Darwin Core Issues 82: http://goo.gl/XhxM
This issue arose in discussions on the tdwg-tag list (http://lists.tdwg.org/pipermail/tdwg-tag/2010-August/000050.html) to which not everyone here has access. The issue tracker entry (URL above) summarizes the proposed solution to the problem, which is to re-use the W3C standard geographic coordinate terms geo:lat and geo:long from the namespace "http://www.w3.org/2003/01/geo/wgs84_pos#. These terms would be added as recommended terms organized within the Location class. They would not replace the existing terms dwc:decimalLatitude and dwc:decimalLongitude, which are not the same except under one special circumstance - that the dwc:geodeticDatum is WGS84 (or equivalent). Since this is not always the case, the existing Darwin Core terms cannot be omitted.
Open Issues:
Determine if there is any objection to include these two terms as recommended terms to use in the Darwin Core.