The Affine Projection Model as a Tool for Rapid Geo-coding of Irs-p5 Satellite Imagery

Nowadays, the information content of the satellite imageries as a means for the disaster forecasting and management has attracted the worldwide attention more than before. On the other hand, linear array satellite images such as Spot, Ikonos, QuickBird, IRS, etc., with their flexibility in acquiring stereo coverage over any part of the globe, have proven to be an excellent replacement for the other space-borne imaging systems such as digital frame cameras or whiskbroom technologies. The first step for using such data is Geocoding. High resolution data increase the need for higher accuracy data modeling. Up to now different models with different accuracy have been discussed. These models are divided into two main groups of the so called rigorous and non-rigorous models. The rigorous approaches are the most accurate but need crucial data such as satellite ephemeris and inner orientation parameters which are not always available. The non-rigorous models such as rational polynomials, DLT or 3D affine transformations on the other hand are less accurate but enjoy the advantage of being independent from the auxiliary information. In line with several other research works already performed by other researchers, this paper sets its main goal to compare the simple 3D affine model, as a replacement transformation for the more sophisticated rational function approach. The adopted strategy is based on generating virtual ground control points using rational polynomials intersection by means of available RPCs. The generated virtual GCPs provide a reliable data for estimating the degree of fitness of the 3D affine model to the rational polynomial transformation. This paper reports the result of the tests conducted on a high resolution stereo IRS-P5 satellite image. Other related issues including different methods for estimating initial values needed for the solution of the rational polynomials intersection, such as DLT, 3D affine and truncated rational polynomials are also presented and discussed.