[GRASS5] displaying raster vectors

[Michael Barton]

There are several ways to do this in GRASS.

This is most generically handled by d.rast.arrow. This routine will 
draw arrows within (preferably coarse, as you suggest) raster grid 
cells indicating the 'downslope' direction of an aspect grid cell. You 
can theoretically define any raster directional vector as an aspect map 
and do the same.

Another way is to use r.direct, which creates a flow-direction map from 
any 'elevation' surface. Again, you can define any conceptual surface 
as an elevation map in this case. Several of the watershed 
analysis/modeling routines also generate flow-direction maps as part of 
their outputs.

Michael Barton

On Friday, April 2, 2004, at 12:58  PM, grass5-request at grass.itc.it 
wrote:

> Subject: display of vector fields
>
> Platform: GNU/Linux/i386
> grass binary for platform: Compiled from Sources
> GRASS Version: 5.0.2
>
> It would be nice to have a display module for vector fields:
> it takes two rasters as arguments (one for direction, one for 
> magnitude), and it
> draws arrows representing the direction and magnitude at each point 
> (probably
> only good for low resolution rasters).
> That way you could use it to get a nice visual representation of wind 
> or water
> flow, and similar things.
> It might also be a good thing to add the resolution drop into the 
> program (instead
> of depending on low resolution rasters) so that you could display a 
> relatively high
> resolution DEM and then overlay a vector field representing water flow 
> (or wind,
> or whatever) at a lower resolution so that there's room to draw the 
> arrows without
> them interfering with each other
>
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>
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______________________________
Michael Barton, Professor & Curator
Department of Anthropology
Arizona State University
Tempe, AZ  85287-2402
USA

voice: 480-965-6262; fax: 480-965-7671