Working principle of light curtain arrays (LC) and shoot silhouette extraction. (A) LC are scanning a row of plants. The light barriers, arranged on the two vertical poles, emit and receive light beams (examples of which are shown by the red horizontal lines). The blue arrow depicts the movement of LC during the scan. Pot height is 13 cm. (B) Plant profile of a row of rapeseed plants. The green colour indicates the segmentation step during which the plant silhouette is separated from the pot silhouette. (C–E) Estimation of maximum height (base to the highest leaf tip; depicted by the vertical line) from the silhouette of tomato plants differing in size.