514 Subfield $g - Horizontal position accuracy value:

Subfield $g contains an estimate of the accuracy of the horizontal coordinate measurements in the data set expressed in (ground) meters. The use of this subfield is usually limited to cartographic items.

Example:

514 ##$aHorizontal position accuracy 1-3 meters$fDifferential GPS$g3 meters$hStatic tests$iBar test$jOne foot$kBar check