Effect of Row Orientation on Maize Green Area Index Retrieval from L-Band Synthetic Aperture Radar Imagery

Green area index (GAI) is a key indicator of crop status and is therefore fundamental for crop monitoring and yield forecasting. A common tool for its retrieval from synthetic aperture radar (SAR) data in an operational context is the inversion of the Water Cloud Model (WCM). This semi-empirical model, however, does not specifically account for the anisotropy induced by the maize rows. This study makes use of extensive ground-truth measurements and synchronous high-resolution fully-polarimetric airborne SAR data in L-band to show the impact of the maize row orientation relative to the SAR sensor beam on backscattering measurements and on GAI retrieval accuracy via the WCM. However, with respect to the latter, a larger data set with a broader range of SAR and in situ measurement values would be needed to support these results.