U.S. patent application number 09/804732 was filed with the patent office on 2001-10-04 for navigation system.
This patent application is currently assigned to Alpine Electronics, Inc.. Invention is credited to Shimabara, Daisuke.
Application Number | 20010027377 09/804732 |
Document ID | / |
Family ID | 18604072 |
Filed Date | 2001-10-04 |
United States Patent
Application |
20010027377 |
Kind Code |
A1 |
Shimabara, Daisuke |
October 4, 2001 |
Navigation system
Abstract
A guidance information setting unit specifies, during a route
guidance operation, a first intersection that the vehicle is about
to pass and a second intersection that the vehicle is to pass
thereafter, where the vehicle makes a right-turn or a left-turn.
Next, the guidance information setting unit sets a recommended
travel lane by which the vehicle minimizes the lane change
frequency until it reaches the second intersection, and outputs
information concerning the recommended travel lane to an
intersection guidance unit as the guidance information. The
intersection guidance unit produces, as the intersection guidance
information concerning the first intersection, drawing data of the
intersection guidance information that displays with emphasis the
recommended travel lane set by the guidance information setting
unit, and displays the data on the screen of a display unit through
an image synthesizing unit. As a consequence, the navigation system
of the invention ensures an appropriate travel state for the
vehicle.
Inventors: |
Shimabara, Daisuke;
(Iwaki-city, JP) |
Correspondence
Address: |
BRINKS HOFER GILSON & LIONE
P.O. BOX 10395
CHICAGO
IL
60610
US
|
Assignee: |
Alpine Electronics, Inc.
|
Family ID: |
18604072 |
Appl. No.: |
09/804732 |
Filed: |
March 13, 2001 |
Current U.S.
Class: |
701/437 ;
340/990 |
Current CPC
Class: |
G01C 21/3658
20130101 |
Class at
Publication: |
701/209 ;
340/990 |
International
Class: |
G01C 021/34 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 28, 2000 |
JP |
2000-088159 |
Claims
What is claimed is:
1. A navigation system comprising: a route search means that sets a
travel route of a vehicle by executing a route search processing; a
guidance information setting means that sets, on the basis of the
travel route, guidance information concerning a first intersection
that the vehicle passes, in consideration of the conditions of
passage at a second intersection that the vehicle is to pass
thereafter; and an intersection guidance means that communicates
the guidance information.
2. A navigation system as claimed in claim 1, wherein the guidance
information setting means sets, on the basis of travelable lanes at
the first intersection and the second intersection, the guidance
information that minimizes the frequency of lane changes until the
vehicle reaches the second intersection.
3. A navigation system as claimed in claim 1, wherein a display
area for displaying the guidance information concerning the first
intersection and the second intersection and a display area for a
map image are divided.
4. A navigation system as claimed in claim 1 or claim 2, wherein
the second intersection is an intersection at which the vehicle
next makes a right-turn or a left-turn.
5. A navigation system as claimed in claim 1 or claim 2, wherein
the intersection guidance means displays all the lanes at the
intersections as intersection guidance information, and further
displays with emphasis only the recommended travel lanes.
6. A navigation system as claimed in claim 2, wherein the
intersection guidance means displays the recommended travel lanes
and the travelable lanes at the intersections as intersection
guidance information, and does not display the lanes that the
vehicle is not permitted to travel.
7. A navigation system as claimed in claim 2, wherein, when the
vehicle approaches the first intersection within a specific
distance, the guidance information setting means displays the
guidance information concerning the first intersection.
8. A navigation system as claimed in claim 2, wherein, when the
vehicle passes the first intersection, the guidance information
setting means deletes the guidance information concerning the first
intersection.
9. A navigation system as claimed in claim 2, wherein the
intersection guidance means displays only recommended travel lanes
at the intersections as intersection guidance information, and does
not display the other lanes.
10. A navigation system as claimed in claim 2, wherein the
intersection guidance means displays by arrows only recommended
travel lanes at the intersections as intersection guidance
information.
11. A navigation system comprising: a route search means that sets
a travel route of a vehicle by executing a route search processing;
a guidance information setting means that sets, on the basis of the
travel route, guidance information concerning a first intersection
that the vehicle passes, in consideration of the conditions of
passage at a second intersection that the vehicle is to pass
thereafter; and an intersection guidance means that displays the
guidance information concerning the first intersection and the
guidance information concerning the second intersection with a
dislocation of display positions thereof.
12. A navigation system as claimed in claim 11, wherein, when the
lanes are reduced after passing the first intersection, the
intersection guidance means displays the guidance information
concerning the first intersection and the guidance information
concerning the second intersection with a dislocation of display
positions thereof.
13. A navigation system as claimed in claim 11, wherein, when a
right-turn lane or a left-turn lane is added at the second
intersection, the intersection guidance means displays the guidance
information concerning the first intersection and the guidance
information concerning the second intersection with a dislocation
of display positions thereof.
