Comparing 3D Point Cloud Data from Laser Scanning and Digital Aerial Photogrammetry for Height Estimation of Small Trees and Other Vegetation in a Boreal–Alpine Ecotone

Changes in vegetation height the boreal-alpine ecotone are expected over coming decades due to climate change. Previous studies have shown that subtle changes (<0.2 m) can be estimated with great precision short time periods (~5 yrs) for small spatial units (~1 ha) utilizing bi-temporal airborne laser scanning (ALS) data, which is promising operation monitoring. However, ALS data may not always available multi-temporal analysis and other tree-dimensional (3D) such as those produced by digital aerial photogrammetry (DAP) using imagery acquired from aircrafts unmanned systems (UAS) add flexibility an operational monitoring program. There little existing evidence on performance of DAP estimation alpine pioneer trees ecotone. The current study assessed compared 3D extracted UAS prediction tree evaluated how size species affected predictive ability two sources. Further, estimates (trees vegetation) across a 12 ha area were compared. Major findings showed smaller regression model residuals when solitary tended smoothed out data. Surprisingly, overall (0.64 (0.76 m), respectively, differed significantly, despite use same ground observations calibration. It was concluded more in-depth understanding behavior algorithms scattered low needed even systematic effects particular technology compromise validity system since change processes encountered often slow.