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We are grateful to the Italian National Research Project entitled Digital surface modelling by laser scanning and GPS 
for 3D city models and digital ortophoto, financed by the Italian Ministry of the University for the 1998 year, and 
chaired by the prof. Galetto, of the University of Pavia, for providing the data we used. We are also personally grateful 
to prof. Galetto for giving us some good suggestions on our job. 
We would like to thank the people who helped us to take ground measurements: the two technicians of our Geomatic 
Laboratory, geom. Paolo Marchese and geom. Giuseppe Girone, who also helped us to prepare some drawings, and Elio 
Casella. 
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Ackermann F. (1996) — Airborne laser scanning for elevation models — GIM, Geomatics Info Magazine, Vol. 10, n. 10, 
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Casella V., Galetto R. (1998) — Tecniche innovative per il rilevamento terrestre, aereo e da satellite (Innovative techni- 
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International Archives of Photogrammetry and Remote Sensing. Vol. XXXIII, Part B3. Amsterdam 2000. 163