 |
Description  |
|
|
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to navigation apparatuses and, more
particularly, to a navigation apparatus in which a guide picture for
guiding a motor vehicle to a destination is displayed on a display unit.
2. Description of the Related Art
A vehicle navigation apparatus of a well known type performs vehicle travel
guidance, enabling a driver to easily drive the vehicle to a desired
destination. The navigation apparatus detects the position of the vehicle,
reads out map data pertaining to an area at the vehicle position from e.g.
a CD-ROM (compact disk read-only memory), and displays a map image on a
display screen while superposing a mark representing the position of the
vehicle (user's vehicle position mark) on a predetermined portion of the
map image. As the present position of the vehicle changes with movement of
the vehicle, the vehicle position mark in the image is moved or the map is
scrolled while the vehicle position mark is fixed at a predetermined
position, for example, at the center of the image, thereby enabling the
driver to recognize the map information of the area at the vehicle
position at a glance.
Such a navigation apparatus has a route guidance function for setting a
guided route from a starting point to a destination and performing
intersection guidance (displaying an enlarged intersection diagram and the
direction in which a vehicle is to advance) while displaying the guided
route on a map. When a starting point and a destination are input, a guide
route control section of the navigation apparatus automatically determines
a most suitable guided route and successively stores nodes (in terms of
longitude and latitude) constituting the guided route in a memory. During
actual traveling, the node series stored in the memory is searched for a
portion of the guided route to be displayed on a map display area of the
display screen and the portion of the guided route is displayed so as to
be discriminable from other routes. When the vehicle is within a
predetermined distance of and approaching an intersection, an intersection
guidance diagram (an enlarged intersection diagram with an arrow
indicating the direction in which the vehicle is to travel at the
intersection) is displayed to inform the driver of the desired one of the
roads or directions at the intersection. If the vehicle deviates from the
guided route (off-route travel), the guided route is updated by
recalculating a new route from the present vehicle position to the
destination.
FIG. 17 is a diagram of an example of a guided route display containing a
vehicle mark CM, a guided route RT (dotted line) and an enlarged
intersection diagram EL1 of an intersection Q. The enlarged intersection
diagram EL1 showing intersection formation links B1 to B4, represented by
link figures having a predetermined width, is converted into a perspective
view (as shown) before being displayed. Each link is displayed with a name
of a place to which a corresponding route leads (OHMIYA, TOKOROZAWA, URAWA
STATION, NIHONBASHI). An arrow ARR is also displayed to indicate the
direction in which the guided route leads to the destination. To draw such
an enlarged intersection diagram as shown in FIG. 18, an area through
360.degree. about the intersection Q is divided into eight equal sections
symmetrical about the direction of entry into the intersection (the
direction of an intersection entry link L1), thereby obtaining eight
angular ranges (reverse-to-entry-direction range A1, off-to-lower-left
range A2, left turn range A3, off-to-upper-left range A4, straight drive
range A5, off-to-upper-right range A6, right turn range A7,
off-to-lower-right range A8). Then the relationship between intersection
formation links and the angular ranges is examined to determine the
angular ranges within which the intersection formation links fall, and an
enlarged intersection diagram is formed and drawn in which the entry and
diverging links extend in directions corresponding to the angular ranges
within which the intersection formation links fall.
FIG. 19 is a table showing spoken intersection guidance sentences of the
navigation apparatus. If the direction of an exit link corresponds to the
right turn direction, spoken guidance such as "Turn right at the next
intersection" is given. If the direction of an exit link corresponds to
the off-to-upper-right direction, spoken guidance such as "Turn off to the
right at the next intersection" is given. In some navigation systems,
intersection guidance is not performed when driving straight through the
intersection.
The vehicle navigation apparatus described above corresponds to those of
the type commonly used in Japan. A vehicle navigation apparatus
representative of the type commonly used in U.S.A. is arranged to display
guidance pictures such as those shown in FIGS. 20A to 20F, without
displaying a map picture showing a map and a vehicle position mark during
vehicle traveling, and to guide a driver by using spoken information for
designating the direction in which to drive. In each of the guidance
pictures shown in FIGS. 20A to 20F, the distance (in miles) to an
intersection is indicated in a space CDS; the distance (in miles) to a
destination is indicated in a space DDS; sign VCD indicates a state of
providing spoken guidance; the present time is displayed in a space TDL;
and a heading direction is indicated in a guidance image NVG. If there is
no intersection or a branching point in a guided route within a
predetermined distance of the present vehicle position, a guidance picture
such as FIG. 20A designating straight travel is displayed. If there is an
intersection being approached within the predetermined distance, a
guidance picture such as one of FIGS. 20B to 20E is displayed which
contains an enlarged diagram of the intersection or branching point and an
arrow indicating a heading direction. Where a U-turn is required, a U-turn
figure as shown in FIG. 20F is displayed. When a point at a predetermined
distance from the branching point or intersection is reached, spoken
guidance is provided to designate a heading direction.
