FAQ n.116465

Your maximum flight height is generally 120 m from the earth’s surface. Please check whether the National Aviation Authority imposes a geographical zone with a lower limit in the area where you fly. If you need to fly over an obstacle taller than 120 m, you are allowed to fly up to 15 metres above the height of the obstacle, but only if there is an explicit request from the owner of the obstacle (e.g. a contract with the owner to perform an inspection). In such a case, you may fly within a horizontal distance of 50 metres from the obstacle. 

When you are operating in hilly environments, the height of the drone above the surface of the earth should be within the grey zone in the picture below: you need to keep the drone within 120 m of the closest point of the terrain. This means that there may be conditions such as on top of a hill where even if you keep your drone 120 m from the side of the hill, you are actually flying at a distance higher than 120 m above the bottom of the valley. So as long as you keep your drone within 120 m of the shoulder of the hill (as in the grey area in the picture below), your flight is legal.

Regulatory reference: UAS.OPEN.010 (2) (3) Annex Part A of EU Regulation 2019/947