REFERENCING A MAP TO THE COORDINATE SPACE OF A POSITIONING SYSTEM

• US 20100171757A1
• Filed: 01/31/2008
• Published: 07/08/2010
• Est. Priority Date: 01/31/2007
• Status: Abandoned Application

• Current Assignee: Hewlett-Packard Development Company, L.P. (HP Inc.)
• Original Assignee: Hewlett-Packard Development Company, L.P. (HP Inc.)
• Inventors: Melamed, Thomas J.
• Application Number:
  US12/525,365
• Publication Number:
  US 20100171757A1
• Time in Patent Office: Days
• US Class Current: 345/632
• CPC Class Codes: G01S 19/51 Relative positioning
• CPC Class Codes: G06F 16/29 Geographical information databases

Abstract

Methods and apparatus are provided for referencing a map to the coordinate space of a positioning system, such as a GPS system. For each of a number of real-world positions (X1, X2, X3), the location (L_P1, L_P2, L_P3) of the real-world position in a coordinate space of the map, is associated with a location(L_G1, L_G2, L_G3) in the coordinate space of the positioning system determined by taking at least one positioning-system reading at the real-world position (X1, X2, X3). Using these associated locations, a master transform is determined for converting relative location information between the coordinate spaces. The relative location information is information that serves to specify a location relative to the already-known locations and can take the form of displacement vector information.

Claims

1. A method of referencing a map to the coordinate space of a positioning system, the method comprising:

for each of a plurality of real-world positions, associating the location of the real-world position in a coordinate space of the map, with a location in the coordinate space of the positioning system determined by taking at least one positioning-system reading at the real-world position; and

using the associated locations to determine a master transform for converting relative location information between said coordinate spaces, said relative location information serving to specify a location relative to the already-known locations of said plurality of real-world positions.

2. A method according to claim 1, wherein at least one said real-world position corresponds to a real-world feature marked on the map.

3. A method according to claim 1, wherein at least one said real-world position is a position estimated by a human as corresponding to a selected map location.

4. A method according to claim 3, wherein selected map location is a map corner location.

5. A method according to claim 1, wherein for at least one said real-world position the corresponding map location is estimated by a human.

6. A method according to claim 1, wherein the location of a said real-world position in the coordinate space of the positioning system is determined as an average of a plurality positioning-system readings taken at the real-world position.

7. A method according to claim 6, wherein the standard deviation of the readings used to determine said mean is determined and compared to a predetermined threshold value, the mean being discarded where the standard deviation of the readings is greater than the threshold value.

8. A method according to claim 1, wherein further real-world positions are progressively added to said plurality and their locations in said coordinate spaces associated, the master transform being re-determined for each n further points added where n is an integer ≧

1.

9. A method according to claim 1, wherein said master transform is determined by a process comprising:

determining first vectors between locations of said real-world positions in the coordinate space of the positioning system;

determining second vectors between locations of said real-world positions in the coordinate space of the map;

determining, for each first vector, an individual angle and scaling transform for converting the vector to a corresponding one of the second vectors; and

deriving said master transform as an average of said individual transforms;

the master transform being usable to convert, between said coordinate spaces, relative location information having the form of said vectors.

10. A method according to claim 9, further comprising:

determining the location, in the coordinate space of the positioning system, of a further real-world position by taking at least one positioning-system reading at the real-world position;

determining, in the coordinate space of the positioning system, further first vectors between the location of said further real-world position and the locations of at least some of said plurality of real-world positions;

using said master transform to convert the further first vectors to corresponding further second vectors;

combining, in the coordinate space of the map, the second vectors and the locations of said at least some of said plurality of real-world positions whereby to derive a set of estimated locations for said further real-world position in the coordinate space of the map; and

processing said set of estimated locations to derive a mean and standard deviation for said further real-world position in the coordinate space of the map.

11. A method according to claim 10, further comprising

determining a standard deviation of the set of estimated locations;

and

providing a visual indication of said mean location and standard deviation in the form of an ellipse displayed on an image of the map.

12. A method according to claim 9, further comprising:

determining, in the coordinate space of the map, a set of vectors between a specific map location and the locations of said real-world positions;

using said master transform to convert said set of vectors to a corresponding set of transformed vectors;

combining, in the coordinate space of the positioning system, the set of transformed vectors and the locations of said real-world positions whereby to derive a set of estimated locations for said specific map location in the coordinate space of the positioning system; and

processing said set of estimated locations to derive a mean value.

13. A method according to claim 12, wherein said specific map location is the location of one said real-world positions, the method further comprising

determining a standard deviation of the set of estimated locations;

determining a difference value, as a proportion of the standard deviation of said set of estimated locations, between the location of said one real-world position as determined using the positioning system and the mean derived using said set of estimated locations; and

rejecting the locations of said one real-world position in said coordinate spaces where said difference is greater than a predetermined threshold.

14. A method according to claim 12, wherein said specific map location is a map boundary location.

15. A method according to claim 14, wherein said map boundary location is a map corner.

16. A method according to claim 1, wherein said positioning system is a GPS system.

17. A method according to claim 1, wherein the map is an image displayed on a display screen, the coordinate space of the map being the pixel space of the image.

18. Portable apparatus comprising:

a positioning system for deriving a location in a coordinate space of the positioning system corresponding to a current real-world position of the apparatus;

a user interface arranged to display a map and enable locations in the coordinate space of the map to be selected by/identified to a user;

a memory for storing locations in both said coordinate spaces; and

a processing arrangement arranged to associate the location in the coordinate space of the positioning system of a said current position of the apparatus with a corresponding location in the map coordinate space for a plurality of different said current positions, the processing arrangement being further arranged to use the associated locations to determine a master transform for converting relative location information between said coordinate spaces, said relative location information serving to specify a location relative to the already-known locations of said plurality of current positions.