[GRASSLIST:2757] Re: r.patch multiple maps

[Hamish]

> > > 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.


also note r.patch uses the maps in order for priority, e.g.

input=map7,map5,map3


if data exists for all maps, the value from the first one (here map7) is
used.

So if your buffer map covers the whole space, only its values will be used.

Better to use r.mask.



Hamish