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I have a KML style file provided of burnt areas from significant wildfires. As the fires continue, seven of the polygons out of about 30 appear to be corrupted with duplicate nodes and overlapping areas from repetitive updating.

I have been using grass v.clean and validate geometry which has been successful however that has stopped working on a windows 3.4.4 install and I am at a loss of how to import this successfully.

Can anyone recommend a way to fix the file within QGIS please?

The file is available https://drive.google.com/file/d/1mRCU5fLphDmDAt1hNlDA-WPgF3I6XW1E/view?usp=sharing

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(Sorry I have to answer instead of comment as not at 50 rep yet!) I downloaded your file and opened it in QGIS 3.4.4 and can't see any overlap or corruption... See my screenshot below - is this what yours looks like? Could you indicate on a screenshot which areas you are concerned about?

Screenshot of your burnt_stack.kml file

  • Hi @BSiggery - Thanks for your help. Try importing this into geojson.io and see the difference in the south west corner. I took a snapshot here gist.github.com/EwenH/03a49eef16b4c40b5473f23784de3842 to show the large Huon Valley fire. Try running a vector -> Geometry tools -> check validity in QGIS and you should see 7 errored polygon objects. I appreciate you looking at this. – Ewen Feb 6 at 4:46
  • Actually the vector -> Geometry tools -> check validity fails to find anything incorrect. Sorry for misleading you. – Ewen Feb 6 at 4:53
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    Hi @Ewen - no problem. I've tried importing onto geojson.io as you said but not quite sure what you mean in the SW corner? But there appear to be two large polygons present that aren't in the QGIS display of the file (one just NE of Lake Gordon and one just W of Geeveston) – BSiggery Feb 6 at 7:00
  • Yes @siggery, the 6 or 7 errored polygons are represented below in red and sadly it looks like the grass v.clean is no longer capable to cope with it. The errored polygons are availale at drive.google.com/file/d/19-g9N0BLpONpOJ_fjTLB0puzSJU4LzvK/… . Imgur – Ewen Feb 6 at 11:50
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Thank you for all your help however I believe this file was far too corrupted to fix. The process that has been working for me for the vast majority has been:

  1. Download the damaged KML file
  2. Upload to GeoJson.io and then save as a Shapefile which appears to improve it a little
  3. Upload the Shapefile to QGIS (and Grass)
  4. Run the check Validity that will give you two layers of valid and invalid polygons
  5. On the invalid layer run the grass plugin v.clean that should repair any issues
  6. Merge the valid and cleaned layers using the merge layers process.

Hope this helps

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