[GRASS-dev] ascii export and import, large file problem

Glynn Clements glynn at gclements.plus.com
Fri Apr 13 10:51:47 EDT 2007

Gerald Nelson wrote:

> Helena, I think grass assumes x,y, and z are all in the same units
> when it does the slope calculation. At least when I run r.slope.aspect
> on my lat long file I get junk out but when I project it to utm and
> then run r.slope.aspect I get numbers that look reasonable.

I get reasonable slope values out of r.slope.aspect for a lat/lon

As Helena says, it uses geodesic distance for lat/lon locations (if
you haven't specified an ellipsoid, it defaults to WGS84).

Glynn Clements <glynn at gclements.plus.com>

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