[GRASSLIST:2751] Re: r.patch multiple maps

[Glynn Clements]

Martin du Saire wrote:

> I attempted to use r.patch -z input=bufferzone,map1,map2,... 
> output=map_data_in_bufferzone
> 
> to fill a zone with data from multiple maps, but the procedure only merged 
> data from the first map in the list (map1).  No error was reported.  In 
> order to map all maps into bufferzone, I ended up
> 
> 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".

-- 
Glynn Clements <glynn.clements at virgin.net>