The navigation apparatus of the type used in the U.S.A. displays guidance
pictures instead of map pictures during navigation, as described above.
However, it detects the position of the vehicle, reads out map data
corresponding to the vehicle position from a map data base such as a
CD-ROM, displays, by using map data, an enlarged diagram of an approached
intersection or a branching point, which may exist in a guide route in a
predetermined distance range from the present vehicle position, along with
an arrow indicating a heading direction in the same manner as the
intersection enlarged diagram display in the Japanese type navigation
apparatus, and performs speech guidance by designating the heading
direction. The navigation apparatus displays a guidance picture indicating
driving straight if there is no branching point or intersection being
approached within the predetermined distance.
If the navigated vehicles moves off of the guided route (off-route travel),
the navigation apparatus updates the guided route by recalculating a new
route from the present vehicle position to the destination. Further, at
the time of guided route setting, the display changes to show a map
picture, thereby enabling a starting point and a destination to be input
for guided route setting.
As described above, the navigation apparatuses of the types in Japan and
U.S.A. have generally the same internal configurations. Reduced to
essentials, they differ only in display picture control.
The vehicle position is measured by self-contained navigation sensors (a
distance sensor and a bearing sensor) mounted in the vehicle
(self-contained navigation) or by a global positioning system (GPS)
including a satellite (satellite navigation). Vehicle position measurement
based on self-contained navigation can be performed at a comparatively low
cost but entails the problem of sensor errors reducing the measuring
accuracy, and therefore requires correction processing such as map
matching processing. Satellite navigation enables absolute-position
detection. However, measured position data obtained by satellite
navigation includes drift position errors resulting from various causes.
The nominal accuracy of the U.S. GPS system is 100 m or less (95% of the
time). Satellite navigation also entails the problem of position detection
failure in e.g. a tunnel or a building where the satellite radio signals
are obstructed.
Vehicle navigation apparatuses using both self-contained navigation and
satellite navigation have recently been developed to avoid these problems.
In such navigation apparatuses, the position and bearing are dead-reckoned
by self-contained navigation in an ordinary situation, and the
dead-reckoned vehicle position is corrected by map matching processing to
determine the actual vehicle position on a traveled road. If the
navigation apparatus is disabled from map matching by some cause with the
result that the vehicle position measured by self-contained navigation
deviates from the actual vehicle position so that the distance between the
vehicle position measured by self-contained navigation and vehicle
position measured by the GPS exceeds an error range of the GPS, then the
position measured by the GPS is used as a corrected vehicle position, to
find the traveled road by map matching processing, thereby determining the
actual vehicle position.
In self-contained navigation, the vehicle position is detected by
integration of output signals from a distance sensor and a relative
direction sensor, as described below. FIG. 21 is a diagram of a vehicle
position detection method using self-contained navigation. The distance
sensor is assumed to output a pulse each time a unit distance L.sub.0 is
traveled by the vehicle. A reference bearing (.theta.=0) corresponding to
the plus direction of X-axis is set, and the direction of anticlockwise
rotation from the reference bearing is assumed to be a plus direction. If
a preceding vehicle position is represented by a point P.sub.0 (X.sub.0,
Y.sub.0); an absolute bearing of a vehicle heading at the point P.sub.0 is
.theta..sub.0 ; and an output from the relative bearing sensor when the
unit distance L.sub.0 is traveled is .DELTA..theta..sub.1, a change in the
vehicle position is represented by
.DELTA.X=L.sub.0.multidot.cos(.theta..sub.0 +.DELTA..theta..sub.1)
.DELTA.Y=L.sub.0.multidot.sin(.theta..sub.0 +.DELTA..theta..sub.1)
A dead-reckoned bearing .theta..sub.1 of the vehicle heading direction and
a dead-reckoned vehicle position (X.sub.1, Y.sub.1) at a present point P1
can be calculated by vector addition expressed by the following equations:
.theta..sub.1 =.theta..sub.0 +.DELTA..theta..sub.1 (1)
X.sub.1 =X.sub.0 +.DELTA.X=X.sub.0 +L.sub.0.multidot.cos.theta..sub.1 (2)
Y.sub.1 =Y.sub.0 +.DELTA.Y=Y.sub.0 +L.sub.0.multidot.sin.theta..sub.1 (3)
Accordingly, if the absolute bearing and the position coordinates at a
starting point are given, the vehicle position can be detected
(dead-reckoned) in a real time manner by repeating the calculation of
equations (1) to (3) each time the vehicle moves through the unit
distance.
