4. Method of surveying 
The methods used for surveying may be classified in respect 
to accessibility to antennae frame centre. In some cases it is 
too hard to access to the antenna centre because of the height, 
which on the other hand could be an advantage from the 
visibility point of view, (such as, selecting the baselines 
around the antenna). 
1- Accessibility at the frame centre with GPS or DGPS 
receivers. 
Taking into account the considerations made above, the 
possibilities of surveying are : 
a- for sub-metric accuracy: 
1- using one DGPS receiver at the frame centre and 
then using the parameters transformation to 
obtain the co-ordinates in the National system. 
2- for the orientation of antenna frame, one DGPS 
receiver may be used to find the reference co 
ordinates of one point in WGS84 with sub 
metric precision and another single frequency 
receiver in fast-static mode (5-10 minutes), 
allows a precise orientation. Then we can use the 
symmetry and alignment to find the co-ordinates 
of the frame centre. 
b- for decimetric accuracy: 
1- Using one dual GPS receiver at the frame centre 
and processing the data respect to the nearest 
permanent station or known master station. The 
alternative methodology of surveying is to use 
precision DGPS technique, where the phase 
measurements corrections from the reference 
receiver are transmitted to the remote receiver to 
be incorporated into the position solution in 
order to solve for the phase ambiguity (RTK). 
2- for the orientation of the frame we can use the 
same procedure reported above. 
The sequence of work of this method have been implemented 
at the BO-ASST station, (Tab. 1). 
Tab. 1 - co-ordinates of the antenna frame centre of ASST- 
station in the WGS84 system with relative rms in meters. 
Static mode respect to Medicina permanent station 
Static GPS 
N 
E 
H 
Co-ordinates 
44 29 59.557 
11 20 47.692 
117.258 
rms 
0.002 
0.002 
0.004 
differential GPS 
N 
E 
H 
Co-ordinates 
44 29 59.514 
11 20 47.672 
118.6 
rms 
1.4 
0.8 
1.4 
2- Difficult accessibility to the frame centre. 
The common field work in this case is to determine one or 
more external baseline using GPS technique and then use a 
conventional surveying for antenna frame. Of course this 
work procedure may also be done, in the case of accessibility 
at the frame antenna centre. 
Procedure of surveying 
1- determine at least two baselines around the antenna 
frame, in such a way that the zenith angle is wide 
enough since the antenna frame could be very high 
respect to the selected points and this could cause some 
difficulties in pointing the top of the antenna frame with 
classical instruments. 
2- Use GPS technique (non-precision DGPS or precision 
DGPS or static techniques) to determine at least one 
point of the selected baselines and then fast-static 
technique (single frequency receiver) may be used for 
the other ends of baselines to obtain a good orientation. 
The use of fast-static save time and cost, particularly in 
the case of static and non-precision DGPS techniques. 
In Fig. 6, we can see the local Stadio - network, where the 
stations have been surveyed using both static and non 
precision DGPS techniques respect to the Medicina 
permanent station and to the Faculty of Engineering Tower 
(known station in the WGS84). 
3- Classical surveying: Theodolite, total station and MDL 
are the instruments used to determine the orientation and 
position of antenna elements. Which have been pointed 
from stations determined with GPS: 
a- using Theodolite or total station instruments. The 
difficulties of using these instruments, in our case, is 
to point the same target from different stations and 
to use the reflectors. 
b- using MDL instrument. The difficulty in using this 
instrument is to determine which elements of the 
antenna reflect the LASER, therefore maximum care 
should be taken when operating with them. 
In the Fig. 7, it is shown the classical measurements at the 
antenna Stadio, by using intersection and radiation surveying 
from the three reference GPS stations. 
Generally, we should have to distinguish between the 
precision of GPS techniques and classical techniques 
(Theodolite or total station or MDL instruments). The 
precision of GPS surveying (static, non-precision DGPS, 
precision DGPS) to determine the co-ordinates of one point 
in WGS84 and consequently into the Italian National system 
depends on the technique used. In any case in order to obtain 
good orientations, when using classical survey, one has to 
achieve at least sub-decimetric accuracy.