I would like to calculate the angles of my vector polylines (and later use this value to colour them, so all the similarly angled lines (i.e. that have the same orientation / have the same colours). As it's microscopic data (vectorised in Inkscape on a scan, and imported in QGIS using dxf), there is no CRS projection.


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This sounds similar to Tanaka Contours which are contours that are shaded similarly to to a hillshade, e.g. contours on the north-west of a mountain are lighter in colour than contours on the south-east of a mountain.

I did this myself by following Klas Karlsson's tutorial here: https://www.youtube.com/watch?v=ORvdWyGCUVQ

It's trying to achieve a similar result just for a different application. The idea is the same however, calculate the orientation of the by calculating the azimuth from start to end and then colour the lines by the resulting angle.

  • Could you please include instructions how to calculate the azimuth, as well as how to colour the lines later on? Though it might be in the video, links are subject to change, and I personally very much prefer written instructions over spoken ones in a video. Thank you!
    – Erik
    Aug 10, 2021 at 15:39

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