Ortho-rectification of Ikonos panchromatic images using detailed maps

IKONOS panchromatic images (1 m geometric resolution, 11 bit radiometric resolution) can be ortho-rectified using Polynomial Rational Functions without knowledge of the full sensor information: corrected coordinates are determined with several Ground Control Points (GCPs), of which both elevation and X,Y positioning must be known. GCPs coordinates can be not only obtained with GPS, but also derived from detailed maps (scale 1:10.000 – 1:5.000 or greater). In this paper possibilities to ortho-rectify IKONOS images using as GCPs points on maps and validate achieved geometrical quality are considered. The research is performed on IKONOS panchromatic image of an area in Campania Region: differences among the GCPs values (as well as Check Points values) on the maps and the corresponding points values on the derived image are calculated and analyzed to define geometrical quality of resulting product. Ortho-rectification is conducted using Polynomial Rational Functions: coordinates of GCPs are derived from digital maps at 1:5.000 scale. The variability of results in relation to the number of GCPs is analyzed and considerations about their geometrical accuracy so to define scale use of the corresponding ortho-rectified image are supplied.