Accuracy and Precision

Accurate results may not be precise and precise results may not be accurate

Accuracy = how close is the measurement to the actual value, can only be calculated if the ground truth is known
Precision = how close is the measurement to other measurements, might be high even though some systematic error causes all measurements to be off

The quality of the measurement can be assessed through the carrier-to-noise-density ratio \(C/N_0\) (signal strength).

The precision of the measurement depends on the method used:

Table 1: Precision of GNSS measurements
	Pseudorange	Carrier Phase
Precision	Few meters to few decimeters	Few centimeters to millimeter