I have 5 groups of 4 lines, all the lines in all the data sets are centred around the same point. I need to algorithmically combine these lines into one line that is only the furthest from the point. They overlap in multiple locations.


Source: https://drive.google.com/file/d/19_dpKZUIaNpnfxk7KZF3AJJULXrURdum/view?usp=sharing

These lines came from points which came from a CSV file, they were combined using the 'Pointstopath' function in QGIS.

I am very new to GIS in general but have a working knowledge of python. My first thought was to load the CSV files into python pandas and calculate the distance from each point and only keep the furthermost. However, this won't work as the files have different "resolutions".

Am I missing something obvious?

  • Please use the image tool within the SE framework. Images in third party sites are less likely to be followed, and much more likely to fail over time.
    – Vince
    Commented Aug 21, 2019 at 2:13
  • Thanks Vince, Unfortunately I couldn't as Imgur isn't available though my work's firewall.
    – Noah
    Commented Aug 21, 2019 at 4:49

1 Answer 1


If I understand this correctly, you need an outer boundary of the combination of all geometries in the layer. For that you can try this:

  1. convert all lines to polygons (Lines to polygons algorithm)
  2. union all polygons (Union algorithm)
  3. dissolve unioned polygons (Dissolve algorithm)

These steps should produce polygon which represents the outer boundary (or cumulative area) of all geometries.

  • Thank you, Exactly the solution I was looking for!
    – Noah
    Commented Aug 21, 2019 at 6:10
  • 1
    If you want to do that in pure Python, take a look at the Shapely library...
    – DavidP
    Commented Aug 21, 2019 at 6:20

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.