Re: Query Distance from User

On Sun, 15 Jul 2012 16:18:40 -0700 (PDT), JJ Zolper
<codingatmt@gmail.com> declaimed the following in
gmane.comp.python.django.user:

> By UTM do you mean Universal Transverse Mercator?
>
> Well hmm I'm not quite sure what issue i would run into with someone living
> on the edge of the zone.
>

http://en.wikipedia.org/wiki/Universal_Transverse_Mercator_coordinate_system

Someone in the west side of a UTM zone on the equator ("northing"
10000000) may have an "easting" of 167000m. Somebody else on the east
side of the immediately adjacent zone is 833000m... Yet in reality, the
two may be standing less than a meter apart. So Pythagoras falls apart:
sqrt((833000 - 167000)^2 + (10000000 - 10000000)^2) => 666000m

Including corrections for crossing zone edges complicates the math
heavily. Works great for finding locations within a zone, or measuring
from a known point in the zone.

--
Wulfraed Dennis Lee Bieber AF6VN
wlfraed@ix.netcom.com HTTP://wlfraed.home.netcom.com/

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