In self-contained navigation, however, errors are accumulated during
traveling, so that the dead-reckoned position deviates from the traveled
road. Therefore, the dead-reckoned vehicle position is collated with road
data by map matching processing to be corrected to the actual vehicle
position on the road. FIGS. 22 and 23 are diagrams explaining map matching
based on a projection method. It is assumed here that the present vehicle
position is at a point P.sub.i-1 (X.sub.i-1, Y.sub.i-1), and that the
vehicle heading direction is .theta..sub.i-1 (FIG. 22 shows a case where
the point P.sub.i-1 does not coincide with a road RDa.) If a relative
bearing when a certain distance L.sub.0 (e.g. 10 m) is traveled from the
point P.sub.i-1 is .DELTA..theta..sub.i, a vehicle position P.sub.i
'(X.sub.i ', Y.sub.i ') dead-reckoned by self-contained navigation and a
dead-reckoned bearing .theta..sub.i at P.sub.i ' are obtained by the
following equations:
.theta..sub.i =.theta..sub.i-1 +.theta..sub.i-1
X.sub.i '=X.sub.i-1 +L.sub.0.multidot.sin.theta..sub.i
Y.sub.i '=Y.sub.i-1 +L.sub.0.multidot.sin.theta..sub.1
In this situation, (a) road data is searched for a link (an element
constituting a road) which is contained in a 200 m square area surrounding
the dead-reckoned vehicle position P.sub.i ', to which a perpendicular
having a length not larger than a certain distance (e.g., 100 m) can be
drawn from the dead-reckoned vehicle position P.sub.i ', and which is at
an angle not larger than a certain value (e.g. 45.degree.) from the
dead-reckoned vehicle bearing .theta..sub.i at the dead-reckoned position
P.sub.i '. In this case, a link LKa.sub.1 of a bearing .theta.a.sub.1 on
the road RDa (straight line connecting nodes Na.sub.0 and Na.sub.1) and a
link LKb.sub.1 of a bearing .theta.b.sub.1 on a road RDb (straight line
connecting nodes Nb.sub.0 and Nb.sub.1) are searched out as such a link.
(b) Then the lengths of perpendiculars RLia and RLib drawn from the
dead-reckoned vehicle position P.sub.i ' to the links LKa.sub.1 and
LKb.sub.1 are obtained. (c) Thereafter, a coefficient Z is calculated by
the following equations:
Z=dL.multidot.20+d.theta..multidot.20(d.theta..ltoreq.35.degree.) (4)
Z=dL.multidot.20+d.theta..multidot.40(d.theta.>35.degree.) (4)'
where dL is the length of the perpendicular drawn from the dead-reckoned
vehicle position P.sub.i ' to each link (the distance between the
dead-reckoned vehicle position and the link) and d.theta. is the angle
between the dead-reckoned vehicle bearing .theta..sub.i and the link. A
larger weighting function is used when the angle d.theta. is large.
(d) After the coefficient value Z has been obtained, some of the links
satisfying the following conditions 1, 2, and 3,:
1) Distance dL.ltoreq.75 m (=maximum absorbable distance),
2) Angular difference d.theta..ltoreq.30.degree. (=maximum absorbable
angle),
3) Coefficient value Z.ltoreq.1500 are obtained and the one having the
smallest coefficient value in the links satisfying these conditions, i.e.
