[GRASS-dev] [GRASS GIS] #3030: v. generalize fails to generalize polygons in a random manner

[GRASS GIS]

#3030: v. generalize fails to generalize polygons in a random manner
---------------------+--------------------------
  Reporter:  dido    |      Owner:  grass-dev@…
      Type:  defect  |     Status:  new
  Priority:  major   |  Milestone:  7.0.5
 Component:  Vector  |    Version:  7.0.3
Resolution:          |   Keywords:  v.generalize
       CPU:  x86-64  |   Platform:  MSWindows 7
---------------------+--------------------------
Changes (by neteler):

 * keywords:  v.generalize fails 7.0.4 => v.generalize


Old description:

> Trying to generalize Greece shoreline + landmass, polygons fishnet'ed
> with cell size of 5000 m. Random polygons are not being generalized while
> they should be. If fishnet is made bigger (e.g 50 km cell size), then
> more non-generalized polygons are visible.
>
> Input is topologically error-free (no overlaps or gaps in input data).
> v.generalize output is as follows:
>
> v.generalize --overwrite input=c100_sea_dis_fish at Greece_UTM
> output=c100_sea_G120 method=douglas threshold=120
> WARNING: Vector map <c100_sea_G120> already exists and will be
> overwritten
> Copying features...
> Building topology for vector map <c100_sea_G120 at Greece_UTM>...
> Registering primitives...
> 105726 primitives registered
> 832947 vertices registered
> Building areas...
> 36099 areas built
> 2921 isles built
> Attaching islands...
> Attaching centroids...
> Number of nodes: 36449
> Number of primitives: 105726
> Number of points: 0
> Number of lines: 0
> Number of boundaries: 69627
> Number of centroids: 36099
> Number of areas: 36099
> Number of isles: 2921
> -----------------------------------------------------
> Generalization (douglas)...
> Using threshold: 120 meters
> WARNING: 1953 boundaries were not modified because modification would
> damage topology
> WARNING: 1951 lines/boundaries were not modified due to over-
> simplification
> -----------------------------------------------------
> Building topology for vector map <c100_sea_G120 at Greece_UTM>...
> Registering primitives...
> 105726 primitives registered
> 323843 vertices registered
> Building areas...
> 36099 areas built
> 2921 isles built
> Attaching islands...
> Attaching centroids...
> Number of nodes: 36449
> Number of primitives: 105726
> Number of points: 0
> Number of lines: 0
> Number of boundaries: 69627
> Number of centroids: 36099
> Number of areas: 36099
> Number of isles: 2921
> -----------------------------------------------------
> v.generalize complete. Number of vertices for selected features reduced
> from 796848 to 287744 (36% remaining)
> (Mon May 09 22:54:11 2016) Command finished (1 min 42 sec)

New description:

 Trying to generalize Greece shoreline + landmass, polygons fishnet'ed with
 cell size of 5000 m. Random polygons are not being generalized while they
 should be. If fishnet is made bigger (e.g 50 km cell size), then more non-
 generalized polygons are visible.

 Input is topologically error-free (no overlaps or gaps in input data).
 v.generalize output is as follows:


 {{{
 v.generalize --overwrite input=c100_sea_dis_fish at Greece_UTM
 output=c100_sea_G120 method=douglas threshold=120
 WARNING: Vector map <c100_sea_G120> already exists and will be overwritten
 Copying features...
 Building topology for vector map <c100_sea_G120 at Greece_UTM>...
 Registering primitives...
 105726 primitives registered
 832947 vertices registered
 Building areas...
 36099 areas built
 2921 isles built
 Attaching islands...
 Attaching centroids...
 Number of nodes: 36449
 Number of primitives: 105726
 Number of points: 0
 Number of lines: 0
 Number of boundaries: 69627
 Number of centroids: 36099
 Number of areas: 36099
 Number of isles: 2921
 -----------------------------------------------------
 Generalization (douglas)...
 Using threshold: 120 meters
 WARNING: 1953 boundaries were not modified because modification would
 damage topology
 WARNING: 1951 lines/boundaries were not modified due to over-
 simplification
 -----------------------------------------------------
 Building topology for vector map <c100_sea_G120 at Greece_UTM>...
 Registering primitives...
 105726 primitives registered
 323843 vertices registered
 Building areas...
 36099 areas built
 2921 isles built
 Attaching islands...
 Attaching centroids...
 Number of nodes: 36449
 Number of primitives: 105726
 Number of points: 0
 Number of lines: 0
 Number of boundaries: 69627
 Number of centroids: 36099
 Number of areas: 36099
 Number of isles: 2921
 -----------------------------------------------------
 v.generalize complete. Number of vertices for selected features reduced
 from 796848 to 287744 (36% remaining)
 (Mon May 09 22:54:11 2016) Command finished (1 min 42 sec)
 }}}

--

--
Ticket URL: <https://trac.osgeo.org/grass/ticket/3030#comment:5>
GRASS GIS <https://grass.osgeo.org>