Drawing boundary of set of points using QGIS?

I assume that you know which points belong to the "left" or "right", because otherwise there are many solutions. If so, you could use the delaunay triangulation followed with a selection of the "central" triangles. With this method, no need to have the points in a specific order. All you need to consider is the fact that the triangles you need must touch at least one point from each side.

open attribute table > select by expression > "code" = 1

vector > research tool > select by location (new selection, intersect)

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open attribute table > invert the selection of the points (ctrl + R)

vector > research tool > select by location (remove from selection, disjoint)

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vector > geoprocessing tool > dissolve

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I have the same result as @radouxju.

Operations :

  1. Select 1 polyline [select on click]
  2. Update your polyline table and affect a number to each feature [field calculator]
  3. Select the points which intersects one polyline [spatial query tool]
  4. Update the selected points by the polyline value previously affected [field calculator]

  5. Keep the selection point and select the delaunay triangles which intersects these selected points [spatial query tool]
    enter image description here
    enter image description here

  6. Invert the point selection or select the points which intersect the other polyline [selection by expression] or [invert selection]

  7. Remove from the current selection the delaunay triangles which are disjoint with the other points [spatial query tool]
    enter image description here
    enter image description here

  8. Merge the features by selection [geoprocessing tool > dissolve]
    enter image description here
    enter image description here


IMPORTANT : You MUST have the polylines to obtain this result !

Tags:

Qgis

Polyline Creation

Qgis Processing

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