[GRASS-user] v.in.ogr suddenly slow?

Nikos Alexandris nikos.alexandris at felis.uni-freiburg.de
Mon Jul 26 18:26:20 EDT 2010


Giovanni Manghi wrote:
> > > I just made a fresh install on my pc, Ubuntu 10.04 and GRASS 6.4 rc6
> > > from the Ubuntugis repository.
> > > It seems to me that v.in.ogr is quite slower if compared with my old
> > > installation (6.4 rc5 on Ubuntu 9.04)
> > > 
> > > for example this
> > > http://thematicmapping.org/downloads/TM_WORLD_BORDERS-0.3.zip
> > > takes nearly 5 minutes and before it took much less.
 
Markus Metz wrote:
> > Here it takes nearly 30 minutes with grass64, all versions, RC5 is not
> > faster than RC6 or current svn. This vector is extremely dirty,
> > boundaries of adjacent polygons don't match, resulting in about 2300
> > overlapping areas and about 2400 spurious areas (gaps between adjacent
> > polygons) equaling about 4700 erroneous areas for only 3775 input
> > polygons. Import time was reduced to 4 minutes when snapping
> > boundaries during import. With snapping during import and grass7, it's
> > down to 1 min 46 sec and the result is topologically clean.

> > I would rather use another world boundary layer, e.g. UN FGGD from FAO
> > geonetwork.

Nikos Alexandris wrote:

in grass64 (without snapping): 
> time v.in.ogr dsn=TM_WORLD_BORDERS-0.3.shp out=tm_world_borders_03

> --%<---
> 3775 input polygons
> Total area: 1.473113e+14 (8484 areas)
> Overlapping area: 3.402229e+09 (2294 areas)
> Area without category: 3.994093e+11 (2292 areas)

> real    55m10.964s
> user    54m50.060s
> sys     0m8.040s
> -->%---
> 
> :-O

in grass64 with snapping=0.1:
time v.in.ogr dsn=TM_WORLD_BORDERS-0.3.shp out=tm_world_borders_03_snapped_01 
snap=0.1

--%<---
3775 input polygons
Total area: 1.480245e+14 (4647 areas)
Overlapping area: 0.000000e+00 (0 areas)
Area without category: 1.139301e+12 (1628 areas)

real    0m52.400s
user    0m49.730s
sys     0m1.250s
-->%---

in grass70 with snapping=0.1:
time v.in.ogr dsn=TM_WORLD_BORDERS-0.3.shp 
out=tm_world_borders_03_grass70_snapped_01 snap=0.1

--%<---
3775 input polygons
Total area: 1.37653E+14 (4375 areas)
Overlapping area: 0 (0 areas)
Area without category: 1.11988E+12 (1475 areas)

real    0m53.130s
user    0m51.160s
sys     0m1.240s
-->%---

Nikos


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