[GRASS-user] r.shaded.relief strangeness

[Glynn Clements]

Patton, Eric wrote:

> >Not sure if this is very critical, but I have noticed a problem with 
> >r.shaded.relief. If the region is set to 10m and then a shaded rel. map is 
> >produced from a 30m input data, a corrupt map is produced. 
> >
> >example with spearfish data:
> >
> ># set region, and force 10m resolution
> >g.region rast=elevation.10m -p
> 
> I assume you meant g.region rast=elevation.10m res=10 -ap ?
>  
> ># compute shaded rel. map from 30m res data:
> ># see image [1]
> >r.shaded.relief map=elevation.dem shade=shade
> 
> I can't reproduce this. I can produce a Moire-patterned shaded-relief map, 
> since I didn't resample the 30m data to 10m:

> Try r.resample first?

r.resample won't help. That uses libgis' built-in nearest-neighbour
resampling, so you will get exactly the same result as with using the
lower resolution map.

Using r.resamp.interp with method=bilinear or method=bicubic should
eliminate the problems with generating slope and aspect maps.

-- 
Glynn Clements <glynn at gclements.plus.com>