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I performed an object-based image analysis using ENVI EX, and each of the classified features were exported as a shapefile. I transferred those shapefiles into ArcMap 10, and tried to intersect them with other shapefiles of the same area that were acquired from GeoBase.

When I try to run the intersect tool, I get an error message stating that the topology of the shapefiles extracted from ENVI EX are invalid. I tried to turn on the topology tool to repair the topology of those shapefiles, but the buttons are greyed out, and I can't seem to click on them. The topology tool does not work for any of the shapefiles that I have.

Any solutions? How I can I fix the topology and run the intersect?

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up vote 5 down vote accepted

I encountered similar issues as well with polygons. Maybe you have a similar problem.

Error Message by ESRI: "Invalid Topology (Incomplete Void Poly)"

Actual Error: "Invalid Geometry"

Fix: Run "Repair Geometry" (changes data in-place, be careful, there is no undo)

What happens is that the error reported is not using the ESRI terminology of Topology/Geometry and confuses everyone. In my case, while the error was talking about topologies, there were no topologies defined (topology as in an ESRI topology). But when I checked the geometry (using the "Check Geometry" tool) I found out that my geometry (as in an ESRI geometry) there were errors.

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This did the trick. Thanks for your help! – mapr Sep 21 '12 at 17:50

Just in case ArcMap doesn't work, you might want to try GRASS' v.clean tool. You can install GRASS with QGIS. After installing:

Cleaning of topology of a SHAPE file using the GRASS Toolbox

  1. Load the SHAPE file into QGIS
  2. Use existing GRASS mapset (or create a new one) with matching projection settings
  3. Now you have to transfer the SHAPE file from QGIS to GRASS using Toolbox -> File management -> Import into GRASS -> Import vector into GRASS -> Import vector into GRASS from QGIS view ( Some topological problems may be reported depending on the quality of your SHAPE file.
  4. These topological problems we can fix now in GRASS via toolbox using the topology tools: Vector -> Develop map -> Toolset for cleaning topology of vector map -> v.clean.break. Define a threshold in map units (for example 0.5 [m] or likewise). Analyse the printed report, probably the threshold needs to be adjusted or a different topology cleanup tool to be used. Click then on view output to show the result as map.
  5. Export the cleaned map to SHAPE format: File management -> Export from GRASS -> Export vector from GRASS -> v.out.ogr
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