14. A lane guidance method in a navigation system comprising:
executing a route search to a destination to set a travel route;
setting, on the basis of the travel route, lane guidance
information concerning a first intersection that the vehicle is
going to pass, in consideration of the conditions of passage at a
second intersection that the vehicle is to pass thereafter; and
presenting the lane guidance information.
15. A lane guidance method in a navigation system, as claimed in
claim 14, wherein the second intersection is an intersection at
which the vehicle next makes a right-turn or a left-turn, and the
lane guidance information minimizes the frequency of lane changes
until the vehicle reaches the second intersection.
16. A lane guidance method in a navigation system, as claimed in
claim 14, wherein, when the vehicle passes the first intersection,
the lane guidance information displays with emphasis a recommended
travel lane.
17. A lane guidance method in a navigation system, as claimed in
claim 14, wherein the lane guidance information displays all the
lanes at the first intersection and the second intersection, and
further displays with emphasis only recommended travel lanes.
18. A lane guidance method in a navigation system, as claimed in
claim 14, wherein the lane guidance information displays
recommended travel lanes and travelable lanes at the first
intersection and the second intersection, and does not display the
lanes that the vehicle is not permitted to travel.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a navigation system that
provides a driver with route guidance information by displaying the
maps and intersections surrounding the driver's vehicle.
[0003] 2. Related Art
[0004] In general, a navigation system for a vehicle detects the
current position of the vehicle and reads out the map data for the
area surrounding the vehicle from a storage medium such as a CD,
DVD, and the like to present the map on a display. The system also
displays a vehicle position mark that illustrates the vehicle
position at a specific place on the display, and scrolls the map
surrounding the vehicle to follow its movement with the vehicle
position mark in the center, whereby the driver is kept informed of
the map information for the area surrounding the vehicle
position.
[0005] Further, almost all of the recent vehicle navigation systems
are equipped with a route guidance function whereby a user is able
to travel to a desired destination without taking a wrong road.
This route guidance function automatically searches for the route
of a minimum cost that connects the starting point and the
destination set by the user, and draws the searched guidance route
thicker on the map with a different color than the other roads.
When the vehicle approaches an intersection on the guidance route,
the system also displays an enlarged map for the area surrounding
the intersection, and displays an arrow, for example, indicating
the lane that the vehicle should take, whereby the user is able to
recognize the route to take.
[0006] When guiding along the travel lanes in the intersection
(hereunder, referred to as "the first intersection") that the
vehicle is about to pass through, the conventional navigation
system does not pay attention to the state of the guidance route
after passing through the first intersection, and displays an arrow
or the like to all the lanes that the vehicle can take when passing
through the first intersection. However, there is a possibility,
depending on the state of the guidance route, that all the lanes
that the vehicle can take at the time of passing through the first
intersection are not always appropriate for the travel along the
guidance route thereafter.
[0007] As a specific example, suppose that the vehicle travels
straight through the first intersection along the guidance route,
and turns right at the next intersection (hereunder, referred to as
"the second intersection"). It is also assumed that there are three
lanes at the first intersection, all of which are directly
advancing lanes, and there are three lanes at the second
intersection, among which two are directly advancing lanes and one
is a right-turn lane. In such a situation, considering that the
vehicle turns right at the second intersection, it is desirable
that the vehicle should change the travel lane into the right lane
at the first intersection if possible. However, in the guidance of
the travel lane in the conventional navigation system, when the
vehicle travels in the left lane of the three directly advancing
lanes immediately before passing through the first intersection,
the system will display arrows or the like on all three lanes as a
lane that the vehicle can take, since the three lanes are directly
advancing and the guidance route at that moment is directly
advancing at the first intersection. The driver, viewing this
guidance of the travel lane, might remain in the left lane that the
vehicle took until then.
[0008] Here, if the distance between the first intersection and the
second is relatively short, or if there is much traffic on the
road, the driver will not be able to change the travel lane into
the innermost right-turn lane before the vehicle reaches the second
intersection, after the lane guidance relating to the second
intersection is presented. Consequently, the vehicle travels along
a lane that deviates from the guidance route at the second
intersection.
SUMMARY OF THE INVENTION
[0009] As described in the foregoing example, lane guidance at an
intersection that the conventional navigation system provides has
the problem that it does not provide a more appropriate travel
state in consideration of the state of the guidance route after
passing through the first intersection.
[0010] The present invention has been made in view of the foregoing
problem, and it is an object of the invention to provide a
navigation system whereby a vehicle can receive the appropriate
travel state as described above. In order to accomplish this, in
the navigation system of the invention, a route search means
executes route search processing to thereby set a travel route of a
vehicle. On the basis of the set travel route, a guidance
information setting means sets guidance information concerning a
first intersection that the vehicle passes, in consideration of the
conditions of passage at a second intersection that the vehicle
passes thereafter, and an intersection guidance means communicates
the set guidance information to the driver. Thereby, since the
navigation system is able to provide guidance concerning the first
intersection that the vehicle is going to pass, in consideration of
the conditions of passage at the second intersection that the
vehicle passes thereafter, the driver easily attains an appropriate
travel state.
