[Geoprisma-users] 900913 to 4326

[Yves Moisan]

Hi List,

This is more of an openlayers question, but I gather OL can transform
from/to 900913 to 4326.  I know there is 'projection' and
'displayProjection' and I also saw functions forwardMercator and
inverseMercator in the OL API, but I wonder how it all fits in the
context of geoprisma.

Say I have a mapfile that points to a 4326 dataset :

LAYER
  NAME         aeropuertos
  TYPE         POINT
  DEBUG 5
# My data's native projection
  PROJECTION
      "init=epsg:4326"
  END
...

In the MAP section of the mapfile, I set :

WEB
    ...                   
    METADATA
      ...
      "wms_srs"  "EPSG:4326 EPSG:900913"
...
    END  # Metadata

which means the two projections are dealt with in the context of the
mapfile, from what I gather.

In the GeoPrisma config :

<map>
<name>DefaultMap</name>
<options>
    <units>m</units>
    <projection>EPSG:900913</projection>
    <maxextent>-20037508,-20037508,20037508,20037508.34</maxextent>
    <displayprojection>EPSG:4326</displayprojection>
	...

<layer>
    ...
    <servicetype>wms</servicetype>
    <options>
        ...
        <projection>EPSG:4326</projection>
        ...
    </options>
</layer>

The question is : by virtue of my mentioning the two coordinate systems
in the WEB section of the mapfile and on the geoprisma side by setting
the projection of the map to 900913 and that of the layer to 4326, does
my vector layer data get automagically reprojected to 900913 by OL ?  

Or am I better off to set a projection object for the MAP to 900913 (and
change the EXTENT and UNITS accordingly) and use EPSG:900913 in my
<layer> object ?

TIA,

Yves