From:
"Lucien Van Elsen" <lucien@prodigy.net>
Sent: 1/16/2001 4:42:12 PM
To:
gpsstash@egroups.com
Cc:
Bcc:
Subject:

Re: [gpsstash] Re: WGS84!


This isn't quite right; how much the locations actually vary between
WGS84/NAD27 will depend on the exact location, but it's generally within
100m or so.

The difference between WGS84/NAD-83/NAD-27 datums has nothing to do with 100
point or 60 second scales; they in fact can all use the same representation
of locations. Instead, how they differ is how they model the earth's shape
as an ellipsoid - it's not the perfectly round sphere we all intuitively
think of. A good basic description of this is at
http://joe.mehaffey.com/maps.txt - there's a good number of other links to
everything GPS under http://joe.mehaffey.com/ as well.

-Lucien

----- Original Message -----
From: "Matt Peckham"
To:
Sent: Tuesday, January 16, 2001 4:51 PM
Subject: RE: [gpsstash] Re: WGS84!


> well, 72 degrees 00.000' would be identical in either format, where
> 71degrees 59.500' would be a long long way off between the two. one
> measures with a 100 point scale, the other with a 60 second scale. You
> could be as far as 40% of a degree off in either direction. that could
put
> you in another state.
>
> My knowledge of the data is not 100%, but then again, I'm a lowly artist.
> Matt