However, terrestrial images reveal unfavourable viewing angles at shallow surroundings, i.e. gully beds as well as areas above the gully edges. High-precision gully measurement for larger areas and long-term assessment Wortmannin best possible if data of both sources are fused. While UAV images allow area-based terrain monitoring, terrestrial images are suitable for small-scale 3D reconstruction (e.g. gully wall morphology). Furthermore, terrestrial data acquisition can be performed fast as well as flexible permitting spontaneous implementation during ongoing field campaigns, if on-site findings reveal complex relief conditions for sufficient UAV measurement.