Preprocessing procedures for automatic plotting in photogrammetry

In order to develop a new method for automatic plotting in photogrammetry, proposed by the Istituto di Geodesia, Topografia e Fotogrammetda, University of Pisa, a data acquisition and preprocessing procedures has been implemented at the Istituto di Elaborazione Informazione (lEI), CNR. A set of test images, obtained with the metric camera UMK, Zeiss-Jena, has been digitized by using the computer. controlled microphotometer MFA/250/LS; several preprocessing procedures have been executed on digitized row data in order to reduce photographic noise and photometric and geometric distorsions; an algorithm for data binarization and line-thickness reduction has been implemented, in order to obtain the skeleton of the grid contained in raster image. Preprocessed data are then analized by using the programs implemented to obtain plate and spatial coordinates of test objects. Tne preprocessing procedure are partially interactive, and are executed on the Computing Structure 'SADAF2 of the IEI.