U.S. patent application number 13/278448 was filed with the patent office on 2012-04-19 for method for locating road shapes using erroneous map data.
This patent application is currently assigned to PANASONIC CORPORATION. Invention is credited to Shinya Adachi, Yukio Ichikawa, Takashi Kawasato, Hiroyuki Maeda, Satoko Miyama, Naoki Yamada, Seiji Yoshida.
Application Number | 20120095672 13/278448 |
Document ID | / |
Family ID | 42027721 |
Filed Date | 2012-04-19 |
United States Patent
Application |
20120095672 |
Kind Code |
A1 |
Adachi; Shinya ; et
al. |
April 19, 2012 |
METHOD FOR LOCATING ROAD SHAPES USING ERRONEOUS MAP DATA
Abstract
A system includes a transmitting apparatus having a first
digital map and a receiving apparatus having a second digital map.
The second digital map shows a road segment at a different location
from the first digital map due to errors. The transmitting
apparatus transmits location information to the receiving
apparatus. The location information includes coordinates
information, attribute information, and relative information. After
receiving the location information from the transmitting apparatus,
the receiving apparatus identifies the location of a road segment
on the second digital map by using the coordinates information and
the attribute information and identifies a location of a traffic
event on the road segment on the second digital map by using the
relative information. The relative information includes a distance
from a start point of a road segment on the first digital map to
the location on the road segment on the first digital map.
Inventors: |
Adachi; Shinya; (Kanagawa,
JP) ; Miyama; Satoko; (Kanagawa, JP) ; Yamada;
Naoki; (Kanagawa, JP) ; Yoshida; Seiji;
(Kanagawa, JP) ; Ichikawa; Yukio; (Kanagawa,
JP) ; Kawasato; Takashi; (Tokyo, JP) ; Maeda;
Hiroyuki; (Kanagawa, JP) |
Assignee: |
PANASONIC CORPORATION
Osaka
JP
|
Family ID: |
42027721 |
Appl. No.: |
13/278448 |
Filed: |
October 21, 2011 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
12625076 |
Nov 24, 2009 |
8078563 |
|
|
13278448 |
|
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|
10075164 |
Feb 14, 2002 |
7634452 |
|
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12625076 |
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Current U.S.
Class: |
701/117 |
Current CPC
Class: |
G08G 1/096775 20130101;
G01C 21/34 20130101 |
Class at
Publication: |
701/117 |
International
Class: |
G08G 1/00 20060101
G08G001/00 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 27, 1999 |
JP |
11-242166 |
Claims
1. A system for identifying a location of a road segment in digital
maps, each map containing errors inherent in the reduced-scaling of
the digital maps and/or depending on the kind of the digital maps,
the digital maps including a first digital map and a second digital
map, the second digital map showing the road segment at a different
location from the first digital map due to the errors, the system
comprising: the transmitting apparatus that has the first digital
map and transmits the location information which indicates the road
segment on the first digital map to the receiving apparatus;
wherein the location information including: coordinates information
which indicates a list of coordinates of points on the road
segment, attribute information about the points or the road
segment, and relative information which indicates a location where
a traffic event occurred on the road segment, and the receiving
apparatus that has the second digital map, wherein after the
receiving apparatus receives the location information from the
transmitting apparatus, the receiving apparatus identifies the
location of the road segment on the second digital map by using the
coordinates information and the attribute information included in
the location information and identifies the location of the traffic
event on the road segment on the second digital map by using the
relative information included in the location information, wherein
the relative information includes a distance from a start point of
the road segment on the first digital map to the location on the
road segment on the first digital map.
2. A transmission apparatus adapted for operating as the
transmitting apparatus of the system according to claim 1.
3. A receiving apparatus adapted for operating as the receiving
apparatus of the system according to claim 1.
