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I have been trying to dissolve a shapefile with more than 38000 rows. I used query as follows

ogr2ogr -f "ESRI Shapefile" dissolved.shp Barangays.shp -dialect sqlite -sql "select ST_union(Geometry),* from input  GROUP BY concated"

It gave me error that geometry is invalid because of self-intersecting polygons.

I found out there are 86 features which have invalid geometries using QGIS. I tried Make Valid tool as suggested in this question. But this is also not working, giving error undefined symbol, which I couldn't understand. So I decided to validate using ogr2ogr and after searching through google I tried this query

ogr2ogr -f "ESRI Shapefile" valid_barangays.shp Barangays.shp -dialect sqlite -sql "select Geometry.MakeValid(),* from Barangays"

It gave me this error

ERROR 1: In ExecuteSQL(): sqlite3_prepare(select Geometry.MakeValid(),* from Barangays):
  near "(": syntax error

How can I solve this problem?

I also imported my shapefile using ogr2ogr in phpmyadmin mysql. It saved geomtry column as [geometry some_number B]. I am not able to query. I always give error function not exist.

  • What about using QGIS ? – Shiko Jul 30 '16 at 15:39
  • @shiko As an automated process? – Fábio Dias May 1 '18 at 18:41
  • @FábioDias in QGIS you can do both, either manually or programmatically using python (Inside QGIS as a plugin or as a standalone application). check this gis.stackexchange.com/questions/159699/… – Shiko May 1 '18 at 20:41
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Based on the post: https://www.gaia-gis.it/fossil/libspatialite/wiki?name=liblwgeom-4.0

SpatiaLite should support the ST_MakeValid argument. So this should work. Without your data it is hard to test. But it should work if you specify your geometry within the ST_MakeValid statement

So if you run:

ogr2ogr -f "ESRI Shapefile" valid_barangays.shp Barangays.shp -dialect sqlite -sql "select ST_MakeValid(geometry) as geometry, * from Barangays"

If that does not work, you will likely have to specify each other column instead of selecting *.

  • I tried query as suggested by you but I got error no such function: ST_MakeValid – AMahajan Aug 1 '16 at 4:47
  • That means that your version of GDAL is compiled either without SpatiaLite at all or with so old SpatiaLite version that ST_MakeValid was not implemented yet. – user30184 Aug 1 '16 at 18:37

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