I need to combine polygons of similar geological classes which are stored in a vector file called geology. I was looking for somethiing like "union selected features" or similar. In the GRASS Book 3ed I found that v.overlay could be useful, however I did not manage to merge/union my classes.
To illustrate it, here an example: I have a polygon with class (column MAIN_LITHO) 'biotite granite' but also 'biotite granite (foliated) and others. These should be all combined into one single multipolygon 'biotite granite'. Later, I want to turn that vector into a raster map but that should be easy.
here is also an image of that example
thank you in advance!