4. A method for identifying a location of a road segment in digital
maps, each map containing errors inherent in the reduced-scaling of
the digital maps and/or depending on the kind of the digital maps,
the digital maps including a first digital map and a second digital
map, the second digital map showing the road segment at a different
location from the first digital map due to the errors, the method
comprising: transmitting the location information which indicates
the road segment on the first digital map from the transmitting
apparatus; wherein the location information including: coordinates
information which indicates a list of coordinates of points on the
road segment, attribute information about the points or the road
segment, and relative information which indicates a location where
a traffic event occurred on the road segment; receiving the
location information from the transmitting apparatus at the
receiving apparatus; identifying the location of the road segment
on the second digital map by using the coordinates information and
the attribute information included in the received location
information at the receiving apparatus, and identifying the
location of the traffic event on the road segment on the second
digital map by using the relative information included in the
received location information at the receiving apparatus, wherein
the relative information includes a distance from a start point of
the road segment on the first digital map to the location on the
road segment on the first digital map.
Description
[0001] This application is a continuation of U.S. patent
application Ser. No. 12/625,076 filed Nov. 24, 2009, which is
incorporated herein by reference in its entirety.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to an information transmission
method for reporting on-road location information such as traffic
jams and accidents in a traffic information provision system, and
in particular to such a method that can correctly report a location
on a digital map.
[0004] 2. Description of the Related Art
[0005] In recent years, the number of vehicles that have
car-mounted navigation apparatus has been increasing rapidly. The
car-mounted navigation system has a digital map database and is
capable of displaying the map around the vehicle on a screen based
on the latitude/longitude data received by a GPS receiver as well
as displaying the travel locus and the result of search for a route
to the destination on the map.
[0006] In Japan, digital map databases are prepared by several
companies. The problem is that map data contains errors inherent in
the reduced-scale maps. Some of the maps on the market drawn on the
scale of 1:25000 contains errors of about 50 meters depending on
the location, and the errors vary with digital maps available from
those companies.
[0007] Latitude/Longitude data obtained from a GPS receiver may
contain errors of several tens of meters.
[0008] Some models of car-mounted navigation apparatus on the
market receive traffic jam information and accident information
from a traffic information provision system and display the traffic
jam and accident locations on the map or performs route search
using such information as additional search conditions.
[0009] In a prior traffic information provision system, as shown in
FIG. 8, traffic information is provided from a traffic information
collecting center 71 that has local jurisdiction over an area to an
information delivery center 72. Traffic information edited for each
transmission medium including FM broadcasts, road beacons and cell
phones is transmitted via respective media.
[0010] The traffic information collecting center 71 exchanges
traffic information with a traffic information collecting center 78
in other areas to collect traffic information in a wide service
area including the peripheral areas.
[0011] In the traffic information, for example, in case
latitude/longitude data on the location is presented alone in order
to report a traffic jam location or accident location, various
errors are contained depending on the kind of digital map database
of the car-mounted navigation apparatus as mentioned earlier. Thus,
different locations on the road could be recognized as the accident
location by the car-mounted navigation apparatus retaining a
digital map database from Company A and the car-mounted navigation
apparatus retaining a digital map database from Company B.
[0012] In order to alleviate incorrect information transmission, as
shown in FIG. 9A, crossings a, b on a road network are assumed as
nodes, and a road c connecting the nodes as a link. Each node is
assigned a node number uniquely representing the node (a=1111,
b=3333). Each link is assigned a link number uniquely representing
the link (c=11113333). The node numbers and link numbers thus
assigned are stored in the digital map database of each company, in
correspondence with each crossing and road.
[0013] Traffic information represents a point on the road by first
specifying a link number then the distance in meters from the start
of the link. For example, a representation "Location 200 meters
from the start of the road with link number=11113333" allows the
user to obtain the location P on the same road by tracing the road
with link number=11113333 as far as 200 meters from the node with
node number 1111, irrespective of what digital map data is used by
the car-mounted navigation system in question.
[0014] Node numbers and link numbers defined on a road network must
be changed to new numbers in case a road d is constructed or a road
is modified as shown in FIG. 9B. Such modifications to node numbers
and link numbers require updating of digital map data from each
company.
