Position Dilution of Precision (PDOP)

A unitless value that expresses the relationship between the error in user position and the error in satellite position. It indicates when the satellite geometry can provide the most accurate results. The best data collection time can be selected based on reports and graphs showing PDOP.

Geometrically, PDOP is proportional to 1 divided by the volume of the pyramid formed by lines running from the receiver to four satellites observed. It is the result of a calculation that takes into account each satellite’s location relative to the other satellites in the constellation. Good values are small, less than 3. Values greater than 7 are poor. Thus, small PDOP is associated with widely separated satellites. A low DOP indicates a higher probability of accuracy. A high DOP indicates a lower probability of accuracy. PDOP is related to horizontal and vertical DOP by PDOP2 = HDOP2 + VDOP2.