[gdal-dev] vrt performance with 1000's of tiles?

[Matt Klaric]

On Mon, Apr 5, 2010 at 2:52 PM, John C. Tull <jctull at gmail.com> wrote:

>
> Looking at the vrt from the file I built with my drg images, I have this:
>
>     <SimpleSource>
>       <SourceFilename
> relativeToVRT="1">./barrett_canyon/o39117a4.tif</SourceFilename>
>       <SourceBand>1</SourceBand>
>       <SourceProperties RasterXSize="4463" RasterYSize="5710"
> DataType="Byte" BlockXSize="4463" BlockYSize="1"/>
>       <SrcRect xOff="0" yOff="0" xSize="4463" ySize="5710"/>
>       <DstRect xOff="92733" yOff="134498" xSize="4473" ySize="5723"/>
>     </SimpleSource>
>
> So, presumably, gdalbuildvrt generates this for you. Is there something
> missing here to achieve what you are talking about, Matt?
>
>
That looks very similar to what I have with only one exception.  I'm using
an absolute path.  Could it be the case that you created this VRT and have
since moved it?  Or the data that it's referring to?  If so, the VRT file
may not be able to find the TIFF files that it's pointing to.

I'd suggest testing this by using gdal_translate to extract a piece of the
VRT where you expect there to exist data.  Run gdal_translate with
CPL_DEBUG=ON in your environment so that you can see debug info to
understand what files it's trying to open.  You should be able to see it
opening one of your TIFF files.....and verbose info if it's failing to.

--Matt
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