Potential of Sentinel-1 Time Series Data for the Estimation of Season Length in Winter Wheat Phenology

Abstract

Time series analysis has high potential for the monitoring of agricultural management intensity and crop yield. The C-band synthetic aperture radar (SAR) data from Sentinel-1 provide a unique source to create area-wide dense time series of indicators that are sensitive to crop parameters. Here, time series of backscattering coefficient ratio from Sentinel-1 were established in individual winter wheat fields over three consecutive years. Phenology metrics were computed in order to indicate the length of the season, where the plant is substantially growing in height and building biomass. The average estimated lengths of season of winter wheat were 112 days in 2017, 77 days in 2018 and 91 days in 2019. The observed lengths of the season in the reference were 114 days in 2017, 73 days in 2018 and 88 days in 2019. The results for the individual winter wheat fields show that the length of the season was estimated with an RMSD (root mean squared deviation) of less than 2 weeks for all three years. The results confirmed that the VH/VV ratio has high potential for monitoring phenological features.

Multi-year monitoring of wheat phenology and effect of climate change in the south Asian region using Sentinel-2 NDVI time series analysis

“…Therefore, the proposed method of data collection and phenology estimation for a heterogeneous site through trend-based temporal analysis accurately identifies five phenological stages of wheat in near-real time as opposed to numerous studies which considered only the sowing and harvest stages. 12,16 Additionally, the stages were detected with a minimum difference of 1 day across multi-years, where weather varied largely, unlike 2,10,11,17 which detected phenology for a single year only, limiting the transferability of the approaches followed and hence, the results and approach of this study highlight the capability of the proposed method to be transferable to multiple years with varying weather conditions and number of satellite observations for a heterogeneous crop distribution site. In addition to that, none of the previously conducted work studies the effect of the rate of change on 5 different phenological stages in wheat.…”

“…The authors conclude that higher temperatures lead to shorter growth duration however, the change in temperature and rainfall is constant throughout the study years. Limited work has been carried out in the domain of phenology estimation and, the studies have considered detecting only the sowing and harvest dates of crops 12,16 rather than focusing on the significant phenological stages through out a crops life cycle which holds critical information for yield estimation and crop management strategies. Moreover, the studies have carried out the detection for single year 2,6,10,11,17 which limits the applicability of the method for future data since, satellite data is largely effected by atmospheric variables and the weather varies significantly each year.…”