to my parents

I sincerely thank my advisor /. Nievergelt for his encouragement and for supporting this project first at die University of North Carolina at Chapel Hill and dien here at ETH Zürich. I am also grateful for die many fruitful discussions we had about geometric algoritiims and die problem of consistency which helped to shape my ideas. Furthermore I thank for his constructive criticism and many helpful hints regarding style and presentation of this dissertation. The following people also deserve special mention: • Anders Kierulffor constructive discussions and his help witii die Macintosh Toolbox. • Gaston Gönnet for his willingness to be co-referee and his useful suggestions to the dissertation. • Christoph Ammann and Michele De Lorenzi for helping in the evolution of the XYZ GeoBench. • MartinMidler for proofreading and spotting some mistakes. • Ralph Gasser for his careful reading and commenting on diis dissertation