基于多时相TM影像的冬小麦面积变化监测

利用北京1992年、2000年、2004年、2009年的多时相Landsat TM5影像数据,结合实际调查数据,分析了近20年来北京冬小麦种植面积的变化趋势及演变特征。采用决策树、PCA、缨帽变换等手段对地物进行分类,利用多时相影像,NDVI组合阈值提取小麦种植区面积。研究结果表明:北京地区1992年、2000年、2004年、2009年冬小麦种植面积分别为:113671ha,84322ha,40410ha,61529ha。北京冬小麦种植面积呈现为明显的先减少后增加的趋势。从1992年到2009年共减少52143ha。其中,从1992年到2000年冬小麦种植面积减少了29349ha,减少的面积中城区扩张占用和转变为裸地的最多,分别为39.7%和42.8%,另外有13.3%变为设施用地,3%成为水体(鱼塘和水田);从2000年到2004年冬小麦种植面积共减少43921ha,减少的面积中转变为裸地和城区扩张占用的最多,分别为39.8%和33.1%;从2004年到2009年冬小麦种植面积共增加了21119ha,其中裸地转变为小麦种植区面积最大。

Change Detection of Winter Wheat Area Based on Multi-temporal TM Images

In recent 20 years,the winter wheat planting area is decreasing obviously in Beijing region owning to the development of urbanization.This study focused on the change detection of winter wheat area of Beijing.Multi-temporal Landsat-TM images collected during the wheat growth period of 1992,2000,2004 and 2009 were used to analyze the trend and characteristics of winter wheat planting area variation in Beijing in recent two decades.The winter wheat planting area of Beijing at different history stages was extracted using the threshold of NDVI of multi-temporal images.PCA and Tasseled Cap transform technique were adopted in this study for feature classifying.The results showed that the winter wheat area of 1992,2000,2004 and 2009 in Beijing is 113671 Ha,84322 Ha,40410 Ha and 61529 Ha respectively.It indicated that winter wheat planting area in Beijing has a significantly decreasing trend and the total reduced area is 52143 Ha from 1992 to 2009.Where,winter wheat planted area decreased by 29349 Ha from 1992 to 2000,and most of reduced wheat areas were occupied by urban expansion or transformed into bare lands,accounting for 39.7% and 42.8%.In addition,lands for greenhouse and water bodies(fish ponds and water fields) account for 13.3% and 3%.The winter wheat area decreased by 43921 Ha from 2000 to 2004.Most of reduced wheat areas were transformed into bare lands or occupied by urban expansion,accounting for 39.8% and 33.1%.The winter wheat areas increased by 21119 Ha from 2004 to 2009.