[OpenLayers-Users] Overlays with google maps

[Jon Blower]

Hi Chris,

I'm afraid still haven't quite understood how OL can be used to
overlay layers (e.g. WMS) on top of Google Maps images (also, the
example page http://www.openlayers.org/dev/examples/google.html
doesn't work for me in Firefox 1.5: it comes up with an error "'$' is
not defined" in line 25 of google.html).

In this post you said "For Google (for reasons I don't really
understand) this is non-deterministic: If you set a different center,
the tiles draw differently."  I don't understand what this means.
Google Maps are in a straight Mercator projection (not modified in any
way, as far as I can tell) so I can't see what's non-deterministic
about it.  Also, I don't understand how simply stretching the tiles on
the client will work - Mercator projection is not a linear stretch of
a lat-lon (Plate Carree) projection.

Perhaps I've misunderstood something, or perhaps this is related to
the issues I bored this list about recently concerning how the
Mercator projection is constructed. ;-)

Regards, Jon

On 3/10/07, Christopher Schmidt <crschmidt at metacarta.com> wrote:
> On Fri, Mar 09, 2007 at 10:57:44AM -0800, Graham Davis wrote:
> > Chris,
> >
> > Does this mean that I can't use a Kamap layer to overlay tiles on a
> > Google maps base layer?  Is a WMS layer the only layer type that
> > Openlayers can overlay ontop of a Google map?
>
> Yes.
>
> I don't know if it's possible to change the design to support other
> things. I'm glad to have people evaluate it. The 'reproject' switch that
> is in SVN is *not* actual reprojecting: instead, it simply stretches the
> tiles to request whatever the base map says is the correct tile to use
> for that location. For Google (for reasons I don't really understand)
> this is non-deterministic: If you set a different center, the tiles draw
> differently.
>
> The functionality you want doesn't exist for layers which don't accept
> arbitrary bounding boxes at the moment.
>
> Regards,
> --
> Christopher Schmidt
> MetaCarta
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> Users at openlayers.org
> http://openlayers.org/mailman/listinfo/users
>


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