ogr2ogr: running with simplify flag is creating topology issues.

[kashmir772]

Running ogr2ogr with the simplify flag is creating topology issues. I am seeing overlapping polygons and gaps in the output shapefile. I am running v1.9.1 on a 64 bit build.

Here is the command that I am running. ogr2ogr -overwrite -progress -f "ESRI Shapefile" "input.shp" "output.shp" -nlt POLYGON -simplify 0.00002

[kashmir772]

screen capture of the topology issues.

[Jukka Rahkonen]

I believe that ogr2ogr is working per feature basis and when it simplifies features it does not care about other features. You must use other tools for simplifying features so that layer topology is preserved. Notice that for example PostGIS ST_SimplifyPreserveTopology is not such a tool. It preserves the topology of features but not the whole layer.

[Jukka Rahkonen]

I just found a how-to for avoiding gaps and overlaps ​http://trac.osgeo.org/postgis/wiki/UsersWikiSimplifyPreserveTopology

[Even Rouault]

Jukka is right. I've improved the documentation of -simplify in r25332. I'm thus closing this ticket, since layer topology preservation would be a very different beast, not easily doable with the way OGR works