[0015] Construction of and modification to a road continue into the
future. As long as on-road location representation is made using
node numbers and link numbers, maintenance of digital map databases
is permanently accompanied by huge workload and resulting
costs.
[0016] The information delivery center must send information that
complies with past node numbers and link numbers for a
predetermined period, for example three to five years, as well as
the information of the latest year, in order to support navigation
systems sold in the past. This causes huge maintenance
workload.
[0017] In order to solve such problems, the inventor of the
invention has proposed a location information transmission method
that can report a location on a digital map without excessive
maintenance workload (JP2001-041757 A).
[0018] In this location information transmission method, an
information provider transmits on-road location information by
using road shape data consisting of string of coordinates
representing the road shape of a road section including the on-road
location having a predetermined length and relative data indicating
the on-road location in the road section. A party receiving the
on-road location information performs shape matching to identify
the road section on the digital map and uses relative data to
identify the on-road location in this road section.
[0019] For example, in case a traffic j am has occurred in the
section A to B on the road shown in FIG. 6, the road shape of the
road including the section is displayed in a string of coordinates
consisting of 601 points in 5-meter intervals, P.sub.0 (x.sub.0,
y.sub.0), P.sub.1 (x.sub.1,y.sub.1), . . . ,
p.sub.600(x.sub.600,y.sub.600). Here, x.sub.k and y.sub.k are
latitude and longitude data of the on-road point P.sub.k acquired
from the digital map database retained by the information provider.
Further, the distance l.sub.1 from the point
P.sub.0(x.sub.0,y.sub.0) to the traffic jam start point A and the
distance l.sub.2 from the point P.sub.0(x.sub.0,y.sub.0) to the
traffic jam end point B are obtained and the road shape data:
(x.sub.0,y.sub.0) (x.sub.1,y.sub.1), . . . , (x.sub.600,y.sub.600)
and traffic jam distance data: l.sub.1 to l.sub.2 m are generated
as location information. This location information is converted to
a predetermined transmission format and sent to the receiving
party.
[0020] The receiving party that has received this information
performs shape matching of map data in the digital map database
retained by the receiving party and the received map shape data,
and identifies the map shape on its own digital map. The receiving
party identifies the traffic jam section to be displayed on its
digital map based on the distance data from the start point of the
road section.
[0021] FIG. 7 shows an example of shape matching.
[0022] Roads Q, R included within the error range around the
P.sub.0 (x.sub.0, y.sub.0) point of map data read from the digital
map database 7 are selected as candidates.
[0023] Then, locations Q.sub.0, R.sub.0 on each candidate road
closest to P.sub.0 (x.sub.0, y.sub.0) are obtained and distance
P.sub.0-Q.sub.0 and distance P.sub.0-R.sub.0 are calculated.
[0024] This operation is carried out for each point
P.sub.1(x.sub.1, y.sub.1), . . . , P.sub.600 (x.sub.600,y.sub.600)
and the road section where the summation value of the root mean
square of the distances from each point P.sub.0, P.sub.1, . . . ,
p.sub.600 is smallest is obtained.
[0025] Then the section l.sub.1-l.sub.2 meters from the start point
of the road section is identified as a traffic jam section.
[0026] In this way, it is possible for the receiving party to
identify an on-road location without defining node numbers or link
numbers, by providing road shape data representing a road shape
using a string of coordinates. This location information can be
used when traffic information is exchanged between traffic
information collecting centers or when traffic information is
provided from an FM station or road beacon.
[0027] This method is disadvantageous in that it requires location
information on a great number of points on the road to be
transmitted in order to correctly report the road shape and is
consequently accompanied by huge transmit data. Reducing the number
of points on the target road could invite erroneous matching at the
receiving party.
SUMMARY OF THE INVENTION
[0028] The invention solves such problems and aims at providing a
location information transmission method that can report a road
shape by using only a small amount of data in transmitting the road
shape by using location information on a plurality of points on the
road.