[0011] Further, it is preferable that the guidance information set
by the guidance information setting means includes information
concerning the recommended travel lanes when the vehicle passes the
first intersection, and the intersection guidance means
communicates the guidance information by distinctly displaying the
recommended travel lanes. Consequently, since the navigation system
provides guidance of the travel lane suitable for passing the
second intersection after passing the first intersection, the
driver is able to avoid an abrupt lane change or a useless lane
change after passing the first intersection, and to attain an
appropriate travel state with fewer lane changes.
[0012] It is also preferable that, when the second intersection is
an intersection where the vehicle makes a right-turn or a left-turn
next, the guidance information setting means sets guidance
information that minimizes the lane change frequency until the
vehicle reaches the second intersection. When there are lanes
having the same travel conditions, for example, when there are
plural directly advancing lanes at an intersection where the travel
route of a vehicle is set as directly advancing, since the vehicle
is able to travel with the minimum lane change frequency, the
driver easily attains an appropriate travel state.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] FIG. 1 is a block diagram illustrating the general
construction of a vehicle navigation system according to one
embodiment of the present invention;
[0014] FIG. 2 is a chart illustrating detailed contents of various
types of tables contained in a road unit;
[0015] FIG. 3 is a chart illustrating detailed contents of an
intersection unit;
[0016] FIG. 4 is a chart illustrating one example of data stored in
a guidance route memory;
[0017] FIG. 5 is a flow chart illustrating the operation procedure
of the navigation system in displaying intersection guidance
information;
[0018] FIG. 6 is a chart explaining a method of specifying the
second intersection;
[0019] FIG. 7 is a chart explaining the processing executed at step
104 in FIG. 5;
[0020] FIG. 8 is a chart explaining the processing executed at step
105 in FIG. 5;
[0021] FIG. 9 is a chart illustrating an example of displaying the
intersection guidance information;
[0022] FIG. 10 is a chart illustrating an example of displaying the
intersection guidance information, with an exclusive area
provided;
[0023] FIG. 11 is a chart illustrating an example of displaying the
intersection guidance information including only a recommended
travel lane;
[0024] FIG. 12 is a chart illustrating an example of displaying the
intersection guidance information, which presents the recommended
travel lanes and other possible travel lanes and does not present
the lanes where travel is not possible; and
[0025] FIG. 13 is a chart illustrating an example of displaying the
intersection guidance information including specific additional
information.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0026] The preferred embodiment of a navigation system according to
the invention will now be described with reference to the
accompanying drawings.
[0027] (1) General Construction of the Navigation System
[0028] FIG. 1 is a block diagram illustrating the general
construction of a vehicle navigation system according to a
preferred embodiment to which the invention is applied. The
navigation system illustrated in FIG. 1 includes a navigation
controller 1 that administers overall control, a DVD 2 in which
various map data necessary for displaying maps and searching routes
and the like are recorded, a disk read-out drive 3 that reads out
the map data recorded in the DVD 2, a remote control unit 4 through
which a user inputs various types of instructions, a GPS receiver 5
and a self-contained navigation sensor 6 that detect the vehicle
position and the vehicle azimuth, and a display unit 7 that
displays map images, guidance routes and the like.
[0029] The disk read-out drive 3 can be loaded with one or more
disks of the DVD 2 and reads out the map data from any one of the
DVD 2 under the control of the navigation controller 1. The disk
loaded is not necessarily a DVD, and it may be a CD. Further, both
a DVD and a CD may be loaded so as to be selectable.
[0030] The remote control unit 4 is equipped with several types of
keys that a user operates, such as a search key to give a route
search instruction, a route guidance mode key to set a route
guidance mode, a destination input key, a vertical/horizontal
cursor key, a map reduction/expansion key, and a setting key to
identify an item at the cursor position on the display. The remote
control unit transmits an infrared signal according to the state of
a key operation toward the navigation controller 1.
[0031] The GPS receiver 5 receives radio waves transmitted from
plural GPS receivers, executes three-dimensional position
measurement processing or two-dimensional position measurement
processing, calculates an absolute position and azimuth of a
vehicle (the azimuth is calculated on the basis of the vehicle
position at the present time and the vehicle position before one
sampling time .DELTA.T), and outputs these together with the time
of the position measurement. The self-contained navigation sensor 6
is equipped with an angular sensor such as a vibrational gyroscope
that detects a rotation angle of the vehicle as a relative azimuth
and a distance sensor that outputs one pulse at each specific
travel distance, and it calculates a relative position and azimuth
of the vehicle.
[0032] The display unit 7 displays, on the basis of the drawing
data outputted from the navigation controller 1, a map image for
the area surrounding the vehicle together with a vehicle position
mark, a starting point mark, a destination mark, etc., and displays
a guidance route, intersection guidance information and the
like.
