Re: [GRASS-user] digitizer

2013-12-13 Thread Vaclav Petras 
On Fri, Dec 13, 2013 at 6:03 AM, Martin Album Ytre-Eide <
martin.album.ytre-e...@nrpa.no> wrote:

>  Hello all.
>
> I have been trying the digitizer in 6.4.2, and I am having several
> difficulties. I am working with a polygon map, and as a test, I am trying
> to create a polygon which I try split into four smaller polygons. First I
> divide it in half and then a divide one of the new halves in two.
> Afterwards, I have generated centroids for the area. I have used only the
> "new boundary" tool for this - and that may be wrong? But I have tried some
> other options without any luck.
>
> Does anyone know how to do this? There also seems to be a problem that the
> map is saved even though I say no thanks. So, if you do a mistake - it
> could be hard to fix - is there an undo function in an other version?
>
> Hi, I'm not using digitizer regularly, so I cannot answer you first
question. However, there are definitively some improvements in GRASS 7
digitizer including the undo button. I'm not sure about GRASS 6.4.3, so if
nightly build (or what ever) of GRASS 7 is acceptable for you, try it.


> Thanks!
>
> Martin
>
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Re: [GRASS-user] Cannot change directory via GRASS command console

2013-12-13 Thread Helmut Kudrnovsky 
> no joy with your suggestion.  When I use ls or pwd it shows I'm still in
the /osgeo4w/bin directory. 

please provide more information about what are you doing exactly, used
commands, used environment (osgeo4w shell or osgeo4w msys shell), QGIS
standalone, osgeo4w bundled QGIS, etc. ... without such information it's
hard to say what's going wrong...

> Does it perhaps have something to do with the fact that its bundled with
> qgis2? 

osgeo4w shell (windows command line) or osgeo4w msys shell should work
idependently to what it is bundled.





-
best regards
Helmut
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Re: [GRASS-user] Extraction 3D vectors ridges/Thalweg from raster DEM ?

2013-12-13 Thread Micha Silver 

  
  
On 12/13/2013 06:33 PM, image wrote:


  Ok thanks. 

And acording to you, is it possible to add the field HeightZ to my vector3D
Grass generated? 



Yes, you do this as follows:
v.db.addcol map= columns="x_coord double
precision, y_coord double precision, z_coord double precision"
v.to.db map= option=coor columns="x_coord,
y_coord, z_coord"


  
Thanks? 



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Re: [GRASS-user] Cannot change directory via GRASS command console

2013-12-13 Thread PB 
Hi Helmut - no joy with your suggestion.  When I use ls or pwd it shows I'm
still in the /osgeo4w/bin directory.

Does it perhaps have something to do with the fact that its bundled with
qgis2?
PB




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Re: [GRASS-user] Extraction 3D vectors ridges/Thalweg from raster DEM ?

2013-12-13 Thread image 
Ok thanks. 

And acording to you, is it possible to add the field HeightZ to my vector3D
Grass generated? 

Thanks? 



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Re: [GRASS-user] Extraction 3D vectors ridges/Thalweg from raster DEM ?

2013-12-13 Thread Micha Silver 

  
  
As far as I know, the shapefile format
  does not really support 3D vectors.
  
  On 12/13/2013 05:41 PM, image wrote:


  Hello,

And thank you again for your help. I have a last little question. I succeed
in generating with grass vector 3D. I would like now export it to
shapefile3D. Do you know how to do that? 

Thanks. 





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Re: [GRASS-user] Extraction 3D vectors ridges/Thalweg from raster DEM ?

2013-12-13 Thread image 
Hello,

And thank you again for your help. I have a last little question. I succeed
in generating with grass vector 3D. I would like now export it to
shapefile3D. Do you know how to do that? 

Thanks. 





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Re: [GRASS-user] Extraction 3D vectors ridges/Thalweg from raster DEM ?

2013-12-13 Thread Micha Silver 

  
  
Hi
  
  On 12/13/2013 01:14 PM, image wrote:


  Hello,

Thank you very much for your reply. I made some tests following your
recommandations. For information, the surface of my raw raster DEM is 15.000
km². Resolution : 1 pixel X & pixel Y = 30 meters. (SRID 2154 UTM).

