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Aside from using r.fill.dir in GRASS, is this the script to produce the Flow or directional raster map? Is this the output for the script (http://grass.fbk.eu/grass63/screenshots/images/drastarrow.png)?

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first create the aspect raster with r.slope.aspect then display the arrows with d.rast.arrow.

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I used r.slope.aspect elevation=rastermap. It produced the error: ERROR: You must specify at least one of the parameters: <slope>, <aspect>, <pcurv>, <tcurv>, <dx>, <dy>, <dxx>, <dyy> or <dxy>. Which parameter to use for the r.slope.aspect is best to use in order to obtain a Flow or directional raster map ? – teamAngat Feb 1 '11 at 17:49
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Use r.slope.aspect elevation=inmap aspect=outmap min_slp_allowed=0.04 and adjust min_slp_allowed and the region resolution to get good results. – Pablo Feb 1 '11 at 18:23
I used: r.slope.aspect elevation=bul2 aspect=outmap1 min_slp_allowed=0.04. It produced a gray map with slope-like structures. and I used: d.rast.arrow map=outmap1. It produced a raster map with a solid color. It did not contain arrows. I think the problem with the map is that its resolution is high that is why it did not produce arrows. How do I resolve it? Are my scripts correct? I need the arrows in order to know the direction of the elevation areas for a flood modelling algorithm that I will use. Thanks! – teamAngat Feb 2 '11 at 14:23
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I've just tried it here, strange results, very small arrows. – Pablo Feb 2 '11 at 17:43
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The Z value of the ASPECT map is the flow heading. You can try something with that. – Pablo Feb 3 '11 at 16:23
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