María Luisa Casado
_{Department of Surveying Engineering and Cartography
Universidad Politécnica de Madrid
Campus Sur, Autovía de Valencia km 7, E-28031 Madrid (Spain)
ml.casado@upm.es}

Abstract
The geometric conflation problem is really pressing nowadays. New demands and challenges arisen from SDI (Spatial Data  Infrastructures) make the coordination of diverse information more and more necessary in order to answer new questions. As the inception of a PAI (Program of Accuracy Improvement), the UPM (Polytechnic University of Madrid) has signed a collaboration agreement with the IGN (National Geographic Institute) in order to research the harmonization procedures between its 1:25 000 series, the cadastral cartography 1:1000 and the street guide information 1:1000 collected by the INE (National Statistical Institute) This paper does not tackle the attribute issue but the geometry one, so just the two first mentioned cartographies have been considered. A number of situations found in this geometric conflation project are analysed in this work. The different types of geometric transformations that can correct these defects are commented. We also collect and formalize some basic mathematical constraints derived from cartography rules  like topology relationship preservation.

Keywords: geometric conflation, mathematical constraints, cartographic restrictions

In: Caetano, M. and Painho, M. (eds). Proceedings of the 7th International Symposium on Spatial Accuracy Assessment in Natural Resources and Environmental Sciences, 5 – 7 July 2006, Lisboa, Instituto Geográfico Português