Optimal phase selection for extracting distribution of winter wheat and summer maize over central subregion of Henan Province based on Landsat 8 imagery
Optimal phase selection for extracting distribution of winter wheat and summer maize over central subregion of Henan Province based on Landsat 8 imagery
Remote sensing technology provides an ideal mean for the real-time monitoring of large-scale agriculture production.And the best phase of remote sensing images for vegetation classification is important to monitor crop area by means of remote sensing.In this study,we selected 6 Landsat 8 images from 2020 to 2021,including the growth period of summer maize from milk ripening to harvest and winter wheat from overwintering to ripening.Based on these data,we analyzed the differences in spectral characteristics and NDVI between winter wheat-summer maize and other landcovers at different phases.Then we extracted the spatial distribution of winter wheat-summer maize by the decision tree in central region of Henan province.The results showed that the area ratio of winter wheat-summer maize changed during growth period.For summer maize,the extraction effect at milky stage was better than that at the later stage,and the overall precision was the highest on August 26th,2020,accounting for 83.60%,and the Kappa coefficient was 0.72,indicating that the classification quality was good.For winter wheat,the best identification period was in the wintering period,and its overall precision on January 1st,2021 had the highest of 92.36%,and the Kappa coef-ficient was 0.81,which suggesting it was good for information extraction.In addition to the coverage change of the crop's own growth process,imaging at different stages also affected the classification accuracy.The multi-temporal information extraction also found that the planting areas of summer maize and winter wheat were not completely overlapped due to the limitation of weather and other environmental conditions.The local weather in the mountainous area was not suitable for winter wheat growth,and it was not consistent with the planting area of summer maize.This study helps us to make timely and effective judgments on crop distribution and growth status at a macro level,and has broad application prospects for agricultural monitoring,especially for information management of rotation farmland and crop phenology and planting area.
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