Traffic information providing device, traffic information providing system, traffic information transmission method, and traffic information request method

• US 7,555,381 B2
• Filed: 08/07/2007
• Issued: 06/30/2009
• Est. Priority Date: 08/07/2006
• Status: Active Grant

• Current Assignee: Clarion Co., Ltd. (Faurecia SA)
• Original Assignee: Xanavi Informatics Corporation (Hitachi, Ltd.)
• Inventors: Kumagai, Masatoshi, Okude, Mariko, Tanikoshi, Koichiro
• Primary Examiner(s): Black; Thomas G
• Assistant Examiner(s): Chen; Shelley
• Application Number:
  US11/835,387
• Publication Number:
  US 20080030371A1
• Time in Patent Office: 693 Days
• Field of Search: 701117-119
• US Class Current: 701/117
• CPC Class Codes: G01C 21/26 specially adapted for navigation in a road network

Abstract

A probe center server (10) previously performs filtering to determine whether or not a projection norm of a link in a feature space can be interpolated, and notifies a probe terminal (20) to preferentially collect and upload detected probe data for the link whose missing data can not be interpolated.

Claims

1. A traffic information providing device for providing traffic information about links located in an area where the traffic information is provided, comprising:

a filter basis calculating device which acquires a traffic information history with missing data of a plurality of links located in the area, the traffic information history containing at least the traffic information, performs principal component analysis with missing data for the traffic information contained in the traffic information history to obtain components of traffic information which vary according to correlation between the plurality of links, and outputs the obtained components as feature space basis vectors for a group of such links;

a projective norm calculating device which generates a feature space with the output feature space basis vectors as axis vectors, the feature space indicating the correlation between the plurality of links, and calculates a projective norm, which is a norm of a projective vector formed by projecting a vector expressing the plurality of links to the feature space;

a correlation filter which compares the calculated projective norm with an interpolation threshold value to determine, based on the result of the comparison, whether or not the missing data can be interpolated for each link, and generates and outputs a list of links to be interpolated which contains the information about the links to be interpolated;

an interpolation basis calculating device which, among the traffic information contained in the traffic information history, performs the principal component analysis with missing data for the traffic information of the links to be interpolated to obtain components of traffic information which vary according to correlation between the traffic information of the links to be interpolated, and outputs the obtained components as interpolation bases for the group of links, the principal component analysis with missing data being performed to the links listed in the list of links to be interpolated;

a combined coefficient calculating device which calculates combined coefficient bases based on both current traffic information acquired from a probe car and the interpolation bases, and calculates combined coefficients as weights for the combined coefficient bases; and

a traffic information estimating device which calculates an estimated value of the traffic information of the links with missing current traffic information data by linearly combining the interpolation bases output by the interpolation basis calculating device.

2. The traffic information providing device according to claim 1,

wherein the correlation filter determines whether or not the missing data can be interpolated based on an interpolation threshold value determined by the number of the feature space basis vectors output by the filter basis calculating device.

3. The traffic information providing device according to claim 1,

wherein the combined coefficient calculating device acquires traffic information formed by substituting statistical information for the missing data of the current traffic information, calculates weighting interpolation bases, which performed weighting process to the components of the interpolation bases, based on the traffic information formed by substituting the statistical information for the missing data, and calculates the combined coefficients based on the traffic information formed by substituting the statistical information for the missing data and the calculated the weighting interpolation bases.

4. The traffic information providing device according to claim 1, further comprising:

an upload request device which refers, upon receiving an upload notice issued by a probe terminal connected via a communication network, to the current traffic information, calculates an area cover ratio of links to be interpolated, which represents a percentage of the links to be interpolated whose current traffic information is collected over a predetermined time period among the group of links located in a certain area, and compares the calculated area cover ratio of links to be interpolated with an upload threshold value of the links to be interpolated, which represents an upper limit of a preset communication capacity of the communication network, to determine whether or not the area cover ratio is smaller than the upload threshold value, notifies, if the area cover ratio is smaller than the upload threshold value, the probe terminal to preferentially upload the current traffic information of the links to be interpolated, calculates, if the area cover ratio is greater than the upload threshold value, the area cover ratio of the links not to be interpolated, determines whether or not the area cover ratio of the links not to be interpolated is smaller than the upload threshold value, notifies, if the area cover ratio of the links not to be interpolated is smaller than the upload threshold value, the probe terminal to preferentially upload the current traffic information of the links not to be interpolated to the traffic information providing device, and notifies, if the area cover ratio of the links not to be interpolated is greater than the upload threshold value, the probe terminal to preferentially upload the current traffic information of the links to be interpolated to the traffic information providing device.

