Five quick checks before you trust a position fix
A position that looks fine on screen can still be wrong. These five checks take a minute and catch most problems early.
- Geometry. Look at the dilution of precision (HDOP/PDOP) and the number of satellites in use. Poor geometry amplifies every other error.
- Corrections. Confirm the correction source is active and that the age of the corrections is within the limit set in your procedure. A frozen correction stream often looks like a normal fix.
- Quality indicators. Check the fix type and the quoted accuracy, and compare them with what the job specification requires, not with what is merely typical.
- Independent comparison. Compare two independent systems, for example two GNSS receivers or GNSS against an inertial or acoustic solution. Record the offset and watch for it to change.
- Offsets and datum. Verify the antenna-to-reference offsets, the heading source and the coordinate system. A correct fix in the wrong datum is still wrong.
Write down what you checked and when. A short log entry is worth more than a perfect memory when a client asks questions weeks later.
These habits are covered in depth, with the equations behind them, in the Tidehunter training.