In cases where the resource position is less accurate than a few kilometres, datum issues may be ignored. For accurate positions, however, the WGS-84 datum should be used. In North America, this corresponds to the NAD-83 datum. Many maps and charts still use the older NAD-27 datum, and there is a difference in coordinates of as much as a couple of hundred metres, depending on the exact position. Conversion software is available, and most recently issued topographic maps and charts will give the offsets.
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The Geo Tag Generator incorporates an optional check map which may be used for a quick sanity check on geographic co-ordinates. Co-ordinates may also be checked against country and region codes, if given. Icon Pages which have included geotags may include a geotag icon to indicate that geographic search capability may be available. The tags are described in terms of current HTML practice, which does not preclude them being represented in another manner such as RDF or XML . The tags are intended for use by a wide base of authors who are probably not well versed in GIS or formal metadata techniques.