Greg,
OpenJump is a good topology/geometry fixing tool. Load your shapefile and do
Tools->Generate->Buffer, set the Buffer distance to 0 to clean up the polygon
vertices. I seem to recall it may have a problem preserving attributes when the
results are saved as a shapefile, but you may be able to just use the new .shp
portion with the old .dbf and .shx if the resulting geometry records are not
re-ordered.
Brent
Greg Ederer wrote:
Brent,
My Google search didn't turn up much of use (most of the results were
PostGIS-specific). Do you know of a tool that would tell me which
feature(s) have problems? Do you know of a tool that might be able to
fix these polygons?
Thanks!
Greg
Brent Fraser wrote:
Greg,
It means the GEOS topology library is having problems with geometry
of your input shapefile. Most likely related to duplicate vertices
(or near-duplicate) in a polygon. Do a Google for "side location
conflict". It would be nice if it spat out the FID of the offending
polygon...
Brent
Greg Ederer wrote:
Hi Brent,
Thanks for the example. Here's what I got:
Macintosh-4:starspan_tests gregederer$ starspan2 --progress --RID
none --vector
/Users/gregederer/servers/geoserver_data/data/shapefiles/Admin/afadmn2n.shp
--raster rfe_2006_04_pct.tif --stats results.txt avg
starspan: --out-prefix: ?
Type `starspan --help' for help
I then added a --out-prefix, like so:
Macintosh-4:starspan_tests gregederer$ starspan2 --progress --RID
none --vector
/Users/gregederer/servers/geoserver_data/data/shapefiles/Admin/afadmn2n.shp
--raster rfe_2006_04_pct.tif --stats results.txt avg --out-prefix bar
starspan: --out-type: ?
Type `starspan --help' for help
I then added '--out-type table' (I found in the source that valid
--out-types are: table, mini_raster_strip, mini_rasters, rasterization):
Macintosh-4:starspan_tests gregederer$ starspan2 --progress --RID
none --vector
/Users/gregederer/servers/geoserver_data/data/shapefiles/Admin/afadmn2n.shp
--raster rfe_2006_04_pct.tif --stats results.txt avg --out-prefix
bar --out-type table
Number of features: 550
starspan_csv: 1: Extracting from rfe_2006_04_pct.tif
0% terminate called after throwing an instance of
'geos::util::TopologyException'
what(): TopologyException: side location conflict -8.25 23.1536
Abort trap
Any idea what the TopologyException indicates?
Thanks!
Greg
Brent Fraser wrote:
Greg,
I've used StarSpan to do similar things; in my case I wanted "mode"
not "avg". Using v1.2.01 (I don't think I made major mods to the
source):
starspan2.exe --progress --RID none --vector boundaries.shp
--raster big.tif --stats results.txt mode
I edited the resulting results.txt text (csv) file and used GDAL's
ogr2ogr to do a join on the shapefile's DBF file based on the FID.
Brent Fraser
Greg Ederer wrote:
Hello all,
I'm a GDAL newbie. I have a shape file containing subnational
boundaries for Africa. I have a raster containing rainfall for
Africa. I need to pull out the spatial average of rainfall for
each of the subnational units.
I think that I might be able to pull this off using StarSpan. But,
the docs on the StarSpan wiki do not line up with the current
version of the program (the changelog mentions that certain command
line switches have been eliminated, and others added; but it
doesn't say what the new switches do, or how to use them). I am
digging through the StarSpan sources to try to figure out how to
use it.
Does anyone have any suggestions as to how I might get the needed
data using GDAL (with, or without StarSpan)?
Thanks!
Greg
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