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Fig. 2 - Available detailed drawing for two different antennae (Stadio and Bo-ASST) with the orientation of
panels respect to the North
3. DGPS and possible applications in our case.
Nowadays there are many interests in using DGPS technique
in surveying, and there are many private corporations
entering the DGPS service industry. It becomes increasingly
more important and more difficult for professional DGPS
users to choose the most appropriate system for their
application. All the services tend to provide the same
accuracy, (1-3 m, where that accuracy depend on the range
between the master and remote station), therefore a matter of
reliability, availability and cost tend to dominate.
There are different ways to disseminate the correction of
GPS: via satellite, cellular carriers and FM-sub carrier.
The use of DGPS in surveying depends on the requested
precision. As it is well known, there are two types of DGPS
corrections: Precision and non Precision (centimetric and
sub-metric accuracy, respectively).
Actually, the fundamental field work in positioning mobile
phone antennae in the Italian National system, is performed
using DGPS technique, which means saving time and cost.
At first, precision and reliability of DGPS should be verified.
In order to do that (as shown in figures 3, 4 and 5), we have
to compare the results obtained in DGPS technique with
static techniques at different stations. The corrections used in
these tests are coming from OmniStar system. The
OmniStar system provides differential GPS correction data
to user’s mobile receiver units via L band satellite. The
second step consists in using IGM95 stations to transform co
ordinates between WGS84 and Italian National system.
Fig. 3 - Co-ordinate differences between static and DGPS techniques in some stations.
The planimetric differences are in the order of one meter but of the order of couple meter in the height.
Due to the obstacle problems of GPS signals and multipath phenomena, in the urban zone, the co-ordinate
differences becomes larger.
