Mapping of continuous floristic gradients in grasslands using hyperspectral imagery

Transitions between plant species assemblages are often continuous with the form of the transition dependent on the ‘slope’ of environmental gradients and on the style of self-organization in vegetation. Image segmentation can present misleading or even erroneous results if applied to continuous spatial changes in vegetation. Even methods that allow for multiple-class memberships of pixels presuppose the existence of ideal types of species assemblages that constitute mixtures—an assumption that does not fit the case of continua where any section of a gradient is as ‘pure’ as any other section like in modulations of grassland species composition.Thus, we attempted to spatially model floristic gradients in Bavarian meadows by extrapolating axes of an unconstrained ordination of species data. The models were based on high-resolution hyperspectral airborne imagery. We further modelled the distribution of plant functional response types (Ellenberg indicator values) and the cover values of selected species. The models were made with partial least squares (PLS) regression analyses. The realistic utility of the regression models was evaluated by full leave-one-out cross-validation.The modelled floristic gradients showed a considerable agreement with ground-based observations of floristic gradients (R²=0.71 and 0.66 for the first two axes of ordination). Apart from mapping the most important continuous floristic differences, we mapped gradients in the appearance of plant functional response groups as represented by averaged Ellenberg indicator values for soil pH (R²=0.76), water supply (R²=0.66) and nutrient supply (R²=0.75), while models for the cover of single species were weak.Compared to many other vegetation attributes, plant species composition is difficult to detect with remote sensing techniques. This is partly caused by a lack of compatibility between methods of vegetation ecology and remote sensing. We believe that the present study has the potential to increase compatibility as neither spectral nor vegetation information gets lost by a classifying step.     

一种改进的高光谱数据自适应波段选择方法

高光谱遥感数据具有的波段数目多、波段宽度窄、数据量庞大等特点给图像的进一步解译带来了困难。为了解决这一问题,对自适应波段选择的降维方法进行了改进,不仅考虑了高光谱遥感图像波段的信息量和波段间的相关性,更重要的是考虑了各地物连续光谱间的可分性。光谱间的可分性距离越大,表明类间的可分性越大,地物越清晰。首先选出了能有效区分图像上任意两类别的理想波段子集,再根据波段子集中任意3波段的相关系数之和最小和它们的均方差最小两个指标,选出任意两类对间那些包含信息量大、相关性又小、谱间差异又大的3波段组合(且不唯一),最后对整幅影像选出的最佳3波段45、75、85合成的假彩色图像用光谱角度制图法(SAM)进行了分类,总体分类精度达到91.7%,Kappa系数达到0.82。     

基于包络线消除的高光谱图像分类方法研究

在高光谱遥感中,包络线消除法一般仅局限于对单个像元的光谱进行光谱分析,从中提取出有助于分类识别的特征波段。而该文则以包络线消除算法为基础,应用VC++语言编程实现了对整个高光谱图像文件去包络、归一化并且提取出分类的特征空间的功能,并且针对原图像文件和去包络线后的图像文件,比较了应用最大似然分类法和光谱角度匹配法进行分类的结果。     

一种基于多项式逻辑回归高光谱影像分类方法的改进

针对多项式逻辑回归分类器在参数寻优过程中精度提升不明显和运行速度缓慢的问题,提出一种利用DFP修正拟牛顿算法进行多项式逻辑回归参数求解的方法来提高多项式逻辑回归参数优化的效率,该算法以弦截法代替牛顿算法中的二阶Hessian矩阵,并采用DFP修正法不断修正。利用该算法对两幅高光谱影像进行分类实验,结果表明:与传统的多项式回归分类方法相比,该算法在分类精度和效率方面都有明显的改进。     

新庙泡叶绿素a浓度高光谱定量模型研究

利用吉林省新庙泡的高光谱实测数据和水质采样分析数据,尝试通过单波段、波段比值、一阶微分和峰谷间距法建立叶绿素a反演模型。结果表明:单波段光谱反射率与叶绿素a浓度的相关性较差,不宜用于该区域的叶绿素a浓度估算;680 nm和700 nm波段反射率之比、700 nm处光谱一阶微分值和两波段峰谷间距反演模型都具有较高的决定系数,分别为0.783 4、0.792 7、0.796 9,验证模型的决定系数为0.651 3、0.431 7、0.756 4,均方根误差分别为8.69μg·L-1、14.50μg·L-1、10.04μg·L-1,显著水平P<0.01。这3种方法皆可以用于新庙泡叶绿素a浓度的定量遥感,其中又以峰谷间距法为最优。     

高光谱遥感油气勘探进展

遥感方法用于油气勘探已有多年的历史。随着高光谱遥感技术的发展,高光谱遥感油气勘探近年来取得了很大的进展。简要介绍了高光谱油气勘探的基本原理和流程,重点讨论了烃渗漏引起地表烃异常、岩石矿物蚀变异常以及植被异常的高光谱响应机制,以及目前研究中存在的问题。归纳总结了目前用于油气勘探的高光谱影像数据类型及特点。高光谱遥感方法用于油气勘探,在高光谱异常响应机制、数据来源以及数据处理和分析方面还有许多问题有待解决,针对这些问题,提出了相应的解决思路。     

