Hello Hy,
I've attached a screenshot taken with an older version of kstars that shows how the horizon map actually should look. In the area of the overhang it is painting things twice it seems. But your further text explains why:
This of course is completely different from how it worked before. You cannot mark general obstructions anymore, as they often do not follow this linear approach and have overhangs. So I think this constraint brings a substantial reduction in usefulness of the horizon map sad.png

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