Single angle, dual angle and multi-temporal viewing: assessing through modelling the implications for forest structure variable extraction

摘要

A three-dimensional forest model and a geometric ray-tracing model were used to investigate the implications of forest bi-directional reflectance on the use of dual view or multi-temporal imagery for forest variable extraction. Previous studies have shown links between forest structure, shadow patterns and bi-directional reflectances. The emphasis in these studies was on the relationship between the shape of the hotspot and the full principal plane reflectance curve with variables such as canopy cover, crown size and crown shape. In this work these relationships are analysed to determine if they allow for the discrimination of canopy cover and crown shape from dual view or multi-temporal imagery. The analysis shows that a well chosen single viewing angle may give discrimination results similar to those obtained through use of a combination of two viewing angles. The addition of reflectance data recorded when the Sun is at a larger solar zenith angle is likely to have little impact on discrimination results for most viewing angles.