基于AVIRIS高光谱数据的海表甲烷异常识别

研究海洋表面烃类富集状况在监测海洋环境和探测海底油气资源中具有重要意义,海表渗漏烃中,甲烷是气态烃中最具代表性的组分。为了精准识别海表甲烷异常,研究设计了相应光谱实验,以海水为背景测定甲烷光谱反射率,基于实测数据分析甲烷的光谱特征,运用比值导数光谱法削弱海水背景组分的光谱干扰,提取出甲烷光谱吸收特征波段。研究发现甲烷在1 642—1 672 nm和2 169—2 378 nm波长范围存在光谱吸收,通过比值导数处理后显著增强了其中1 642—1 672 nm和2 169—2 208 nm区间的甲烷吸收特征,在Rebecca等提出的CH4I甲烷反演指数的基础上加入比值导数参数,建立了基于AVIRIS数据的海表甲烷含量指数MI,与甲烷含量的相关系数R2=0.994 2,将其应用于美国加利福利亚州圣芭芭拉海峡Coal Oil Point(COP)烃渗漏区甲烷异常识别,并与CH4I指数和Bradley等提出的AVIRIS CH4指数ζ(L2298/L2058)进行反演效果对比。结果表明：运用MI指数可以有效识别海表甲烷浓度异常,与ζ、CH4I指数反演结果相比,MI指示的甲烷浓度异常分布与ζ指数反...     

资源一号02D可见近红外和高光谱影像辐射质量评价

资源一号02D(ZY1-02D)卫星搭载了我国自主研制的可见近红外相机（VNIC）和高光谱相机（AHSI）,是我国首颗民用高光谱业务卫星,具有广泛的应用前景。通过整体辐射精度、信噪比、清晰度以及信息熵4个评价指标,对ZY1-02D VNIC和AHSI数据进行辐射质量评价,并分别采用Sentinel-2 MSI和GF-5 AHSI数据进行对比。结果表明：ZY1-02D VNIC数据在可见光波段具有亮度高、信噪比高等优势;在红边近红外等波段,影像具有灰度范围大、信息量大的特点。ZY-1-02D VNIC数据在影像亮度、灰度范围、清晰度和信息量方面均优于Sentinel-2,二者信噪比近似。ZY-1-02D AHSI数据在395—1 341 nm范围内辐射质量良好;在1 929—2 501 nm范围,存在噪声严重的波段,影像质量较差。与GF-5 AHSI数据对比,ZY-1-02D AHSI数据的影像亮度和信噪比相当,但ZY-1-02D AHSI数据在灰度范围方面优势明显,且短波红外谱段的清晰度和信息量优于GF-5 AHSI数据。     

Potential prediction of the microbial spoilage of beef using spatially resolved hyperspectral scattering profiles

Spoilage in beef is the result of decomposition and the formation of metabolites caused by the growth and enzymatic activity of microorganisms. There is still no technology for the rapid, accurate and non-destructive detection of bacterially spoiled or contaminated beef. In this study, hyperspectral imaging technique was exploited to measure biochemical changes within the fresh beef. Fresh beef rump steaks were purchased from a commercial plant, and left to spoil in refrigerator at 8 °C. Every 12 h, hyperspectral scattering profiles over the spectral region between 400 and 1100 nm were collected directly from the sample surface in reflection pattern in order to develop an optimal model for prediction of the beef spoilage, in parallel the total viable count (TVC) per gram of beef were obtained by classical microbiological plating methods. The spectral scattering profiles at individual wavelengths were fitted accurately by a two-parameter Lorentzian distribution function. TVC prediction models were developed, using multi-linear regression, on relating individual Lorentzian parameters and their combinations at different wavelengths to log₁₀(TVC) value. The best predictions were obtained with r² = 0.95 and SEP = 0.30 for log₁₀(TVC). The research demonstrated that hyperspectral imaging technique showed potential for real-time and non-destructive detection of bacterial spoilage in beef.     

星载高光谱成像仪光学系统的选择与设计

本文概述了目前高光谱成像仪所采用的光学系统结构,分析讨论了棱镜色散、光栅色散、傅立叶变换三种主流高光谱成像仪分光方式的结构原理和优缺点,棱镜色散光能利用率高,但体积大,棱镜材料受空间环境变化影响较大,光栅色散效率低,但体积小,受环境影响小,傅立叶变换光谱成像系统由于分光棱镜的存在,能量至少损失50%以上。文中对国内外高光谱成像仪采用较多的Offner凸光栅光谱成像系统进行了论述,根据应用目标设计了一个离轴三反射镜望远系统和变倍Offner凸光栅组合的高光谱成像仪光学系统,该系统具有体积小、成像质量好、无光谱畸变的优点,通过加大光学系统的相对孔径,增加系统的入射光能量,弥补了光栅衍射效率低的缺点。