Evaluating the capabilities of optical/TIR imaging sensing systems for quantifying soil water content

Surface Soil Moisture (SSM) is a key parameter of global energy and water cycle, and knowing its spatiotemporal variability is of key importance in an array of research topics and practical applications alike. Recent developments in Earth Observation (EO) have indicated that SSM can be retrieved from different regions of electromagnetic spectrum, and numerous approaches have been proposed to facilitate this. Herein, are reviewed the SSM retrieval techniques exploiting optical and thermal EO data, including synergistic techniques with other types of EO datasets. The challenges and limitations of EO in this respect are discussed, aiming at providing a roadmap on which future research should be directed. It is also apparent that to satisfy the requirements for SSM information for practical applications, effort should be towards the investigation of the synergistic use of EO systems in deriving SSM for water resources applications.