Fig 3. Leica System 500 - main hardware components.
The experimental tests will consist in the survey of some IGM
95 Network vertexes taken with a GPS mobile receiver
connected with GSM modem. In this way it’s possible to take
data corrections in real time from GeoTIM network and to make
two kinds of comparison:
1. with the coordinates given by GPS national reference
system (IGM95);
2. with static coordinates coming from post-processing
operations, using permanent GPS-station of Polythenic of
Bari and the vertexes of GeoTIM network (data available
on the Web),
The vertexes IGM95 chosen for the experimental tests, has
been:
1. 177701 (Bari S. Spirito- 7,5 Km)
2. 177901 (Palombaio - 7 Km )
3. 177702 (Palo del Colle — 14 km)
4. 189701 (Altamura — 35 Km)
5. 190702 (Locorotondo — 65 Km).
The choice is due to the increasing of the vertex distances from
permanent GPS-station of Polythenic of Bari and from TIM
permanent stations: the purpose it’s to verify the possible
diluition of precision with the increasing of distance among the
two receivers.
The parking has been effected with the method of high precision
on the “station point” to assure the evaluation of the points
coordinates with millimetric accuracy.
3. CONCLUSIONS
The results gotten in the surveys are brought in attached table n.
1, in which are given the following vertexes coordinates :
l. known (furnished by the IGMI - Italian Geographical
Military Institute);
2. surveyed with RTK system in connection with the TIM
Permanent local Stations;
3. surveyed with a static survey of few minutes (less than
10") on the same point, subsequently connected in post
processing with the same station of TIM network and
with the Permanent Station of the Polytechnic of Bari, to
obtain closure-differences in each triangle.
In the graphs of the figures n. 4,5,6 are brought the differences
among the values of coordinates gotten with the different
methods, respectively:
J: differences IGM95 — RTK;
2. differences IGM95 — STATIC;
3. differences RTK — STATIC.
70
It's possible to notice the linearity of the differences among the
different methods that don't introduce appreciable variations
with the growth of the distance.
COMPARISON RTK / STATIC
> © | na DN
: » we] [ |
: e DE lm
e" e
S - © = Dh [m
G. t
Qa e
01
0
PALO (d=75 | SSPIRITO | PALOMBAIO | AL RA LOCOROTOND
km) (d=7,7 km) (dz14 km) {d=36 km} O (d=60 km)
museum A (e 0.047 0.014 0.014 0 0.125
m—R m oy 0.035 0.046 0.047 0.029 0.048
x = ER Dh {m} 0.2804 0.2341 0.3467 0.3823 0.4836
Fig 4. Comparison between RTK and Static.
COMPARISON IGM85/ STATIC
i ,9-e6 —e9—- DN [m]
e e = — D -DE [m]
ua Moris "os Dh m]
PALO S SPIRITO PALOMBAI ALTAMURA LOCOROTO
(d=7 5 km) |(d=7 7 km) O(d=14 km) (d=36 km) | NDO(d-60
mmus Le 0.035 0.037 0.006 0.001 0.015
m-—A Dium DE | m) 0.031 0.042 0.022 0.014 0.064
- -om "Dh m] 0.384 0.371 0.461 0.452 0.0933
Fig 5. Comparison between IGM95 and Static.
— Du LIN [m] JOMPARISON IGM95 / RTK
—p -DE [m]
S.SPIRITO
(d=7.7 km) km) km) (d60 km)
PALOMBAIO(d=14 ALTAMURA (d=36 LOCOROTONDO
PALO(d=7.5 km)
—————w 0.012 0.023 0.008 0.001 0.14
-—a Dm IDE [m] 0.004 0.004 0.025 0.043 0.112
- -o m BDh[ m] 0.1036 0.1369 0.1143 0.0697 0.259
Fig 6. Comparison between IGM95 and RTK.
This springs from the consideration related to the resolution of
the ambiguity effected by the permanent station in very fast
times and the following transmission of the corrections to the
rover. This modality , therefore, is not influenced in strong way
by the growth of the distance between master and rover.
All the ambiguities have been resolved in very small times with
the attainment of the default accuracy of the tool (2 cm) after
few minutes.
The "anomalous" value of the altimetric result gotten on the
most distant vertex (60 km), it can be justified from the
contemporaneity of connection both with the TIM station in
Bari and
that has
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- ASI-CC
