40
• two external antennas (Legant microstrip zero
centered) (Fig. 4) with incorporated choke and
certificate of calibration on the GPS L1+L2 carriers;
Fig. 4. The Legant antenna.
• 32-bit Control Data Unit or Data Logger (CDU-2 -
Psion 5) (Fig. 5) with 8 Mb of RAM for data storage
under the Epoch 32 operating system, equipped with
RTK Field Face software. The software is able to
manage each measurement and recording function
and to perform a co-ordinate transformation between
the datum and different projections;
Fig. 5. The Psion 5 Data Logger.
• 433-34 MHz external radio modem (Satel) with 1 W
of power, approved for use in Italy.
Finally, the entire GPS+GLONASS RTK system was
equipped with connecting cables and power supply
batteries. Figure 6 illustrates the connections of the
various components both for the Master station and the
Rover station.
2. FIELD TEST
2.1 Marking out transverse sections of a road
embankment
The first example of an application of the system involves
the marking out (Fig. 7 and 8) of transverse sections and
the surveying of 3 road embankments under construction.
The purpose was to quantify the volume of fill used in the
works.
The transverse sections of the road embankments had the
geometric characteristics reported in Figure 9. Their
lengths varied between 1.5 and 2.5 km.
Fig. 6. Master and Rover receivers of the
GPS+GLONASS RTK system.
Fig. 7. View of the road embankment under construction.
Fig. 8. Positioning of the Rover receiver on the measuring
point.
Before the GPS+GLONASS RTK measurements, we
performed a traditional survey to determine on the ground
the planned sections of the road embankments (Zero
survey). The instrumentation used consisted of a Pentax
PTSV1 integrated electronic theodolite. The
instrumentation sites were organised planimetrically and
altimetrically with respect to existing vertices of known
co-ordinates. From them, we measured, with simple polar
co-ordinates, some new vertices which were then used to
perform the operations of plane calibration of the
GPS+GLONASS measurements. In view of the limited
area of the zone and the low precision required for
measurement of the height (rms between 10 and 15
centimeters), we assumed the relative variations between
geoid and ellipsoid to be zero.