[0033] (2) Detailed Contents of the Map Data
[0034] Next, the contents of the map data recorded in the DVD 2
will be explained in detail. The map data recorded in the DVD 2
assume a rectangular pattern partitioned by a specific longitude
and latitude as a unit, and the map data of the patterns each can
be specified and read out by designating the pattern number. The
map data of the patterns each include a "drawing unit" composed of
various data required for displaying a map, a "road unit" composed
of necessary data for various processing such as map matching,
route searching, and route guiding, and an "intersection unit"
composed of detailed data of intersections and the like.
[0035] In the road unit, a line connecting two arbitrary points on
a road is called a link, and a point connecting two or more links
is called a node. The road unit also includes a "unit header" that
identifies the road unit, a "connection node table" that contains
detailed data of all the nodes, a "node table" that indicates a
storage location of the connection node table, and a "link table"
that contains detailed data of a link specified by two adjoining
nodes.
[0036] FIG. 2 illustrates the detailed contents of various types of
tables contained in the road unit. The node table stores, as shown
in FIG. 2(A), the node records #0, #1, . . . corresponding to all
the nodes which are contained in the pattern being identified. The
node records each are assigned the node numbers sequentially from
#0 in the listed order, and indicate the storage locations of the
connection node tables corresponding to the nodes.
[0037] The connection node table contains, as shown in FIG. 2(B),
in correspondence with each of the existing nodes:
[0038] a. normalized longitude/latitude,
[0039] b. attribute flag of the node including an intersection node
flag indicating whether or not this node is an intersection node,
an adjoining node flag indicating whether or not this node is
located on the border with another pattern, and a branch
information indicating whether or not the link is branched at this
node, and if it is branched, indicating whether the branch is a
T-shape or a Y-shape,
[0040] c. number of connected nodes, when there are links of which
one end constitutes this node, indicating the number of nodes
constituting the other ends of the links,
[0041] d. number of traffic regulations, when there are traffic
regulations such as no right-turn, no U-turn, etc., for the links
connected to this node,
[0042] e. connection node records for the number of links,
indicating the link number of each of the links for which one end
constitutes this node,
[0043] f. traffic regulation records, when there are traffic
regulations, indicating the specific contents of the traffic
regulations corresponding to the number thereof,
[0044] g. adjoining node record, when this node is a node located
on the border with another pattern, indicating the storage location
of the connection node table of the corresponding node in the
adjoining pattern,
[0045] h. when this node is an intersection node, storage location
and size of the corresponding intersection record in the
intersection unit, etc.
[0046] Further, the link table contains, as shown in FIG. 2(C),
plural link records in the order of the link numbers, corresponding
to all the links that are contained in the pattern being
identified. Each of these link records contains:
[0047] a. link ID being a code applied to each link mainly for a
route search display,
[0048] b. node number 1 and node number 2 that specify two nodes
located on the ends of the link,
[0049] c. distance (length) of the link,
[0050] d. cost in traveling this link,
[0051] e. various road attribute flags including road attribute
information (presence of one-way road, etc.) associated with this
link,
[0052] f. road type flag indicating the kind of a road, e.g., the
actual road corresponding to this link is a high way or a general
road, and the breadth of a road, and
[0053] g. route number given to a road corresponding to this
link.
[0054] FIG. 3 illustrates the detailed contents of the intersection
unit. As shown in FIG. 3, the intersection unit stores an
intersection record including data relating to the intersection
itself for each intersection, an intersection direction information
record including data relating to the destinations of the road, an
intersection lane information record including data relating to the
lanes of the road existing in the intersection, etc.
[0055] (3) Construction and Operation of the Navigation
Controller
[0056] Next, the navigation controller shown in FIG. 1 will be
explained in detail. The navigation controller 1 includes a data
buffer 10 that provides the display unit 7 with the map image for
the area surrounding the vehicle position and the intersection
guidance information including the lane guidance at an
intersection, etc., a map read-out control unit 12, a map-drawing
unit 14, a VRAM 16, an intersection guidance unit 18, a guidance
information setting unit 20, an image-synthesizing unit 22, a
vehicle position calculating unit 30 that calculates the vehicle
position and map matching processing, route search processing, and
route guidance processing, a route search processing unit 32, a
guidance route memory 34, a guidance route drawing unit 38, a mark
image drawing unit 40, a remote control unit controller 60 that
provides a user with several types of operating images on the
display and transfers operating instructions from the remote
control unit 4 to the related units, a cursor position calculating
unit 62, and an operation image generating unit 64.
[0057] The data buffer 10 temporarily stores the map data from the
DVD 2 read out by the disk read-out drive 3. When the vehicle
position calculating unit 30 calculates the vehicle position, the
map read-out control unit 12 sends to the disk read-out drive 3 a
read-out request for the map data within a specific area including
the vehicle position, and causes the read-out drive 3 to read out
the map data for displaying the map from the DVD 2 and store the
data in the data buffer 10.
[0058] The map-drawing unit 14 produces map drawing data for the
display on the basis of the drawing unit contained in the map data
stored in the data buffer 10, and stores the produced map drawing
data in the VRAM 16.
