新一代Landsat系列卫星：Landsat8遥感影像新增特征及其生态环境意义

美国Landsat 8卫星的成功发射使一度中断的Landsat对地观测得以继续。Landsat 8除了保持Landsat 7卫星的基本特征外,还在波段的数量、波段的光谱范围和影像的辐射分辨率上进行了改进。基于该卫星的首幅影像,针对这些新的特性进行了分析和研究。研究发现:(1)新增的卷云波段有助于区别点云和高反射地物;(2)卷云波段设计的波长范围位于粘土矿物光谱反射的强吸收带,有利于土壤与建筑不透水面信息的区别; (3)新增的深蓝波段有助于水体悬浮物浓度的监测;(4)全色影像波长范围的收窄有利于该影像上植被和非植被的区别; (5)辐射分辨率的提高可避免极亮/极暗区的灰度过饱和现象,这对反射率极低的水体的细微特征识别有很大帮助。显然,Landsat 8这些新增的优点将会对全球生态环境变化的监测产生积极的作用。

Analysis of new characteristics of the first Landsat 8 image and their eco-environmental significance

The successful launch of Landsat 8 on February 11, 2013 has made it possible for the continuity of Landsat earth observation mission once stopped due to the failure of the aged Landsat 5 in late 2011. The satellite has two sensors, the Operational Land Imager (OLI) and the Thermal Infrared Sensor (TIRS), which collect remotely-sensed data over a 185 km swath. Landsat 8 has several new characteristics as well as those of Landsat 7. These include adding two spectral bands (deep blue and cirrus bands), refining spectral range of some bands of Landsat 7 ETM+, splitting one thermal band to two bands, and improving radiometric resolution from 8 bits to 16 bits. This paper aims to examine the new characteristics of the satellite''s image. Image processing and analysis have been carried out on the satellite''s first image acquired on March 18, 2013. The results show that (1) the addition of the cirrus band can be useful for the separation of cloud from bright ground objects; (2) the band is also helpful for the distinguishing soil from building materials because the spectral range of the cirrus band is designed within a strong water vapor absorbing zone of the clay minerals; (3) the addition of the deep blue band can be useful for monitoring suspended materials in open waters; (4) the narrowing of spectral range of the panchromatic band can help the differentiation of vegetated and non-vegetated area in the panchromatic image; and (5) the enhancement of radiometric resolution from 8 bits to 16 bits would avoid spectral saturation of the data in extremely dark/light regions. In general, Landsat 8 has technical advantages over Landsat 7 except a lower spatial resolution in thermal data. Its launch and operation can undoubtedly make significant contributions to the morning of global ecosystem and environmental changes.