Map generation system and map generation method by using GPS tracks

• US 20080262721A1
• Filed: 02/05/2008
• Published: 10/23/2008
• Est. Priority Date: 04/17/2007
• Status: Active Grant

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Guo, Tao, Koga, Masashi
• Granted Patent: US 8,359,156 B2
• Time in Patent Office: Days
• US Class Current: 701/208
• CPC Class Codes: G01C 21/3819 Road shape data, e.g. outline of a route
• CPC Class Codes: G01C 21/3837 Data obtained from a single source

Abstract

A map generation system comprising: a mobile device for acquiring location data of a vehicle and a status of the vehicle at a time of acquisition of the location; and a server for processing the acquired location data of the vehicle. The server comprises an input interface, a first storage unit, a processor and a second storage unit. The server includes a management unit for collecting a plurality of pieces of the track data obtained by a motion of the vehicle, an extraction unit for extracting feature points of the plurality of pieces of the track data on a road from which the plurality of pieces of the track data are collected to calculate a Spline curve satisfying the extracted feature points, and an update unit for adding the calculated Spline curve as a lane central line to the digital road map to update map data.

Claims

1. A method of generating a digital road map, comprising:

a first step of collecting a plurality of pieces of track data obtained by a movement of a vehicle;

a second step of extracting feature points of the plurality of pieces of track data for a road from which the plurality of pieces of track data are collected to calculate a Spline curve satisfying the extracted feature points; and

a third step of adding the calculated Spline curve as a lane central line to the digital road map to update map data.

2. The method of generating a digital road map according to claim 1, wherein:

the first step includes the steps of acquiring location data of the vehicle obtained over time by a GPS as the track data and collecting the obtained plurality of pieces of track data to generate a database;

the second step includes the steps of partitioning a road to be updated into a plurality of segments, interpolating the collected plurality of pieces of track data into each of the plurality of segments of the road obtained by the partition, extracting the feature points from the plurality of pieces of track data by using a least square method for each of the plurality of segments, and calculating the Spline curve passing through the extracted feature points as a candidate of a road central line; and

the third step includes the step of updating, when an error of the Spline curve calculated as the candidate is sufficiently converged, the map data with the Spline curve calculated as the candidate.

3. The method of generating a digital road map according to claim 2, wherein:

a process of acquiring the location data of the vehicle in the first step can be selected any one of a first mode, a second mode, and a third mode;

in the first mode, it is allowed whether the location data is recorded to be set by an operator of the vehicle;

in the second mode, it is controlled the location data not to be recorded when there is no more recording capacity for the location data; and

in the third mode, it is controlled the location data to be recorded when an external signal is received.

4. The method of generating a digital road map according to claim 3, wherein the first step further includes the steps of:

recording location data including the location of the vehicle obtained by the GPS, a data acquisition time, an identifier of a road on which the vehicle is present, and a velocity and a running direction of the vehicle when the location data is controlled to be recorded;

generating data for recording the recorded location data in association with a road on the map; and

linking the generated data for recording in order of acquisition time of the location data to be stored as track data in a track database.

5. The method of generating a digital road map according to claim 2, wherein the first step further includes the steps of:

receiving an input of the location data of the vehicle;

verifying validity of the input location data;

generating track data corresponding to an identifier of a road when the input location data is valid; and

storing the generated track data.

6. The method of generating a digital road map according to claim 2, wherein the second step further includes the steps of:

determining necessity of update of the map data of the road from which the plurality of pieces of track data are collected;

specifying track data used for update based on an identifier of the road determined as being required to be updated and a date and a time of acquisition of each of the plurality of pieces of track data;

interpolating the specified track data into each of the plurality of segments obtained by partitioning the road;

extracting a ridge point from the specified track data by using the least square method for each of the plurality of segments; and

calculating the Spline curve passing through the extracted ridge point as a candidate of the road central line.

7. The method of generating a digital road map according to claim 6, wherein the second step further includes the steps of:

comparing an error of the track data used for update with a predetermined threshold value; and

interpolating the specified track data into each of the plurality of segments obtained by partitioning the road when it is judged that the error is converged.

8. The method of generating a digital road map according to claim 6, wherein the second step further includes the steps of:

comparing the number of pieces of the track data used for update with a predetermined threshold value; and

interpolating the specified track data into each of the plurality of segments obtained by partitioning the road when it is judged that the number of pieces of the track data is larger than the threshold value.

9. The method of generating a digital road map according to claim 2, wherein the third step further includes the steps of:

determining whether the calculated Spline curve is sufficiently converged and further comparing an attribute of the calculated Spline curve and an attribute of a current lane central line with each other; and

updating the map data with the calculated Spline curve when accuracy of the calculated Spline curve is higher than accuracy of the current lane central line and the attribute of the calculated Spline curve and the attribute of the current line central line are identical with each other.

10. The method of generating a digital road map according to claim 9, wherein the attribute of the calculated Spline curve includes a lane node-link, a width of the lane, and a curvature of the lane.

11. The method of generating a digital road map according to claim 1, further comprising a fourth step of correcting the lane central line by referring to a set of highly accurate reference positions.

