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List:       grass-user
Subject:    [GRASS-user] Working with a large number of maps
From:       craig () pid ! co ! za (Craig Leat)
Date:       2007-12-19 8:18:32
Message-ID: 4769199A.9020905 () pid ! co ! za
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Glynn Clements wrote:
> Craig Leat wrote:
>   
>> I have 139 high resolution images, which I need to use as a background map
>> for some digitizing work. 
>>     
> How do the individual maps relate to the overall region?
>
> If they are (approximately) tiles, I would suggest using a
> hierarchical approach, patching groups of adjacent tiles into larger
> tiles, then patching the larger tiles together, so that each r.patch
> operation has relatively few maps, and the earlier stages have
> relatively small regions.
>
> The total time taken by r.patch is roughly proportional to the total
> number of cells in the region multiplied by the number of input maps,
> so the combination of a large region and a large number of maps will
> be slow.
>
>   
Thanks for the advice Glynn. The images are tiles and the filenames 
follow a regular pattern, so I am able to patch blocks together quite 
easily with a simple script. I included lots of echos in the script and 
now I even have verbose messages ;-)   

The script is running right now and making good progress...

Craig

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