[GRASSLIST:2473] [5.7] remove islands and U-dangles?

[Hamish]

Hi,

more questions about 5.7 vectors....


I've got a vector area which contains a bunch of islands and polygons
attached to the inside edge of the outer polygon. What commands would
one use to remove and 'flatten' the overlapping areas?


eg


/-------+---+----------\
|       | X |          |
|       | X |  <- area |
|       |---|          |
|                      |
|  |=| <- island       |
|                      |
\----------------------/


In the end I want a convex hull of the outer polygon as a single entity,
without losing resolution from a points->v.hull step.

I've tried a few things with v.overlay, but they just produced empty
maps (No tables or databases, probably bad topology in there.. d.vect
does draw the input as an area though, and the output coor file is huge 
while other vector files are just a couple of hundred bytes).

'v.overlay op=or' might do the trick if it made 1 polygon out of two 
input polygons instead of three and I could use the same map for ainput=
and binput=.



thanks for any ideas,
Hamish


ps [grass5 list]:
  I fixed the hidden dangling node bug in 5.7's v.digit.