Detecting Growth of Paddy in Punjab Using SAR Sentinel-1 and Sentinel-2 Data

Paddy is a major Kharif crop in Indian Punjab. One of the most critical parameters for ensuring a good harvest and production of paddy is to monitor paddy growth. Satellite data, including optical and radar data can be used to monitor seasonal crops like paddy, which can span a broad region and have a high observation frequency. Cloudy days are common during paddy growing season, making it difficult to obtain cloud-free data. Using radar data, which can penetrate through the clouds, can solve the problem either as a complement to optical data or by itself, to monitor the growth phase of paddy. A study was conducted to detect the three phenological stages (planting, maximum tillering, and harvest) of paddy using VH and VV polarization of Sentinel-1 synthetic aperture radar (SAR) multi-temporal satellite data for Bathinda district of Punjab. Polarization ratio index (RPI = VH/VV) was used to detect the different phenological stages of paddy. The multidate Setninel-2 multi-spectral instrument (MSI) derived normalized difference vegetation index (NDVI) and ground truth locations were used to validate the SAR derived phenological stages. Sentinel-1 data in dual polarization (VH, VV) and both combinations can be used to detect paddy phases such as planting, vegetative, generative, and barren condition after harvesting, according to the findings.