1. Department of Geography and Geology; University of Turku; FI-20014 Turku Finland
2. Hydrological Research; Swedish Meteorological and Hydrological Institute (SMHI); SE-601 76 Norrköping Sweden
3. Department of Forest Sciences; University of Helsinki; PO Box 27 FI-0014 Helsinki Finland
4. Finnish Geospatial Research Institute; National Land Survey of Finland; Geodeetinrinne 2 FI-02430 Masala Finland