[GRASS-user] stream extraction from ASTER dem

[Markus Metz]

Milton Cezar Ribeiro wrote:
>  
> Any colleague that could suggest a way of I extract some 
> geomorphometry features (sensu Tom Hengl!) from "large" DEM 
> (10,000x6,000), please let me know.

Maybe r.watershed in grass 6.5? The A* Search section of r.watershed in 
6.5 needs only about 40% of the memory needed in 6.4 and is about 30% 
faster than in 6.4. Both the reduced memory consumption and increased 
speed are more noticeable on larger maps with > 50 million non-NULL 
cells. In 6.5, r.watershed also supports floating point DEMs and MFD, 
each of which and particularly the combination of both produce more 
realistic results.

r.terraflow was designed particularly for massive datasets and should 
have no problems with a map of 60 million cells.

Lastly, an environment where GRASS (and SAGA rev Tom Hengl) can be 
compiled as 64bit application helps processing large datasets.

Best wishes,

Markus M

>  
> bests
>  
> milton
>
> 2009/9/28 Markus Metz <markus.metz.giswork at googlemail.com 
> <mailto:markus.metz.giswork at googlemail.com>>
>
>
>     Milton Cezar Ribeiro wrote:
>
>         Dear all,
>          I have a DEM with dimensions 10,000 x 6,000. Now I need to
>         extract all the stream or drainage, as well as generated some
>         other stream/flow related features like flow direction,
>         stream lenght, etc.
>          I work on a computer with 6Gb under Vista, and the grass
>         version is the OSGeo4W one. But when I try to run the command
>         below I get one error relate to r.watershed.seg.exe:
>          r.watershed elevation=aster_dem stream=aster_dem_stream
>         threshold=150 -m memory=2048
>          Any idea of how to solve that?
>
>     Maybe it is the Vista UAC problem, there were recently other posts
>     related to this.
>
>     Just a guess,
>
>     Markus M
>
>