[Fwd: [Proj] Re: Problem overlaying georeferenced images in Google, Maps(projection problem!)]

Jorge jorge.arevalo at gmail.com
Wed Jun 4 09:15:31 EDT 2008

 > The Mercator-based coordinate system used by Google Maps can be 
thought of in

> two ways. 
> 1) It uses a sphere with radius=6378137.0 m. Sent to Mercator, hopefully, the 
> code is smart enough to use the spherical equations.
> 2) It uses WGS84 with spherical Mercator equations. 
> No ellipsoid-to-sphere conversion should take place. Data that's really on WGS84 
> is assumed to be on the major auxiliary sphere (R=6378137.0m) and just projected 
> using the spherical math. This means that you can't create a custom 3 or 7 
> parameter datum transformation to convert directly to the sphere (because the 
> latitude values are converted to the sphere).
> So you might try transforming your data from ED50 (or other datum) to WSG84 
> first. Then project those coords to the Google Mercator.
> Melita
> ESRI, Inc.

I forget it...

Really, what I put over the GMaps' frame isn't an only image. Really, I put many images of 100x100 pixels
(based on the raster) together. And after putting them, I "move" to avoid the overlap, as you can see
in this screenshot


I thought that I could avoid the overlap by reprojecting the raster, obtained from a MIF/MID files with UTM
projection and ED50 datum, of course, but I'm not sure now...

Anyway, thanks a lot everyone!

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