[GRASS-dev] v.in.ogr: islands not recognized

Wed Feb 11 12:34:19 PST 2015

HI,

I tried to import the NUTS3 map(s) from EU which leads to some obscur
warnings (see below). While most can be solved with a "mild" snapping,
still four islands are reported as an error. They are Andorra, etc and
apparently really valid. The error message though suggests that the
import was not successful. Could this be fixed?

# Download NUTS3 2010, 3M and 10M
# http://ec.europa.eu/eurostat/web/gisco/geodata/reference-data/administrative-units-statistical-units

# create new location from SHP file
grass70 -c NUTS_BN_03M_2010.shp ~/grassdata/eu_etrs89
g.proj -w

# import NUTS3 polygons (performs topology check)
v.in.ogr input=NUTS_RG_03M_2010.shp output=NUTS_RG_03M_00
...
Cleaning polygons
-----------------------------------------------------
Breaking polygons...
...
-----------------------------------------------------
Building areas...
WARNING: Area of size = 0.0 ignored
WARNING: Area of size = 0.0 ignored
WARNING: Area of size = 0.0 ignored
WARNING: Area of size = 0.0 ignored
...
WARNING: Area of size = 0.0 ignored
WARNING: Area of size = 0.0 ignored
 100%
16926 areas built
1325 isles built
Number of nodes: 113763
Number of primitives: 355557
Number of points: 0
Number of lines: 0
Number of boundaries: 355557
Number of centroids: 0
Number of areas: 16926
Number of isles: 1325
WARNING: Number of incorrect boundaries: 157
-----------------------------------------------------
Removing bridges...
 100%
-----------------------------------------------------
Registering primitives...
48083 primitives registered
343316 vertices registered
Building areas...
WARNING: Area of size = 0.0 ignored
WARNING: Area of size = 0.0 ignored
WARNING: Area of size = 0.0 ignored
...
WARNING: Area of size = 0.0 ignored
WARNING: Area of size = 0.0 ignored
 100%
16925 areas built
1335 isles built
Attaching islands...
 100%
Number of nodes: 32451
Number of primitives: 48083
Number of points: 0
Number of lines: 0
Number of boundaries: 48083
Number of centroids: 0
Number of areas: 16925
Number of isles: 1335
WARNING: Number of incorrect boundaries: 36
WARNING: Vect_get_point_in_poly_isl(): collapsed area
WARNING: Unable to calculate area centroid
WARNING: Vect_get_point_in_poly_isl(): collapsed area
WARNING: Unable to calculate area centroid
WARNING: Vect_get_point_in_poly_isl(): collapsed area
WARNING: Unable to calculate area centroid
WARNING: Vect_get_point_in_poly_isl(): collapsed area
...
WARNING: Unable to calculate area centroid
WARNING: Vect_get_point_in_poly_isl(): collapsed area
WARNING: Unable to calculate area centroid
-----------------------------------------------------
Finding centroids for OGR layer <NUTS_RG_03M_2010>...
 100%
-----------------------------------------------------
Writing centroids...
 100%
WARNING: 9912 areas represent more (overlapping) features, because polygons
         overlap in input layer(s). Such areas are linked to more than 1
         row in attribute table. The number of features for those areas is
         stored as category in layer 2
-----------------------------------------------------
7007 input polygons
Total area: 5.75852E+12 (16925 areas)
Overlapping area: 5.74784E+12 (9912 areas)
Area without category: 5.32057E+08 (19 areas)
-----------------------------------------------------
Copying features...
 100%
Building topology for vector map <NUTS_RG_03M_2010 at PERMANENT>...
Registering primitives...
59076 primitives registered
354309 vertices registered
Building areas...
WARNING: Area of size = 0.0 ignored
WARNING: Area of size = 0.0 ignored
WARNING: Area of size = 0.0 ignored
...
WARNING: Area of size = 0.0 ignored
WARNING: Area of size = 0.0 ignored
 100%
16925 areas built
1335 isles built
Attaching islands...
 100%
Attaching centroids...
 100%
Number of nodes: 32451
Number of primitives: 59076
Number of points: 0
Number of lines: 0
Number of boundaries: 48083
Number of centroids: 10993
Number of areas: 16925
Number of isles: 1335
WARNING: Number of incorrect boundaries: 36
-----------------------------------------------------
WARNING: Errors were encountered during the import
Estimated range of snapping threshold: [1e-13, 1e-05]
Try to import again, snapping with at least 1e-13: 'snap=1e-13'

# --> the "WARNING: Vect_get_point_in_poly_isl(): collapsed area"
looks like a debug message to an average user.

# NEW ATTEMPT WITH SNAPPING
GRASS 7.0.0svn (eu_etrs89): > v.in.ogr input=NUTS_RG_03M_2010.shp
output=NUTS_RG_03M_2010 snap=1e-8 --o
...
Writing centroids...
 100%
WARNING: 2748 areas represent more (overlapping) features, because polygons
         overlap in input layer(s). Such areas are linked to more than 1
         row in attribute table. The number of features for those areas is
         stored as category in layer 2
-----------------------------------------------------
7007 input polygons
Total area: 5.75852E+12 (2759 areas)
Overlapping area: 5.74784E+12 (2748 areas)
Area without category: 5.32057E+08 (4 areas)
-----------------------------------------------------
Copying features...
 100%
Building topology for vector map <NUTS_RG_03M_2010 at PERMANENT>...
Registering primitives...
8419 primitives registered
217332 vertices registered
Building areas...
 100%
2759 areas built
1315 isles built
Attaching islands...
 100%
Attaching centroids...
 100%
Number of nodes: 4220
Number of primitives: 8419
Number of points: 0
Number of lines: 0
Number of boundaries: 5664
Number of centroids: 2755
Number of areas: 2759
Number of isles: 1315
-----------------------------------------------------
WARNING: Errors were encountered during the import
Estimated range of snapping threshold: [1e-13, 1e-05]
Try to import again, snapping with 1e-07: 'snap=1e-07'

v.build NUTS_RG_03M_2010 error=NUTS_RG_03M_2010_errors
...
Number of nodes: 4
Number of primitives: 4
Number of points: 0
Number of lines: 0
Number of boundaries: 4
Number of centroids: 0
Number of areas: 4
Number of isles: 4

The "WARNING: Errors were encountered during the import" is scary
while it seems to be valid islands (Andorra, San Marino, two islands
near Rome).

thanks
Markus