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Oxford Technical Solutions
Repeatability
Differential corrections change the way a GNSS receiver works. When using
differential corrections, the GNSS receiver is effectively measuring the position
relative
to the base station, not the absolute position on earth. This leads to several
effects that the user should be aware of:
1.
If the base station antenna is moved, then the remote GNSS receivers move too. It
is important to put the GNSS antenna in a location where it cannot move or be
moved. See Figure 21.
2.
The base station has to measure its own position. If the base station gets this
position wrong, then the remote GNSS receivers will also be wrong. They will be
correct relative to the base station, but they will have the same error on the earth
that the base station has. This is important when turning the RT-Base S off and on
again. See Figure 22.
Figure 21. Shifting base station antenna example
The problem of shifting the antenna typically occurs when:
The tripod is knocked over and picked up again. It is hard to get the antenna
back to the same location accurate to 1 cm.
If the RT-Base S is used one day, packed up then returned to the same location
the next day. It is very hard to replace the tripod in the same location. It is better
to have a pole that is fixed to the ground if you intend to use the same surveyed
location on several days.