Compressed edge map representation for image aided navigation

1. A method of generating a map for image aided navigation, the method comprising:

detecting one or more edges in one or more terrain images; and

obtaining a compressed edge representation of the one or more edges, the compressed edge representation obtained by a method comprising:

fitting a geometric form or other mathematical model to the one or more edges;

calculating one or more coefficients based on the fitted geometric form or other mathematical model; and

storing the one or more coefficients in a database for use in generating the map for image aided navigation;

wherein fitting the geometric form or other mathematical model to the one or more edges comprises fitting one or more line segments to the one or more edges, wherein fitting the one or more line segments to the one or more edges comprises:

dividing the one or more terrain images into multiple pixel blocks of a uniform size; and

fitting the one or more line segments to edge pixels inside of each pixel block.

2. The method of claim 1 , wherein the one or more edges in the one or more terrain images are detected with a Canny edge detector.

3. The method of claim 1 , wherein fitting the one or more line segments to the edge pixels inside of each pixel block is carried out using a routine comprising a least-squares fit technique or a singular value decomposition.

4. The method of claim 1 , wherein calculating the one or more coefficients comprises determining coordinates of endpoints for the one or more line segments.

5. The method of claim 4 , wherein storing the one or more coefficients comprises storing the coordinates of the endpoints for the one or more line segments.

6. The method of claim 1 , wherein the map for image aided navigation comprises a world map.

7. The method of claim 6 , wherein portions of the world map are locally indexed.

8. The method of claim 7 , wherein during image aided navigation, the method further comprises decompressing one or more relevant portions of the world map to generate a binary pixel image representation of the one or more edges.

9. A system for generating a map for image aided navigation, the system comprising:

at least one processor; and

a memory unit in operative communication with the at least one processor and including a database, the memory unit comprising a non-transitory computer readable medium having instructions executable by the at least one processor to perform a method comprising:

detecting one or more edges in one or more terrain images; and

obtaining a compressed edge representation of the one or more edges, the compressed edge representation obtained by a method comprising:

fitting a geometric form or other mathematical model to the one or more edges;

calculating one or more coefficients based on the fitted geometric form or other mathematical model; and

storing the one or more coefficients in the database for use in generating the map for image aided navigation;

wherein fitting the geometric form or other mathematical model to the one or more edges comprises fitting one or more line segments to the one or more edges, wherein fitting the one or more line segments to the one or more edges comprises:

dividing the one or more terrain images into multiple pixel blocks of a uniform size; and

fitting the one or more line segments to edge pixels inside of each pixel block.

10. The system of claim 9 , wherein the one or more edges in the one or more terrain images are detected with a Canny edge detector.

11. The system of claim 9 , wherein calculating the one or more coefficients comprises determining coordinates of endpoints for the one or more line segments.

12. The system of claim 11 , wherein storing the one or more coefficients comprises storing the coordinates of the endpoints for the one or more line segments.

13. A computer implemented system for generating a map for image aided navigation, the computer implemented system comprising:

an edge detector configured to identify multiple edges in each of a plurality of terrain images; and

means for obtaining a compressed edge representation of the edges in the terrain images, wherein the means for obtaining the compressed edge representation is configured to:

fit a geometric form or other mathematical model to the edges;

calculate coefficients based on the fitted geometric form or other mathematical model; and

store the coefficients in a database for use in generating the map for image aided navigation;

wherein the fit of the geometric form or other mathematical model to the edges comprises a fit of a plurality of line segments to the edges, wherein the fit of the plurality of line segments to the edges comprises:

divide the terrain images into multiple pixel blocks of a uniform size; and

fit the plurality of line segments to edge pixels inside of each pixel block.

14. The computer implemented system of claim 13 , wherein:

the coefficients stored in the database comprise coordinates of endpoints for the plurality of line segments.