Dilution of Precision (DOP)

Dilution of Precision (DOP) quantifies how the spatial geometry of the visible GNSS satellites affects positioning accuracy. If four satellites are clustered in one part of the sky, small ranging errors translate into large position errors (high DOP). If they're well-distributed — spread across the sky and at different elevations — the same ranging errors produce much smaller position errors (low DOP). DOP acts as a multiplier: position error ≈ ranging error × DOP. Variants include HDOP (horizontal), VDOP (vertical), PDOP (3D position), TDOP (time), and GDOP (geometric, all combined). A PDOP below 2 is considered excellent; above 6 is poor.