[OpenLayers-Users] Projection over the north pole (EPSG:3573)

[Mike Adair]

John,

Please note that EPSG:3573 uses an laea projection which is supported in 
proj4js, but the code is from the GCTPC package which only supports the 
spherical form of laea. That will get you close to the correct coords 
but not an exact transformation. What needs to happen to fix this is a 
port of Proj4 code which supports both spherical and elliptical spheroids.

Your application also needs to include proj4js separately to enable 
this, whereas the transformation code for 900913 to 4326 is included by 
default in OpenLayers.

Mike

John Bennett wrote:
>
> Hi,
>
> I am trying to get the mouse position to display in lat/lon when using 
> EPSG: 3573 (http://nsidc.org/data/atlas/epsg_3573.html ). I’m using 
> the trunk in hope of openlayers having proj4js support.
>
> In the following example if I use option1 with layer ‘gsat’ and 
> sphericalMercator projection everything works great, the mouse 
> position is displayed in lat/lon. If I use option2 with layer 
> ‘sat_north’ and EPSG:3573 the mouse position is displayed in meters, 
> but I want it displayed in lat/lon. Is this possible?
>
> function init(){
>
> var options1 = {
>
> projection: new OpenLayers.Projection("EPSG:900913"),
>
> displayProjection: new OpenLayers.Projection("EPSG:4326"),
>
> units: "m",
>
> maxResolution: 156543.0339,
>
> maxExtent: new OpenLayers.Bounds(-20037508, -20037508,20037508, 
> 20037508.34)
>
> };
>
> var options2 = {
>
> projection: new OpenLayers.Projection("EPSG:3573"),
>
> displayProjection: new OpenLayers.Projection("EPSG:4326"),
>
> units: "m",
>
> maxResolution: "auto",
>
> maxExtent: new 
> OpenLayers.Bounds(-9036842.762,-9036842.762,9036842.762,9036842.762)
>
> };
>
> map = new OpenLayers.Map('map', options2);
>
> var gsat = new OpenLayers.Layer.Google(
>
> "Google Satellite",
>
> {type: G_SATELLITE_MAP, 'sphericalMercator': true}
>
> );
>
> sat_north = new OpenLayers.Layer.WMS( "Satellite imagery MODIS",
>
> "http://nsidc.org/cgi-bin/atlas_north?", {layers: 'blue_marble_01', 
> projection: new OpenLayers.Projection("EPSG:3573")});
>
> map.addLayer(sat_north);
>
> map.addControl(new OpenLayers.Control.Permalink());
>
> map.addControl(new OpenLayers.Control.MousePosition());
>
> map.zoomToMaxExtent()
>
> }
>
> Regards,
>
> John Bennett
>
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