Changes of winter wheat planting area detected by using multitemporal remote sensing images—A case study from Sanhe City and Hui Autonomous Co unty of Dachang of Hebei Province

The changes of winter wheat planting area in Sanhe City and Hui Autonomous County of Dachang of Hebei Province were analyzed by using multitemporal remote sensing images. The results show that the winter wheat planting area is decreasing in the studied area as a whole， but it may be increase or decrease in different zones in a year. Reclaiming cropland at the bank of river makes its increa se. The construction taking up the cropland and the adjustment of crop planting m ake its decrease.