Geometric correction by GPS
3. Experimental and result
The raw image which needs to correct the geometric distortion is shown in fig. 1. the coordinates of GCP form CPS are circled in the image ( while the coordinates of GCP form MAP are assigned by triangles ). By using the mention transform polynomials and interpolation, the corrected image is shown in Fig. 2, while the corrected image in Fig. 4. is obtain by using the coordinates of map in Fig. 3.
Figure 1 Raw image
Figure 2 Geometric correction image by using GPS
Figure 3 Map (D is GCP)
Figure 4 Geometric correction image by using Map.
Figure 5 Difference of extracted roads
4. Conclusion
As we know, the acculate ground control points are essential to an acculte correcting [2]. So the coordinates of points acquired form GPS are surely more aculate than the coordinates which obtain from the map because of the roughness of map scale. By comparing with the map, more ground control points can be acquired form GPS, because of the new construction roads which are not appeared yet in the map. Therefore, the geometric correction by GPS will give more correctly when comparing the image in fig. 2. with the image in fig .4. Since, we used other personal compute for processing images, therefore the size of image is limited. Here the image of size 1593x1137 pixels is use for demonstration.
Acknowledgement
The author would like to thank the National research council of Thailand (NCRT) for providing the satellite images.
Reference
-
J.A. Richaeds, " Remote Sensing Digital Image Analysis: An Introduction ,Springer - for providing, Berlin, New York, 1989.
-
Erdas Field Guind, 2nd Edition, Version 7.5, July 1991.
- Berastein, " Image Geometry and Rectification. In. R.N.Colwell ( Ed.)," Manual of Remote Sensing, 21, Chapter 21, Falls Church. Va American Sosiety of photogrammetry.
