[OpenLayers-Users] Questions: Projections, Google, Yahoo, etc

[Stephen Woodbridge]

Hi all,

I am trying to research the various commercial layer providers and I 
think Google, Google Earth, and Yahoo Virtual all claim to use Mercator 
projections.

Are they all using the same projection?
Does anyone have a list of the projects that the various commercial 
layer providers are using? In terms of Proj4 definitions?

In OpenLayers, if I want to use one of these commercial layers and 
overlay it with a WMS layer, how good it the registration of the images?
Which is best/worst or are they all the same?

Is this already documented somewhat like a FAQ?

I have read that with Google Layers there is some kind of stretching of 
the tiles or something to get them to align. Is there are write up of 
what is getting stretched and why? and how this might impact overlaying 
other data in an application build around OL.

Ok, thats a lot! but I think it would be great to get these questions 
documented and added to a FAQ or whatever if they are not already there 
and I just missed them.

Thanks,
   -Steve