Method and apparatus for generating an orthorectified tile

1. Method for generating a geo-positioned orthorectified tile, comprising:

retrieving a sequence of source images obtained at different times by a terrestrial based camera mounted on a moving vehicle when driving across a road surface;

retrieving position data associated with each of the retrieved source images and representative of the position of the vehicle in a geographic coordinate reference system, wherein the position data includes constant position parameters defining the position of the camera with respect to a reference position within the vehicle and variable position parameters defining the position of the vehicle's reference position in said geographical coordinate reference system;

retrieving orientation data associated with each of the retrieved source images and representative of the orientation of the vehicle within the geographic coordinate reference system, wherein the orientation data includes constant orientation parameters defining the orientation of the camera with respect to a reference orientation of the vehicle and variable orientation parameters defining the orientation of the vehicle's reference orientation in said geographic coordinate reference system;

using the position and orientation data associated with the retrieved source images to determine the position and orientation of the road surface below the vehicle at the time each source image is obtained;

estimating the plane of the road surface seen in a first source image using the position and orientation of the road surface below the vehicle determined from a second source image in which the vehicle is positioned over the road surface seen in the first image; and

converting the first source image using the estimated plane of the road surface seen in the first source image and an angle defined by a difference in elevation between two sides of the road surface with respect to a horizontal plane to obtain the geo-positioned orthorectified tile and corresponding metadata defining a conversion of pixel coordinates in the geo-positioned orthorectified tile to a position in the geographic coordinate reference system.

2. Method according to claim 1 , wherein the geo-positioned orthorectified tile comprises pixels, and said converting includes:

determining at least one pixel in the source image corresponding to a pixel of the geo-positioned orthorectified tile; and

determining the value of the pixel of the geo-positioned orthorectified tile from the values of the at least one pixel in the source image.

3. Method according to claim 2 , wherein a shape of the geo-positioned orthorectified tile is a rectangle.

4. Method according to claim 2 , wherein determining the value of the pixel of the geo-positioned orthorectified tile from the values of at least one pixel in the corresponding source image includes at least one of averaging and interpolating the values of a plurality of neighboring pixels of a corresponding pixel in the corresponding source image.

5. Method according to claim 1 , wherein a shape of the geo-positioned orthorectified tile is a rectangle.

6. Method according to claim 1 , wherein the converting includes:

correcting geometric distortion in the source image;

performing a 90 degree rotation over a focal point of the camera to obtain a geo-positioned orthorectified image, the orthorectified image being perpendicular to the plane of the geographic reference.

7. Method for generating a geo-positioned orthorectified mosaic, comprising:

generating geo-positioned orthorectified tiles from source images obtained by a terrestrial based camera mounted on a moving vehicle when driving across a road surface by the method according to claim 1 ; and

generating the geo-positioned orthorectified mosaic and metadata from the generated geo-positioned orthorectified tiles and corresponding metadata.

8. Method according to claim 7 , wherein generating of the geo-positioned orthorectified mosaic includes:

defining a projected coordinate reference system for the geo-positioned orthorectified mosaic from the position data;

determining an area of geo-positioned orthorectified tile in the geo-positioned orthorectified mosaic by way of the projected coordinate reference system and metadata corresponding to the geo-positioned orthorectified tile; and

converting pixels of the determined area of the geo-positioned orthorectified tile into pixels of the geo-positioned orthorectified mosaic.

9. A non-transitory processor readable storage medium carrying a geo-positioned orthorectified mosaic obtained by the method according to claim 7 .

10. A non-transitory processor readable medium carrying a computer program product which, when loaded on a computer arrangement, allows the computer arrangement to perform the method according to claim 1 .

11. The method of claim 1 wherein the variable orientation parameters comprise pitch and roll of the vehicle measured at the time when the source images are retrieved.

12. The method of claim 1 , wherein the first source image is an intermediate image.

13. The method of claim 12 , wherein the first source image is 3D processed.

14. The method of claim 1 wherein the orthorectified tile is a scaled version of an orthorectified view.

15. The method of claim 1 , wherein the metadata comprises geo-reference data corresponding to an image describing a one-to-one relationship from an image coordinate system to the geographic coordinate reference system.

16. A computer arrangement comprising:

an input device;

a processor readable storage medium;

a processor in communication with said input device and said processor readable storage medium; and

an output device in communication with the processor, said processor readable storage medium storing code to program said processor to perform a method comprising

retrieving a sequence of source images obtained at different times by a terrestrial based camera mounted on a moving vehicle when driving across a road surface;

retrieving position data associated with each of the retrieved source images and representative of the position of the vehicle in a geographic coordinate reference system, wherein the position data includes constant position parameters defining the position of the camera with respect to a reference position within the vehicle and variable position parameters defining the position of the vehicle's reference position in the geographical coordinate reference system;

retrieving orientation data associated with each of the retrieved source images and representative of the orientation of the vehicle in the geographic coordinate reference system, wherein the orientation data include constant orientation parameters defining the orientation of the camera with respect to a reference orientation of the vehicle and variable orientation parameters defining the orientation of the vehicle's reference orientation in said geographic coordinate reference system;

using the position of and orientation data associated with the retrieved source images to determine the position and orientation of the road surface below the vehicle at the time each source image is obtained;

estimating the plane of the road surface seen in each source image using the position and orientation of the road surface below the vehicle determined from another source image in which the vehicle is positioned over the road surface seen in each image;

converting each source image using the estimated plane of the road surface seen in each source image and an angle defined by a difference in elevation between two sides of the road surface with respect to a horizontal plane to obtain a geo-positioned orthorectified tile and corresponding metadata defining a conversion of pixel coordinates in the geo-positioned orthorectified tile to a position in the geographic coordinate reference system;

generating an geo-positioned orthorectified mosaic and corresponding metadata from the obtained geo-positioned orthorectified tiles; and

storing the orthorectified mosaic and associated metadata on the processor readable storage medium.