[GRASS-user] Number of centroids outside area: difficulty with cleaning

[RichardC]

I tried with a length of 1000 (which I guess should represent 1000m given the
projection is Lambert Azimuthal Equal Area) and the with a length of 500 as
shown below in more detail. The file I'm working with quite a large
shapefile (50MB).

Topology of original imported shapefile (Lambert Azimuthal Equal Area):
Attaching centroids...
Number of nodes: 33748
Number of primitives: 44546
Number of points: 0
Number of lines: 0
Number of boundaries: 30931
Number of centroids: 13615
Number of areas: 13615
Number of isles: 2817


Topology after v.split length=500
Attaching centroids...
Number of nodes: 3274443
Number of primitives: 3285241
Number of points: 0
Number of lines: 0
Number of boundaries: 3271626
Number of centroids: 13615
Number of areas: 1218
Number of isles: 0
Number of incorrect boundaries: 3271358
Number of centroids outside area: 12397

Topology after v.build.polylines
v.build.polylines input=as_bas_shp_vsplit500 at PERMANENT
output=as_bas_shp_vsplit500_vpoly
Attaching centroids...
Number of nodes: 33748
Number of primitives: 44546
Number of points: 0
Number of lines: 0
Number of boundaries: 30931
Number of centroids: 13615
Number of areas: 13615
Number of isles: 2817

Topology after importing into CRS WGS84 (lat long)
Attaching centroids...
Number of nodes: 33748
Number of primitives: 44546
Number of points: 0
Number of lines: 0
Number of boundaries: 30931
Number of centroids: 13615
Number of areas: 13601
Number of isles: 2828
*Number of incorrect boundaries: 26
Number of centroids outside area: 14*

If the length=1000 for v.split (then followed by v.build.polylines), then
the toplogy after importing into WGS84:
Attaching centroids...
Number of nodes: 33748
Number of primitives: 44546
Number of points: 0
Number of lines: 0
Number of boundaries: 30931
Number of centroids: 13615
Number of areas: 13602
Number of isles: 2828
Number of centroids outside area: 13
*Number of duplicate centroids: 109
Number of areas without centroid: 109*



--
View this message in context: http://osgeo-org.1560.x6.nabble.com/Number-of-centroids-outside-area-difficulty-with-cleaning-tp5046717p5046819.html
Sent from the Grass - Users mailing list archive at Nabble.com.