I set a temporary base using the survey-in options and I got a position accuracy 0.98 m for my Base, so the base sent RCTM corrections to the Rover and It got an accuracy of 14 mm (PACC H) for the horizontal and 10 mm for the vertical (PACC V), so I was wondering how I can interpret the two accuracies, for example:
*Does the rover have in the horizontal component a location that is 0.98 m + 14 mm deviation from the real position
*Does the rover have in the vertical component a location that is 0.98 m + 10 mm deviation from the real position?
*Does the vertical component mean “Y” component in a plane “XY”? I assumed this, however, I want to be sure.
*How do we Interpretation the altitude Alt (MSL)? is this affected by the survey-in (0.98 m)?
The accuracy reported by the rover is relative to the base. You can think of it as the accuracy of the vector between the rover and the base. If the base coordinates are off by a certain Dx, Dy, Dz then all the rover coordinates for that session will have that error + any error in the vector between the rover and the base.
Vertical would be the up. I don’t know which XYZ you are referring to, there are a few and some of them are vastly different. If you mean XYZ from freshman physics, the Z is up.
Vertical datums are a complicated subject. You might want to do some reading about height above the WGS84 ellipsoid vs. height above the geoid (orthometric). MSL hasn’t been used in any serious context in the US for 25 years or more.
The stated/reported accuracies are probably 1-sigma, which is typical for GPS/GNSS receivers. So 50% of the measurements are better, and, well, you can figure out the rest.
And the reported accuracies usually don’t include the PDOP. PDOP is a unit less factor greater than one based on the geometry of the vehicle constellations (the positions of the satellites). Multiply the reported accuracy by the PDOP to get a better idea of the 1-sigma bounds.
The SparkFun RTK devices are amazingly capable and are at a wonderful price point. And experienced surveyors know to double and triple check their measurements.
Surveyors have a joke:
Q: What’s the difference between used car salesmen and survey equipment salesmen?