System and method for georeferencing digital raster maps with resistance to potential errors

• US 7,190,377 B2
• Filed: 03/29/2001
• Issued: 03/13/2007
• Est. Priority Date: 03/29/2000
• Status: Expired due to Fees

• Current Assignee: Sourceprose Corporation (TransUnion Corporation)
• Original Assignee: Sourceprose Corporation (TransUnion Corporation)
• Inventors: Higgins, Darin Wayne, Scott, Dan Martin
• Primary Examiner(s): Tung; Kee M.
• Assistant Examiner(s): AMINI, JAVID A
• Application Number:
  US09/821,638
• Publication Number:
  US 20010033291A1
• Time in Patent Office: 2,175 Days
• Field of Search: 345/427, 345/569, 345/665, 345/667, 345/682, 345/709, 345/712, 345/800, 345/815, 345/619, 345/629, 701/211
• US Class Current: 345/629
• CPC Class Codes: G06T 17/05 Geographic models

Abstract

Systems and methods for georeferencing digital raster maps by assigning points on the raster map with geographic coordinates corresponding to points on a georeferenced vector map or another georeferenced raster map. The raster map and a corresponding vector map are simultaneously displayed to a user, wherein the user then locates a common geographic point or feature on each map, and marks each of them as a unique point-pair. When the user has marked at least two point-pairs, the system then computes a georeferencing function, based on the pixel-coordinates of the points marked on the raster map and the corresponding geographic coordinates of the points on the vector map. Thereafter the geographic coordinates of any point on the map may be easily computed. The preferred embodiment provides that as more point-pairs are identified, the georeferencing function is modified for increased accuracy.

Claims

1. A method for georeferencing a raster map, comprising:

displaying a first map and a second map, the first map being a digital raster map, having a plurality of pixel locations, and the second map being a previously georeferenced map, having associated geographic coordinates, wherein the first map displays at least a portion of an identical geographic region displayed in the second map, each pixel location includes an associated x-coordinate and y-coordinate, and each geographic coordinate includes an associated longitude coordinate and an associated latitude coordinate;

receiving an entry identifying a first point pair, wherein a first pixel location on the first map is associated with a first geographic coordinate on the second map and the first pixel location is located at a position on the first map corresponding to the first geographic coordinate on the second map;

receiving an entry identifying a second point pair, wherein a second pixel location on the first map is associated with a second geographic coordinate on the second map and the second pixel location is located at a position on the first map corresponding to the second geographic coordinate on the second map;

assigning to the first pixel location the longitude coordinate and the latitude coordinate associated with the first geographic coordinate;

assigning to the second pixel location the longitude coordinate and the latitude coordinate associated with the second geographic coordinate;

creating a mathematical georeferencing function, based on the first point pair, the second point pair, and a third point pair, for assigning corresponding geographic coordinates to any one of the plurality of pixel locations, wherein the mathematical georeferencing function is based on a linear transformation; and

revising the mathematical georeferencing function when a new point pair is received.

2. The method of claim 1, wherein the point pairs used by the georeferencing are widely dispersed so that an accuracy of the georeferencing function is increased.

3. The method of claim 2, wherein the point pairs are widely dispersed when a polygon defined by vertices chosen among the point pairs covers a substantial portion of the first map.

4. A method for georeferencing a raster map, comprising:

displaying a first map and a second map, the first map being a digital raster map, having a plurality of pixel locations, and the second map being a previously georeferenced map, having associated geographic coordinates, wherein the first map displays at least a portion of an identical geographic region displayed in the second map, each pixel location includes an associated x-coordinate and y-coordinate, and each geographic coordinate includes an associated longitude coordinate and an associated latitude coordinate;

receiving an entry identifying a first point pair, wherein a first pixel location on the first map is associated with a first geographic coordinate on the second map and the first pixel location is located at a position on the first map corresponding to the first geographic coordinate on the second map;

receiving an entry identifying a second point pair, wherein a second pixel location on the first map is associated with a second geographic coordinate on the second map and the second pixel location is located at a position on the first map corresponding to the second geographic coordinate on the second map;

