Spectra Precision ProFlex 800 Reference Manual - Manual (Page 713)

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Troubleshooting
Therefore, poor satellite geometry will result in poor solution
precision. The smaller the DOP value, the better the geometry
and solution precision.
FAST Survey can view current DOP values. If your precision
estimates (HRMS, VRMS) do not meet expected values, use
this feature to examine the current DOP values.
1. If DOP values are too high, look for a satellite window with
more suitable DOP values to perform the survey:
Use the Mission Planning utility from GNSS Solutions to
examine expected DOP values for periods during which
you would like to perform your survey. Avoid surveying
during periods where DOP values are above 4. For the
highest level of accuracy, limit surveying to periods where
DOP values are between 1 and 2.
Remember that obstructions to line of sight between the
GPS antenna and the satellites will block out satellite
signals. Every time a satellite is lost due to obstructions,
DOP values will be adversely affected. An obstructed area
may not be suitable to meet your precision needs due to
the adverse effect on satellite geometry.
2. If DOP values are not too high, go to step 4 below.
Step 4. Are
Precision
Requirements Too
Stringent for RTK?
If the RTK system is not delivering the precision requirements
you need for your specific task, it is possible that your
precision requirements are too stringent for the RTK system.
Review your system documentation to determine the
precision specifications for the RTK system.
• If the precision is not beyond capability, then the rover
may be malfunctioning. Contact your local dealer or email
Ashtech technical support for assistance.
• If the precision is beyond capability, your precision
requirements are not attainable through RTK surveying.
You will need to find some other measurement system to
perform your survey.
This concludes the troubleshooting section. If the tips given
here did not help you to resolve your problem with your
system, please call your local dealer or email Ashtech
Technical Support for assistance.