The potential of sentinel-1 InSAR coherence for grasslands monitoring in Eastern Cape, South Africa

This study evaluates the potential of the repeat-pass synthetic aperture radar interferometry (InSAR) coherence for grasslands monitoring in Eastern Cape Province, in South Africa. We used 12 pairs of InSAR data in the Interferometric Wide swath mode (IW), in VV-polarization (with different spatial baseline B? and different temporal repeat intervals between the subsequent acquisitions), covering grasslands in the study area during two growing seasons; drought season (2015/2016) and non-drought season (2016/2017). Results show that non drought season has higher variability in the coherence between the different regions of interest (ROIs) than the drought season and higher variability in the backscattering coefficient. Based on our results, we conclude that InSAR-based data have shown potential for grasslands monitoring, and the regularity of Sentinel-1 data is well suited for InSAR applications. However, the potential to separate grasslands from other vegetation categories appears to be limited with longer temporal baselines of 12 days intervals using only Sentinel-1A data. This potential will be improved with the 6 days intervals that will become available with Sentinel-1B in the study area.

Automated summary

This study found that InSAR coherence can be used for grasslands monitoring, with higher variability in coherence during non-drought season and higher backscattering coefficient. The regularity of Sentinel-1 data is beneficial for InSAR applications, and the potential will be improved with the availability of Sentinel-1B data.