Convex hull that follows irregular points distribution

Using PostGIS ST_ConcaveHullyou may get the envelope to follow more closely the irregular shape, as stated in your post;

ogr2ogr -f GPKG concave.gpkg points.gpkg -nln concave_layer -dialect sqlite -sql "select 'a', ST_ConcaveHull(st_collect(geometry),0.9) from points_layer"

A few remarks:

1. You are using a point layer, so if you call st_concave_hull directly on your geometry it will try to make a polygon for each point, which will return empty geometries, so first we call st_collect(geometry);

2. The layer name in the sql query can be retrieved with ogrinfo file.gpkg, it is often not the same name as the layer.

3. For some functions to work in ogr2ogr you need a non-geometry field, that's why I passed 'a' to the command, here it works without it.

4. It is an expensive algorithm, to test it you may use a subset of your layer passing where fid < 1000 to the query