[GRASS-user] v.patch eats my large polygons

[Robert Nuske]

Dear GRASS-Users,

after an abstinence period I started again to use GRASS 7.4 on Ubuntu 
18.04 and am now facing v.patch eating my large polygons.


38 vector maps (polygon) cover separate parts of my study area. A few 
share a boundary with their neighbor, most do not. To further work with 
all polygons from all sub plots, I want to merge all sub plots into one 
vector map. I do NOT need the polygons to get dissolved (disected & 
rebuild) at the boundary of two sub plots.

Large (area, number of vertices and number of islands) polygons, which 
touch another large polygon at the common border of two sub plots are 
not in the patched vector map.


What I did:
v.patch in=gaps_1,gaps_2 out=gaps_merged

What did not help was the -b flag. Lot's of boundaries but no areas anymore.


To illustrate my problem, an image (https://imgur.com/4n3le65) with two 
sub plots (left an right) with a common border at the smallest part. All 
colored area are polygons. The islands are white. The orange polygons 
are the results of v.patch. The light gray and dark gray polygon are 
missing in the resulting v.patch-map.


Did anyone experience similar behavior before and know of a cure?


Thanks
   Robert