[0059] The intersection guidance unit 18, which provides guidance
concerning the intersection that the vehicle is going to pass,
produces guidance information for a specific intersection including
recommended travel lane information and displays the guidance
information on the display screen of the display unit 7.
[0060] The guidance information setting unit 20 sets a recommended
travel lane, and outputs guidance information including the set
travel lane information to the intersection guidance unit 18.
Particularly, the guidance information setting unit 20 specifies an
intersection that the vehicle is about to pass (hereunder, referred
to as "the first intersection") and an intersection that the
vehicle passes thereafter, where the vehicle makes a right-turn or
a left-turn (hereunder, referred to as "the second intersection"),
sets as the recommended travel lane a travel lane by which the
vehicle achieves the minimum lane change frequency until it reaches
the second intersection, and outputs the set guidance information
to the intersection guidance unit 18. The method of setting the
guidance information will be detailed later.
[0061] The image-synthesizing unit 22 superimposes the map drawing
data read out from the VRAM 16 and the drawing data outputted from
each of the intersection guidance unit 18, the guidance route
drawing unit 38, the mark image drawing unit 40, and the operation
image generating unit 64 to synthesize the images, and outputs the
synthesized drawing data to the display unit 7.
[0062] The vehicle position calculating unit 30 calculates the
vehicle position on the basis of the detected data by the GPS
receiver 5 and the self-contained navigation sensor 6, and when the
calculated vehicle position is not on the road of the map data,
executes the map matching processing that corrects the vehicle
position. The route search processing unit 32 searches a travel
route that connects the destination and the starting point set in
advance under a specific condition. For example, under the
conditions of the shortest distance, the shortest time, and the
like, the travel route of the minimum cost is set as a guidance
route. As typical techniques for the route search that are
generally known, there are the Dijkstra method and the
breadth-first search method. Thus, the guidance route data set by
the route search processing unit 32 are expressed as a set of nodes
from the starting point to the destination, and are stored in the
guidance route memory 34.
[0063] FIG. 4 illustrates one example of data stored in the
guidance route memory 34. As shown in the drawing, the guidance
route data set by the route search processing unit 32 are expressed
as the set of nodes NS, N1, N2, . . . ,ND from the starting point
to the destination, and are stored in the guidance route memory
34.
[0064] The guidance route drawing unit 38 selects the data
contained in the map area which are to be drawn in the VRAM 16 at
that time. The data are selected from the guidance route data
stored in the guidance route memory 34 which are set by the route
search processing unit 32, and the guidance route drawing unit 38
produces the guidance route drawing data for superimposing the
guidance route on the map image. The mark image drawing unit 40
generates the vehicle position mark at the vehicle position after
the map matching is processed, and produces the drawing data for
generating a cursor mark having a specific shape.
[0065] The aforementioned route search processing unit 32
corresponds to the route search means, the guidance information
setting unit 20 corresponds to the guidance information setting
means, and the intersection guidance unit 18 corresponds to the
intersection guidance means.
[0066] The navigation system of this embodiment having the above
construction provides the display of the intersection guidance
information in parallel with the image display of the map
surrounding the vehicle position during route guidance. The
operation of the display will now be explained.
[0067] FIG. 5 is a flow chart illustrating the operation procedure
of the navigation system in the display of the intersection
guidance information, which is executed in parallel with the
display operation of a guidance route during route guidance.
[0068] When the route guidance mode key of the remote control unit
4 is pressed, a specific route guidance operation is started (step
100). For example, the guidance route drawing unit 38 reads out the
nodes on the guidance route stored in the guidance route memory 34,
selects the data stored in the area of the map image displayed at
that time out of the links connecting these nodes, and draws a
thick emphasized guidance route to superimpose it on the map image
corresponding to the links.
[0069] In parallel with this display operation of the guidance
route, the route search processing unit 32 reads out the next node
on the guidance route from the guidance route memory 34 (step 101),
and judges whether or not the node read out is the node ND of the
destination (step 102). The guidance route data stored in the
guidance route memory 34 contain the nodes N1, N2, . . .
corresponding to the transit points along the way and the node ND
corresponding to the destination. If the node read out is the node
ND of the destination, the intersection guidance operation is
terminated. If the node read out is an intersection node other than
the destination node, the data specifying the intersection node
(the node corresponding to the first intersection) are transferred
to the intersection guidance unit 18 and the guidance information
setting unit 20.
[0070] Next, the guidance information setting unit 20 specifies the
second intersection, namely, the intersection that the vehicle
passes after passing the first intersection, where the vehicle
makes a right-turn or a left-turn (step 103).
[0071] A method of specifying the second intersection will now be
described. FIG. 6 is a chart explaining a method of specifying the
second intersection. In the drawing, the links corresponding to the
roads are illustrated by "straight lines", and the nodes connecting
these links are shown by ".smallcircle.". The vehicle is assumed to
advance from the vehicle position G to the node N1 and make a
right-turn at the node N4 to the node N5. Here, the node N1
corresponds to the first intersection, and the node N4 corresponds
to the second intersection. In this case, the vehicle position G
can be acquired from the vehicle position calculating unit 30. The
nodes N1-N5 corresponding to the guidance route can be acquired
from the route search processing unit 32. To acquire the above node
N4 will specify the second intersection. Next, the method of
obtaining the node N4 corresponding to the second intersection will
be described.
