Automatic generation of image ground control features from a digital map database

A C Morris T J Ibbs M J Jackson1 1 Laser-Scan Laboratories Ltd. Cambridge England CB4 4FY :2 Dept. of Photogrammetry and Surveying, University College London London England WCIE 6BT Commission Number II/3 J-P Muller2 In order to register satellite image data to ground coordinates, it is necessary to identify corresponding features in the image and in a reference dataset in a known position on the earth's surface. Previous work in this Alvey project3 has shown that digital map data of sufficient quality can provide such reference information. This paper reports work on the automated selection of reliable ground control features from a digital map database. Techniques include the use of a quad tree spatial index to extract data. on the basis of feature type and location. Other methods based on fea.ture size and shape are reported. An important aspect is shown to be the establishment of reliability criteria for each feature. The selected control features may be directly converted for use in automatic image matching software to allow absolute orientation of satellite images based on a large number of control points.