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iG5 User Manual 56
The two observations were performed Monday afternoon
(the red bars). One is a section corner, the other is vertical
bench mark which is only 400 feet northeast of the section
corner. Both locations enjoy completely open sky
– no
canopy. Both observations are exactly three hours in length.
The first observation starts at 1:59 pm Mountain Time (20:59
UTC) and ends at 4:59 pm Mountain Time (23:59 UTC).
The second observation starts two minutes after the first at
2:01 pm Mountain Time (21:01 UTC) and ends two minutes
after the first observation ends at 5:01 pm Mountain Time.
We submit both occupations to OPUS Tuesday morning, the
day after we collect the observations.
OPUS returns the first solution and it looks fantastic with 98%
observations used and an ellipsoid height RMS error estimate
of 0.011 meters.
OPUS returns the second solution with an ominous warning
‘the observation data is noisy’, only 62% of the observations
were used and the ellipsoid height RMS error estimate is
0.219 meters!
Q: Is the second receiver defective?
The first OPUS solution was able to use all of the nearby
UNAVCO PBO CORS sites which surround Wendover Utah.
Data from these sites were available in the archive at 2:35 am
Mountain (09:35 UTM) on Tuesday; in this case 9 hours and
34 minutes after the end of the first occupation.
The second occupation extended one minute into Tuesday.
Data from the UNAVCO PBO sites will not be available until
after 2:35 am on Wednesday; 33 hours and 32 minutes after
the end of the second occupation.
Because no other nearby CORS data is available, OPUS has
used hourly files from CORS sites over 250 KM away to
process the second file. These long baselines have much
higher uncertainty and result in higher peak-to-peak error
estimates. If we resubmit the 2
nd occupation on Wednesday,
it will have excellent results, similar to the first observation.
A: The receivers are identical and neither is defective.