[0072] The link numbers of the links for which one end constitute
this node are extracted with reference to the connection node table
corresponding to the nodes, and the numbers of the nodes on the
other ends of the links are extracted on the basis of the link
numbers with reference to the link table. Thus, the acquisition of
the numbers of the nodes on the other ends of the links will allow
calculating the orientations of the links on the basis of the
normalized longitudes and latitudes of the node of interest and the
node on the other end thereof. In the example shown in FIG. 6, the
calculation results of the orientation of the link connecting the
node N3 and the node N4 and the orientation of the link connecting
the node N4 and the node N5 will allow specifying the second
intersection where the vehicle should make the right turn.
[0073] As the second intersection is specified in this manner, the
guidance information setting unit 20, using the map data (mainly
the intersection unit) stored in the data buffer 10, specifies the
lanes that the vehicle is permitted to travel along the guidance
route in each of the first intersection and the second intersection
(step 104).
[0074] Next, among the lanes that the vehicle is permitted to
travel in the first intersection and the second intersection,
specified at step 104, the guidance information setting unit 20
specifies the travel lane (recommended travel lane) whereby the
vehicle makes the fewest lane changes until reaching the second
intersection (step 105).
[0075] FIG. 7 is a chart explaining the contents of the processing
executed at step 104. In the same manner as shown in FIG. 6, the
vehicle is assumed to advance to the node N1 from the vehicle
position G and make the right-turn to the node N5 at the node N4.
It is also assumed in regard to the lane configuration in each of
the nodes N1-N4 that the node N1 provides three directly advancing
lanes, the node N2 provides a right-turn and two directly advancing
lanes, the node N3 provides two directly advancing lanes and a
left-turn lane, and the node N4 provides a right-turn, directly
advancing, and left-turn lanes, as shown in FIG. 7. In this case,
it can be specified that the lane in which the vehicle is permitted
to travel at the node N4 corresponding to the second intersection
is the lane a, and the lanes in which the vehicle is permitted to
travel at the node N1 corresponding to the first intersection are
any of the lanes b, c, d, as shown in FIG. 7.
[0076] FIG. 8 is a chart explaining the processing executed at step
105. As the lane a is specified as the lane that the vehicle is
permitted to travel at the node N4 corresponding to the second
intersection, at the node N3 one node before, the lane e is
specified as the travel lane that does not involve a lane change in
advancing to the lane a at the node N4. As the lane e is specified
as the travel lane at the node N3, at the node N2 one node before,
the lane f is specified as the travel lane that reduces the
frequency of lane changes to the minimum in advancing to the lane e
at the node N3. As the lane f is specified as the travel lane at
the node N2, at the node N1 one node before (the node corresponding
to the first intersection), the lane c is specified as the travel
lane that does not involve a lane change in advancing to the lane f
at the node N2. As a result, a combination of the lane c, the lane
f, the lane e, and the lane a is specified as the recommended
travel lane that minimizes the frequency of lane changes until the
vehicle reaches the second intersection.
[0077] In this manner, in the direction facing to the node
corresponding to the first intersection from the node corresponding
to the second intersection, specifying as the travel lane the lane
that minimizes the frequency of lane changes between the adjoining
nodes will lead to specifying the recommended travel lane that
minimizes the frequency of lane changes until the vehicle reaches
the second intersection.
[0078] Next, the guidance information setting unit 20 outputs the
information regarding the guidance information including the
specified recommended travel lane to the intersection guidance unit
18. Receiving the guidance information, the intersection guidance
unit 18 produces, on the basis of the guidance information, the
drawing data for the intersection guidance information to display
the recommended travel lane with emphasis.
[0079] In parallel to producing the drawing data, the intersection
guidance unit 18 judges whether or not the first intersection is
approaching within a specific distance from the vehicle position
(step 106). Specifically, the intersection guidance unit 18
calculates the lengths of the links lying on the route before the
first intersection, on the basis of the map data (road unit, etc.)
stored in the data buffer 10, and determines whether the lengths
have become shorter than a specific value (for example, 300 m) to
thereby judge whether the first intersection approaches within the
specific distance or not. If the first intersection is beyond the
specific distance, the judgment at step 106 is repeated.
[0080] If the first intersection approaches within the specific
distance, the judgment becomes affirmative at step 106 and the
intersection guidance unit 18 outputs the drawing data of the
produced intersection guidance information to the
image-synthesizing unit 22. As the result, the recommended travel
lane is displayed with emphasis on the display screen of the
display unit 7 as the intersection guidance information (step
107).
[0081] FIG. 9 illustrates an example of displaying the intersection
guidance information. The example shown in FIG. 9 corresponds to
the recommended travel lane shown in FIG. 8, in which intersection
guidance information 100 corresponds to the node N1 shown in FIG.
