U.S. patent application number 09/300606 was filed with the patent office on 2001-11-29 for route searching device.
Invention is credited to OHTA, KAZUTAKA.
Application Number | 20010047242 09/300606 |
Document ID | / |
Family ID | 14748877 |
Filed Date | 2001-11-29 |
United States Patent
Application |
20010047242 |
Kind Code |
A1 |
OHTA, KAZUTAKA |
November 29, 2001 |
ROUTE SEARCHING DEVICE
Abstract
A processor calculates an estimated travel time required to
travel from a current point to a destination or a passing point on
a route on the basis of a travel time represented by traffic-jam
information for a traffic-jam place which is represented by the
traffic-jam information received by a traffic information receiver,
and on the basis of a traffic-jam time calculated on the basis of
map data for the other places; accordingly, the travel time
required can be calculated in consideration of traffic-jam
conditions.
Inventors: |
OHTA, KAZUTAKA; (YAMATO-SHI,
JP) |
Correspondence
Address: |
PENNIE AND EDMONDS
1155 AVENUE OF THE AMERICAS
NEW YORK
NY
100362711
|
Family ID: |
14748877 |
Appl. No.: |
09/300606 |
Filed: |
April 27, 1999 |
Current U.S.
Class: |
701/423 ;
340/988 |
Current CPC
Class: |
G01C 21/3691
20130101 |
Class at
Publication: |
701/210 ;
701/209; 340/988 |
International
Class: |
G01C 021/32 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 28, 1998 |
JP |
10-118935 |
Claims
What is claimed is:
1. A route searching apparatus for searching a recommendable route
to a destination comprising: means for storing map data
representing road maps; means for receiving traffic jam information
representing traffic jam places and a travel time needed to pass
through a section in which each traffic jam place is located by
communication; and travel time calculating means for setting the
travel time represented by the traffic jam information as an
effective travel time for each traffic jam section represented by
the traffic jam information thus received while setting a travel
time calculated on the basis of the map data as an effective travel
time for the other sections, calculating the sum of effective
travel times for respective sections located between the current
position on the searched recommendable route and a destination or a
point on the recommendable route for which an estimated travel time
is calculated, and displaying the sum of the effective travel times
thus calculated as the travel time needed to travel from the
current position to the destination or the point on the
recommendable road for which the estimated travel time is
calculated.
2. The route searching apparatus as claimed in claim 1, wherein
said travel time calculating means calculates the rate of the sum
of the travel times for said traffic jam sections represented by
the traffic-jam information to the sum of the effective travel
times and displays the rate thus calculated.
3. A required travel time calculating method for calculating a
travel time required to travel from a current position to an end
point on a given route or a point on the route, comprising the
steps of: storing map data representing road maps in advance;
receiving traffic-jam places and a travel time required to pass
through a section in which each of the traffic-jam places is
located by communication; setting the travel time represented by
the traffic jam information as an effective travel time for each
traffic jam section represented by the traffic jam information thus
received while setting a travel time calculated on the basis of the
map data as an effective travel time for the other sections; and
calculating the sum of effective travel times for respective
sections located between the current position on the searched road
and the end point or the point on the route for which an estimated
travel time is calculated, as the travel time needed to travel from
the current position to a destination or a point on a recommendable
road for which the estimated travel time is calculated.
4. A storage medium for storing programs which are read out and
executed by a computer, characterized in that said program makes
said computer execute a step of receiving traffic-jam places and a
travel time required to pass through a section in which each of the
traffic-jam places is located; a step of setting the travel time
represented by the traffic jam information as an effective travel
time for each traffic jam section represented by the traffic jam
information thus received while setting a travel time calculated on
the basis of the map data, previously stored by the computer, as an
effective travel time for the other sections; and calculating the
sum of effective travel times for respective sections located
between the current position on the searched road and the end point
or the point on the route for which an estimated travel time is
calculated, as the travel time needed to travel from the current
position to a destination or a point on a recommendable road for
which the estimated travel time is calculated.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a technique for searching a
recommendable route to a destination and calculating an estimated
travel time needed for the route in a navigation apparatus
installed in a vehicle, etc.
