[Taxacom] GPS units that record the time a waypoint was taken, accuracy, datum

Una Smith una.smith at att.net
Wed Mar 25 00:19:23 CDT 2009

Frederick W Schueler wrote:
>The big problem is authors (and editors!) who don't know about datums, 
>and submit mss with co-ordinates to ever-so-many decimal places, without 
>mentioning which datum they're based on.

Yup.  And when you ask someone for the datum that goes with the
coordinates they reported, they *assume* it was one or another.

Sometimes you can determine the datum after the fact.  Eg, if
they read the coordinates of a point marked on a USGS map, you
can check in a moment or two to see if that map has ever been
re-issued with a change of datum.  Or you can ask them for the
coordinates of the trailhead where they parked or some other
feature that is marked on a map and was used as a waypoint by
the researcher.  This serves also as a consistency check, when
a datum is reported but you have doubts that it is the correct
one.  Eg, when a location described as an outcrop maps to the
deep sand bottom of an arroyo.

	Una Smith
	New Mexico

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