[OpenLayers-Users] maxResolution change

[Christopher Schmidt]

On Tue, Jun 20, 2006 at 07:51:38PM -0400, Chris Holmes wrote:
> 
> 
> Tom Carden wrote:
> >On 20/06/06, Chris Holmes <cholmes at openplans.org> wrote:
> >>Schuyler Erle wrote:
> >>> * On 19-Jun-2006 at  3:14PM EDT, Chris Holmes said:
> >>>> Interesting.  Does it match it at the levels all the way zoomed 
> >>out?  My
> >>>> understanding is that Gmaps uses Mercator for the first five or so 
> >>zoom
> >>>> levels...
> >>>
> >>> Well, we haven't gotten that far yet. It's an interesting
> >>> consideration if true. I'd had the impression they used Mercator all
> >>> the way down.
> >>
> >>See:
> >>http://cfis.savagexi.com/articles/2006/05/03/google-maps-deconstructed
> >>for the real deal on what they're doing.
> >
> >This doesn't seem to mention switching projections at all, it's just a
> >thorough (and good) overview of how the tiles are defined and how to
> >do mercator projection in javascript.
> >
> >I recall that when Google introduced aerial and hybrid imagery for the
> >UK there were alignment problems with the hybrid map due to projection
> >issues. For example the outer circle of Regent's Park in London (so
> >long the first thing seen on OpenStreetMap) was not circular.  That's
> >corrected now of course.
> >
> >Comparing with MS and Y! imagery (e.g.
> >http://www.mapstraction.com/ljn.html using +/- keys on the Y! map to
> >zoom) I don't see any significant differences in projection or
> >alignment... only a pixel here and there.  This leads me to believe
> >all three are using the same projection.
> Hmmm...  But are the requests for the area to be viewed in lat/lon?  If 
> all three are making the same requests in lat/lon I think they might 
> look similar, even if ones in a bit of a different projection?  The 
> thing to do would likely be to overlay them directly?  Though I'm not 
> sure at all...  Would probably be better to overlay from a WMS that you 
> know is mercator or lat/long and compare...  Any plans for mapstraction 
> to support WMS as well?

Overlaying them on top of each other is possible in OpenLayers. You
can't do stuff with WMS yet, but we're working on making that better in
the next couple days.

http://openlayers.org/gallery/gym.html

I'll respond to the rest of the bits later, but just wanted to ensure
that we didn't spend too much time reinventing the wheel here

-- 
Christopher Schmidt
Web Developer