[0003] 2. Description of Related Art
[0004] With respect to a navigation apparatus installed in a
vehicle, there has been known a technique of searching a route
extending from a departure place to a destination on the basis of
road map data and suggesting the route thus searched as a
recommendable route to a user.
[0005] Such a recommendable route searching operation is carried
out by searching (selecting) a route needing the minimum cost in
available routes between the departure place and the destination
according to a technique called as "Dijkstra algorithm" or the
like. In this method, the total distance of the route or the travel
time needed for the route is usually selected as the "cost" defined
in this method.
[0006] The estimated travel time needed for the route (hereinafter
merely referred to as "estimated travel time") is calculated as
follows. When a recommendable route is determined, the length of
each of the roads constituting the recommendable route is weighted
with the value corresponding to the type of each road (expressway,
public road or the like) to set the value thus weighted as a travel
time for each road, and the estimated travel time is calculated on
the travel times for the roads.
[0007] Recently, there has been put into practice a traffic
information communicating system for supplying traffic information
to users of vehicles through communications, which is known as VICS
(the trademark of the foundation of Traffic Information
Communication System Center).
[0008] According to this traffic information communication system,
traffic information such as traffic jams, traffic regulations, etc.
is transmitted from the center to vehicles by optical beacons or
electric wave beacons disposed on roads or by FM
multi-broadcasting, thereby enabling real-time use of traffic
information in the vehicles. In a conventional navigation
apparatus, when traffic regulation information is received from
such a traffic information communication system, the contents
representing the traffic regulation information are notified to
users in the form of characters, voices and displays of figures on
a road map.
SUMMARY OF THE INVENTION
[0009] The above-described conventional technique for calculating
an estimated travel time needed for a recommendable route has the
following problem.
[0010] That is, the travel time needed for the recommendable route
is calculated on the basis of fixed parameters such as the length
of each road, the type of each road, etc., and thus when some roads
of the recommendable route suffer from traffic jam for traffic
regulation such as one-way traffic or the like, the estimated
travel time thus calculated differs greatly from actual travel
time.
[0011] Therefore, an object of the present invention is to
calculate an estimated travel time for a recommendable route, which
more meets an actual traffic condition.
[0012] In order to attain the above object, a route searching
apparatus for searching a recommendable route to a destination
includes: means for storing map data representing road maps; means
for receiving traffic jam information representing traffic jam
places and a travel time needed to pass through a section in which
each of the traffic jam places is located by communication; and
travel time calculating means for setting the travel time
represented by the traffic jam information as an effective travel
time for the traffic jam section represented by the traffic jam
information thus received while setting a travel time calculated on
the basis of the map data as an effective travel time for the other
sections, calculating the sum of effective travel times for
respective sections located between the current position on the
searched recommendable road and a destination or a point on the
recommendable route for which an estimated travel time is
calculated, and displaying the sum of the effective travel times
thus calculated as the travel time needed to travel from the
current position to the destination or the point on the
recommendable road for which the estimated travel time is
calculated.
[0013] According to the above route searching apparatus, traffic
jam information is picked up from a traffic information
communication system such as VICS or the like and the estimated
travel time is calculated in consideration of the traffic jam
information. Therefore, even when a traffic jam occurs or traffic
regulation is carried out, an estimated travel time conforming to
the actual traffic conditions can be calculated.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] FIG. 1 is a block diagram showing the constitution of a
navigation apparatus according to an embodiment of the present
invention;
[0015] FIG. 2 is a diagram showing the constitution of map data
according to the embodiment of the present invention;
[0016] FIG. 3 is a flowchart showing the operation of the
navigation apparatus according to the embodiment of the present
invention;
[0017] FIG. 4 is a diagram showing how a dynamic travel time is
calculated according to the embodiment of the present invention;
and
[0018] FIG. 5 is a diagram showing an example of a display
according to the embodiment of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0019] A preferred embodiment of a route searching apparatus
according to the present invention will be described using a case
where the present invention is applied to a vehicle-mount type
navigation apparatus.
[0020] FIG. 1 shows the construction of a navigation apparatus
according to an embodiment of the present invention.
