Assessing the Contribution of Optical and SAR Data for Fractional Savannah Woody Vegetation Mapping

Savannahs are under threat from land degradation, not least due to woody vegetation encroachment. Here, we target the accurate high-resolution mapping of fractional woody vegetation cover in a South African savannah region, and assess the contribution of optical (Sentinel-2, S2), radar (Sentinel-1, S1) and ancillary data (bioclimatic and soils). Firstly, we created fractional woody cover (FCW) samples based on very high resolution satellite imagery and then we performed several regression experiments using different combinations of S1, S2 and auxiliary data temporal metrics for both dry and wet seasons. Highest regression rates of over 80% were documented for the all-data and all-season combined experiments, while S2 only models clearly outperformed the S1 ones. An interesting outcome from the results analysis was that appending ancillary bioclimatic and soils information to the S2-based experiments was proven to be more effective than the inclusion of S1 metrics.