[GIS] Openlayers vector feature coordinates are not transforming,

coordinate systemcoordinatesopenlayers-2polygonvector

I have a OpenLayers vector with a single feature [0]. It's coordinates are in the map projection (EPSG:3413) and I want them in WGS84 (EPSG:4326) decimal degrees. I have the following code which executes with no errors.

    // Transform the polygon to WGS84 (EPSG:4326)
        polybound.features[0].geometry.transform(new OpenLayers.Projection("EPSG:3413"),new OpenLayers.Projection("EPSG:4326"));

        // Get the extent/vertices of the polygon drawn
        var polyBounds = polybound.features[0].geometry.getVertices(); alert(polyBounds);
        var polyExt = polybound.features[0].geometry.getBounds(); alert(polyExt);

However both the alerts show the untransformed coordinates.

Eg:

alert(polyBounds);

POINT(-2486558.28125 -1947299.71875),POINT(-4121511.40625 -1737690.34375),POINT(-3555566.09375 -2722854.40625)

alert(polyExt);

-4121511.40625,-2722854.40625,-2486558.28125,-1737690.34375

How do I get the vector feature coordinates to transform correctly?

Best Answer

Please refer to the OpenLayer Docs for OpenLayers.Projection. The docs state the following:

By default, OpenLayers ships with the ability to transform coordinates between geographic (EPSG:4326) and web or spherical mercator (EPSG:900913 et al.) coordinate reference systems....

Additional transforms may be added by using the proj4js library. If the proj4js library is included, the transform method will work between any two coordinate reference systems with proj4js definitions.

So you need to refer to the Proj4JS library and have your projection file for EPSG:3413.

You should read this User Guide. You can download the library from here: Downloads. You will also need the file for your projection in Proj4 format. You can download that from here: Spatial reference.org

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