ADOP – Ambiguity Dilution of Precision

A scalar measure that quantifies the strength of a GNSS observation model for resolving integer carrier-phase ambiguities. ADOP is defined as a function of the covariance matrix of the float ambiguity estimates and reflects the volume of the ambiguity search space.

ADOP is defined as the geometric mean of the standard deviations of the ambiguity parameters, i.e., the 2n-th root of the determinant of the float ambiguity covariance matrix. As the ADOP is invariant for admissible ambiguity reparametrizations, it measures the intrinsic resolution strength of GNSS models. Smaller ADOP values indicate a stronger model and a higher probability of correct integer ambiambiguity resolution. ADOP is therefore widely used as a performance indicator for ambiguity resolution in precise GNSS positioning.