[gdal-dev] Corner coordinates issue

[Frank Warmerdam]

ldjohn at u... wrote:

> Hey Frank,
> The ASCII art below attempts to describe the situation. In this figure,
> band 2 is at a higher resolution than band 1. Both bands share the same
> corner coordinates, which are located at the centers of the corner pixels
> for each resolution. Thus band 2 actually covers a smaller geographic
> region than band 1.
> 
> +-------+-------+-------+-------+-------+
> band 1 -->| +---+-+-------+-------+-------+-+---+ |
> | | + | | | | | | + | |
> | +---+ | | | | +---+ |
> +-+---+-+-------+-------+-------+-----+-+
> | +---+ | |
> band 2 ---->| | | |
> | +---+ | |
> | | | | |
> | +---+ + = corner coordinate | |
> | | | | |
> | +---+ | |
> | | | | |
> | +---+ | |
> | | | | |
> | +---+ | |
> +-+---+-+ +-----+-+
> | +---+ | | +---+ |
> | | + | | | | + | |
> | +---+-+-----------------------+-+---+ |
> +-------+-----------------------+-------+
> 
> Have you considered options for covering such scenarios with
> center-of-pixel corner coordinates? If we have to handle it ourselves,
> we'll probably use various metadata strings to carry the additional,
> unsupported corner coordinate info along, but that would most likely
> break the GDAL ability to automatically handle format conversions for us.
> 
> This doesn't appear to be an easy problem to resolve, but if you have any
> ideas for best handling these formats in GDAL, we would be happy to hear
> them.

Lowell,

I see your problem, and I don't see any easy way to handle it properly.
I suppose carrying some specialized metadata for this case would do the
trick. Viewing applications that don't understand the metadata will slightly
misplace the rasters, but only by a fraction of a pixel.

Best regards,

-- 
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I set the clouds in motion - turn up | Frank Warmerdam, warmerdam at p...
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and watch the world go round - Rush | Geospatial Programmer for Rent