Full-Waveform Airborne Laser Scanning in Vegetation Studies—A Review of Point Cloud and Waveform Features for Tree Species Classification

In recent years, small-footprint full-waveform airborne laser scanning has become readily available and established for vegetation studies in the fields of forestry, agriculture and urban studies. Independent of the field of application and the derived final product, each study uses features to classify a target object and to assess its characteristics (e.g., tree species). These laser scanning features describe an observable characteristic of the returned laser signal (e.g., signal amplitude) or a quantity of an object (e.g., height-width ratio of the tree crown). In particular, studies dealing with tree species classification apply a variety of such features as input. However, an extensive overview, categorization and comparison of features from full-waveform airborne laser scanning and how they relate to specific tree species are still missing.
This review aims to fill this gap by identifying and evaluating frequently used and indicative point cloud and waveform features for tree species classification, which are derived from decomposed and partly radiometrically calibrated FWF ALS data. The focus here is on features, which are derived from data of previously detected/segmented single tree objects. Furthermore, factors that limit and influence the feature characteristics and the tree classification are discussed with respect to vegetation structure, data acquisition and processing.

Koenig, K., Höfle, B. (2016): Full-Waveform Airborne Laser Scanning in Vegetation Studies—A Review of Point Cloud and Waveform Features for Tree Species Classification. Forests,7(9).