A note on suitable viewing configuration for retrieval of forest understory reflectance from multi-angle remote sensing data

•Suitable angular configuration for accurate understory signal retrieval was identified.•New high angular resolution BRF data set along understory reflectances was used.•Evaluated over RAMI stands in Järvselja, Estonia

The contribution of understory vegetation especially to the reflectance of boreal forest landscapes cannot be ignored. In this letter, we identify the most suitable angular configuration for accurate retrieval of the understory signal. We use a new high angular resolution bidirectional reflectance factor data set with accompanying in situ measurements of understory reflectance in two RAdiation transfer Model Intercomparison (RAMI) mature stands in Järvselja, Estonia. Our results are pertinent towards the ultimate goal of achieving more reliable estimates of biophysical properties of the tree layer through separating the effect of understory on forest reflectance.