Global Positioning System Reference
In-Depth Information
the corners of a square that includes the complete trajectory. Their exact locations are given
in the figure (note that the altitude of the repealites are also given and allow for quite a nice
indoor VDOP). The receiver is considered to be at an altitude of zero meters.
The speed of the receiver is set at 1m/s and the multipath delay appeared to vary between
0.07 and 0.17 chips, equivalent to between 20 and 50 metres roughly. Note that since the
SMICL is more sensitive to noise than the SDLL (or the NC), the simulations were carried
out using 50dB-Hz for the C/N0 value. This is rather a high value for outdoors, but not
impossible indoors since one decides the indoor power transmitted (except that regulations
are limiting the maximum allowed).
The results are given in figure 26 for 2D and 3D positioning. These simulations show a few
decimeters accuracy range for the whole trajectory, and results a little bit better for 2D than
3D. Some skips can be seen in figure 26 which are the ambiguity skips: thus, these skips are
typically a multiple of nineteen centimeters. This allows us to evaluate the efficiency of the
estimation of this ambiguity. Note that it is calculated every second and is based on the
SMICL assisted measurement of the code phase. This once again confirms the very good
performance of the SMICL approach.
Positioning error (m)
0.7
Mean Error 2D = 0.15
Error on 2D Position
Error on 3D Position
Mean Error 3D = 0.21
0.6
0.5
0.4
0.3
0.2
0.1
0
0 5 10 15 20 25 30
Time (s)
Fig. 26. Positioning accuracy obtained with a repealite system
6. Regulatory issues for L1/E1
The problem of using the same frequency band as the outdoor GNSS is that interference
may occur. Of course, when a single system is deployed, these interferences should be very
limited and only disturb locally the outdoor receivers. Nevertheless, if no regulations exist,
there is a potential danger for GNSS. Thus, some countries have worked towards the
development of constraints on the power allowed to be transmitted.
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