assigning to the first pixel location the longitude coordinate and the latitude coordinate associated with the first geographic coordinate;

assigning to the second pixel location the longitude coordinate and the latitude coordinate associated with the second geographic coordinate;

creating a mathematical georeferencing function, based on the first point pair, the second point pair, a third point pair, and a fourth point pair, for assigning corresponding geographic coordinates to any one of the plurality of pixel locations, wherein the mathematical georeferencing function is based on a linear transformation;

executing a validation check; and

revising the mathematical georeferencing function when a new point pair is received.

5. The method of claim 4 further comprising rejecting one of the point pairs when an error associated with the one point pair deviates a pre-determined amount from a standard error computed using the other point pairs.

6. The method of claim 5 wherein the standard error uses a “

least square”

parameter fitting operation.

7. An apparatus for georeferencing a raster map, the apparatus comprising:

means for displaying a first map and a second map, the first map being a digital raster map, having a plurality of pixel locations, and the second map being a previously georeferenced map, having associated geographic coordinates, wherein the first map displays at least a portion of an identical geographic region displayed in the second map, each pixel location includes an associated x-coordinate and y-coordinate, and each geographic coordinate includes an associated longitude coordinate and an associated latitude coordinate;

means for receiving an entry identifying a first point pair, wherein a first pixel location on the first map is associated with a first geographic coordinate on the second map and the first pixel location is located at a position on the first map corresponding to the first geographic coordinate on the second map;

means for receiving an entry identifying a second point pair, wherein a second pixel location on the first map is associated with a second geographic coordinate on the second map and the second pixel location is located at a position on the first map corresponding to the second geographic coordinate on the second map;

means for assigning to the first pixel location the longitude coordinate and the latitude coordinate associated with the first geographic coordinate;

means for assigning to the second pixel location the longitude coordinate and the latitude coordinate associated with the second geographic coordinate;

means for creating a mathematical georeferencing function, based on the first point pair, the second point pair, a third point pair, and a fourth point pair, to assign corresponding geographic coordinates to any one of the plurality of pixel locations, wherein the mathematical for georeferencing function is based on a linear transformation;

executing a validation check; and

means for revising the mathematical georeferencing function when a new point pair is received.

8. The apparatus of claim 7 further comprising means for rejecting one of the point pairs when an error associated with the one point pair deviates a predetermined amount from a standard error computed using the other point pairs.

9. A computer readable medium containing instructions executable by a computer to perform a method to georeference a raster map, the method comprising:

displaying a first map and a second map, the first map being a digital raster map, having a plurality of pixel locations, and the second map being a previously georeferenced map, having associated geographic coordinates, wherein the first map displays at least a portion of an identical geographic region displayed in the second map, each pixel location includes an associated x-coordinate and y-coordinate, and each geographic coordinate includes an associated longitude coordinate and an associated latitude coordinate;

receiving an entry identifying a first point pair, wherein a first pixel location on the first map is associated with a first geographic coordinate on the second map and the first pixel location is located at a position on the first map corresponding to the first geographic coordinate on the second map;

receiving an entry identifying a second point pair, wherein a second pixel location on the first map is associated with a second geographic coordinate on the second map and the second pixel location is located at a position on the first map corresponding to the second geographic coordinate on the second map;

assigning to the first pixel location the longitude coordinate and the latitude coordinate associated with the first geographic coordinate;

assigning to the second pixel location the longitude coordinate and the latitude coordinate associated with the second geographic coordinate;

creating a mathematical georeferencing function, based on the first point pair, the second point pair, a third point pair, and a fourth point pair, for assigning corresponding geographic coordinates to any one of the plurality of pixel locations, wherein the mathematical georeferencing function is based on a linear transformation;

executing a validation check;

rejecting one of the point pairs when an error associated with the one point pair deviates a predetermined amount from a standard error computed using the other point pairs; and

revising the mathematical georeferencing function when a new point pair is received.