[Taxacom] Impossible geocodes

Curtis Clark lists at curtisclark.org
Sat Jan 24 23:52:11 CST 2015


On 2015-01-24 7:58 PM, Fred Schueler wrote:
> Quoting "Fautin, Daphne G." <fautin at ku.edu>:
>
>> All users should be aware, however, of the huge errors that can be
>> introduced by conversion.  Tony Rees made a presentation to OBIS once
>> about this (since marine data were nearly always DMS -- and now DD --
>> because the ocean lacks landmarks; only nearshore records may refer to
>> landmarks), and showed that a conversion moved his home from the nice
>> bayside locality it occupies outside Hobart to the hills well inland.
>> I'd bet he has it archived somewhere that you could find to caution
>> people.
>
> * this may be because of unrecorded or uncompensated-for map datums.
> Around here the old NAD27 map datum gives a position 200m from the
> position given by the modern NAD83 or WGS84 datums.

It pretty much *has* to be a datum difference. If one preserves 
significant figures, converting DMS to DD is simple math, like 
converting inches to centimeters. I wouldn't expect to get taller or 
shorter through unit conversion, and latitude and longitude should be 
the same.


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

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