link LKa.sub.1 in this case, is set as a matching candidate (most probable
road). (e) Then a travel locus SHi connecting the points P.sub.i-1 and
P.sub.i ' is translated in a direction along the perpendicular RLia until
the point P.sub.i-1 comes onto the link LKa.sub.1 (or an extension of the
link LKa.sub.1) to obtain translated points PT.sub.i-1 and PTi' of the
points P.sub.i-1 and P.sub.i ' (f) Finally, the travel locus SHi is
rotated on the point PT.sub.i-1 until the point PTi' comes onto the link
LKa.sub.1 (or an extension of the link LKa.sub.1) to obtain a moved point
of the point PTi', which is set as an actual vehicle position P.sub.i
(X.sub.i, Y.sub.i). The bearing .theta..sub.i is preserved as the vehicle
heading at the actual vehicle position P.sub.i. In a case where the point
P.sub.i-1 representing the preceding vehicle position is on the road RDa,
the translated point PT.sub.i-1 coincides with the point P.sub.i-1, as
shown in FIG. 23.
A situation described below may be taken into consideration, especially in
the U.S.A. and geographically similar countries. As shown in FIG. 24, a
convenience store SHP1 and other stores SHPi (i=2, 3 . . . ) are all
located in a large-area site, a large parking area PKA is located in front
of the stores, and roads RD1 to RD4 stored in the map data base surround
the parking area PKA. The roads RD1 to RD4 are at a short distance from
the parking area PKA. The parking area PKA is not stored in the map data
base (i.e., is off the road net). If a vehicle CR having the navigation
apparatus enters the parking area PKA, the vehicle position is erroneously
determined to be on the adjacent road RD1 by the map matching processing,
resulting in an error in position correction. Thereafter, the navigation
apparatus cannot recognize the correct vehicle position and cannot make an
appropriate guidance picture display or spoken guidance when the vehicle
moves out of the parking area PKA back onto a road on a guided route.
In a situation where a guided route is set as indicated by hatching in FIG.
25, if the vehicle position is determined to be on the road RD1 adjacent
to the parking area PKA by the map matching processing to cause an
erroneous position correction, then an off-route movement is recognized, a
guided route recalculation is performed to newly set guided route NVRT
indicated by the double-dot-dash line, and a guidance picture display and
spoken guidance which are inappropriate or irrelevant are provided. For
example, in a case where the vehicle CR is travelling leftward through a
point Pa, a correct guidance picture such as that shown in FIG. 26A
designating a right turn 500 m ahead is displayed. In such a situation, if
the vehicle enters the parking area PKA and if the vehicle position is
erroneously corrected to a point on the road RD1 by map matching, then
recalculation of guided route NVRT is performed as mentioned above to
display an incorrect guidance picture, such as that shown in FIG. 26B
designating a left turn 100 m ahead. Then, if the vehicle makes a U-turn
in the parking area PK4 as indicated by the broken line, it is erroneously
determined that the vehicle has U-turned on the road RD1 and a guidance
picture as shown in FIG. 26C designating a U-turn is displayed. If the
vehicle returns to the road RD2, guided route recalculation is performed,
the first guided route (hatching) is obtained and a guidance picture such
as that shown in FIG. 26D designating a right turn 200 m ahead is
displayed.
As described above, if the vehicle enters an area other than on the roads
(i.e. not in the map data base), e.g. a parking lot, grounds of a facility
or factory, a park or a campus, the selection of guidance pictures and
spoken guidance becomes incorrect during movement in the off-road area, so
that the driver has a feeling of uncertainty in terms of guidance. Even
after the vehicle exits the off-road area, there is a possibility of the
navigation apparatus performing erroneous position correction to lose the
vehicle position, resulting in failure to display a correct guidance
picture or to give correct spoken guidance.
SUMMARY
A navigation apparatus in accordance with this invention does not output an
inappropriate or irrelevant guidance picture display or spoken guidance,
even when the navigated vehicle enters an area other than on the roads in
the map data base, e.g., a parking lot, factory or facility grounds, a
park or a campus.
The present navigation apparatus also displays a correct guidance picture
and performs correct speech guidance for navigating the vehicle to a
destination when the vehicle exits such an area (an "off-road net area").
According to one aspect of the present invention, a navigation apparatus
includes a map data base for storing map data, a detector for detecting an
entry of a vehicle into such an area other than roads stored in the map
data base, and a display control for changing a guidance picture to a map
picture showing a map image surrounding the vehicle position and a vehicle
position mark when the vehicle enters the off-road net area.
