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THE USE OF DGPS-RTK MEASUREMENTS THROUGH GSM NETWORK FOR GIS 
ENVIRONMENTS 
M. Caprioli*, A. Scognamiglio*, G. Strisciuglio* 
*Dipartimento di Vie e Trasporti — Politecnico di Bari 
(m.caprioli, a.scognamiglio, g.strisciuglio)@poliba.it 
TS-PS: WG II/1 — Real Time Mapping 
Key words: GPS, GSM, DGPS, RTK, geodetic survey, navigation, direct georeferentiation. 
ABSTRACT 
The necessity to get positioning in the most precise way and in the briefest time assumes great importance either in the navigational 
field or in the geodetic surveys. The GPS system is really the most proper tool to meet such expectations. 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. 
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 a GSM mobile phone 
with the Bluetooth wireless connection to the GPS receiver. The rover GPS must be connected to permanent reference station of GPS 
national network (GeoTIM Network) through the GSM phone, provided of a normal telephone card fr data transmission: the 
correction is directly effected during the survey (RTK) using the standard protocol RTCM. An advantage from the economic point of 
view, it’s the possibility to operate in real time for geodetic surveys only with one “low-cost” receiver, continuously connected to a 
permanent 
GPS-station. The results of this experimentation are very useful both to verify the real functionality of the TIM 
"GeoData" system, and to develope the use of a GPS receiver for GIS data collection with sub-meter accuracy. 
1. INTRODUCTION 
The technological development of GPS technologies has 
increased the use of receivers for data collection in Geographic 
Information Systems (GIS). GPS receivers are conceived to 
satisfy the needs of GIS applications as well as to survey 
applications. 
At the same time, with second generation sensors, the diffusion 
of metric and sub-metric satellite data permit better detail and 
definition of geometric propriety than the past. The acquisition 
of GCPs (Ground Control Points) by means of GPS-RTK 
methodology (using Bluetooth wireless connection to receive 
GSM corrections in real time) allows sub-meter accuracy during 
the survey. This is necessary to process spatial data with 
mathematic methods, based on parametric models and not 
parametric models. 
So the necessity to get positioning in the most precise way and 
in the briefest time assumes great importance either in the 
navigational field or in the geodetic surveys. 
The GPS system is really the most proper tool to meet such 
expectations. 
The present note considers a particular application of GPS, and 
that is the D-GPS, known also as Differential GPS: the 
correction is directly effected during the survey (RTK - Real 
Time Kinematic). 
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. 
Since the end of 2002 in Italy is operating a TIM Service 
(Telecom Italia Mobile) called "GeoData". It allows the 
correction of the topographical measurements using the 
GeoTIM network (figure n?1), constituted by 34 (23 certified) 
permanent GPS-stations, uniformly distributed on the whole 
national territory and inserted in the Italian GPS Reference 
Network (IGM95). 
The corrections, elaborated by the GeoTIM network, for 24 
hours a day, are available in RTCM and RINEX data-format. 
  
  
  
  
  
Fig 1. Geo-Data (TIM) Network in South Italy. 
They are possible two ways of access to the service. In “post 
processing”, the data corrections are available on the web 
(figure n°2). After the survey with a GPS mobile receiver, 
memorizing data on magnetic support, it’ s possible to acces to 
differential corrections on the web. It s important to 
specify-the permanent GPS-station, the date and the hours of 
interest, the cycle-rate desired (1 second , 5 seconds, 15 
seconds, 30 seconds), etc.