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I am trying to create several buffer layers around a simple box shaped polygon based on distance in km. CRS is World Mercator(EPSG:54004) and was reprojected beforehand. I am getting buffer polygons with rounded corners (green is box, pink is buffer) but need straight / sharp corners:

green is box, pink is buffer

Changing the number of segments doesn't help. What else can I try?

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You can use GRASS buffer distance tool: v.buffer.distance tool, which gives you the option to Make outside Corner straight, as you can see below:

enter image description here

Here is the input (Dark Green) and buffer (Light Green):

enter image description here

  • Thank you @ahmadhanb that looks like the tool I need. However, I just tried and cannot get it to work, the Error Message is: Vector Map not Found. Might this be due to the projected CRS? – Kristina Jul 12 '17 at 11:46
  • @Kristina I am not sure about the error message that you received of whether it is related to CRS or not, but in the above example I used UTM CRS which uses meter unit. If the CRS that you are using is in degree, you need to change the CRS to a suitable one that uses meter unit. – ahmadhanb Jul 12 '17 at 11:52
  • I'm using projected World Mercator so the unit should be in m. I just tried with a non-projected (WGS84) and the buffer I get with the parameters you have entered is circular. Can you explain what the 'Maximum distance between theoretical arc and polygon segments as multiple of buffer' field does? Thank you! – Kristina Jul 12 '17 at 11:54
  • The ''Maximum distance between theoretical arc and polygon segments as multiple of buffer' does not have influence on the output even you delete value and keep it blank it will give a buffer with square cap. I set the 10000 as a maximum buffer distance. But even if you did not put anything in this field it should give you the correct output. Although the help did not mention anything about it, I will paste it here for your reference: grass.osgeo.org/grass73/manuals/v.buffer.html – ahmadhanb Jul 12 '17 at 12:06
  • Try to load your data in a new QGIS project and run the tool. It may solve the problem. – ahmadhanb Jul 12 '17 at 12:07

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