[GRASS-user] A "list=" option for "v.overlay"?

[Richard Chirgwin]

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> Today's Topics:
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>    1. Re: A "list=" option for "v.overlay"? (Nikos Alexandris)
>    2. Re: A "list=" option for "v.overlay"? (Nikos Alexandris)
>    3. Blank window in MS-Windows GRASS 6.3.0 (Matt)
>    4. Re: Blank window in MS-Windows GRASS 6.3.0 (Moritz Lennert)
>    5. wget (corine) "landcover_tiles_v2" for greece works, but not
>       for europe(?) (Nikos Alexandris)
>
>
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Sun, 11 Jan 2009 18:37:47 +0100
> From: Nikos Alexandris <nikos.alexandris at felis.uni-freiburg.de>
> Subject: Re: [GRASS-user] A "list=" option for "v.overlay"?
> To: GRASS user list <grass-user at lists.osgeo.org>
> Message-ID: <1231695467.10857.18.camel at vertical>
> Content-Type: text/plain
>
> On Sun, 2009-01-11 at 05:58 +0100, Nikos Alexandris wrote:
>   
>> Wouldn't it make sense to have a "list=" option for "v.overlay"?
>>
>> I need to extract samples from the CORINE land cover/use (vector) map in
>> separate maps (one map per sample plot).
>>
>> Currently the only feasible way I see is:
>> (1) put v.extract in a "for" loop and extract the sample plots in
>> separate maps.
>> (2)  use v.overlay in a loop over all samples plot maps.
>>
>> But this is not "nice" if let's say the sample plots are thousands.
>> Thanks in advance, Nikos 
>>     
>
> I guess I just hit a "to do" issue... :-) & :-(
>
> 222 v.overlay
> 223 ---------
> 224 Select only relevant features which will be written to the output if
> 225 'and,not,nor' operators are used. An inspiration is available in
> 226 v.select.
>
> (Taken from
> http://trac.osgeo.org/grass/browser/grass/trunk/doc/vector/TODO)
>
>
>
> ------------------------------
>
> Message: 2
> Date: Sun, 11 Jan 2009 20:17:00 +0100
> From: Nikos Alexandris <nikos.alexandris at felis.uni-freiburg.de>
> Subject: Re: [GRASS-user] A "list=" option for "v.overlay"?
> To: GRASS user list <grass-user at lists.osgeo.org>
> Message-ID: <1231701420.12139.39.camel at vertical>
> Content-Type: text/plain
>
> On Sun, 2009-01-11 at 05:58 +0100, Nikos Alexandris wrote:
>   
>> Wouldn't it make sense to have a "list=" option for "v.overlay"?
>>
>> I need to extract samples from the CORINE land cover/use (vector) map in
>> separate maps (one map per sample plot).
>>
>> Currently the only feasible way I see is:
>> (1) put v.extract in a "for" loop and extract the sample plots in
>> separate maps.
>> (2)  use v.overlay in a loop over all samples plot maps.
>>     
>
> Unfortunately, even that Segfaults.
>
> # step 1: split in separate vector maps all samples, e.g. boxes of
> 40.000m x 40.000m
> for x in `v.category box_40000 option=print | sort -nu | grep -v "/"`;
> do v.extract in=box_40000 list=$x out=box_sample_40000_$x; done
>
> # step 2: intersection of each separate box_sample with corine
> for x in `g.mlist type=vect pat=box_sample*`; do v.overlay ainput=corine
> binput=$x operator=and out=corine_box_sample_$x; done
>
> The result after several minutes of processing is "Segmentation
> fault" :-(
>
> So, the only way is to do this job per smaller CORINE-blocks?
>
>   
Nikos,

You might try inserting a v.build between steps 1 and 2. It will slow
down the process, but I found in a similar 'bulk overlay' exercise that
this improved the stability of the process.

Richard