[GRASSLIST:2755] Re: r.patch multiple maps

[Martin du Saire]

At 11:25 PM 2/25/2004 +0000, you wrote:
> >
> > r.patch input=map1,map2,map3,... output=all_maps
> > r.patch -z input=bufferzone,all_maps output=map_data_in_bufferzone
> >
> > Is it necessary to do this in two steps?
>
>I don't know if this is relevant to your problem, but there appears to
>be a bug in r.patch when the -z switch is used.
>
>Note that the -z switch exists primarily for historical reasons.
>Versions of GRASS prior to version 5 didn't have a distinguished null
>value, but many programs treated zero as no-data.
>
>GRASS 5 uses a distinguished null value for no-data cells. Maps which
>use zero to indicate no-data should be converted to use null using
>"r.null map=... setnull=0".

Okay, I guess I could have reclassed the buffer zone to NULL and then used 
the default r.patch, correct?  If so, that may actually save me a couple of 
steps along the way.

Thanks.

Martin