In this navigation apparatus, when the vehicle enters such an off-road net
area, the guidance picture is changed to a map picture to avoid outputting
an erroneous guidance picture display or guidance speech, so that the
driver has no feeling of uncertainty. Also, a detector for detecting an
exit from such an area is provided to change the map picture to the
guidance picture when the vehicle exits the area, thereby providing a
guidance picture display and spoken guidance for navigation to a
destination after exiting from the area.
According to another aspect of the present invention, a navigation
apparatus includes a map data base for storing map data, a vehicle
position corrector for obtaining, by map matching processing, a most
probable candidate road satisfying a predetermined condition for
correcting the position of the vehicle to a point on the most probable
candidate road, and for thereafter continuing the map matching processing
each time a predetermined distance is traveled, a detector for detecting
an entry of the vehicle into an off-road net area, and a display control
for changing a guidance picture to a map picture showing a map image about
the vehicle position and a vehicle position mark when the vehicle enters
the area, wherein correcting the position by the map matching processing
stops when the vehicle enters the area.
In this navigation apparatus, when the vehicle enters such an area, a
guidance picture is changed to a map picture and correcting the vehicle
position by map matching stops, thereby avoiding occurrence of erroneous
position correction to a position on a road adjacent to the area.
Therefore, the possibility of providing an erroneous guidance picture
display or spoken guidance is eliminated, so that the driver has no
feeling of uncertainty.
A detector for detecting an exit from such an area is also provided to
restart correcting the vehicle position by map matching and to change the
map picture for a guidance picture when the vehicle exits the area. Even
after exiting from the area, this navigation apparatus can recognize the
vehicle position with a certain error, such that the vehicle position can
be corrected by the restated map matching processing. Also, a correct
guidance picture display and a correct spoken guidance to the desired
destination can be output.
According to still another aspect of the present invention, a navigation
apparatus includes a map data base for storing map data, a vehicle
position corrector for obtaining, by map matching processing, a most
probable candidate road satisfying a predetermined condition, for
correcting the position of a vehicle to a point on the most probable
candidate road, and for thereafter continuing the map matching processing
each time a predetermined distance is traveled, a route calculator for
calculating a guide route from the present vehicle position of a vehicle
to a destination when the vehicle deviates from a destination previously
set, a detector for detecting an entry of the vehicle into an off-road net
area, and a display control for changing a guidance picture to a map
picture showing a map image surrounding the vehicle position and a vehicle
position mark when the vehicle enters the area, wherein, when the vehicle
enters the area, the vehicle position correction means stops correcting
the position by the map matching processing and the guided route
calculator stops calculating the guided route.
In this navigation apparatus, when the vehicle enters the above-mentioned
area, a guidance picture is changed to a map picture, correcting the
vehicle position by map matching stops and recalculating a guided route is
also stopped, thereby avoiding occurrence of erroneous position correction
to a position on a road adjacent to the area, while recalculation of a
guided route in response to being off-route is inhibited. Therefore the
possibility of providing an erroneous guidance picture display or spoken
guidance is eliminated, so that the driver has no feeling of uncertainty.
Also, a detector for detecting an exit from such an area is provided to
restart correcting the vehicle position by map matching and recalculating
a guide route when the vehicle exits the area. Even after the exit from
the area, this navigation apparatus can recognize the vehicle position
with a certain error, such that the vehicle position can be corrected by
the restarted map matching processing. Also, a correct guidance picture
display and a correct spoken guidance to the desired destination can be
provided. Further, even if the vehicle exits from the area at a location
different from the entrance, to travel on a road different from the
previously set guided route, a new guided route is recalculated, to
provide a correct guidance picture display and correct spoken guidance for
navigation to the destination.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a diagram of the present navigation system;
FIG. 2 is a diagram showing the structure of road data in terms map data
for the apparatus of FIG. 1;
FIG. 3 is a diagram of a remote controller for use with the apparatus of
FIG. 1;
FIG. 4 is a detailed diagram of the present navigation apparatus in
accordance with the present invention;
FIG. 5 is a diagram of a node series forming a guided route;
