Dilution of precision (GPS)

Dilution of precision (DOP) is a GPS term used in geomatics engineering to describe the geometric strength of satellite configuration. When visible satellites are close together in the sky, the geometry is said to be weak and the DOP value is high; when far apart, the geometry is strong and the DOP value is low.

Note that this situation is not restricted to GPS, but occurs in electronic-counter-counter-measures (electronic warfare) when computing the location of enemy emitters (radar jammers and radio communications devices). Using such an interferometry technique can provide certain geometric layout where there are degrees of freedom that cannot be accounted for due to inadequate configurations.