8, and intersection guidance information 110 corresponds to the
node N2 shown in FIG. 8. A vehicle position mark 200 is displayed
at a specific position on the lower part of the display center. In
the intersection guidance information 100 corresponding to the node
N1, only the center lane of the three is emphatically displayed in
correspondence with the lane c as the recommended travel lane
(shown by hatching in FIG. 9). Also, in the intersection guidance
information 110 corresponding to the node N2, only the center lane
of the three is emphatically displayed in correspondence with the
lane f as the recommended travel lane.
[0082] As shown in FIG. 9, since the recommended travel lane is
emphatically displayed as the intersection guidance information,
this embodiment provides the driver with the opportunity to select
a more appropriate travel lane, as compared with the conventional
system that displays all the lanes that the vehicle can take at
each of the intersections. Further, since the embodiment displays
the intersection guidance information 110 corresponding to the
intersection that the vehicle passes next, at the same time in
addition to the intersection guidance information 100 corresponding
to the first intersection, the driver is able to recognize the
appropriate travel lane in advance, even in the case where the
distance between the first intersection and the next intersection
is short.
[0083] When the intersection that the vehicle passes after passing
the first intersection is not included within the display area for
the map image, the intersection guidance information 110 cannot be
presented in association with the intersection display position.
However, in such a case, it is only needed to set a specific
display position in advance within the display area for the map
image and display the intersection guidance information 110 at this
display position.
[0084] Thereafter, the intersection guidance unit 18 judges whether
or not the vehicle has passed the first intersection (step 108). If
not, the judgment at step 108 is repeated. If the vehicle has
passed the first intersection, the affirmative judgment is made at
step 108, and the processing returns to the step 101 and repeats
the operation after the read-out of the next node.
[0085] Thus, in the navigation system of this embodiment, in
executing the route guidance processing based on the guidance route
set by the route search processing unit 32, the guidance
information setting unit 20 provides a recommended travel lane as
the intersection guidance information concerning the first
intersection that the vehicle is going to pass, considering the
conditions of passage at the second intersection that the vehicle
passes after the first intersection, where the vehicle makes a
right or left turn, and the intersection guidance unit 18
emphatically displays the recommended travel lane as the
intersection guidance information, in accordance with the setting
of the recommended travel lane. In this manner, the navigation
system provides guidance concerning the first intersection that the
vehicle is going to pass, in consideration of the conditions of
passage at the second intersection that the vehicle passes after
the first intersection, and the driver easily attains an
appropriate travel state. Especially in this embodiment, the
guidance information setting unit 20 sets as a recommended travel
lane the travel lane that realizes the minimum frequency of lane
change until the vehicle reaches the second intersection.
Therefore, the driver is able to travel with the minimum frequency
of lane change, referring to the display of the intersection
guidance information including the recommended travel lane, so that
the driver can avoid an abrupt lane change or a useless lane change
after passing the first intersection.
[0086] The present invention is not limited to this embodiment, and
various modifications and changes are possible within the scope and
spirit of the invention. For example, the display example shown in
FIG. 9 provides, other than the intersection guidance information
100 corresponding to the node N1, namely, the first intersection,
the intersection guidance information 110 corresponding to the node
N2, namely, the intersection that the vehicle passes after the
first intersection. However, the display may be designed to provide
only the intersection guidance information 100 corresponding to the
first intersection, or in contrast, it may be made to provide
guidance information for more than two intersections.
[0087] Further, in the display example shown in FIG. 9, the
intersection guidance information 100, 110 are displayed in
superposition on the map image. However, an exclusive area for
displaying the intersection guidance information may be provided
separately from the display area for the map image. FIG. 10 is a
chart illustrating an example of displaying the intersection
guidance information in an exclusive area. In the drawing, the
display area is divided into two areas, right and left, and the
left display area is the exclusive area for displaying the
intersection guidance information and the right is the display area
for the map image. In the exclusive area for the intersection
guidance information, four intersection guidance information 100,
110, 120, 130 are displayed in correspondence with the recommended
travel lanes shown in FIG. 6. When the exclusive area for the
intersection guidance information is provided in this manner, the
driver is able to refer to plural intersection guidance
information, including an intersection that does not lie in the
display area for the map image, to grasp the recommended travel
lanes over a wider distance.
[0088] Further in FIG. 9 and FIG. 10, the intersection guidance
information provides a display of all the lanes in the
intersections and further the displays with emphasis only the
recommended travel lanes. However, it may provide only the
recommended travel lanes with the other lanes hidden on the
display. Or, it may display the recommended travel lanes and the
lanes that the vehicle can travel, and it may hide the lanes that
the vehicle cannot travel on the display.
[0089] FIG. 11 illustrates an example of displaying the
intersection guidance information in which only the recommended
travel lane is displayed. As intersection guidance information 100a
and 110a shown in FIG. 11, displaying only the recommended travel
lanes will simplify the contents of display. Further, in the case
of displaying only the recommended travel lanes, as shown in FIG.
