[GRASS-user] mask "around" a linear feature

[Robert Kuszinger]

Dear Micha,


I realized that the addon is for vector, so I converted my raster (that's
what I have) to points but even when downsampled is was very slow, actually
(~480000 points), I was not able to wait for it.
So, I created a workaround for sparse huge point clouds loaded into a
raster map. The method is not exact, this is a kind of approximation (as
raster is, always).


We start from "startvocer", created with r.in.lidar in my case:

   Type of Map:  raster               Number of Categories: 0
   Data Type:    FCELL
   Rows:         *28222*

   Columns:     * 79670   *

   Total Cells:  *2248446740*




[image: Szövegközi kép 2]

zoom:

[image: Szövegközi kép 3]


final:

[image: Szövegközi kép 5][image: Szövegközi kép 4]



The final vector map in my case is one vector area.... it could now be used
to set MASK for raster operations later on...


*PROCESS (resolution degradation and buffer size /100/ should be tailored
to application:*


g.region raster=startcover    # original resolution is 1m
g.region res=10

r.resamp.stats --overwrite input=00001_rec4 at kana output=00001_rec4_int
method=minimum

r.buffer --o input=00001_rec4_int output=lasmaskbuf distances=100
# let the "paint" flow to fill gaps and smooth edges
r.mapcalc --o
expression="lasmaskbuf2=if(isnull(lasmaskbuf),null(),1)"        # make all
values 1 in the buffer to let r.to.vect create one area
r.to.vect -s --overwrite input=lasmaskbuf2 output=lasmaskbufvec
type=area     # make vector of the buffer
v.generalize --overwrite input=lasmaskbufvec at kana type=area
output=lasmaskbufvecgeneralized method=sliding_averaging threshold=10000  #
make simpler
v.buffer --o input=lasmaskbufvecgeneralized at kana type=area output=final
distance=-100    # cut back



Best regards
Robert




>
> 2017-07-19 11:56 GMT+02:00 Micha Silver <tsvibar at gmail.com>:
>
>>
>>
>> On 07/19/2017 11:57 AM, Robert Kuszinger wrote:
>> Hope about the addon:
>> https://grasswiki.osgeo.org/wiki/AddOns/GRASS7/vector#v.concave.hull
>>
>> --
>> Micha Silver
>> cell: +972-523-665918
>>
>>
>
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