Global Positioning System Reference
In-Depth Information
8. Post-processing positioning accuracies
Raw data files in a RINEX format were stored in order to estimate the accuracies achievable
in post-processing and the performance when the average inter-station distance increases.
These files, with a length of 24 hours, were split in many shorter files with different
duration, in order to statistically evaluate the planimetric and altimetric accuracy.
Fig. 14. Data files split schema
The data files were processed by a commercial software (Leica Geomatics Office™ v.8.0)
based on the double differences approach, using as master station the nearest permanent
station to each considered network and a VRS generated by the network software close to
the measurement site.
The post-processing results show a no significant difference among the three geodetic
receivers, due to the goodness raw data quality. The same behaviour was observed also
when the three GIS receivers were used. For this reason, an “average” instrument for each
class of receivers is considered in the following analysis.
8.1 Geodetic receivers
Raw data files of a geodetic receiver were split in many files of 5 and 10 minutes long, and
they were post-processed as said above. The CDF of the planimetric and altimetric error
(calculated using the “true position” evaluated from the network adjustment previously
described) were computed for each time session.
The Fig. 15, in the next page, shows the results obtained using the nearest station for the
three considered networks. A low deterioration of the positioning accuracy can be observed
when different reference stations (at different distances from the rover) were used as master.
This can be seen, for instance, considering the planimetric accuracy obtained by the post-
processing of the 5 minutes long data. In this case, for the “green” and the “blue” networks,
a significant degradation can be observed only in the last 10% of the distribution.
Considering the 10 minutes long files, no significant improvements are observed, as
expected, in the “red” network, while a better accuracy can be seen when “green” and
“blue” networks are used. Also the percentage of epochs with fixed ambiguities are similar
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