Without getting into the details (and over my head), it seems that most
Geographic Information Systems (used for precise mapping of everything) use
the Universal Transverse Mercatur grid. In Canada, at least, the UTMs are
given in North American Datum (NAD) 83 - even if most paper topo maps are
still in NAD27, especially for remote areas. So locations are given as
Northing and Easting...two numbers and a 'zone'. Hand held gps units will
read something like 10U 66917 620149 ('easting' has more digits). It all
makes perfect sense when entering data into a GIS, but seems much harder for
the average person to pinpoint on a paper map!
Mark Phinney
on 6/20/05 12:37 AM, Dan Dugan at wrote:
> Bill Rainey, thanks for your reply:
>
>> The other parameter you want to report to the park is the map
>> datum you used. U.S. Topo maps are still commonly NAD 27
>> CONUS (North American Datum ...Continental United States). My
>> impression is at least GPS units sold in the US default to
>> another datum (WGS 84), altho you can set them to convert
>> screen output to NAD27 CONUS or many others.
>
> Huh. A different reference point? They've moved Greenwich, or
> something? How far off are you in the wrong system?
>
>> Consumer GPS units can sometimes produce startlingly bad
>> short term fixes, so a reality check via map software (e.g.,
>> National Geographic's Topo or several others) at the position
>> you are about to report is usually educational.
>
> I have TOPO, and plan to hook up a GPS to it. I'm looking for one
> that's compatible with the Mac (USB) so I don't have to use a serial
> port dongle thing.
>
>> The dominant GIS software parks use to map location data
>> 'expects' decimal degrees as input, though conversion is not a
>> big deal (assuming the datum is known).
>
> Thanks!
>
> -Dan
>
>
> "Microphones are not ears,
> Loudspeakers are not birds,
> A listening room is not nature."
> Klas Strandberg
> Yahoo! Groups Links
>
>
>
>
>
>
________________________________________________________________________
________________________________________________________________________
"Microphones are not ears,
Loudspeakers are not birds,
A listening room is not nature."
Klas Strandberg
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