[0029] According to the invention, when reporting an on-road
location on a digital map, an information provider transmits, as
on-road location information, string of coordinates information
representing the road shape of a road section including the on-road
location having a length that depends on the situation, additional
information including at least one information item chosen from a
group of the attribute information on the road including the road
location and detailed information on the nodes in the road section,
and relative information indicating the on-road location in the
road section. A party that has received this on-road location
information performs shape matching to identify the road section on
a digital map and uses the relative data to identify the on-road
location in this road section.
[0030] In this way, by transmitting additional information together
with string of coordinate information, the receiving party can
identify the road shape with high accuracy even when only a small
amount of string of coordinate data is available. This makes it
possible to reduce the amount of data transmissions and identify an
on-load location with high accuracy.
BRIEF DESCRIPTION OF THE DRAWINGS
[0031] FIG. 1A shows a flowchart of the procedure at the sending
party for implementing a location information transmission method
according to the invention;
[0032] FIG. 1B shows a flowchart of the procedure at the receiving
party for implementing a location information transmission method
according to the embodiment of the invention;
[0033] FIG. 2A shows nodes and interpolation points as well as
connecting link angles at crossing nodes in a location information
transmission method according to the embodiment of the
invention;
[0034] FIG. 2B shows connecting link angles by way of another
method;
[0035] FIGS. 3A and 3B are explanatory drawings of the processing
for omitting the interpolation points in a location information
transmission method according to the embodiment of the
invention;
[0036] FIG. 4 is a flowchart showing the procedure for omitting
portions of data from transmit data in a location information
transmission method according to the embodiment of the
invention;
[0037] FIGS. 5A and 5B show the structure of data transmitted via a
location information transmission method according to the
embodiment of the invention;
[0038] FIG. 6 is an explanatory drawing of road shape data and
distance data constituting the on-road location information in a
location information transmission method previously proposed;
[0039] FIG. 7 is an explanatory drawing showing an example of shape
matching;
[0040] FIG. 8 is an explanatory drawing showing a traffic
information provision system;
[0041] FIG. 9A is an explanatory drawing of node numbers and link
numbers;
[0042] FIG. 9B is an explanatory drawing of modifications to node
numbers and link numbers made when a new road is constructed.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0043] A location information transmission method in an embodiment
of the invention, information that already exists in a digital map
database is used to transmit a road shape to the distant party.
[0044] This location information transmission method uses nodes and
interpolation points for nodes included in a digital map database,
as a plurality of points on a road representing string of
coordinates. The nodes are on-road points specified in
correspondence with crossings, entrances/exits of tunnels,
entrances/exits of bridges and boundaries of administrative
districts. The interpolation points are points specified to
reproduce the road shape across nodes.
[0045] FIG. 2A illustrates P.sub.1, P.sub.2, P.sub.3, . . . as
nodes and interpolation points on a digital map. Of these points,
P.sub.2 and P.sub.6 indicating crossings are nodes and the other
point are interpolation points.
[0046] The location information transmission method transmits, as
additional information, detailed information on road types, road
numbers or crossing nodes that already exists in a digital map
database, on top of the string of coordinate information on the
nodes and interpolation points.
[0047] The road type is information to distinguish between
expressways, national highways, and major local highways. The road
numbers are numbers assigned to roads, such as National Highway
246. Detailed information on crossing nodes includes the number of
crossing links that connect to the node and the angle of crossing
links that connect to the node. The number of crossing links of the
crossing node P.sub.6 in FIG. 2A is 2. The angle of connecting
links is represented as d.sub.1, d.sub.2 formed by the links. The
angle between connecting links may be represented as d'.sub.1,
d'.sub.2 measured with respect to the true north of each link
(dotted line) as shown in FIG. 2B.
[0048] The additional information includes crossing names used for
crossing nodes and information on entrances/exits of tunnels,
entrances/exits of bridges and boundaries of administrative
districts represented by nodes.
[0049] The additional information includes information on the
accuracy level of the base map such as data obtained from the map
on a scale of 1 to 25,000 or 10,000, in order to provide a standard
for accuracy of transmitted information.
