Three-dimensional profile classification of standing trees using a stereophotogrammetric method

The three-dimensional (3D) stem profiles of 71 Norway spruce [Picea abies (L.) Karst.] standing trees were assessed visually and by a stereophotogrammetric method. Using 3D profiles of trunks, a series of indicators which characterize the form in the longitudinal direction was developed. Based on these form indicators, a standing tree form classification scheme was proposed. The scheme contains four classes: severe basal sweep, mild basal sweep, straight and arched trees. The results showed that the standing tree forms could be successfully classified using an appropriate indicator. The most important descriptor in determining differences between standing tree forms was the index of slope asymmetry. Comparison of the two assessment methods showed that the visual method was not effective. The study also showed that the slope of the first 12 m of the tree trunk is highly correlated with the slope of the first 4 m of trunk (r(2) = 0.84).