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Date |
Fri, 12 May 2006 17:09:59 +1200
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Hamish <hamish_nospam@yahoo.com>
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Request Tracker <grass-bugs@intevation.de>
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grass-dev@grass.itc.it
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Re: [GRASS-dev] [bug #4452] (grass) r.patch makes mosaics slowly
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> this bug's URL: http://intevation.de/rt/webrt?serial_num=4452
> ---------------------------------------------------------------------
>
> Subject: r.patch makes mosaics slowly
>
> r.patch currently takes current_region_rows * current_region_columns *
> number_of_input_maps time to compile mosaics. It has some reasonable
> optimizations for patching an existing large map with many small
> patches, but is quite unsuited to mosaics.
>
> For mosaics the fast thing to do would be to iterate over input maps
> (bounds of input, resolution of current region), copying values to
> nulls in the output. (and non-zero values to zeros or nulls in the
> output with the -z switch).
isn't this just the r.mapcalc solution?
Eric wrote:
> r.mapcalc "$OUTPUT=if(isnull(Map_A), Map_B, Map_A)"
hint:
g.region rast=map1,map2,map3,map4
extends the region to enclose all listed maps. Helpful for r.patch.
I think in the end you will spend lots of time for little gain on this
problem- no matter how you frame it, you still have to read each cell of
each map. Just set the thing to run from a script before you leave for
the day & the result will wait for you in the morning. (unless you have
10,000 maps to patch or want real time availablility)
Hamish
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