摘要
归一化植被指数(NDVI)是反映植被长势特征的重要参数之一。获取准确的植被指数对揭示植被长势变化等定量遥感分析至关重要。基于不同辐射校正水平(辐射定标与大气校正),分别利用Landsat ETM+影像的灰度值(DN)、表观(TOA)反射率与地表(Surface)反射率计算相应NDVI,并根据鄱阳湖区野外定点观测数据,从农田、景观尺度揭示不同辐射校正水平下水稻生育期内NDVI动态变化特征。结果表明,根据DN、TOA反射率与Surface反射率提取的NDVI基本上可以反映出年内水稻不同熟制种植信息变化特征,即移栽期NDVI处于谷值,孕穗抽穗期NDVI达到峰值。但相应NDVI逐渐增加,且波动范围逐渐增大。就不同熟制水稻生育期而言,根据DN值计算并构建的NDVI曲线差异较小,而根据TOA反射率与Surface反射率反演的NDVI曲线差异明显。在植被定量遥感研究中,通过大气校正反演地表反射率计算植被指数相对客观准确。
Normalized Difference Vegetation Index（NDVI） is an important parameter that can well reflect the growth characteristics of vegetation.The retrieval of vegetation indices through satellite data are usually influenced by the sensor itself,the atmosphere,aerosols and others.Thus,the derivation of objective and accurate vegetation index is essential to reveal the vegetation growth changes and other quantitative remote sensing analysis.Based on the different levels of radiation correction（radiometric calibration and atmospheric correction）,we used the digital numbers（DN） values originally from Landsat ETM＋,TOA reflectance,and surface reflectance for the calculation of NDVI,respectively.According to field survey on paddy rice cropping systems in the Poyang Lake Region in China in mid-to-late September 2010,from the paddy field and the landscape scales,we monitored the temporal dynamics of Landsat-derived NDVI.The results showed that,the NDVI profile calculated from DN values,TOA reflectance and surface reflectance basically reflect the information on the paddy rice growing systems per year,and the corresponding ranges of NDVI became bigger.NDVI dropped to its low level during the transplanting stage and reached a plateau level during the panicle initiation to heading.In the development of paddy rice growth period,the NDVI curves derived from TOA reflectance and Surface reflectance could better demonstrate the growth system characteristics of paddy rice.Therefore,we concluded that the Surface reflectance retrieved from radiometric calibration and atmospheric correction should be a relatively objective and accurate parameter for NDVI calculation in the quantitative remote sensing of vegetation growth condition.
出处
《遥感技术与应用》
CSCD
北大核心
2012年第1期121-127,共7页
Remote Sensing Technology and Application
基金
国家973计划项目(2009CB421106)
国家自然科学基金项目(40901285)资助
关键词
辐射校正
NDVI
对比分析
水稻
Radiation correction
NDVI
Comparative analysis
Paddy rice
