OK, I mixed up accuracy and precision here, sorry about that (I'm only a lowly computing person). However, the input data for our databases is from tachymetric measurements (not GPS), and these people get really nervous if the millimeters they fought very hard to nail down get lost in the GIS. Also, trying to fix topological problems with parcel boundaries that include arcs can be a major pain in the sub-millimetre area...

Martin