Updating Cartography Using Quickbird And Ikonos Ii High Resolution Imagery: Comparison Between Geometric Properties And Accuracy

The paper addresses the usefulness of high resolution satellite imagery as a support to the updates of local technical cartography (scale 1:5 000). Ikonos II and a recently purchased QuickBird images are available in an area including the downtown of the city of Bologna (Italy) and the surroundings. The paper deals with the data processing performed to obtain, from the satellite images, cartographic products in a well suited reference system. In order to do that, the fulfilling of a preliminary geocoding of the entire dataset is of fundamental importance when geometric distorsions have to be detected. Radiometric quality evaluation and orthorectification of geocoded dataset is subsequently carried out using a Digital Terrain Model (DTM) of the investigated area. DTM allows the reduction of relief effect on planimetric object positioning once the orthorectified images is being processed. Geocoding and orthorectification require a certain number of equally distributed Ground Control Points within the area. They also establish an external dataset of checkpoints of great usefulness when the final accuracy of geometric correction has to be verified. After rectification and accuracy evaluation procedures the Ikonos II image was selected for the updating of thematic features of technical cartography at 1:5000 scale. Features extraction and geometric/radiometric properties of the images will be discussed in the paper