Map generation system and map generation method by using GPS tracks

• US 8,359,156 B2
• Filed: 02/05/2008
• Issued: 01/22/2013
• Est. Priority Date: 04/17/2007
• Status: Expired due to Fees

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Guo, Tao, Koga, Masashi
• Primary Examiner(s): Nguyen, John Q
• Assistant Examiner(s): King, Rodney P
• Application Number:
  US12/068,296
• Publication Number:
  US 20080262721A1
• Time in Patent Office: 1,813 Days
• Field of Search: 701/41, 701/213, 701/400, 701/411, 340/435, 340/988
• US Class Current: 701/411
• 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 non-transitory computer-usable storage medium having computer readable instructions stored thereon for execution by a processor to perform a method of generating a digital road map, the method comprising:

using a least square method to extract feature points from a collected plurality of pieces of track data that are captured based on vehicle movement along a road and each include positional data;

determining a lane central line of a lane along the road by calculating a Spline curve satisfying the extracted feature points;

determining whether to update current map data of the digital road map based on a comparison of the number of pieces of track data with a predetermined threshold value and

in response to a determination to update the current map data of the digital road map based on the comparison, writing a new map object for the road corresponding to the determined lane central line to the current map data of the digital road map to form updated map data.

2. The non-transitory computer-usable storage medium according to claim 1, further comprising:

capturing the plurality of pieces of track data by acquiring location data of the vehicle obtained over time by a GPS device as the positional data and collecting the captured plurality of pieces of track data to generate a database;

partitioning the 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 the 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 of the road; and

updating, when an error of the Spline curve calculated as the candidate is sufficiently converged according to a predetermined threshold value, the current map data by writing the new map object corresponding to the Spline curve calculated as the candidate to form the updated map data.

3. The non-transitory computer-usable storage medium according to claim 2, wherein:

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

wherein;

in the first mode, an operator of the vehicle can set whether the location data is recorded;

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

in the third mode, the location data is recorded when an external signal is received.

4. The non-transitory computer-usable storage medium according to claim 3, further comprising:

recording the location data including a location of the vehicle obtained by the GPS device, 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 non-transitory computer-usable storage medium according to claim 2, further comprising:

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 on which the vehicle is present when the input location data is valid; and

storing the generated track data.

6. The non-transitory computer-usable storage medium according to claim 2, further comprising:

determining that a setting indicates a necessity of update of the current map data of the road from which the plurality of pieces of track data are collected;

specifying the 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 the candidate of the road central line.

7. The non-transitory computer-usable storage medium according to claim 6, further comprising:

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 non-transitory computer-usable storage medium according to claim 6, further comprising:

interpolating the specified track data into each of the plurality of segments obtained by partitioning the road upon determining to update the current map data of the digital road map based on the comparison of the quantity of the pieces of track data with the predetermined threshold.

9. The non-transitory computer-usable storage medium according to claim 2, further comprising:

determining whether the calculated Spline curve is sufficiently converged according to the predetermined threshold value and further comparing an attribute of the calculated Spline curve and an attribute of a current lane central line of the current map data with each other; and

updating the current map data by writing the new map object corresponding to 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 non-transitory computer-usable storage medium 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 non-transitory computer-usable storage medium according to claim 1, further comprising correcting the lane central line by referring to a set of reference positions stored in a road map database.

12. The non-transitory computer-usable storage medium according to claim 11, further comprising:

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 a vehicle for acquiring location data of a vehicle obtained by a GPS system and a status of the vehicle at a time of acquisition of the location data; 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 implement;

an extraction unit for using a least square method to extract feature points from a collected plurality of pieces of track data that are captured based on vehicle movement along a road and each include positional data and determining a lane central line of a lane along the road by calculating a Spline curve satisfying the extracted feature points; and

an update unit for determining whether to update current map data of the digital road map based on a comparison of the number of pieces of track data with a predetermined threshold value and, in response to a determination to update the current map data of the digital road map based on the comparison, writing a new map object for the road corresponding to the determined lane central line to the current map data of the digital road map to form updated map data.

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

the processor is further configured to implement a management unit for capturing the plurality of pieces of track data by acquiring location data of the vehicle obtained over time by a GPS system as the positional data and collecting the captured plurality of pieces of track data to generate a database;

the extraction unit is configured to partition the 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 the 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 of the road; and

the update unit is configured to update the current map data by writing the new map object corresponding to the Spline curve calculated as the candidate when an error of the Spline curve calculated as the candidate is sufficiently converged according to a predetermined threshold value.

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;

wherein;

in the first mode, an operator of the vehicle can set whether the location data is recorded in the location data recording unit;

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

in the third mode, the location data is 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 the location data including a location of the vehicle obtained by the GPS receiver, 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 on which the vehicle is present 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 that a setting indicates a necessity of update of the current map data of the road from which the plurality of pieces of track data are collected;

determining that a setting indicates a necessity;

specify the 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 the 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:

interpolate the specified track data into each of the plurality of segments obtained by partitioning the road upon determining to update the current map data of the digital road map based on the comparison of the quantity of the pieces of track data with the predetermined threshold.

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 according to the predetermined threshold value and further compare an attribute of the calculated Spline curve and an attribute of a current lane central line of the current map data with each other; and

update the current map data by writing the new map object corresponding to 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 reference positions stored in the map database.

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.