Global Positioning System Reference
In-Depth Information
Fig. 11. Positioning quality of a GIS receiver when a VRS correction is used: CDF of the
planimetric error (top left) and of the elevation error (top right), cumulative moving average
of the planimetric error (bottom left) and of the three-dimensional positioning error (bottom
right)
The Fig. 12 shows the comparison between the stand-alone positioning error and this one
obtained using the two corrections said above. The figure shows the results obtained
considering the network with inter-station distances of about 100 kms (“green” network),
which in previous tests gave better results. As shown, both the NRT and EGNOS corrections
allow to obtain a positioning quality that is fully comparable to that one achievable using
VRS corrections. This result, although it may seem in contrast with the virtual stations and
with the GNSS network positioning concepts, must not surprise. Common GIS receivers, in
fact, are not able to well use carrier-phase corrections that difficultly can be modelled when
the reference stations are too far from the measurement site.
The analysis of figures above allows also to highlight benefits due to the use of differential
corrections with respect to the stand-alone positioning. The planimetric error (at the 95% of
reliability), for example, decreases from values close to 1.7 m for stand-alone positioning up
to about 70 cms when differential corrections are used. This improvement is even more
evident observing the height accuracy trend (which decreases from about 4.5 ms to 1 m) and
when cumulative moving average is considered (Fig. 13).
Search WWH ::
Custom Search