New to grass -- a couple of questions

Eric G . Miller egm2 at
Fri Jun 2 23:04:43 EDT 2000

On Thu, Jun 01, 2000 at 04:47:17PM -0600, Stephen Griffiths wrote:
> Hi all,
> I am new to Grass so please forgive to simple nature of my questions.
> I have been trying to read my DEMs and Ortho images into grass.  I have
> used "".  This has worked fine if the data is in an 8bit
> unsigned binary format -- thats ok for the image, but not the DEM.  How
> can I read the DEM in as 16bit unsigned or even better 32bit float?  My
> DEM's are all in 32bit float flat binary raster format.  I really do not
> want to convert them to some other format first.

I don't see any way around it ;( Wouldn't be hard to convert to ascii
and then use

> It there a way to have grass generate a null value mask raster given a
> closed polygon (vector) such that outside the poly the values are null,
> while inside the poly the values are 1?  Then could I multiply the mask
> raster with the DEM (image) raster to null the result outside the
> project bounds?  Nulling the raster outside the bounding polygon would
> help out greatly.

I think, if you set the category value to 1 for the vector, then use, you can get a binary raster that is suitable as using as a
mask.  But, there are ways to make the mask from the image/dem bounds
themselves.  You'll want to read up on r.mapcalc and look at setting the
MASK for the grass environment (r.mask).

> Can grass mosaic multiply images together?  How does grass do this?
> Does it use a seam line defined by the user, or some other method?


> Finally, I have tried running NVIZ put had no success.  I have a RH6.0
> linux box with a 16bit color depth display.  I can increase the color
> depth to 24bits if I reduce the screen res.  Is there something I am
> missing?

Umm, what does it do? Does it error on the color depth?

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