[GRASS-user] Question about v.to.rast

Thomas Adams tea3rd at gmail.com
Tue Jun 17 05:02:44 PDT 2014


Margherita

Just to let others know; I was able to solve my problem that I had with so
many polygons created by r.to.vect by using v.db.addcolumn and setting the
value of that column for all the polygons to the same value, 'flood', e.g.
Then use v.dissolve using column=addedColumnName

So, instead of having thousands if pixel-sized polygons, I ended up with
just a handful of polygons, which was my goal

Cheers!
Tom

On Monday, June 16, 2014, Margherita Di Leo <diregola at gmail.com> wrote:

> Hi Thomas,
>
>
> On Mon, Jun 16, 2014 at 1:47 PM, Thomas Adams <tea3rd at gmail.com
> <javascript:_e(%7B%7D,'cvml','tea3rd at gmail.com');>> wrote:
>
>> All:
>>
>> I have used r.lake to simulate flood inundation in an urban area -- the
>> raster looks great! What I want to do (and have done) is to use r.to.vect,
>> export the vector as a KML (which works), bring the simulated flood
>> inundation map KMLs into GoogleEarth and create some animations from the
>> simulated inundation, including showing rising flood levels inundating the
>> city streets in 3D.
>>
>> I can basically do all this, except that the r.to.vect conversion creates
>> a gazillion boxes that are the size of the raster pixels -- I don't want
>> all the tiny boxes.
>>
>
> I'm not sure I understand correctly, but if the tiny pixels are there also
> in the raster map, might be useful r.area (addon) [1].
> Hope this helps,
>
> Cheers,
> madi
>
>
>> What I want, is just a single (albeit, complex) polygon showing the
>> flooded areas. v.dissolve will remove the boundaries of adjacent boxes if
>> their cat or attributes are the same -- is this the way to go, namely, make
>> all the cats or attribute values the same and then use v.dissolve?
>>
>> Or, is there is there a better way to do what I'm attempting to do? That
>> is, is it best to keep the individual small vector boxes for reasons I'm
>> not considering?
>>
>> Thank you,
>> Tom
>>
>>
>> [1] http://grass.osgeo.org/grass70/manuals/addons/r.area.html
>
>
>
> --
> Best regards,
>
> Dr. Margherita DI LEO
> Scientific / technical project officer
>
> European Commission - DG JRC
> Institute for Environment and Sustainability (IES)
> Via Fermi, 2749
> I-21027 Ispra (VA) - Italy - TP 261
>
> Tel. +39 0332 78 3600
> margherita.di-leo at jrc.ec.europa.eu
> <javascript:_e(%7B%7D,'cvml','margherita.di-leo at jrc.ec.europa.eu');>
>
> Disclaimer: The views expressed are purely those of the writer and may not
> in any circumstance be regarded as stating an official position of the
> European Commission.
>


-- 
Thomas E Adams, III
718 McBurney Drive
Lebanon, OH 45036

1 (513) 739-9512 (cell)
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