[0050] In the location information transmission method, from the
viewpoint of reducing the data amount, length of a string of
node/interpolation point coordinates to be acquired from the
periphery of the event location is changed and the coordinates of
interpolation points that contribute less to the improvement of
accuracy in shape matching are omitted.
[0051] Generally, in case the road density is high and a number of
roads are running in parallel, the receiving party tends to suffer
from erroneous matching thus making it more difficult to perform
correct shape matching. Thus, the location information transmission
system retrieves the road density of the periphery of the event
location and presence/absence of roads running in parallel with the
target road when acquiring a string of coordinates of nodes and
interpolation point from the periphery of the event location. The
method then acquires a longer string of coordinates of
node/interpolation point in case erroneous matching is likely to
result by also considering the accuracy level of the map, and a
shorter node/interpolation point string of coordinates in case
erroneous matching is unlikely to result.
[0052] Interpolation point omitting processing determines whether
the interpolation points are to be omitted in accordance with the
omitting conditions that are based on the distance and the angle.
An interpolation point is omitted only when the bearing has changed
by less than an angle of .alpha. (degrees) from the preceding node
or interpolation point against the bearing and the distance from
the preceding node or interpolation point is less than .beta.
(m).
[0053] In FIG. 3A, the interpolation point P.sub.k+1 is omitted
because the bearing d.sub.k from the interpolation point is less
than .alpha. and the distance g.sub.k from the interpolation point
P.sub.k is less than .beta.. For the next interpolation point
P.sub.k+2, it is determined whether the bearing d'.sub.k and the
distance g'.sub.k from the interpolation point P.sub.k satisfy the
thinning-out conditions. In fact, the distance g'.sub.k is shorter
than .beta. but the bearing deviation d'.sub.k is larger than
.alpha. so that the interpolation point P.sub.k+2 is not
omitted.
[0054] In the case of FIG. 3B, the interpolation point P.sub.k+1 is
omitted. For the interpolation point P.sub.k+2, the bearing
deviation d'.sub.k is smaller than a but distance g'.sub.k is
longer than .beta., so that the interpolation point P.sub.k+2 is
not omitted.
[0055] FIG. 4 shows the flow of the thinning-out procedure.
[0056] (Step 21:) For the interpolation point P.sub.n where n=1,
(Step 22:) it is determined whether the bearing deviation d.sub.n
from the preceding interpolation point or node is smaller than
.alpha.. In case it is smaller than .alpha., (Step 23:) it is
determined whether the distance g.sub.n from the preceding
interpolation point or node is shorter than .beta.. In case it is
shorter than .beta., (Step 24:) the interpolation point P.sub.n is
omitted.
[0057] (Step 25:) Processing of Step 22 through 24 is repeated for
interpolation points P.sub.n where n is incremented by 1.
[0058] In case d.sub.n is larger than a in Step 22, and in case
g.sub.n is longer than .beta., execution proceeds to Step 25
without omitting the interpolation point P.sub.n.
[0059] FIGS. 5A and 5B show the data structure of a string of
coordinates of the node and interpolation point data (node line
information) obtained after omitting the interpolation points and
the corresponding additional information.
[0060] The node string information in FIG. 5A assumes the nodes and
interpolation points on the target road as nodes. In the node
string information, longitude/latitude data of the position P.sub.1
is entered as coordinate values of the first node number
Longitude/Latitude data of the positions P.sub.2, . . . , P.sub.n
as well as difference data (x.sub.2,y.sub.2), . . . ,
(x.sub.n,y.sub.n) from the longitude/latitude data of the position
P.sub.1 is entered as coordinate values of the next and subsequent
node numbers P.sub.2, . . . , P.sub.n. In this way, by representing
the second and subsequent node positions in relative coordinates,
it is possible to reduce the data amount.
