[gdal-dev] Spherical Mercator projects and overviews?

[Stephen Woodbridge]

Frank Warmerdam wrote:
> Stephen Woodbridge wrote:
>> Hi all,
>>
>> I have a question regarding imagery in spherical mercator projection 
>> in geotiff images. Do overviews work correctly?
>>
>> For example, I use EPSG:4326 and build lots of overviews and I can 
>> zoom in and out and pan without a problem. Can I do the same thing 
>> with EPSG:900913 (spherical mercator projection).
>>
>> I'm working with LandSat imagery over large area and scale ranges.
> 
> Steve,
> 
> I can't see any reason that overviews would not work on spherical
> mercator when they work on images in other coordinate systems.  The
> overview handling is independent of the georeferencing.
> 

Frank,

Thanks this is what I was hoping the answer would be.

My fear was that I would run into something like UTM zones and that you 
can not have one global data set in UTM. So spherical Mercator is 
projects the world into a single x-y plane similar to the way 
geographical is treating the global as stretched onto a single x-y 
plane.  This seems reasonable, I just never thought about it before.

Now I get to reproject everything yet again :)

Thanks,
   -Steve