While satellites cannot directly see tree trunks due to the cover of the canopy, Rezatec is still able to infer the diameter of the trunks (DBH) through the application of specific variables derived from both multi-spectral and radar data. Specifically, indices are derived which are related to the vigour of the forest canopy, the shadowing visible from variable canopy height and structure, and backscatter and phase information which are sensitive to the tree structural components (trunks and branches). These are directly intersected with ground-based plot information and inputted into a machine learning algorithm, which can establish a relationship between what is seen in the satellite data and the ground plot level, in order to train and calibrate the model, for application across the whole satellite image extent.