[mapserver-users] Reprojection: Maps not lining up

[Matthew Pettis]

(This is a repost, the other one got no responses).

Hi,

I am using Openlayers with Mapserver to show a shapefile of roads in MN that
are in epsg:26915 and allowing users to toggle between that and Google Maps
(spherical Mercator projection per
http://spatialreference.org/ref/user/google-projection/).  I use mapserv.exe
and a .map file to reproject the MN roads into the Google projection, and
when I toggle between them, the extents *almost* match up.  It appears that
the MN roads extent covers a slightly larger area than the Google Maps
extent.

I don't know if this is an OpenLayers or Mapserver question, but I'm
thinking it is a Mapserver one.  Can anyone tell me why the extents *almost*
match up?  I would think that they would either match up almost exactly (or
at least in a tolerance that I cannot tell by the naked eye), or I would
have messed up my transformations, and it would be completely out of sync.
Is it a function of disparities in the data that I cannot fix, or are there
fine tunings that I can adjust to compensate?

Thanks,
Matt

-- 
It is from the wellspring of our despair and the places that we are broken
that we come to repair the world.
-- Murray Waas