Map file projection question

[Antonio Grassi]

Hi all. I don't know if this is a question for this list or the postgis's
user list. We have several layers in a postgres/postgis database. Almost all
layers are in utm zone 21 south, but we have some data in geographic
coordinates. For several years we've data stored in the database with
srid=-1 on the geometry_columns table. We had the utm projection defined in
the MAP section, and the geographic coordinates projection defined in those
LAYER sections corresponding to the layers in geographic coordinates.

Today I loaded the spatial_ref_sys table and updated the srid field for
those layers that are in geographic coordinates. We took out the projection
definition from the LAYER sections corresponding to those layers, and kept
the utm projection definition in the MAP section.

I thought that, as the proj information is stored in the spatial_ref_sys
table and referenced through the geometry_columns table, there was no need
to specify it in the .map file, as mapserver could know it from the database
layer definition, or maybe postgis could return the geometrys converted to
the system specified in the MAP section. Well, in the generated map, all the
utm layers are shown, but the geographic coordinates layers are not drawn.

Looking in both mapserver's and postgis's documentation and mailing lists
I'm almost sure that both assumptions are wrong, and that it's not an error
in the proj WKT or something like that.

So my question is simple: Do i have to specify a projection section in every
layer that is not in the same system of that in the map section, or is there
a way of making any of the different components that participate in the
layer drawing process to reason it?

Thanks very much,
Antonio
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