While measuring an angle in QGIS using measure angle tool, it is showing as 0 to 180 degree for clockwise direction and -1 to -179 for anticlockwise. What I need is, interior angle between vertices of irregular polygon. How should I calculate in QGIS?

  • Do you want to populate an attribute with the value or use the value for further processing? GUI or python based solution? There a several recent Q&A on calculation of angles given 3 points.
    – Detlev
    Feb 3, 2016 at 16:48
  • Yes, I wanna populate using some tools in QGIS.
    – pauline
    Feb 4, 2016 at 6:25

1 Answer 1


http://anitagraser.com/2015/05/24/how-to-create-illuminated-contours-tanaka-style/ contains some way to do this:

First you split the lines/polygons into their atomic segments with v.split.

Then you calculate the azimuth for each of those features, see eg How to add Direction and Distance to attribute table? for the formula.

I don't know a better way but maybe there is.

  • 1
    I have tried to find angle in this way. But what am getting is only true bearing (i.e., an angle of line from true north). I wanna know interior angles of polygon.
    – pauline
    Feb 4, 2016 at 6:28
  • Oh, I misread that, sorry! That sounds like a job for python scripting. Out of my league at the moment. Feb 4, 2016 at 10:15

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