FIG. 6 is a diagram showing guided route data stored in a guided route
memory;
FIG. 7 is a diagram explaining a first set of area entry detection
conditions;
FIG. 8 is a diagram explaining a second set of area entry detection
conditions (Part 1);
FIG. 9 is a diagram explaining the second set of area entry detection
conditions (Part 2);
FIG. 10 is a diagram of the entry/exit detection section;
FIG. 11 is a flow chart of map matching control;
FIG. 12 is a flow chart of guidance control processing;
FIG. 13 is a diagram explaining displayed pictures (Part 1);
FIGS. 14A to 14D are diagrams explaining displayed pictures (Part 2);
FIG. 15 is a diagram explaining displayed pictures in a case where an
entrance and an exit are provided in difference places (Part 1);
FIGS. 16A to 16D are diagrams explaining displayed pictures for a case
where an entrance and an exit are provided in difference places (Part 2);
FIG. 17 is a diagram explaining prior art intersection guidance;
FIG. 18 is a table showing a prior art method of drawing an enlarged
intersection diagram;
FIG. 19 is a table showing prior art spoken guidance;
FIGS. 20A to 20F are diagrams of prior art guidance pictures;
FIG. 21 is a diagram of a prior art method of calculating a position and a
bearing in self-contained navigation;
FIG. 22 is a diagram of map matching based on the prior art projection
method (Part 1);
FIG. 23 is a diagram of map matching based on the prior art projection
method (Part 2);
FIG. 24 is a diagram explaining the problem with the prior art navigation
apparatus (Part 1);
FIG. 25 is a diagram further explaining the problem with the prior art
navigation apparatus (Part 2); and
FIG. 26 is a diagram further explaining the problem with the prior art
navigation apparatus (Part 3).
DETAILED DESCRIPTION
Navigation System
1. System Configuration
FIG. 1 shows a navigation system in accordance with this invention,
including a navigation controller 1, an operating unit (e.g. a remote
controller) 2 for inputting various instructions to the navigation
controller, setting a guided route and setting various kinds of data, and
a display unit 3 for displaying a map, a guide route, an intersection
guidance diagram, various menus, and the like. The navigation system also
includes a compact disk read only memory (CD-ROM 4) in which the map data
base information is stored, an associated CD-ROM drive 5, a GPS receiver 6
for receiving radio signals from GPS satellites to measure the present
position and bearing of the vehicle, a multiple beam antenna 7 for
receiving the radio signals from the GPS satellites, a sensor 8 for
self-contained navigation, and an audio unit 9 for outputting spoken
guidance. The audio unit 9 may be adapted for use with or be part of an
ordinary car audio system.
The GPS receiver 6 calculates the position and bearing of the navigated
vehicle by three-dimensional or two dimensional position-measuring
processing (the bearing being obtained as a line connecting the present
vehicle position and the vehicle position measured one sampling time
.DELTA.T before), and outputs the calculated position and bearing along
with the position-measuring time. The self-contained navigation sensor 8
includes various sensors described below with reference to FIG. 4.
The map information stored in the CD-ROM 4 includes (1) a road layer, (2) a
background layer for displaying objects on a map, (3) a character layer
for displaying names of cities, towns, villages and the like, (4) an
integrated information service (IIS) layer for storing IIS information. Of
these layers, the road layer has, as shown in FIG. 2, road link data RLDT,
node data NDDT and crossing data CRDT.
Road link data RLDT is provided as information on attributes of roads and
includes a total number of nodes in a road, the numbers, of nodes forming
each road, road numbers (road names) and the kinds of road (national road,
expressway, prefectural road and so on). (The roads are represented in the
map database as each being a series of segments linked at nodes defined in
terms of latitude and longitude.)
Crossing data CRDT is a set of nodes closest to each intersection on a map
(intersection forming nodes) in the nodes of links (road segments)
connecting to the intersection. Node data NDDT is a list of all nodes
defining each road and has, with respect to each node, position
information (longitude, latitude), an intersection discrimination flag for
indicating whether the node corresponds to an intersection, and a pointer
which designates intersection data if the node corresponds to an
intersection or designates the road link to which the node belongs if the
node corresponds to no intersection.
2. Remote Controller
FIG. 3 shows the appearance of the remote controller 2 of FIG. 1 having
various keys. Joystick key 2a is operated to move a cursor (focus), a
vehicle mark or the like in eight directions relative to a map or to
select a desired menu item by moving a menu selecting bar in vertical and
horizontal directions, and is depressed when a menu is selected.
Enlargement key 2b is operated to display a map on such a comparatively
large scale as to show the map details. Reduction key 2c is operated to
display a wide-area map. Menu key 2d is operated to display a menu.
