visible with a classical levelling operating with an adequate 
sampling with beatings of a considerable number of meters. 
Finally, as it has been demonstrated in the above paper (see 
results of fig. 8) this method can be used with distant GPS 
reference stations (as in the survey carried out at Trieste airport 
strip, where a master located in Pisa was used) but would result 
inappropriate to survey small variations in the ground. 
However, it would be useful to monitor important sinkings, and 
its use could be of interest for Countries that still do not have a 
high number of GPS reference stations. 
12 T 
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 
Points comparison 
I —•— Series I " t > Series 2 —* Series 3 — 15 Series 4’ 
Figure8: Series of results 
Figure 8: 
The series 1 refers to the altitudes obtained by means of a 
photogrammetric survey used to realize the map of the region 
Friuli Venezia Giulia; 
The series 2, 3 and 4 refer to the altitudes surveyed with the 
GPS proposed method and in particular the series 2 and 3 refer 
to two different days of measure during which a receiver is used 
as a master and located on the side of the airport strip while the 
altitudes of series 4 are measured in the same day as altitudes 
related to series 3 using however as master a receiver located in 
Pisa. During these experiments the vehicle (a normal motorcar, 
therefore with non stopped suspensions) has covered the strip 
approx, at 50 km/h of speed. The analysis of the results show 
that the highest difference among the photogrammetric survey 
and that of the GPS is of 20 centimeters. In general, accuracy of 
GPS surveys is better than 10 centimeters. 
REFERENCES 
[1] G. Manzoni, R. Cefalo, S. Fonzari. "Urban and Suburban 
road survey by means of reai time direct and inverted DGPS" - 
Proceedings international Symposium DSNS '94, Royal 
Institute of Navigation, London, Voi. II, paper No 62, 1994 
B. Palla (1988): “I movimenti del suolo nella città di Pisa e nel 
territorio circostante”, Comune di Pisa, Università di Pisa. 
B. Palla (1983): “Altimetria relativa: la scelta del riferimento. 
Applicazione ad una indagine sui movimenti verticali del suolo 
in terreno alluvionale ed in roccia a nord-est di Pisa”, Atti del 2° 
Convegno annuale del Gruppo Nazionale di Geofisica della 
Terra Solida. Roma 12-14 dicembre.