Not that you're wrong, but when faced with a similar problem, I got a lot of mileage out of telling an intern to try a network trained detect the boundary betwe

Not that you're wrong, but when faced with a similar problem, I got a lot of mileage out of telling an intern to try a network trained detect the boundary between the ground-based-potentially-tall features and not the feature (e.g., background and sky), and measuring the height from a low camera. Voila, tall areas and not-tall areas.