[GRASS-user] r.patch for stitching rasters?

[Hamish]

Charles:
> > > I couldn't figure out how to make gdal_merge output NULLs
> > > instead of 0s (and what formats support NULLs?).
> >
> > r.mapcalc can easily convert your 0s into NULLS with the expression:
> >
> > newmap = if(map == 0, null(), map)

another way is:
 r.null map=yourmap setnull=0


> > r.mapcalc will solve most raster problems. GRASS users are advised to know
> > that program inside and out.

agreed.


Boris Avdeev wrote:
> Well, you assuming that NULL=0, but the sole reason for having NULL
> layer in grass is that those values are not identical.

true, the data is lost when NULL is mixed with 0 in the first place, not when
changing 0->NULL.


Hamish



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