Navigation (NV) key 2e is for displaying a map containing a point
corresponding to the user's vehicle position along with the user's vehicle
mark. Memory (MEMO) key 2f is operated to store a desired point. Functions
frequently used are set in combination with function keys 2g and are each
selected by operating the corresponding one of function keys 2g. Key 2h is
the power key.
Navigation Controller
FIG. 4 shows detail of the navigation controller 1 of FIG. 1 along with the
remote controller 2, the display unit 3, the CD-ROM 4 in which map
information is stored, and the CD-ROM drive 5, the GPS receiver 6, the
multiple beam antenna 7, the self-contained navigation sensor 8 and the
audio unit 9. The self-contained navigation sensor 8a includes a relative
direction sensor (angle sensor) 8a such as a gyrocompass for detecting the
angle of rotation of the vehicle, and a distance sensor 8b which generates
one pulse each time a predetermined distance is traveled.
The navigation controller 1 has a map reading control section 11 for 1)
calculating a focus position (picture center longitude and latitude) in
response to moving a map or selecting a map area by the joystick key, the
reduction key, the enlargement key or the like, and 2) reading
predetermined map information from the CD-ROM 4 on the basis of the
vehicle position, the focus position or the like. Map buffer 12 stores map
information read out from the CD-ROM. Map information for a plurality of
pages (units), e.g., 3.times.3 units of map information surrounding the
current vehicle position or the focus position is read to the map buffer
12 to enable map scrolling described below. Map drawing section 13
generates a map image by using map information stored in the map buffer
12. Video random access memory (VRAM) 14 stores the map image. Read
control section 15 displays a map while scrolling the same according to
the movement of the vehicle position or focus movement by changing the
position of one picture cut out from the VRAM 14 on the basis of the
picture center position (vehicle position, focus position).
It is to be understood that controller 1 typically includes a
microprocessor or microcontroller executing a computer program
(instructions) stored in a computer-readable memory (medium) associated
with the microprocessor/microcontroller. Certain blocks of controller 1
represent other electronic components, e.g. VRAM 14, data storage section
18, and guide route memory 18 are memory. The computer program (a computer
process) is described in further detail below; coding such a program is
well within the skill of one of ordinary skill in the art in light of this
disclosure.
A guidance control section 16 forms and outputs a guidance picture (see
FIG. 20) for guiding the driver to the destination, and guides the driver
by informing the driver of a direction to be selected at a branching point
or intersection. Remote controller control section 17 receives a signal
according to an operation of the remote controller 2 and sends commands to
related sections according to the signal. GPS data storage section 18
stores GPS data supplied from the GPS receiver 6. Vehicle position and
bearing calculation section 19 calculates the vehicle position
(dead-reckoned vehicle position) and a vehicle bearing on the basis of an
output from the self-contained navigation section 8. Map matching control
section 20 performs map matching processing based on a projection method
by using map information read to the map buffer 12, the dead-reckoned
vehicle position and the vehicle bearing each time a predetermined
distance (e.g., 10 m) is traveled, thereby correcting the vehicle position
to a point on a traveled road.
Guided route control section 21 performs calculations for determining a
guided route to an input destination and recalculates a guided route from
the present vehicle position to the destination. Guided route memory 22
stores the guided route. Guided route drawing section 23 draws the guide
route stored in the guide route memory 22. The guided route memory 22
stores data on the positions of all nodes N.sub.s, N.sub.i (i=1, 2 . . .
), N.sub.D on a guided routed IRT (see FIG. 5) from a starting point to a
destination calculated by the guided route control section 21, as shown in
FIG. 6. When a map picture is displayed, the guided route drawing section
23 reads out guide route information (a node series) from the guided route
memory 22 and draws the corresponding guided route on the map.
Operation picture generating section 24 displays various menu pictures
(operation pictures) on display 3. Mark generating section 25 outputs
various marks including the vehicle mark and the cursor at the time of map
picture display. Image synthesis section 26 drives display 3.
Entry/exit detection section 27 detects entry of the navigated vehicle into
an area other than roads stored in the map data base (off the road net)
and an exit of the vehicle from such an area.
Entry/Exit Detection Section
1. Area Entry Detection Conditions
FIGS. 7 and 8 are diagrams explaining the principle of detection of entry
of the navigated vehicle into an area other than roads stored in the map
data base. FIGS. 7 and 8 illustrate an area PKA other than the stored
roads (e.g., a parking lot), roads RDi (i=1, 2 . . . ) stored in the data
base, and the navigated vehicle location CR.
