gps services group c&c technologies, inc., c-nav gcgps system background and accuracy
TRANSCRIPT
GPS Services GroupC&C Technologies, Inc.,
www.cctechnol.com/cnav
C-Nav GcGPS System Background and Accuracy
Overview• What is C-Nav• Empirical accuracy measurements to
date.• Interesting issues• Hand off to Pete and John
– Interesting application to hydrography
– Latest developments in C-Nav
• Closing summary
The RTG Family
Why High Accuracy?
Stand alone GPS but…
• Ionosphere delay free
• Extended carrier smoothing
• Improved orbit and clock
correctors
• Troposphere delay modeling + estimation
This Week’s Schedule
Check Your Watch for Altitude!
Vertical Error (?) Vs Earth Tide
C-Nav AccuracyC-Nav GGA vs Zero Gravity Surveyed Position
95% Horizontal 95% Vertical
Static RTG 0.18 +/- 0.04 m 0.35 +/- 0.05 m
Static RTG Predicted tides
0.18 +/- 0.04 m 0.24 +/-0.04 m
Static RTG - Reference
0.18 +/- 0.04 m ~0.19 m
Dynamic RTG 0.13 +/- 0.7 m 0.25 +/- 0.05 m
Tidal Datums
• Chart datum is based upon historic water levels
• Chart datum is irregular wrt geoids and ellipsoids.
• You can determine chart datum at a point with a tide gauge.
• To projected it away from the tide gauge requires knowledge of tides.
Let the Experiment Begin!!
• Performed during NOAA hydrographic survey in Gulf of Mexico
• Used well surveyed cross-lines as ground truth
• Used verified tides to check ground truth• Collect C-Nav data on survey vessel and at
two monitoring stations• Analyze data
RTG Vertical re Chart Datum
Sea-Surface Height
Vessel Receiver Noisy Probably Antenna Location
Lafayette Houston Vessel
Mean 0.308 0.280 0.402
SD 0.065 0.043 0.173
RMS 0.315 0.283 0.438
146%
GST Vertical Error Estimate
Give it to Pete and John
• 0.2 m to 0.4 m vertical at 95% in preliminary test.
• ~0.3 meters vertical at 95% in tidal datum w/ blockage & 100nm baseline.
• Post processing required to deal with Earth tides.
• Squirrelly transformation into tidal datum.• Sensitivity to blockage and multipath