[OSRS-PROJ] PROJ.4 "proj=latlong ellps=GRS80" functionality?

[Ed McNierney]

Craig -

Thanks!  Somehow that didn't occur to me as I stared at those numbers.
After looking at values with more decimal places, it appears that the
input coordinates are presumed to be relative to the ellipsoid specified
in the output (i.e. no datum shift involved).  That makes sense and is
what I expect.

Now I've got a different problem to solve, but that's a MapServer
discussion, not PROJ.4.  Thanks again.

	- Ed

Ed McNierney
Chief Mapmaker
TopoZone.com
ed at topozone.com
(978) 251-4242


-----Original Message-----
From: Craig Bruce [mailto:csbruce at cubewerx.com]
Sent: Friday, August 03, 2001 12:26 PM
To: osrs-proj at remotesensing.org
Subject: Re: [OSRS-PROJ] PROJ.4 "proj=latlong ellps=GRS80"
functionality?


"Ed McNierney" <ed at topozone.com> wrote:

> That is, my input coordinate (-71, 43) is transformed to (-1.24,
0.75).
> What does this mean?  I would expect the output results to be either
> identical to my input (if the input data is presumed to be in the
output
> ellipsoid or if GRS80 or WGS84 is the default) or I would expect them
to
> be very slightly different (if the input ellipsoid is something else).

It looks to me like the output is the same coordinate value as the
input,
except translated into radians.  Since only two decimal places seem to
be
showing, you probably wouldn't see any difference between GRS80 and
WGS84,
though I don't think the ellipsoid is switched in this invocation.

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