EXPERIMENTAL TEST OF GPS-RTK MEASUREMENTS WITH GPS-GSM NETWORK 
BY T.I.M. (TELECOM ITALIA MOBILE) 
M. Caprioli*, A. Scognamiglio*, G. Strisciuglio* 
*Dipartimento di Vie e Trasporti — Politecnico di Bari — (m.caprioli,a.scognamiglio)@poliba.it, 
g.strisciuglio@katamail.com 
Commission VI, WG VI/3 
Key words: GPS, GSM, DGPS, RTK, geodetic survey. 
ABSTRACT 
The paper describes some experiments in course at the Polytechnic of Bari on the transmission of D-GPS correction signals in local 
region by the use of GSM phones. 
Some correction systems present in Europe are examined, to payment and not; then we introduce the methodology of the GPS 
measurement through a connection between a reference station and a rover station with GSM modem. 
The tests regard some national “IGM95” vertexes so that to evaluate the accuracy of this transmission system. 
This experience requires that the rover GPS must be connected to the permanent reference station of GPS national network through a 
GSM modem, provided of a normal telephone card for data transmission. 
The results of this experimentation are very useful both to verify the real functionality of the TIM "GeoData" system, and in sight of 
the predisposition of a national normative for validation of the measures through GPS. 
1. INTRODUCTION calculate the "baseline" with the Differential Phase method : the 
position of the "rover" is the difference among the values 
The necessity to get positioning in the most precise way and in measured by the “master” and those directly acquired on the 
the briefest time assumes great importance either in the point. 
navigational field or in the geodetic surveys. In the second methodology there isn’t a variation of accuracy in 
The GPS system is really the most proper tool to meet such data acquisition due to a change of satellites configuration. 
expectations. Another advantage, from the economic point of view, it is the 
The present note considers a particular application of GPS, and possibility to operate in real time for geodetic surveys with one 
that is the D-GPS, known also as Differential GPS or RTK receiver, continuously connected to a fixed receiver. 
(Real Time Kinematic). 
  
There are various fields of application of this methodology: ARR Ay " ast rp a ; 
1. terrestrial, maritime and RE e navigation; DIFFERENTIAL GPS POSITIONING 
2. location of vehicles in real time; Là 
3 fleets management of commercial vehicles; 
4 geodetic surveys; 
5 data acquisition for Geographic Information Systems (GIS). 
The purpose of DGPS is, essentially, to transform the absolute 
positioning of a point (fixed or mobile) in a relative positioning 
in comparison with another that can be considered fixed and of 
known coordinates in a determinate reference system. 
In this way it's possible to reduce the intrinsic errors of GPS 
system, expecially those due to the ionosphere, to the 
troposphere, to the time delay of the satellites clocks, to the 
orbits, etc. 
They can be separate two different methodologies of D-GPS. 
  
  
  
  
  
The first, more used in the navigation, consists in giving to the RANGE CORRECTIONS 
GPS "master" the "true" coordinates (fixed and previously BASE E REMOTE n 
note), and in comparising them to the coordinates calculated in KNOWN BOSITION ORRECTED POSITION 
every time of acquisition. Fig 1. Differential GPS Positioning. 
Subsequently the corrections are sent to the "rover" receiver 
which calculates the correct coordinates of its position; in this 
case it's not necessary the visibility of the same satellites. Stations: nowadays it's possible to keep data always from 
Nevertheless, the acquisition from one of the two receivers ofa different stations in every zone of the territory with distances 
new satellite could produce an accuracy variation. less than to 100 kms 
The second method consists in transmitting to the receiver rover 
the same data received by the master, in this way it’s possible to 
In the last years there was a proliferation of Permanent GPS- 
It results opportune, therefore, to effect tests “on the field” to 
verify if this methodology can assure the same accuracies (or at 
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