The horizontal distance (in meters) from the given decimalLatitude and decimalLongitude describing the smallest circle containing the whole of the Location. Leave the value empty if the uncertainty is unknown, cannot be estimated, or is not applicable (because there are no coordinates). Zero is not a valid value for this term.

`30` (reasonable lower limit on or after 2020-05-01 of a GPS reading under good conditions if the actual precision was not recorded at the time). `100` (reasonable lower limit before 2020-05-01 of a GPS reading under good conditions if the actual precision was not recorded at the time). `71` (uncertainty for a UTM coordinate having 100 meter precision and a known spatial reference system).

http://rs.tdwg.org/dwc/terms/