1. Researcher, Dept. of Geography, Section Geomatic Engineering, Ghent Univ., Krijgslaan 281 S8, 9000 Gent, Belgium.
2. Professor, Dept. of Geography, Section Geomatic Engineering, Ghent Univ., Krijgslaan 281 S8, 9000 Gent, Belgium.
3. Postdoctoral Researcher, Dept. of Mathematical Analysis, Ghent Univ., Galglaan 2, 9000 Gent, Belgium.