projection parameters?

[Frank Warmerdam]

On Wed, 5 Jan 2005 13:36:02 -0800, Jose Luis Portillo
<jporti68 at yahoo.com> wrote:
> Hello All
> Before I had work with proj=latlong data and had not problem, but now I am
> working with data which is in utm, zone 16, north, datum = nad27 and I am
> having problems, the data just doesn't appear in the map.
> Can someone tell me which could be the right parameters that I need for this
> projection and the place where I should put this information within the .map

Jose,

For a projection block, you might use:

PROJECTION
  "+proj=utm +zone=16 +datum=NAD27"
END

You would place this on any LAYER objects that are in this
coordinate system.  Is your overall map display going to be in
UTM as well, or are you needing MapServer to reproject to
lat/long?

The most common problems are mixups in the coordinates
(for instance, using lat/long angular values when UTM values
should be used or vice versa), but more generally you need
to examine the extents of your datasets fairly carefully.

If you know the bounds in UTM of a dataset, you can reproject
it to lat/long with the proj.exe program (part of PROJ.4 ... not
always distributed wtih MapServer though).

eg.

proj -I +proj=utm +zone=11 +datum=NAD27 << EOF
? 400000 3700000
? EOF
118d4'32.742"W  33d26'11.277"N

I hope this is somewhat helpful.

Best regards,
--
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