In a recent GPS World article titled "What's Your Occupation Time?",
Mr Eric Gakstatter opened a discussion on the issue of occupation time for RTK points,
in particular the RTK shot where high confidence and accuracy in the RTK position is
required.
The discussion makes several assumptions:
- You have clear view of the sky.
- It is clear of multipath-enabling obstructions.
- Six or more GPS satellites are being tracked with a low PDOP.
Most, manufacturers advise (or design into their software) that 180 seconds of data
is sufficient for an RTK shot to establish secondary control points. But Mr Gakstatter
did a quick check with other GNSS engineers about the advantages of occupying a point
with RTK for longer than 30 seconds.
He found that the preference (rather than collecting for the recommended time of 180
seconds) is for two sessions of 15-30 seconds during the day at times where the GPS
constellation is significantly different, but still with six or more GPS satellites with
a low PDOP to increase confidence in the accuracy of the position.
He will continue on this subject after discussing more with colleagues and newsletter
respondents. Meanwhile, he recommends reading a draft document published by the National
Geodetic Survey outlining that agency's guidelines for single baseline RTK users which
includes the issue of RTK point occupation mentioned above. You can view or download it
here.
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