chapter  8
46 Pages

## Three-Dimensional Geometric Correction of Earth Observation Satellite Data �����������������������������������������������������������������������������������������������������������������������

ByThierry Toutin

Why orthorectify Earth observation (EO) satellite data? Any EO data, regardless of whether they are acquired by a scanner or a frame camera aboard a satellite, or by a photographic system in an aircraft or any other platform/sensor combination, will have various geometric distortions, depending on the manner in which the data are acquired. This problem is inherent in remote sensing, as we attempt to accurately represent the three-dimensional (3D) surface of Earth as a two-dimensional (2D) image. Consequently, raw images contain such signicant geometric distortions that they cannot be used directly with geographic

CONTENTS

8.1 Introduction ........................................................................................................................ 173 8.2 Sources of Geometric Distortions .................................................................................... 175

8.2.1 Distortions Related to the Platform ..................................................................... 177 8.2.2 Distortions Related to Sensors ............................................................................. 180 8.2.3 Distortions Related to the Earth .......................................................................... 181

8.3 Geometric Modeling of Distortions ................................................................................ 182 8.3.1 Two-Dimensional/Three-Dimensional Empirical Models .............................. 182

8.3.1.1 Two-Dimensional Polynomial Functions ............................................ 183 8.3.1.2 Three-Dimensional Polynomial Functions ......................................... 184 8.3.1.3 Three-Dimensional Rational Functions .............................................. 185

8.3.2 Two-Dimensional/Three-Dimensional Physical Models ................................ 188 8.4 Methods, Processing, and Errors ..................................................................................... 191

8.4.1 Acquisition of Images and Metadata .................................................................. 191 8.4.1.1 Raw Level-1A Images ............................................................................. 192 8.4.1.2 Georeferenced Level-1B Images ............................................................ 193 8.4.1.3 Map-Oriented Level-2A Images ........................................................... 194 8.4.1.4 Synthetic Aperture Radar Images ........................................................ 195

8.4.2 Acquisition of Ground Control Points ................................................................ 195 8.4.3 Geometric Model Computation ........................................................................... 197 8.4.4 Digital Elevation Model Generation from Stereo Images ................................200 8.4.5 “Orthorectication” ............................................................................................... 204

8.4.5.1 Geometric Operation .............................................................................. 205 8.4.5.2 Radiometric Operation ........................................................................... 207

References ..................................................................................................................................... 210

information system (GIS)–ready products. Thus, multisource data integration (raster and vector) for geomatics applications requires geometric and radiometric processing adapted to the nature and characteristics of the data in order to keep the best information from each image in the composite orthorectied products.