[GRASS-dev] Re: [GRASS-user] v.build.polylines strange behaviour

[Maciej Sieczka]

Jarosław Jasiewicz wrote:
> Hi
> When v.build.polylines is splied on file with islands ie: small areas
> inside lareger ones:
> 
> 
> _________
> |   ___     |
> |   |   |     |
> |   |__|     |
> |________|
> 
> the boundary of island doubles.

This is a known long standing bug. Please see:

v.build.polylines: fails to build a polyline out of a closed boundary
http://intevation.de/rt/webrt?serial_num=424

It happens only when the input closed boundary already has only 2 nodes
(IOW when it is already a closed polyline). If there are more than two
nodes in the input closed boundary, the bug will not crop out.

However, under any circumstanses, v.build.polylines always outputs
doubled vertices at each input node, which is another bug:
http://intevation.de/rt/webrt?serial_num=4249

A workaround is 'v.clean tool=prune thresh=0'.

I wish somebody could try fixing these for incoming 6.2.1. Rather
serious bugs...

Maciek