[GRASSLIST:2183] Re: Importing a USGS ASCII DEM

[Glynn Clements]

Ben Logan wrote:

> I've imported a USGS ASCII DEM using r.in.gdal, but when I use d.rast
> to display it, it is all red.  I've tried changing the color table,
> but to no avail.  Using d.what.rast show different values at different
> places, so I'm not sure why they won't show up in different colors.

Check the range (r.info) of the data, and optionally the distribution
(e.g. with d.histogram).

A common problem when importing DEMs is that a specific (and usually
extreme) value is often used to represent NULLs. If these aren't
converted, the result is that the colour table gets stretched over an
extreme range, with the "real" data lying in a narrow band (relative
to the overall range).

If this has happened, you can translate the substitute NULL values to
actual NULLs with r.null.

-- 
Glynn Clements <glynn.clements at virgin.net>