[OpenLayers-Users] Overlay Issue

[Tim Schaub]

Hey-

Paul Ramsey wrote:
> Anyone seen this before? Pretty simple page (add map, add two layers, 
> one yahoo, one wms overlay):
> 
> http://mapserver.refractions.net/openlayers/index.html

Note that this is not the issue causing you trouble, but it points to a 
potential misunderstanding.

You are setting layer.sphericalMercator to true.  This suggests that 
you'd like to overlay your yahoo layer with a WMS in 
Mercator/Sphere/meters.  OpenLayers assumes an epsg code of 9009l3 to 
represent this CRS.  Your WMS doesn't support EPSG:900913 (as it is), so 
you won't be getting the spherical mercator overlay.

If you did want to overlay Yahoo with a WMS layer in spherical mercator, 
you would have to instantiate the layer with the sphericalMercator 
option.  It will not work to set this property after creating a layer.

That is, you must do

var layer = new OpenLayers.Layer.Yahoo(
     "Yahoo", {sphericalMercator: true}
);

and not

var layer = new OpenLayers.Layer.Yahoo("Yahoo");
layer.sphericalMercator = true;

In addition, the OpenLayers.js that you are including in your page does 
not recognize the sphericalMercator option on commercial layers.  You 
can get this functionality from the version in trunk or from the 
upcoming 2.5 release.

We'll write up some documentation of how to properly use a spherical 
mercator overlay for the release.  In the meantime, you can follow from 
this example if you're interested:
http://openlayers.org/dev/examples/spherical-mercator.html

Tim