[GRASS-user] patching maps together

[Tim Southern]

Dear All,

I am trying to patch together a number of 1 km by 1 km tiles of a map whose values are either 0 or 1 (black on white background).

If I use r.patch to put 2 tiles together is appears to work fine but if however I try and patch more, even if it is two tiles of already patched tiles I get one set when patched as black background and white features and the other part as white background and black features.  It appears that the second in the case of already patched data or third and subsequent in case of more than 2 tiles is inverted with 1 becoming 0 and 0 becoming 1.

I have tried reducing region to the smallest.  Maps are at 0.2m resolution.  I am hoping to get a 5 tile by 5 tile block

I have tried this across two different platforms (Mac OS and OpenSuse ) on the latest downloadable binary versions of GRASS.

Am I doing something wrong?

Kind regards

Tim
Tim Southern