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There is a set of isolines produced with v.net.iso.

It shows distances in meteres [400, 800, 1200, and everything further] from a certain point.

isochrones

My desired output is an Isochrone map. However, I do not know yet how to merge/aggregate isolines into polygons, where each isoline located exactly in a proper polygon with no overlaps etc. Better to say I want to draw an outline from the most far points of each isoline class. What is the best approach?

I have tried:

  1. extracting nodes from lines Vector > Geometry Tools > Extract nodes, filtering with a certain isoline class, and then Vector > Geometry Tools > Concave Hull.
  2. deploying QGIS plugin, namely QGIS-ConcaveHull-Plugin.

Both outputs are represented on the image below, numbered appropriately. But there is a problem, nodes from the higher-class isoline group overlap the lower-class isoline group. How can I handle this issue?

Output_results

I have seen these articles but nothing spectacular:

  • I think it is necessary to do some interpolations. In the first image, situations are observed in which the union of isochrone points does not produce polygons that only touches. Maybe considering the time as a height, TIN interpolating the points and then extracting contour lines can be a solution. – Gabriel De Luca Dec 12 '18 at 16:04
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Indeed, as was specified by @Gabriel De Luca, I required some interpolation as well as contour lines.

After I produced nodes from isolines, I have applied a QGIS-Contour-Plugin which worked much better than any previous solution.

References:

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