12. The method of generating a digital road map according to claim 11, wherein the fourth step further including the steps of:

extracting a nearest neighboring point for each of the reference positions from points on the lane central line before correction;

obtaining a difference between each of the reference positions and the nearest neighboring point; and

obtaining a correction vector of each of the points on the lane central line according to a distance from each of two nearest neighboring points.

13. A map generation system comprising:

a mobile device set in the vehicle for acquiring location of a vehicle obtained by a GPS system and a status of the vehicle at a time of acquisition of the location; and

a server for processing the acquired location data of the vehicle, the location data being used to generate a digital road map, wherein the server comprises;

an input interface for receiving the location data of the vehicle;

a first storage unit for storing the received location data;

a processor for generating a GPS track from the received location data to generate a map object from the generated GPS track; and

a second storage unit for storing a map database, and

wherein the processor is configured, by executing a predetermined computer program, to including;

a management unit for collecting a plurality of pieces of the track data obtained by a motion of the vehicle;

an extraction unit for extracting feature points of the plurality of pieces of the track data on a road from which the plurality of pieces of the track data are collected to calculate a Spline curve satisfying the extracted feature points; and

an update unit for adding the calculated Spline curve as a lane central line to the digital road map to update map data.

14. The map generation system according to claim 13, wherein:

the management unit is configured to acquire location data of the vehicle obtained over time by the GPS system as track data and collect the obtained plurality of pieces of track data to generate a database;

the extraction unit is configured to partition a road to be updated into a plurality of segments, interpolate the collected plurality of pieces of track data into each of the plurality of segments of the road obtained by the partition, extract the feature points from the plurality of pieces of track data by using a least square method for each of the plurality of segments, and calculate the Spline curve passing through the extracted feature points as a candidate of a road central line; and

the update unit is configured to update the map data with the Spline curve calculated as the candidate when an error of the Spline curve calculated as the candidate is sufficiently converged.

15. The map generation system according to claim 14, wherein:

the mobile device comprises a GPS receiver for measuring a location of the vehicle;

a location data recording unit for recording location data measured by the GPS receiver; and

an output interface for transmitting the recorded location data;

the location data recording unit is configured to be set to operate in any one of a first mode, a second mode, and a third mode as a method of acquiring the location data of the vehicle;

in the first mode, it is allowed whether the location data is recorded in the location data recording unit to be set by an operator of the vehicle;

in the second mode, it is controlled the location data not to be recorded in the location data recording unit when there is no more recording capacity for the location data; and

in the third mode, it is controlled the location data to be recorded in the location data recording unit when an external signal is received.

16. The map generation system according to claim 15, wherein the location data recording unit is configured to:

record location data including the location of the vehicle obtained by the GPS, a data acquisition time, an identifier of a road on which the vehicle is present, and a velocity and a running direction of the vehicle when the location data recording unit is controlled to record the location data;

generate data for recording the recorded location data in association with a road on the map; and

link the generated data for recording in order of acquisition time of the location data to be stored as track data in a track database.

17. The map generation system according to claim 14, wherein the management unit is configured to:

receive an input of the location data of the vehicle;

verify validity of the input location data;

generate track data corresponding to an identifier of a road when the input location data is determined as valid; and

store the generated track data.

18. The map generation system according to claim 14, wherein the extraction unit is configured to:

determine necessity of update of the map data of the road from which the plurality of pieces of track data are collected;

specify track data used for update based on an identifier of the road determined as being required to be updated and a date and a time of acquisition of each of the plurality of pieces of track data;

interpolate the specified track data into each of the plurality of segments obtained by partitioning the road;

extract a ridge point from the track data by using the least square method for each of the plurality of segments; and

calculate the Spline curve passing through the extracted ridge point as a candidate of the road central line.

19. The map generation system according to claim 18, wherein the extraction unit is configured to:

compare an error of the track data used for update with a predetermined threshold value; and

interpolate the specified track data into each of the plurality of segments obtained by partitioning the road when it is judged that the error is converged.

20. The map generation system according to claim 18, wherein the extraction unit is configured to:

compare the number of pieces of the track data used for update with a predetermined threshold value; and

interpolate the specified track data into each of the plurality of segments obtained by partitioning the road when it is judged that the number of pieces of the track data is larger than the threshold value.

21. The map generation system according to claim 14, wherein the update unit is configured to:

determine whether the calculated Spline curve is sufficiently converged and further compare an attribute of the calculated Spline curve and an attribute of a current lane central line with each other; and

update the map data with the calculated Spline curve when accuracy of the calculated Spline curve is higher than accuracy of the current lane central line and the attribute of the calculated Spline curve and the attribute of the current line central line are identical with each other.

22. The map generation system according to claim 21, wherein the attribute of the calculated Spline curve includes a lane node-link, a width of the lane, and a curvature of the lane.

23. The map generation system according to claim 13, further comprising a lane central line correction unit for correcting the lane central line by referring to a set of highly accurate reference positions.

24. The map generation system according to claim 23, wherein the lane central line correction unit is configured to:

extract a nearest neighboring point for each of the reference positions from points on the lane central line before correction;

obtain a difference between each of the reference positions and the nearest neighboring point; and

obtain a correction vector of each of the points on the lane central line according to a distance from each of the two nearest neighboring points.