Geography Reference
In-Depth Information
3.1.1. Leica Smart Station (Scott A., 2006)
A classical example of such optical measurement equipment for observing different targets
with displacement probability is the “Leica Smart Station”, a Total Station with integrated
GPS offered on the market by the “Leica Geosystems AG” company. The introduction of
SydNET, a network of Continuously Operating Reference Station (CORS), allows surveyors
to perform Differential GPS without having to purchase a reference receiver. For distances
of up to tens of kilometres away from the network reference stations, centimetre accuracy
can be achieved, with the RTK-GPS Network.
This equipment involves the optical observation of the proposed object from different static
locations of the operator, locations which are precisely determined by means of the highly
performing GPS receiver. In these conditions, the determination of the geographic
coordinates of a single distant objective involves multiple complex operations and in
consequence, can be considered time consuming.
3.1.2. SEPA's system (Caporali A., 2008)
Another totally different technical solution for this problem, solution which aims to reduce
the length of the measurement times involved by the use of the optical total stations, is
represented by the “Fixed Satellitary Monitoring System of the Territory and Civil
Infrastructures” (or SAMOS for short) achieved by SEPA company (“Sistemi Elettronici Per
Automazione S.p.A.”) from Torino (Italy).
The SEPA's system represents a solution for cost effective applications targeting the real
time monitoring and diagnosis of ground deformation; for instance, landslides and the
subsidence, or the infrastructure deformations affecting buildings, bridges, viaducts and
dams, or even both simultaneously.
Based on measurements from a GPS L1-only carrier phase employing commercial receivers
and using the basic principles of interferometric surveying, SAMOS provides continuous
real-time monitoring of the area of interest, reporting the millimetric displacement of each
sensor relative to a reference sensor.
Measurements are taken at a rate of 1 Hz and the processed results are updated using the
same frequency. The system performance is equivalent, on short baselines up to a few km in
length.
This Satellitary Monitoring System, in fact like other this kind of systems, is composed of
two subsystems, namely:
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a number of Field Sensors, (Fig. 2), deployed to collect the satellite data and which are
fix mounted on different parts of the objective of interest (bridge, dam, building). These
field sensors are continuously relayed by means of a radio connection to
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a Base Station, (Fig. 3), for real-time processing of the data collected from the field
sensors.
For its protection this Base Station is introduced in a Waterproof box (Fig. 4).
