I want to select numerous polygons out of a polygon layer and create an outer line surrounding only selected features. All polygons are part of the same layer.

For example, I want to have an outer line as a new layer around the selected features in photo.

enter image description here

  • 2
    one way: SAVE selected as new shapefile => UNION new shapefile ==> POLYGON TO LINES union shapefile....tools under VECTOR pull down menu in QGIS.
    – ZrSiO4
    Nov 11 '17 at 18:38
  • Create the convex or concave hull around selected polygons. The difference between both is how close the hull is to the polygon boundaries. Use QGIS algorithm or concave hull plugin to get the hull.
    – Detlev
    Nov 12 '17 at 7:58

Vector -> geoprocessing tools -> dissolve

Then style the resulting layer to be a simple line.


you can do it also "on the fly" with the geometry generator:

if(is_selected(), segments_to_lines( buffer($geometry,200)), NULL)

enter image description here

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