[GRASSLIST:2249] Re: How to make mosaic of the raster files?

[Helmer Schack-Kirchner]

Zbigniew Perski wrote:

> Hi everybody,
>
> I have 6 scanned maps which was resampled into one project. The maps 
> are  overlapping a bit and the scans includes also parts outside the 
> map frame. Unfortunately after resampling to the project the mas are 
> not rectangular. I would like cut out unwanted parts and mosaic the 
> pieces into one file using r.patch. I have tried r.mask but it is 
> masking out map values but not map areas. Is there any method in grass 
> how to do it?
>
>
> Thanks in advance.
>
> Regards
>
> Zbigniew 

Use the if(when true, choose A, else choose B) function in r.mapcalc. 
With this function you may decide, which map in case of  overlapping you 
prefer and you may cut undesired areas. To begin it may be easier, to 
build the mosaic step by step with only one r.mapcalc if(a,b,c) (with 
only two maps included) function, but it is also possible to nest the 
if() function to join all 6 maps in one step.
Best regards,
Helmer