Epsilon Open Archive

Abstract

The positions of objects – typically trees and other vegetation – in forest sample plots are often of interest, e.g., as ground truth data in forest surveys in which remote sensing techniques are used, and in environmental monitoring. Laser rangefinders and measurements of bearings using electronic compasses are often used for this purpose. However, use of laser rangefinders is problematic when sighting conditions are poor. In contrast, since ultrasound passes through vegetation and around stems it also enables measurements in dense forest. Thus, the novel ultrasound-based Haglöf PosTex ® instrument provides quick measurements of positions of objects in sample plots even in dense forest with poor sighting conditions. The design of the instrument also enables measurement of positions at the same time as data are recorded for the objects, such as the diameters of trees. The instrument – developed in collaboration between the Swedish University of Agricultural Sciences (SLU) and Haglöf Sweden AB – has been used in various applications, e.g. in forest remote-sensing projects and mapping mountain vegetation, trees in burnt forests and seedlings for monitoring forest regeneration.