[0021] In FIG. 1, reference numeral 1 represents a processor
comprising a microprocessor and a memory, reference numeral 2
represents a display device, reference numeral 3 represents a drive
device for accessing a storage medium such as CD-ROM or the like in
which map data are stored, reference numeral 4 represents an input
device for accepting an instruction input of a user, reference
numeral 5 represents a sensor device comprising a vehicle-speed
sensor, an azimuth sensor, a GPS receiver, etc., and reference
numeral 6 represents a traffic information receiving device for
receiving traffic information from a traffic information
communication system such as VICS or the like as described
above.
[0022] Here, map data is recorded in a storage medium such as
CD-ROM or the like to be loaded in the drive device 3 will be
described.
[0023] As shown in FIG. 2, the map data comprises road data 21
provided for each road, and the road data 21 comprises road
information 22 and link information 23.
[0024] The road information 22 contains a road number 26
representing a road uniquely, a road name 24 representing the name
of a road, a road type 27 representing the type of road (toll road,
national highway, prefectural highway), and other attributes 25
representing other information for the road.
[0025] The link information 23 contains link data 28 representing
information of links provided for every link constituting a road.
Here, "link" is a line segment used for approximating the shape and
position of a road. The link data 28 contains a link number 29
representing a link uniquely and a time required 30 corresponding
to a value proportional to the length of the link.
[0026] Further, the link data 28 contains node information 31 which
is information of a link to be next described, for example,
information representing that the node is an interchange or service
area of an expressway, an intersection or the like.
[0027] Further, the link data 28 contains, for two nodes at both
sides of a link, a node number 32 representing a node uniquely, a
node coordinate 35 representing the position of the node, and an
adjacent node number list 34 in which the node numbers of all the
nodes linked to the node concerned through links are listed. Here,
the linkage between links is necessarily performed through a node.
At a crossroads, a node is located at the center of the crossroads,
and four links are linked to the node at the center. In this case,
the adjacent node number list 34 of the node at the center contains
the description of the node numbers of four nodes at the other ends
of the four links which are linked to the node concerned.
[0028] The link data 28 contains link shape information 36
specifying the shape of a link. The link shape information 36
comprises one or plural sub node coordinates 37. When the number of
the sub node coordinates 37 is equal to two, the shape of the link
is specified as a shape obtained by successively and linearly
connecting a first node coordinate of the link, a first sub node
coordinate, a second sub node coordinate and a second node
coordinate of the link in this order.
[0029] With the above constitution, the processor 1 calculates the
current position of the vehicle by referring to a vehicle travel
azimuth input from the azimuth sensor of the sensor device 5, a
vehicle speed input from the vehicle-speed sensor of the sensor
device 5 and mesh map data to which the measured current position
input from the GPS receiver of the sensor device 5 belongs, and
calculates an estimated route from the current position to the
destination on the basis of a destination input through the input
device 4 by a user and the current position input through the input
device 4 by the user or calculated from the input from the sensor
device 5.
[0030] The processor 1 controls the drive device 3 to read out the
map data on the basis of the current position thus calculated, the
travel azimuth of the vehicle and the content indicated through the
input device 5 by the user, and displays a map represented by the
map data on the display device 2. The map display is carried out by
displaying a map of an area around the calculated current position
on a predetermined reduced scale, displaying a map of a district
indicated by the user on a predetermined or indicated reduced
scale, or displaying a map covering a region from the current
position to the destination in a proper reduced scale together with
a searched recommendable route. At this time, marks representing
the current position and the travel azimuth of the vehicle are
displayed on the map while overlaid on the map.
[0031] The estimated travel time calculation processing executed by
the processor 1 will be described below.
[0032] FIG. 3 is a flowchart showing the estimated travel time
calculation processing.
[0033] In this processing, the link data 28 of links on a searched
recommendable route are checked to select calculation points used
to calculate the estimated travel time. As the calculation points,
there are selected the destination, and nodes which are described
in node information 31 as intersections, interchanges and service
areas, or which serve as transfer points between different roads on
the recommendable route, among nodes located in a predetermined
range from the current position to a position on moving direction
(step 301).
[0034] Next, the estimated travel time required to travel to each
calculation point is calculated (step 302).
[0035] The calculation of the estimated travel time required is
performed as follows.
