[Gdal-dev] GeoQuadTree - an open format forstoringgeoreferencedimages

Norman Vine nhv at cape.com
Wed Nov 15 04:58:13 EST 2006

Jordi Gilabert Vall wrote:
> In GeoQuadTree there is no 
> need of a spatial index, tile index, catalog of images, or a 
> database. There is a simple algorithm that calculates the 
> specific level of the pyramid, and the specific tiles to 
> access. The algorithm calculates the path in the filesystem 
> needed to retrieve the tiles. The XML file in the GeoQuadTree 
> doesn't include a catalogue/index, it only need 6 attributes: 
> the name of the tile file names, the number of levels in the 
> pyramid of overviews, the size of the pixel in CRS units, and 
> the size of the tile in pixels. If you import overlapped 
> images into the same GeoQuadTree image, the common region of 
> one will be overwritten with the other. 


Nice work.  

This is very similar to several tile caches used for programs such as 
NASA's World Wind and ossimPlanet

Several comments

1) It 'might' be useful if this was made to appear as a GeoTiff
   e.g. if there were a mechanism to support the same metadata that
        is stored in the required GeoTiff GeoTags

2) If when constructing the quadtree one could pass in the desired 
   levels to be 'constructed'.  This could be just the minimum level
   one wants built where the maximum level was determined by the 
   'pixel ground footprint size'

I have collected bits of older similar code used to build similar caches
that I am willing to share if you are interested 

The exciting part of your work is the attempt to GDAL'ize this concept.



More information about the Gdal-dev mailing list