# Orthorectification Using Rational Polynomials

You can orthorectify certain types of satellite images that are supplied with a mathematical model of the image geometry in the form of a set of rational polynomial coefficients. This procedure also requires a digital elevation model. You can often improve the fit of the rational polynomial model to a particular image by regeoreferencing the image using accurate 3 D ground control points.

About Rational Polynomial Models

Acquiring a DEM

Elevation Units and Reference Surfaces

Obtaining the Geoid Height

Regeoreferencing the Image

Georeference with RPC Model

Control Points from GPS Survey

Evaluating Control Points