11, the intersection guidance information may save an emphatic
display with a color or the like, and it may provide only the
display by an arrow that simply indicates the recommended travel
lane, or the like.
[0090] FIG. 12 illustrates an example of displaying the
intersection guidance information which presents the recommended
travel lanes and the travelable lanes and does not present the
lanes where traveling is not possible. As the intersection guidance
information 100b and 110b shown in FIG. 12, the display can be
simplified by presenting only the recommended travel lanes and
travelable lanes, without presenting the lanes where traveling is
not possible, so that the driver may easily grasp visually the
lanes in which the vehicle cannot travel.
[0091] Although the above-described embodiments provide the user
with the intersection guidance information by presenting the image
display on the screen of the display unit 7, the intersection
guidance information may be communicated to the user by outputting
specific guidance voice instructions that explain the recommended
travel lanes.
[0092] The above-described embodiments also have assumed the
intersection that the vehicle passes after the first intersection,
where the vehicle makes a right or left turn, is the second
intersection. However, the second intersection may be specified on
the basis of other conditions. For example, the intersection that
the vehicle passes next after passing the first intersection may be
specified as the second intersection. In this manner, it is
conceivable that an optimum recommended travel lane can be provided
in most cases by considering only two intersections from the
current vehicle position. In this case, the setting procedure of a
recommended travel lane can be simplified.
[0093] Further, the above-described embodiments have assumed the
intersection that the vehicle passes after the first intersection,
where the vehicle makes a right or left turn, is the second
intersection. However, if there continue many intersections where
the vehicle is to go straight, and if there exist many
intersections between the first intersection and the second, it may
be that the acquisition of a recommended travel lane in
consideration of all the intersections requires considerable time
for calculations. In such a case, it is possible to establish an
upper limit for the number of intersections (for example, 10
intersections) that are taken into consideration for the
calculation, or to establish an upper limit of time on the basis of
an estimated time for the travel of the set guidance route (for
example, 30 minutes), or to establish an upper limit of distance
(for example, 10 km); and it is only needed to set a recommended
travel lane in consideration of the intersections that lie within
the range of the upper limit. Also, if it is difficult to make a
judgment of choosing the travel lanes, all the travelable lanes at
the first intersection that the own vehicle is going to pass can be
chosen for guidance.
[0094] Additionally, there exists a type of road in which the
number of lanes in the adjoining intersections is coincident and
the lanes are dislocated for one lane. Therefore, it is preferable
to include information as to the state of connection of the lanes
in the lane information as additional information, or it is
preferable to associate each of the plural lanes with one link and
clarify the relation between the lanes in each adjoining
intersection.
[0095] FIG. 13 illustrates an example of displaying the
intersection guidance information in including specific additional
information. For example, as shown in FIG. 13(A), all three lanes
are directly advancing at the intersection 300, but the lanes are
reduced to two lanes after passing the intersection 300, and one
right-turn lane is added before the intersection 310 to make three
lanes again. In such a guidance route, the vehicle is assumed to
advance directly and pass each of the intersections 300, 310. In
this case, the intersection guidance information according to the
above-described embodiments, as shown in FIG. 13(B), provides the
display with emphasis of two lanes, the left and the center, as the
intersection guidance information 301 of the intersection 300, and
also provides the display with emphasis of two lanes, the left and
the center, as the intersection guidance information 311 of the
intersection 310 as well. However, it is preferable to provide the
display with emphasis of two lanes, the center and the right,
because the lanes are reduced after passing the intersection 300
along the actual travel route and such a display will match the
actual travel route more accurately.
[0096] In this case, if the additional information is given in such
a manner that the right lane and the center lane at the
intersection 300 are associated with the center lane and the left
lane at the intersection 310, respectively, the right lane and the
center lane are displayed with emphasis in the intersection
guidance information 301a of the intersection 300, and the center
lane and the left lane are displayed with emphasis in the
intersection guidance information 311a of the intersection 310, as
shown in FIG. 13(C), whereby the display will match the actual
travel route more accurately. In addition, a dislocation of the
display positions of the intersection guidance information 301a and
311a by a specific distance will make it easy for the driver to
visually grasp the associated lanes, in relation to the actual
travel lanes. Further, as shown in the intersection guidance
information 311a, providing the right-turn lane with a display
different from the other lanes (in FIG. 13(C), slant line and
hatching on the lower right corner) will notify the driver visually
that the right-turn lane is being added just before the
intersection 310.
[0097] According to the invention as described above, since the
navigation system is able to provide guidance concerning the first
intersection that the vehicle is going to pass in consideration of
the conditions of passage at a second intersection that the vehicle
passes after the first intersection, the driver can easily attain
an appropriate travel state. Particularly, since the navigation
system provides such guidance information so as to minimize the
frequency of lane changes before the vehicle reaches the second
intersection, the driver is able to achieve the minimum frequency
of lane change, to thereby avoid an abrupt lane change or a useless
lane change after passing the first intersection, and to thereby
attain an appropriate travel state.
* * * * *