133 
■ time necessary for initializing (however, with 
respect to the 15 min that the manufacture stated 
as necessary, we found that 5 min was sufficient). 
Instrument advantages were: 
■ the high precision and 
■ reduced number of personnel (only two GPS 
operators and one car-driver), 
■ reduced time for measurements, 
■ predetermination of operational time. 
cases, in fact, the difficulties and the uncertainties of 
inserting the survey in a cartographic system risk 
accepting times and precision that are not acceptable. 
However, the potentiality of G.P.S. and the prospect of 
further technological enhancements for greater 
precision, together with the necessity of cataloguing the 
extensive road infrastructure, make the research in the 
road sector interesting from the point of view of new 
and more efficient means of surveying. 
Figure 1 - Surveyed curves (example). 
7. Conclusive Considerations 
The great versatility of GPS and the high precision also 
in the field of navigation, immediately allowed the 
researches to hypothesize its use for surveying road 
infrastructures. After the first encouraging experiments 
in Italy in 1990, its widespread use has not been seen. 
In fact, despite the good experimental results obtained, 
there are a series of conditions that limit the fields of 
use of GPS methods for road surveys. 
The greatest obstacle is the obstruction of the satellite 
signals along any stretch of road especially urban ones. 
The precision, furthermore, is referred to the covered 
trajectory of the vehicle and not to the road axes, which 
are obtained by interpolation curves and/or 
approximations and that, consequently, are affected by 
further errors. 
Finally, we must consider the difficulty of the operations 
(also topographic) that are necessary for the passage of 
the ellipsoidal WGS84 co-ordinates to those of the local 
cartographic system, which requires the connection of 
the GPS points to the vertices and bench-marks 
determined in the national system with traditional 
instruments 
In particular, in the case of road surveys, it should be 
borne in mind the altimetric profile found with GPS is 
not directly connected to local cartography. The GPS 
heights, in fact, are ellipsoidal heights, while the official 
cartographic system has geodetic heights. The 
transformation of the GPS co-ordinates into 
cartographic or local Cartesian co-ordinates is still 
complex and uncertain, as the knowledge of local 
shifting between geodetic and ellipsoidal is not yet 
sufficiently precise and diffused (it is surely not 
comparable to the precision with which GPS provides 
geocentric co-ordinates). 
These considerations induce a certain cautiousness in 
believing that the use of GPS techniques are always 
correct for plano-altimetric surveying of roads, above all 
when the survey is for cartographic up-dating. In these 
Selected Bibliography 
W. Paterson , 1991 “Choosing an appropriate 
information System for road management”, “XIX World 
road congress AIPCR” - Marrakech. 
M. Bordin, S. Rossi, E. Salvatori, 1994.“Rilievo 
automatizzato delle caratteristiche geometriche e 
funzionali della strada per la costituzione del catasto 
stradale” - tema IV, p. 163-167, “XXII Convegno 
nazionale stradale AIPCR” - Perugia 
Ministero Italiano dei LL.PP. 1995,- Direzione Generale 
della Viabilità e Mobilità urbana ed extraurbana. “Studio 
ed apprestamento di supporti conoscitivi per la 
definizione delle modalità di istituzione ed 
aggiornamento del Catasto delle Strade” 
M.R. De Blasiis, 1996 “Il catasto delle strade per la 
gestione del patrimonio e la programmazione 
territoriale”, Collana di Ingegneria delle Infrastrutture 
Viarie n.2, supplemento n.1, Infrastrutture e territorio, 
maggio 1996. 
G. Bitelli, G. Dondi, 1996 “L’impiego delle tecniche di 
rilievo GPS nella realizzazione del catasto stradale”, 
Collana di Ingegneria delle Infrastrutture Viarie n.2, 
supplemento n.1, Infrastrutture e territorio, maggio 
1996. 
L. Leone, G. Mussumeci, 1996 “Problematiche e 
prospettive dell’impiego del GPS per il rilievo plano- 
altimetrico delle strade”, Collana di Ingegneria delle 
Infrastrutture Viarie n.2, supplemento n.1, Infrastrutture 
e territorio, maggio 1996. 
L. Leone, G. Mussumeci, 1996 “Standard della 
cartografia di base per Sistemi Informativi Territoriali 
delle Infrastrutture Viarie (SITIV)”, Collana di Ingegneria 
delle Infrastrutture Viarie n.2, supplemento n.1, 
Infrastrutture e territorio, maggio 1996. 
C.B. Gauer, M. Trzaski, M. Paoli, 1997 “Integration of 
computer applications into a highway planning 
process”, “XIII World meeting IRF” - Toronto, Ontario, 
Canada, giugno 1997. 
M. Barbarella, L. Vittuari, 1998 “Il rilevamento GPS: 
sviluppi recenti” - voi. I, p. 7-16, “Il Conferenza 
nazionale della federazione delle Associazioni 
Scientifiche per le Informazioni Territoriali e Ambientali” 
- Bolzano, novembre 1998. 
V. Casella, R. Gaietto, 1998, “Tecniche innovative per 
il rilevamento terrestre, aereo e da satellite” - voi. I, p. 
33-54, Il Conferenza nazionale della federazione delle 
Associazioni Scientifiche per le Informazioni Territoriali 
e Ambientali” - Bolzano, novembre 1998. 
J. Wolf, S. Hallmark, M. Oliveira, R. Guensler, W. 
Sarasua, 1999 “Accuracy issues with route choice data 
collection using GPS”, 78 th Annual meeting TRB - 
Washington, D.C. gennaio 1999.