Evaluating the potential of temporal Sentinel-1A data for paddy rice discrimination at local scales

Abstract

A mapping algorithm is proposed in this letter on the application of Sentinel-1A data in discriminating paddy rice from other land-cover categories at local scales. The study region is Chongming Island located in the Shanghai metropolitan area, southeast China. We have acquired five temporal images of the new Sentinel-1A satellite in interferometric wide swath (IW) mode, covering a critical period of the 2015 paddy rice growing season in Chongming Island. Temporal backscatter at vertical transmitted and horizontal received (VH) polarization of Sentinel-1A was exploited and we observed that from early June to mid September, temporal backscatter profiles of the classes water/pond, built/urban, trees/forest and others were relatively stable. On the other hand, paddy rice exhibited a marked change in temporal backscatter coefficients, increasing steeply from flooding/planting to tillering/booting, and decreasing slightly at heading. Backscatter profiles also differ between paddy rice fields of different flooding/planting periods. These observed temporal microwave (radar) backscatter dynamics were employed in a decision tree mapping algorithm to discriminate paddy rice from other land-cover classes. An overall classification accuracy and Kappa statistic of 88.3% and 0.85 were recorded, respectively, which demonstrates the operational applicability of temporal Sentinel-1A data in paddy rice discrimination at local or district scales.​​​