Mapserver Projection


I am not a projection expert. So, who know projection very well, this article does not come to any help. Here I give some reference information for new mapserver developer.

We can add projection parameter in map file by two ways,

1. Inline projection
It use detail projection parameter. If you use shape file, using arcgis parameter can be found. And also there .prj file where contains this parameters. Below I give the projection parameter of wgs84,

PROJECTION
“proj=longlat”
“ellps=WGS84”
“datum=WGS84”
“no_defs”
END

2. EPSG Projection reference
For simplicity, some reference number is introducing to identify a set of projection parameter, known as ESPG. We can find epsg from below site,
http://spatialreference.org

In all list reference tab, require reference number can be search. For example, if we search Bangladesh then we get EPSG:3106 code for Bangladesh(BUTM).

EPSG list can be found also in local pc in “OSGeo4W\share\proj\epsg” file.

Now for WGS84 projection, we have add below projection code in map file in EPSG,

PROJECTION
“init=epsg:4326”
END

The projection can be add in layer level in map file. But if the entire layers are in same projection, then no need to add projection in layer level. It is better at in map level.

If we use WMS layer, wms_srs is a mandatory parameter. So the for wgs84 parameter value should be,

METADATA
“wms_srs” “EPSG:4326”
END

Fow more mapserver project documentation, click here.

…………………………
Abul Khayer
GIS programmer
CEGIS

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