[Taxacom] Impossible geocodes

Curtis Clark lists at curtisclark.org
Fri Jan 30 11:27:42 CST 2015


On 2015-01-30 1:43 AM, mesibov at southcom.com.au wrote:
> By an interesting coincidence, the implied uncertainty in
> DMS-to-the-nearest-second is about the same as the horizontal uncertainty
> in a handheld GPS reading (unless conditions are exceptionally good). The
> DD-to-4-places uncertainty is optimistic for handheld GPS, and the
> DD-to-5-places you often see in published papers is +/- half a metre and
> evidences a religious faith in numbers. DMS is definitely handy for
> GPS-determined locations.

Handheld GPS units characteristically give an estimated uncertainty 
figure. It would be computationally simple for the firmware in the unit 
to limit the significant figures provided in a DD output to roughly 
match that uncertainty. Too bad they don't.

-- 
Curtis Clark, PhD                        http://www.cpp.edu/~jcclark
Professor Emeritus
Biological Sciences                                                  +1 
909 869 4140
Cal Poly Pomona, Pomona CA 91768

Please note new email address: jcclark at cpp.edu





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