[GRASS-user] Re: grass-user Digest, Vol 47, Issue 52

[Micha Silver]

Nathaniel Iwuchukwu wrote:

> I figured it out.
> here are my new output. though the lines are scattered. can it be 
> improved?
Again, Nathaniel, keep the discussion on the list, both to get more 
responses, and for future generations.
The next step you might try is using the v.clean command on this vector 
to remove very small lines. It has a tool, rmdangle to get rid of all 
the small X's around the actual roads. You will have to experiment with 
the "thresh" parameter to get it right.

Regards,
Micha
>
> On Fri, Apr 2, 2010 at 5:41 AM, Nathaniel Iwuchukwu 
> <ikechinedu at gmail.com <mailto:ikechinedu at gmail.com>> wrote:
>
>     Thanks Micha,
>     I was thinking of running the r.mapcalc command but not sure of
>     the exact argument to use.
>     is there a command i can run to show me the values of the colors
>     on the map?
>     Thanks
>     Nathaniel
>
>     On Fri, Apr 2, 2010 at 8:27 AM, Micha Silver <micha at arava.co.il
>     <mailto:micha at arava.co.il>> wrote:
>
>         Nathaniel Iwuchukwu wrote:
>
>             here are the image results of my works. am trying to
>             upload it on my page
>
>         If you do upload the images, post also to the list.
>
>         It looks like all the areas that are *not* roads are also
>         being classified. Everywhere that appears purple in you
>         classification image needs to be set to null. You do this with:
>         r.null <classified_raster> setnull=<the value which displays
>         purple>
>
>         You want to be left with a raster with values *only* where
>         there are roads. Everything else should be null. Then go ahead
>         and run:
>         r.thin and r.to.vect <classified_raster_thin> feature=line
>         out=roads
>
>         Cheers,
>         Micha
>
>
>             2010/4/1 Micha Silver <micha at arava.co.il
>             <mailto:micha at arava.co.il> <mailto:micha at arava.co.il
>             <mailto:micha at arava.co.il>>>
>
>
>                On 04/01/2010 02:52 PM, Nathaniel Iwuchukwu wrote:
>
>                    i created 11 polygons from different portions of
>                 the road.
>
>                So if I understand correctly, the procedure is working,
>             but you're
>                not getting the results you'd expect?
>
>                Maybe you could supply to the grass-users list some
>             URL's of
>                images of what the satellite rasters look like, with
>             your training
>                polygons, and the resulting roads. Then perhaps someone
>             will be
>                able to suggest how to get more complete results.
>
>
>
>                    
>
>
>
>
>
>
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-- 
Micha Silver
Arava Development Co. +972-52-3665918
http://www.surfaces.co.il