Using Rational Polynomial Functions for rectification of GeoEye-1 imagery

GeoEye-1 panchromatic images (geometric resolution: 0.5 m) can be rectified using Rational Polynomial Functions (RPFs) without knowledge of the full sensor information: rectification is conducted using DEM (Digital Elevation Model) of the area as well as Ground Control Points (GCPs) of which both elevation and X,Y positioning must be known. Check Points with the same characteristics of GCPs (but not coincident with them) are used to verify the accuracy of the product. For both GCPs and CPs coordinates can be not only obtained with survey, but also derived from detailed maps or orthophotos (scale 1:5,000 or greater). In this paper methods to rectify GeoEye-1 images using orthophotos (scale 1:2,000) for GCPs and CPs detection are considered, with particular attention to achieved positional accuracy. The research is performed on one GeoEye-1 panchromatic image of an area in Campania region around the mouth of Volturno river and Domitian coast: differences between the coordinates of GCPs (as well as of the Check Points) on the ortophotos and the corresponding values on the rectified image are calculated and analyzed to define quality of resulting product. The variability of results in relation to the number of GCPs is analyzed and considerations about their positional accuracy so to define scale use of the corresponding rectified image are supplied.