included in the newly retrieved peripheral unit maps M66,
M67, and M77. Thus, the RAM 26 always stores four pieces of unit maps
retrieved from the external storage device 6, thereby allowing an
expedited change of road map to be displayed by the display 14.
Following step 230, where a road map is displayed by the display 14 with
the registered route intersection at its center, or following step 190
determining that intersection number j is not designated, the flow goes to
step 240 to determine whether a cancellation instruction has been input
through a cancel key provided on the input device 4. If it is determined
that no cancellation is instructed, it is next determined at step 250
whether an instruction has been input via the input device 4 to end the
route determination process.
If "YES" is determined at step 250, the process step ends. If "NO" is
determined at this step, the process goes back to step 180 and awaits an
instruction either to scroll the displayed road map, designate an
intersection number j, or to cancel the determined route.
On the other hand, if it is determined at step 240 that cancellation of the
determined route is instructed, the flow goes to step 260 and a
cancellation process is performed in the following manner to cancel the
determined route.
First, the number of times the cancellation instruction is input, i.e. the
number of times the cancel key was operated, is counted. The registration
of the corresponding number of route intersections are next deleted.
Consequently, the indication of the route between the deleted route
intersections is erased. Processes similar to those at steps 130 and 140
are performed after the route cancellation, thereby displaying on the
display 14 a road map situating at its center the last route intersection
that is not canceled.
When it is determined at step 180 that an instruction is input to scroll
the displayed road map, the process step goes to step 270, and the
displayed road map is scrolled in the direction designated by an arrow
key. Subsequently, it is determined at step 280 whether the currently
stored map data needs to be changed. The determination is made, similarly
to step 220, according to whether the center of the road map now displayed
by the display 14 is within the area S defined by the four units of map
data currently stored in the RAM 26. When it is determined that no change
of map data is required, i.e. the center of the displayed road map is
within the area S, the process goes directly to step 190. When it is
determined that the map data needs to be changed, i.e. the center of the
displayed road map is beyond the area S, the process goes back to step 130
in the same manner as in step 220. Thereby, a central unit map, situating
at its center the center of the displayed road map, and peripheral unit
maps are retrieved, a corresponding road map, obtained by scrolling the
road map for a desired time period with the arrow key, is displayed by the
display 14. Intersection numbers j are prepared for the map data newly
retrieved by the RAM 26, and consequently the prepared intersection
numbers j are indicated on the road map displayed by the display 14.
For example, when a road map of range B3 shown in FIG. 5 is currently
displayed by the display 14 with the intersections corresponding to
intersection numbers 1 and 2 registered as route intersections, operation
of an arrow key pointing above and to the left direction on the map
results in, as long as the center of the road map to be newly displayed is
within the area S as defined by the unit maps M76, M66, M67, and M77,
scrolling of the displayed road map up and to the left without changing
the map data. When that arrow key is further operated and the center of
the road map to be newly displayed goes beyond the area S, the processes
at steps 130-170 are performed. Thereby, a central unit map M76 and
peripheral unit maps M66, M65, and M75 are retrieved by the RAM 26, an
intersection included in the newly retrieved unit map M65 is temporarily
numbered with an intersection number 14, and the displayed road map is
scrolled up and to the left. Further, if it is determined at step 190 that
an intersection number 14 is input, a road map of range B4, situating at
its center the intersection corresponding to the intersection number 14,
is displayed by the display 14 as shown in FIG. 5.
Explained hereinafter is a procedure to determine a route using a
navigation system constructed according to the embodiment of the present
invention.
First, via the input device 4, an instruction is input to start the route
determination process. Responsively, a road map is displayed by the
display 14 by the process at step 110. If the area shown on the displayed
road map differs from the one on which a user desires to determine a
route, information is input concerning the area from which to start the
route determination. The processes at steps 120-140 are then performed and
a road map of the desired area, from which to start the route
determination, is displayed by the display 14.
In response to the display of the road map by the display 14, the processes
at steps 150-170 are performed and thereby intersection numbers j (j: an
integer value from 1 to 99) are indicated adjacent the respective
intersections on the displayed road map. If the intersection the user
desires to designate as the starting point is not included in the
currently displayed road map, an arrow key pointing in a desired direction
is depressed. Responsively, the displayed road map is scrolled by the
process at steps 180, 270, and 280. When the desired intersection is found
on the displayed road map, the intersection number j corresponding to the
desired intersection is input via numeral keys provided on the input
device 4.
The intersection thus identified and designated by its intersection number
j is registered as a route intersection, steps 190-230. Likewise, by
repeating the process at steps 240, 250, 180-230, every time the
intersection number j is input, the corresponding intersection is
registered as a route intersection. Since the route between the registered
route intersections is indicated on a real-time basis on the displayed
road map, the user can confirm the determined route.
When canceling the thus determined route, a cancel key on the input device
4 is to be operated. Responsively, the processes at steps 240 and 260 are
performed, thereby canceling the determined route according to the number
of times the cancel key was operated. Even after cancellation of the
route, the process step is on a stand-by condition awaiting either a
scrolling operation, input of an intersection number j, or an instruction
to end the route determination, and the processes at step 180-250 are thus
repeated.
Thus, according to the navigation system of the instant embodiment, a
desired route is readily and correctly determined since a user can
designate desired route intersections by inputting their corresponding
intersection numbers j indicated on the display 14.
Moreover, according to the embodied navigation system, the map data itself
does not contain any information concerning intersection numbers j.
Instead, the present invention constantly prepares and indicates on the
displayed road map the intersection numbers j every time units of map data
are newly retrieved for obtaining new map data and a new road map. The map
data can thus be smaller in volume. Map data with a different display
color, layout, or other variation can be adopted for determining a route
using the present navigation system.
Also in the embodied navigation system, if an intersection number j reaches
99, the further intersection numbers restarts from 1. The displayed road
map can therefore remain easy to see by displaying only a one or two digit
intersection number j, not three or more-digit intersection numbers j.
If the map is a detailed one and the four unit maps have a hundred or more
intersections on them, the intersections may be numbered by intersection
numbers j from 1 to 999, if desired. Alternatively, if an intersection
number j reaches 99, a further intersection numbers j may restart from 1
and be indicated with a different color. In this case, in registering a
route intersection at step 190 during the route determination, an
intersection may be designated by both the intersection number j and a
color.
Moreover, since a route is determined intersection by intersection, the
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