[0036] That is, for each link on the recommendable road between the
current position and the destination, the travel time 30 of the
link data of each link is weighted with a value corresponding to
the road type 27 of the road information of the road data 21 to
which the link data 28 concerned belongs, thereby obtaining the
static travel time required. At the same time, the link length of
each link is calculated on the basis of the link data 28.
[0037] Subsequently, a travel time required to travel between a
traffic-jam starting point and a traffic-jam ending point which are
represented by traffic-jam information received by the traffic
information receiver 6 is taken. Here, the travel time represented
by the traffic-jam information received by the traffic information
receiver 6 represents the current travel time required between the
traffic-jam starting point and the traffic-jam ending point which
is actually measured. A dynamic travel time required for each link
is calculated from the static travel time required for the link by
the following equation:
Dynamic travel time=M-(M.times.Y/X)+N
[0038] Here, as shown in FIG. 4, X represents the link length of a
link 400, M represents a static travel time calculated for the link
400, Y represents the length of a part 401 contained in the link
400 of a section between the traffic-jam starting point and the
traffic-jam ending point, and N represents a travel time of the
part 401 which is calculated on the basis of the travel time
received by the traffic information receiver 6.
[0039] If the value of the dynamic travel time calculated by the
above equation is larger than the static travel time by a
predetermined rate or more (two times or more), it is estimated
that the reception content of the traffic information receiver 6
may contain an error, and thus the static travel time is directly
used as the dynamic travel time.
[0040] Subsequently, for each calculation point, the sum of the
dynamic travel times calculated for the respective links between
the current position and the calculation point is calculated, and
it is set as an estimated travel time required to travel from the
current point to the calculation point concerned. Further, the
total link length calculated from the respective links between the
current point and the calculation point is set as a travel distance
from the current point to the calculation point (step 303).
[0041] Subsequently, the sum of the static travel time required for
the respective links from the current position to the destination
is subtracted from the estimated travel time calculated, and the
ratio of the subtraction result to the estimated travel time is
calculated as a traffic-jam rate (step 304).
[0042] The travel time required to travel to each calculation point
is displayed together with the travel distance to the calculation
point concerned as shown in FIG. 5, for example.
[0043] In FIG. 5, the estimated travel time 502 and the travel
distance 503 to each calculation point are displayed at both the
right and left sides of the name 501 of each of the interchanges,
intersections and services represented by the node information 31
of nodes (excluding the destination) selected as calculation
points. A road between calculation points is displayed as a line
segment 505 connecting the names of the nodes, and the name 504 of
the road is displayed on its side. A line segment 506 approximately
representing a traffic-jam section specified by a traffic-jam
starting point and a traffic-jam ending point, the information of
which is received by the traffic information receiver, is displayed
with every different color on the line segment 505. A mark 510
representing a regulation content represented by regulation
information received by the traffic information receiver 6 is
displayed in the neighborhood of a regulated place. Further, the
estimated travel time 507 and the travel distance 509 to the
destination and a bar graph showing the traffic-jam rate are
displayed at the upper side.
[0044] In the calculation of the dynamic travel time described
above, the static travel time is directly used as the dynamic
travel time when the dynamic travel time is larger than the static
travel time by a predetermined rate or more. On the basis of
regulation information received by the traffic information receiver
6, the predetermined rate for the dynamic travel time of a
traffic-jam section containing a traffic-jam place which is
estimated to be caused by a traffic regulation may be set to a
value larger than that in the other cases. This is because when a
traffic jam is caused by a traffic regulation, the dynamic travel
time may be large irrespective of a reception error of the traffic
information receiver 6.
[0045] As described above, according to this embodiment, the
estimated travel time is calculated in consideration of the
traffic-jam and traffic regulation information taken from the
traffic information communication system. Therefore, even when a
traffic jam occurs or traffic regulation is carried out, an
estimated travel time conforming more to actual traffic conditions
can be calculated.
[0046] In this embodiment, the processor 1 may be a computer having
a CPU, a memory and a proper OS. In this case, each process
executed by the processor 1 is implemented by the CPU executing a
program in which the procedure of each process is described. In
this case, these programs may be supplied to the processor 1
through a storage medium such as a CD-ROM or the like.
[0047] As described above, according to the present invention, an
estimated travel time conforming more to actual traffic conditions
can be calculated.
* * * * *