This is a result of a short baseline (about 3.7 km) in a low multipath
environment, using two high quality C/A code/ carrier receivers.
The 'truth' has been established with carrier phase double diffenrence processing
and is believed to be within a few mm's.
The blue line is difference in the height from single difference C/A code
processing and the true height and contains about 2900 points. The red dots
are 10 sec averages, the blue dots 100sec averages.
The deviations from zero are believed to result from multipath only, S/A
induced satellite position errors of 100 m (a conservative estimate) result
in position errors of less than a few cm's at this baseline length, S/A induced
satellite clock errors cancel because both receivers were well aligned to
the GPS system time.
The first 1500 seconds suggest effective averaging to within 1 m, while the
last 1500 second contradict this suggestion ! This is a fine proof of how
cautious one should be with the results of averaging, even in the differential
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