[0061] While relative coordinate is represented by using
differences from the longitude/latitude of the position P.sub.1 in
this example, it is possible to represent relative coordinates in
difference from the immediately preceding node (for example
difference from P.sub.n+1 in the case of P.sub.n). By doing so, it
is possible to further reduce the data amount in the data line
information.
[0062] The additional information in FIG. 5B displays the road type
code, road number of the target road and the number of crossings
representing the number of crossing nodes included in the
additional information. Moreover, for crossing nodes, the
additional information displays the node number (P.sub.2) linked to
the node string information, the number of connecting links (12) to
the crossing node (P.sub.2), the connecting link angle of the first
connecting link (1) to the crossing node (P.sub.2), . . . , the
connecting link angle of the twelfth connecting link (12) to the
crossing node (P.sub.2) respectively for each crossing node.
[0063] The node line information and the additional information are
used to set the road shape of a predetermined road section. The
relative data is used to set the on-road location in the road
section to be identified.
[0064] FIGS. 1A and 1B show flowcharts of the procedures at the
sending party and the receiving party for implementing the location
information transmission method.
[0065] The Sending Party,
[0066] (Step 1:) on input of the location of an on-road event such
as a traffic jam or an accident,
[0067] (Step 2:) acquires the string of coordinates of the nodes
and interpolation points on the periphery of the event location
from the digital map database retained by the sending party,
[0068] (Step 3:) acquires the additional information from the
digital map database,
[0069] (Step 4:) omits the interpolation points, represents the
resulting string of coordinates of nodes and interpolation points
after omitting the interpolation points in relative coordinates,
generates node string information,
[0070] (Step 5:) converts the node string information and
additional information representing the road section as well as the
relative data representing the event location in the road section
to the transmission format,
[0071] (Step 6) and transmits the resulting information.
[0072] The Receiving Party
[0073] (Step 11) upon receiving data,
[0074] (Step 12:) performs shape matching by checking the received
node string information and additional information against the data
in a digital map database retained by the receiving party, and
identifies the road section corresponding to the transmitted road
shape information.
[0075] The shape matching can be made using the approach shown in
FIG. 7 as mentioned earlier. In this practice, it is possible to
limit the candidate roads based on the road type code and the road
number in the additional information. When the locations Q.sub.k,
R.sub.k on each candidate road corresponding to the location
P.sub.k having each node number in the node line information is
obtained while P.sub.k is a crossing node, it is possible to check
the received data against the crossing information on the crossings
located in the close vicinity of Q.sub.k, R.sub.k thereby removing
the nonconforming roads from the candidate roads. This obtains the
corresponding road section quite accurately and quickly.
[0076] (Step 13:) The receiving party, identifying the target road
section, verifies the event location in the identified road section
based on the relative data representing the event location, then
displays the event location in the display screen.
[0077] In this way, according to the location information
transmission method, additional information is transmitted so that
it is possible for the receiving party to correctly grasp the
on-road location on a digital map even when the data amount in the
string of coordinates is reduced.
[0078] It is of course possible to use some location information
represented on a digital map beside traffic information as long as
the location information is calculated by using shape matching. The
location information transmission method may be also used in the
following applications:
[0079] Shape data other than road data (house shape, river shape,
administrative boundary, contour line) is used together with
additional information to transmit location information.
[0080] When a plurality of events are adjacent to each other, a
plurality of events are defined in a single shape data item to
reduce the information amount.
[0081] More than one reference points are defined on shape data.
Each event point off the road is represented in distance and
direction from each reference point. Shape data matching is made,
then the off-road event points are obtained using the distance and
direction from each reference point obtained anew.
[0082] As understood from the foregoing description, a location
information transmission method according to the invention can
correctly transmit the location on a digital map to a distant party
without using node numbers or link numbers on a road network. The
method transmits additional information as well as node line
information. This substantially reduces the amount of data
transmission necessary for reporting location information and
allows the receiving party to grasp the location quite accurately
and quickly.
[0083] With this method, it is possible to substantially reduce
workload and costs for maintenance of digital map databases thus
reducing the social costs for maintaining the traffic information
provision system.
* * * * *