Transcript PowerPoint Presentation - 12.215 Modern Navigation

Understanding what sh_gamit does
E-mail summary assesses
over-all quality
• Number of stations
• Worst/best RMS scatter
• postfit normalized RMS from solve
– theoretically should be unity
– typically around 0.2
• (daily position scatter in accord with sigma)
• Large adjustments to site positions
• Any fatal messages
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Output files
• Cleaning summary:
– autcln.prefit.sum
– autcln.post.sum -- Final postfit run
• Solution files output by solve
– qexpta.doy
• human-readable
– oexpta.doy
• machine-readable
– hexpta.yyddd
• Full-precision for GLOBK suite
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Status files common to all
GAMIT/GLOBK runs
• File names, e.g, GAMIT.fatal
• One long line per event
• Three levels of severity
– Status
• Time of steps in processing
– Warning
• Items that might be in error
– Fatal
• Errors so large that the processing stopped
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Example GAMIT.status
• STATUS :020119:1201: 6.0 ARC/aversn: Started ARC,
\
Version 9.53 of 2001/01/03 10:30:00 (Linux)
• STATUS :020119:1201: 6.0 ARC/arc: Integrating \
•
satellite 1 PRN 1
• STATUS :020119:1201: 6.0 ARC/arc: Integrating
\satellite 2 PRN 2
• ....…
• To watch progress as it happens:
•
tail -f GAMIT.status
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Analyzing a solution:
bias parameters
• Number of biases fixed
– Fixed bias have no sigmas in Q-file
– 608 B1L1 SMYC-TBLE 4- 2 0.0000000000
10.0000 \
– 609*B1L1 SMYC-TBLE 4- 5 0.0000000000
2.3133 \ 0.0367
-2.31330402
– The * means not fixed and sigma is given
• Adjustments
– parameters should not change much
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Analyzing a solution:
adjustment sizes
• Adjustments should not be too large
– Convergence rate is 100 or 1000 to 1
– Suppose an adjustment of 1 m in position
– residual error could be 1-10 mm
– solution needs to be iterated
• Atmospheric delay variations
• Magnitude of gradients
• EOP adjustments
• Some examples (shown externally)
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autcln output
• autcln.out.Z
– full output
– automatically compressed
– use uncompress or use zcat to view
– Lists actions taken by autcln
• autcln.prefit.sum
• autcln.post.sum
– Summaries
– Look at these
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autcln summary files
• Clock & range stats from range data
– Repeated twice since solution is iterated
• List of double difference bias flags
– Number of bias flags added to jumps in double
differences
– If too many flags are added, then autcln removes
the site/satellite combination completely. This can
happen if a satellite burns. Rare if IGS orbits are
used since satellite is removed from orbit files.
– Bad site coordinates can cause many bias flags
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autcln summary file
• One-way post-fit residual statistics
– Only in postfit autcln summary
– Gives RMS in mm
• by station and each satellite for a station
• Normal values are 3-10 mm
• >10 mm is not good
– sky plots show residuals
– cview views residual time series interactively
• reads C-files
• default is to delete these files during batch runs)
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Autcln summary file
• AMS -- Averaged RMS of residuals
– statistics for 25-point averages of residuals
– theoretical white noise
• should be 5X smaller than for single-point value
– typically, though
• AMS is 2X smaller than single point RMS
• due to correlations in phase residuals
– ratio of RMS/AMS
• values to close to 1 mean systematic residuals
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Autcln summary files
• NUM
– number of values used to compute RMS
• ATELV
– Elevation angle-dependence of RMS
– fit to data noise model of the form
• variance = A^2+(B/sin(elev))^2
• Sky-Plots
– residuals v. elevation angle
– show effects of multipath and antenna gain
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Autcln summary:
data amounts
• Data counts by site and satellite:
– N(good)
– N(deleted)
– N(bias flags)
• ignoring rising satellites
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Bias flag report
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Reports number of bias flags added for
GAP -- Due to gap in data
JMP -- Large jump on phase-range difference
ION -- Ionospheric delay jump
DDS -- Double difference scanning
WLS -- Wide lane scanning
DDC -- Double difference jump while cleaning data
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