[GRASS-dev] [GRASS GIS] #3319: v.overlay: incorrect results with "not" operator
GRASS GIS
trac at osgeo.org
Sat Mar 25 14:25:35 PDT 2017
#3319: v.overlay: incorrect results with "not" operator
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Reporter: sbl | Owner: grass-dev@…
Type: defect | Status: new
Priority: major | Milestone: 7.2.1
Component: Vector | Version: svn-releasebranch72
Resolution: | Keywords: v.overlay
CPU: Unspecified | Platform: Unspecified
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Comment (by mmetz):
Replying to [ticket:3319 sbl]:
> In a project I want to clip away the sections from a river network that
are within lakes.
>
> Unfortunately, some streams vanished from the result completely (which
should not)...
Please try v.overlay in trunk r70800.
The problem lies with Vect_break_lines() and Vect_break_lines_list() which
create new vertices that are sometimes too close to existing vertices
(floating point representation error). Radim was aware of that problem in
v.overlay. I (hopefully) fixed the symptom in v.overlay. The real fix
would be to not use a fixed value for rethresh (Radim was also aware of
that problem) in Vect_line_intersection() and Vect_line_intersection2(),
but instead set rethresh to the smallest representable difference (ULP).
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Ticket URL: <https://trac.osgeo.org/grass/ticket/3319#comment:1>
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