A first set of area entry conditions is 1) that the heading of the vehicle
changes by 60.degree. or more, 2) that the speed of the vehicle at the
time of this change is 20 km/h or less, and 3) that no road exists as a
map matching calculation object (candidate road). The condition that no
candidate road exists is expressed as a case where no road can be found as
a link defined (1) by being contained in a 200 m square area surrounding
the dead-reckoned position, (2) by being at an angle not larger than a
certain value (e.g., 45.degree. ) from the vehicle bearing at the
dead-reckoned position, and (3) by having thereon a perpendicular drawn
from the dead-reckoned position and having a length not larger than a
certain distance (e.g., 100 m).
Entry into area PKA, e.g. a parking lot, is made almost always 1) by
reducing the vehicle speed to 20 km/h or less and 2) by gradually changing
the direction of movement of the vehicle by 60.degree. or more, as shown
in FIG. 7. However, such a driving situation may occur in the case of
traveling on a road. Therefore, there is a need to set some additional
condition to enable detection of entry into the above-mentioned off-road
net area. As long as the vehicle is traveling on a road, a candidate road
is always found by map matching. However, if in the case of entry into an
off-road net area, and the distance of all the roads generally parallel to
the area entry direction A is 100 m or more, there is no candidate road to
be found. Accordingly, the condition 3 is added to the set of conditions 1
and 2 and, if these conditions 1, 2 and 3 are satisfied, it is determined
that the vehicle has entered an off-road net area.
However, the above-described first set of detection conditions is not
sufficient. This is because there is a possibility of road RD3, generally
parallel to the area entry direction, being at a distance not larger than
100 m from an entrance ET to an off-road net area. In such a case, a map
matching candidate road exists and the area entry cannot be detected if
only the first set of area entry conditions is set. Therefore, there is a
need for an additional area entry condition.
A second set of area entry detection conditions is 1) that the vehicle
heading changes by 60.degree. or more, 2) that the vehicle speed at the
time of this change is 20 km/h or less, and 3) that the distance L2 to any
map matching candidate road is greater than 3% of the distance L1 on the
road traveled straight to the turning point, and 4) that the distance to
the map matching candidate road is 30 m or more.
Entry into the above-described off-road net area must be detected even if
road RD3 (map matching candidate road) generally parallel to the area
entry direction is at a distance not greater than 100 m from the entrance
ET to area PKA, as shown in FIG. 8. As long as the self-contained
navigation sensor has no detection error, entry into area PKA can be
determined if it is confirmed that the vehicle is not on the map matching
candidate road RD3 generally parallel to the area entry direction when
conditions 1 and 2 are satisfied. However, the self-contained navigation
sensor has a detection error, and this detection error must be taken into
consideration. Then, the distance Li' between a point at which the vehicle
starts moving straight after changing its heading and a point at which it
next changes the heading and the distance L2 between the second heading
changing point (an entrance to the area) and map matching candidate road
RD3 are obtained, and the ratio of L2 to the straight drive distance L1
(=Li'+L2) in terms of percent is calculated (see FIG. 9) by the following
equation:
a=100.multidot.L2/L1 (5)
When the percent a is equal to or higher than a value set by considering
the detection error, it is determined that entry into an off-road net area
has been made. However, if the width of the traveled roads is large, a
situation is possible in which the above-described conditions 1, 2 and 3
are satisfied. Therefore, the condition that "the distance to the map
matching candidate road is not less than 30 m" is added to the
above-described conditions by considering the width of the roads.
2. Area Exit Detection Conditions
When after entering an off-road net area, the vehicle exits from the area
to travel on one of the roads, the vehicle speed is increased and a
candidate road appears on which map matching is to be performed.
Therefore, an exit from the area is determined if the conditions:
1) that the vehicle speed is e.g. 32 km/h or higher, and
2) that some candidate road exists on which map matching is to be performed
are satisfied.
3. Configuration of the Entry/Exit Detection Section
FIG. 10 is a diagram showing the entry/exit detection section 27 of
controller 1. Entry detection section 31 detects an entry of the vehicle
into an off-road net area. An exit detection section 32 detects an exit of
the vehicle from such an area. Speed detection section 33 detects the
speed of the vehicle on the basis of the distance dL travele | | |