1/"r.watershed": the main input parameter seems to be the minimum size for
each basin. I typed 10 (unit pixels i think). I think it's a low value. I
would like know how enter a coherent value. How to ensure that our input
value is coherent?



You choose the threshold value as the minimum size of drainage area
that is of interest. In your case, with resolution 30m, then 1 pixel
= 900 sq.m. So a threshold of 11000, for example, would give a
minimum drainage area of 10 sq km.
(A threshold of 10 is way too small!)

  

  
2/"r.watershed" process generates several new raster layers. Could you
confirm to me that for *streams* r.thin & r.to.vect process i have to select
the third layer generated called "water_segments". And for the basins i have
to select the 4th layer called "Basin label"? 

The names of the basin and stream rasters are whatever you entered
as the "basin=..." and "stream=..." parameters

I suggest that you have a look at the manual page:
http://grass.osgeo.org/grass65/manuals/r.watershed.html
 

  

3/For basins and the v.extract process. I made a test with v.extractwhere.
But i don't find how to enter the value type=boundary. For information i'm
working with easy GUI interface via Qgis., no with command lines interface.

Perhaps for this job you could try the actual GRASS interface. It's
a bit harder to learn, but well worth the effort...

  

4/ The final vector output data for streams seems to be rather coherent.
However, my basins vector segmentation seems to be really too detailed and
inexploitable.


Change the threshold value... If you need a very detailed stream
layer, you can run the module once with a small thresh for streams,
then a second time with a large thresh to delineate the basins.

And one more thought: If you can manipulate the original DEM, so
that areas with zero value or no values (all the lower left corner,
etc), are actually set to NULL, then you will avoid those funny
straight stream segments.


  
Please find below usefull SS showing : A: My raster raw data /
B:Streams_vect_3D / C: Basins_labels_raster D: Basins_area_vector

A
 

B
 

C
 

D
 



If you can throw light for me. Thanks.

With kind regards. 




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Re: [GRASS-user] Extraction 3D vectors ridges/Thalweg from raster DEM ?

2013-12-13 Thread image 
Hello,

Thank you very much for your reply. I made some tests following your
recommandations. For information, the surface of my raw raster DEM is 15.000
km². Resolution : 1 pixel X & pixel Y = 30 meters. (SRID 2154 UTM).

1/"r.watershed": the main input parameter seems to be the minimum size for
each basin. I typed 10 (unit pixels i think). I think it's a low value. I
would like know how enter a coherent value. How to ensure that our input
value is coherent?

2/"r.watershed" process generates several new raster layers. Could you
confirm to me that for *streams* r.thin & r.to.vect process i have to select
the third layer generated called "water_segments". And for the basins i have
to select the 4th layer called "Basin label"? 

3/For basins and the v.extract process. I made a test with v.extractwhere.
But i don't find how to enter the value type=boundary. For information i'm
working with easy GUI interface via Qgis., no with command lines interface.

4/ The final vector output data for streams seems to be rather coherent.
However, my basins vector segmentation seems to be really too detailed and
inexploitable.

Please find below usefull SS showing : A: My raster raw data /
B:Streams_vect_3D / C: Basins_labels_raster D: Basins_area_vector

A
 

B
 

C
 

D
 



If you can throw light for me. Thanks.

With kind regards. 




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[GRASS-user] digitizer

2013-12-13 Thread Martin Album Ytre-Eide 
Hello all.

I have been trying the digitizer in 6.4.2, and I am having several 
difficulties. I am working with a polygon map, and as a test, I am trying to 
create a polygon which I try split into four smaller polygons. First I divide 
it in half and then a divide one of the new halves in two. Afterwards, I have 
generated centroids for the area. I have used only the "new boundary" tool for 
this - and that may be wrong? But I have tried some other options without any 
luck.

Does anyone know how to do this? There also seems to be a problem that the map 
is saved even though I say no thanks. So, if you do a mistake - it could be 
hard to fix - is there an undo function in an other version?

Thanks!

Martin
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