5. A traffic information transmission method in a traffic information providing system configured by connecting a probe terminal, which includes at least a calculating device, a storage device and a communication device, with a traffic information providing device, which includes at least a calculating device and a storage device, via a communication network,

the calculating device of the traffic information providing device performing the steps of:

acquiring a traffic information history with missing data of a plurality of links located in a predetermined area, the traffic information history containing at least traffic information, performing principal component analysis with missing data for the traffic information contained in the traffic information history to obtain components of traffic information which vary according to correlation between the plurality of links, and outputting the obtained components as feature space basis vectors for a group of such links;

generating a feature space with the output feature space basis vectors as axis vectors, the feature space indicating correlation between the plurality of links, and calculating a projective norm, which is a norm of a projective vector formed by projecting a vector expressing the plurality of links to the feature space;

comparing the calculated projective norm with an interpolation threshold value to determine, based on the result of the comparison, whether or not the missing data can be interpolated for each link, and generating a list of links to be interpolated which contains the information about the links to be interpolated;

performing the principal component analysis with missing data for, among the traffic information contained in the traffic information history stored in the storage device, the traffic information of the links to be interpolated to obtain components of traffic information which vary according to correlation between the traffic information of the links to be interpolated, and outputting the obtained components as interpolation bases for the group of links, the principal component analysis with missing data being performed to the links listed in the list of links to be interpolated;

calculating combined coefficient bases based on both current traffic information acquired from the probe terminal and the interpolation bases, and calculating combined coefficients as weights for the combined coefficient bases; and

calculating an estimated value of the traffic information of the links with missing current traffic information data by linearly combining the interpolation bases output by the interpolation basis calculating device, and

the calculating device of the probe terminal performing the steps of;

receiving, at a timing when a transmission request for the traffic information is issued to the traffic information providing device via the communication device, the list of links to be interpolated from the traffic information providing device via the communication device, and storing the received list of links to be interpolated in the storage device; and

referring to the traffic information collected by the probe terminal itself and stored in the storage device, comparing a traffic information capacity with the upper limit of an upload capacity calculated based on a communication capacity of the communication network, and, when the traffic information capacity is greater than the upper limit of the upload capacity, referring to the list of links to be interpolated stored in the storage device to preferentially transmit the traffic information of the links not to be interpolated to the traffic information providing device via the communication device.

6. A traffic information request method in a traffic information providing system configured by connecting a plurality of probe terminals with a traffic information providing device, which includes at least a communication device, a calculating device and a storage device, via a communication network,

the calculating device of the traffic information providing device performing the steps of:

acquiring a traffic information history with missing data of a plurality of links located in a predetermined area, the traffic information history containing at least traffic information, performing principal component analysis with missing data for the traffic information contained in the traffic information history to obtain components of traffic information which vary according to correlation between the plurality of links, and outputting the obtained components as feature space basis vectors for a group of such links;

generating a feature space with the output feature space basis vectors as axis vectors, the feature space indicating the correlation between the plurality of links, and calculating a projective norm, which is a norm of a projective vector formed by projecting a vector expressing the plurality of links to the feature space;

comparing the calculated projective norm with an interpolation threshold value to determine, based on the result of the comparison, whether or not the missing data can be interpolated for each link, and generating a list of links to be interpolated which contains the information about the links to be interpolated;

performing the principal component analysis with missing data for, among the traffic information contained in the traffic information history, the traffic information of the links to be interpolated to obtain components of traffic information which vary according to correlation between the traffic information of the links to be interpolated, and outputting the obtained components as interpolation bases for the group of links, the principal component analysis with missing data being performed to the links listed in the list of links to be interpolated;

calculating combined coefficient bases based on both current traffic information acquired from the probe terminals and the interpolation bases, and calculating combined coefficients as weights for the combined coefficient bases;

referring, upon receiving a transmission request for transmitting the traffic information issued by the probe terminals via the communication device, to the current traffic information, calculating an area cover ratio of links to be interpolated, which represents percentage of the links to be interpolated whose traffic information is collected over a predetermined time period among the group of links located in the area, and comparing the calculated area cover ratio of links to be interpolated with an upload threshold value of the links to be interpolated, which represents an upper limit of a preset communication capacity of the communication network;

notifying, when the area cover ratio is smaller than the upload threshold value, the probe terminals via the communication device to preferentially transmit the current traffic information of the links to be interpolated to the traffic information providing device; and

calculating, when the area cover ratio is greater than the upload threshold value, the area cover ratio of the links not to be interpolated, determining whether or not the area cover ratio of the links not to be interpolated is smaller than the upload threshold value, notifying, when the area cover ratio of the links not to be interpolated is smaller than the upload threshold value, the probe terminals via the communication device to preferentially transmit the current traffic information of the links not to be interpolated to the traffic information providing device, and notifying, when the area cover ratio of the links not to be interpolated is greater than the upload threshold value, the probe terminals via the communication device to preferentially transmit the current traffic information of the links to be interpolated to the traffic information providing device.