[Turk]

Estimated Position Error (EPE) and Error Sources

EPE (1-sigma) = HDOP * UERE (1-sigma) (1)



Multiplying the HDOP * UERE * 2 gives EPE (2drms) and is commonly taken as the 95% limit for the magnitude of the horizontal error. The probability of horizontal error is within an ellipse of radius 2drms ranges between 0.95 and 0.98 depending on the ratio of the ellipse semi-axes. User Equivalent Range Error (UERE) is computed in the tables lower on this page.

EPE (2drms) = 2 * HDOP * SQRT [URE^2 + UEE^2] (2)