Combining Decision Trees with Angle Indices to Identify Mangrove Forest at Shenzhen Bay,China

Mangroves are woody plant communities in the intertidal zone of tropical and subtropical coasts that play an important role in these zones. The infrared wave band is one of the key bands in the remote sensing identification of mangrove forest, and ALI (advanced land imagery) has a large number of infrared bands. Two angle indices were proposed based on liquid water absorption at band 5p and band 5 of EO-1 ALI, denoted as β_1.25 and β_1.65 respectively. A decision tree method was adopted to identify mangrove forest using remote sensing techniques for β_1.25-β_1.65 and NDVI (normalized difference vegetation index) for EO-1 ALI imagery acquired at Shenzhen Bay. The results showed that the reflectance of mangrove forests at band 5p and band 5 was significantly lower than that of terrestrial vegetation due to the characteristics of coastal wetlands of mangrove forests. This resulted in a greater β_1.25-β_1.65 value for mangrove forest than terrestrial vegetation. The decision tree method using β_1.25-β_1.65 and NDVI effectively identifies mangrove forest from other land cover categories. The misclassification and leakage rates were 4.29% and 5.11% respectively. ALI sensors with many infrared bands could play an important role in discriminating mangrove forest.     

基于ALI数据的柴达木油气区含铁矿物制图

烃类微渗漏造成的油气藏上方红层褪色是遥感间接找油气的重要标志之一，因此，在油气遥感勘探中，含铁矿物的分布制图和铁异常信息的提取至关重要。作为新一代的多光谱图像，ALI（Advanced Land Imager）和ETM+图像相比，光谱分辨率有了很大提高，它在0.4~1.3 μm波长范围内有7个波段，可以有效地反映出不同含铁矿物在此波长范围内独特的光谱特征，可以用于含铁矿物制图和铁异常信息提取。本文选取有天然气分布的柴达木盆地东部三湖地区为研究区，对ALI图像运用光谱角度制图方法进行含铁矿物分布制图。     

Discriminating lava flows of different age within Nyamuragira’s volcanic field using spectral mixture analysis

In this study, linear spectral mixture analysis (LSMA) is used to characterize the spectral heterogeneity of lava flows from Nyamuragira volcano, Democratic Republic of Congo, where vegetation and lava are the two main land covers. In order to estimate fractions of vegetation and lava through satellite remote sensing, we made use of 30 m resolution Landsat Enhanced Thematic Mapper Plus (ETM+) and Advanced Land Imager (ALI) imagery. 2 m Pleiades data was used for validation. From the results, we conclude that (1) LSMA is capable of characterizing volcanic fields and discriminating between different types of lava surfaces; (2) three lava endmembers can be identified as lava of old, intermediate and young age, corresponding to different stages in lichen growth and chemical weathering; (3) a strong relationship is observed between vegetation fraction and lava age, where vegetation at Nyamuragira starts to significantly colonize lava flows ∼15 years after eruption and occupies over 50% of the lava surfaces ∼40 years after eruption. Our study demonstrates the capability of spectral unmixing to characterize lava surfaces and vegetation colonization over time, which is particularly useful for poorly known volcanoes or those not accessible for physical or political reasons.     

多源遥感影像水体指数的交互对比

在对地观测系统中,Landsat和EO-1数据比较适合于监测城市水体变化。但是这两种传感器数据的水体指数之间的关系不清楚,针对这一问题。该文利用两对同日过空的Landsat-7ETM+与EO-1ALI影像来查明二者水体指数之间的定量关系,通过回归统计分析来求出两种传感器水体指数之间的转换方程。结果表明,Landsat-7ETM+与EO-1ALI影像分别基于DN数据、IACM反射率数据计算的MNDWI水体指数间,均存在较好的线性相关关系,决定系数均在0.75以上;基于EO-1ALI的MNDWI指数影像信息更为丰富,因为其动态范围大于Landsat-7ETM+。     

ALI 遥感数据在岩矿信息提取中的应用研究

论文对研究区ALI数据进行了纯净像元提取,在此基础上,对纯净像元进行N-D散点图分析,选择出不同端元并进行归类分析,作为后期分类识别的样本.这里采用决策树方法对研究区岩矿进行识别,研究发现:样本区在MNF变换后图像上的波谱(前几个波段)可分性远远大于其在变换前图像上的波谱可分性,基于此的决策树分类方法能够识别出岩矿.     

Comparison of the response of the Landsat 7 Enhanced Thematic Mapper Plus and the Earth Observing-1 Advanced Land Imager over active lava flows

Using near simultaneously acquired Landsat 7 Enhanced Thematic Mapper Plus (ETM+) and Earth Observing-1 Advanced Land Imager (ALI) data we assess the relative radiant responses over active lava flows from the Mt. Etna July/August 2001 flank eruption. By assessing the extent of saturation between the two instruments and using the dual-band method of extracting sub pixel thermal information, we show that the ALI represents an improvement over the ETM+ in the present ability to assess temperatures of hot active lava flows for a number of reasons. (1) The extra spectral channels provided by ALI compliment the current SWIR channels on ETM+ by providing a greater number of paired channel combinations for input into the dual-band method. Thus, dual-band temperature solutions can be determined for a greater range of lava flow types than previously possible using the two paired channel combinations available with the ETM+. (2) The ALI instrument is less susceptible than ETM+ to saturation within the SWIR, especially when using channels 5, 5p and 4p at wavelengths of 1.65, 1.25 and 0.87 μm respectively. (3) The greater radiometric sensitivity of the ALI 12 bit electronics coupled with a significantly higher signal to noise ratio aid in obtaining successful dual-band solutions.     

ALI遥感数据的岩矿反射率反演方法研究

岩矿反射率反演是遥感蚀变信息提取中最基础、最关键的一个过程。本介绍了卫星EO-1携带的先进陆地成像仪(ALI)为及其定标方式,分析了两种重要的岩矿反射率反演方法:表观反射率的计算和地表真实反射率的反演。通过分析表明:表观反射率实现关键是参数的获取,地表真实反射率反演关键是模型的选择和参数设置。就反演效果来说,基于大气辐射传输的FLAASH模型优于公式计算的表观反射率,这对应用遥感数据进行岩矿蚀变信息提取的研究人员有一定的参考价值。     

利用ALI遥感图像进行矿化蚀变信息提取方法探讨

矿化蚀变信息提取是遥感找矿的重要手段之一。Advanced Land Imager（ALI）遥感图像信噪比高达100～200,且有较高的波谱分辩率,能够区分具有标示性波谱特征的岩矿。以美国Cuprite地区ALI遥感图像为例,通过数字处理、最小噪声分离变换（MNF）,分离和均衡数据中的噪声。然后提取纯净像元（PPI）,输入到N维可视化器中开发端元组分光谱,并与波谱库中的波谱进行比对分析。将提取的端元作为样本,进行数据集合评估,最后进行蚀变信息的提取。结果表明,ALI遥感数据由于其波段多,波谱空间分辨率高,经过MNF-PPI后的三维散点图端元提取,能够识别更微弱的岩矿信息。