A Method For Geometric Processing Of Optical Satellite Images Using Automatically Determined Ground Control Information

Orthorectification is the process to convert imagery into map-accurate forms by removing sensor, satellite motion and terrain related geometric distortions from raw imagery and is one of the main pre-processing steps for application oriented evaluations. Although optical satellite data of high geometric resolution can be orthorectified to absolute geometric accuracies of about 5 m to several hundred meters - depending on the satellite mission - using the metadata information from the satellite data providers (e.g. satellite position, velocity and attitude at any instant of time during data acquisition, camera internal geometry), there is still a need to improve the geometric accuracy by using Ground Control Points (three dimensional real world coordinates, which have to be identified in the satellite image). The manual measurement of such Ground Control Points by operators is a time consuming work leading to a cost and time ineffective project completion. This paper proposes a method and procedure to automatically extract Ground Control Points from already existing orthorectified images of superior geometric quality (reference images), which are used to improve the geometric accuracy as well as to produce at least consistent data sets.