rOPTRAM - Derive Soil Moisture Using the OPTRAM Algorithm

The OPtical TRapezoid Model (OPTRAM) derives soil moisture based on the linear relation between a vegetation index and Land Surface Temperature (LST). The Short Wave Infra-red (SWIR) band is used as a proxy for LST. See: Sadeghi, M. et al., 2017. <https://doi.org/10.1016/j.rse.2017.05.041> .