基于实测光谱的太湖水体表面离水反射率研究

水体表面离水反射率是研究水体光学特征的一个重要参数。以2008年11月10日、11日太湖水面实地光谱和水体样本为基础,探讨了蓝藻污染对太湖水体表面离水反射率的影响:蓝藻的存在提高了水体在近红外波段的离水反射率,使红波段出现了明显的吸收谷。通过FY-3A和MODIS卫星的通道响应函数,建立了卫星数据与水体表面离水反射率间的函数关系。在此基础上,利用MODIS卫星数据构建了比值指数(RI),利用该指数成功反演了2008年11月12日太湖水体叶绿素含量(R2=0.72),并获得了叶绿素含量的空间分布。这一结果为分析太湖水面光学特性、水质污染状况提供了重要依据。     

江苏近海辐射沙洲水域水深与光谱的相关性研究

通过对实测光谱数据和水深数据的分析研究发现，泥沙浓度在水深遥感中具有重要意义。泥沙含量决定水体光谱反射率与 水深的相关性方向： 泥沙含量较少的清水区，光谱反射率与水深呈负线性相关； 而在泥沙含量较高的浊水区，光谱反射率与水深 数据呈正线性相关。以此为依据，对水体进行清/浊水体的光谱分别处理，可提高水深的光谱反演精度。同时，结合实测水体光谱 进行不同光谱分辨率的模拟分析，发现高光谱分辨率遥感将有助于提高水深反演精度。     

基于神经网络的二类水体大气校正

以MERIS高光谱影像为数据源,根据现有大气传输模型和大气校正方法,探索了适合于内陆湖泊二类水体的高光谱遥感影像大气校正方法。在6S辐射传输模型的基础上,构建了基于神经网络的二类水体大气校正算法。通过构建输入卫星辐亮度直接提取离水反射率的模型,无需同步气溶胶参数,即可实现大气校正。对2010年8月9日的MERIS影像进行大气校正,并将校正后的遥感反射率与准同步实测离水反射率进行对比分析,结果表明,大气校正过程有效去除了大气效应的影响,经过大气校正的13个波段的平均相对误差分布在10%～40%,得到了与实测值相近的水体遥感反射率。     

基于海色遥感应用的 MODIS 数据预处理简

较系统地介绍了从MODIS 原始分发数据到海洋水色遥感反射率、离水辐射率等数据产品的产出过程;分析了各步骤原理,尤其针对标准大气校正算法无法计算出近岸二类水体离水辐射率问题提出邻近清洁水体外推混浊水体的思路;探索并改进了大气校正算法,计算出大部分近岸水体的离水辐射率数据.     

基于海色遥感应用的MODIS数据预处理

较系统地介绍了从MODIS原始分发数据到海洋水色遥感反射率、离水辐射率等数据产品的产出过程;分析了各步骤原理,尤其针对标准大气校正算法无法计算出近岸二类水体离水辐射率问题提出邻近清洁水体外推混浊水体的思路;探索并改进了大气校正算法,计算出大部分近岸水体的离水辐射率数据。     

江苏近海岸水深遥感研究

以江苏近海辐射沙脊群海域为典型研究区,通过实测水深数据和水体光谱测量与分析,发现对应TM3和TM4波段的水体光谱反射率对水深信息敏感,线性相关系数分别达到-0.561和-0.694。结合多光谱遥感信息传输方程所推导出的水深信息对数反演模式,针对本研究区TM4和TM3波段数据所建立的水深预测模式的复相关系数R2为0.4793,对0-15m水深,预测水深和实测水深之间拟合较好。利用TM5波段反射率、出露沙洲反射率以及海水反射率的差异,通过建立掩膜图像,可较有效地对TM遥感图像进行水陆分离,提取TM图像中海水部分,进一步可通过常用的图像处理软件绘制每隔5m的TM水深遥感制图、等深线图。随着高空间、高光谱、高辐射分辨率遥感技术的发展,对浅海水域的水深和水下地形进行遥感探测的技术方法和应用将会不断地深入开展。     

水体光谱测量与分析Ⅰ：水面以上测量法

水色遥感的基础之一是水体光谱特征测量与分析。水体光谱特性包括两个方面 :表观光学特性(AOPs)和固有光学特征 (IOPs)。该文主要讨论与水色遥感基本参数直接相关的表观光学量的测量与分析。现场表观光谱的测量从方法上可分为两类 :剖面测量法和水表面以上测量法。两种方法相对独立 ,适用范围上具有互补性。该文主要针对水面以上测量法进行讨论。水色遥感一般要求表观光谱特性的测量必须能够导出离水辐射率LW、归一化离水辐射率LWN、遥感反射率Rrs、和刚好处于水面以下 0 -深度的辐照度比R等。国际上有关水色的测量规范中 ,仅有针对大洋一类水体的。中国的近岸水体和湖水绝大部分是二类水体 ,因此该文也将对二类水体光谱测量的有关参数化问题进行讨论。同时 ,对数据分析处理中的一些关键参数的确定 ,提出新方法     

基于HY-1C卫星CZI影像的多类型内陆水体大气校正及水质参数反演

海洋一号C星(HY-1C)上搭载的海岸带成像仪(CZI)在内陆水体水色遥感应用方面具有较大潜力。目前,HY-1C CZI影像在内陆水体的大气校正和水质反演研究较少,仍然需要解决适用于不同类型内陆水体的大气校正和水质参数建模等问题。因此,本研究在华北平原的小浪底水库、官厅水库、丹江口水库、白龟山水库、白洋淀5个不同浑浊程度的湖泊和水库开展了星地同步实验,获取了85个采样点的水面遥感反射率光谱和水质参数实测数据。发展了基于Sentinel-2 MSI影像均匀不变地物的HY-1C CZI影像相对大气校正算法和系统定标模型。HY-1C CZI的蓝、绿、红、近红外波段遥感反射率反演平均无偏相对误差(AURE)分别为14.7%、11.2%、28.9%、41.7%,蓝、绿、红波段的大气校正精度相对较高;此外,大气校正与实测光谱的相关系数r的平均值为0.978,光谱角度距离(SAD)的平均值为0.109,说明大气校正遥感反射率光谱形状与实测光谱一致性较高。基于实测数据构建了叶绿素a浓度和透明度反演模型,经独立数据验证,HY-1C CZI影像叶绿素a浓度反演的AURE为33.8%,均方根误差(RMSE)...     

星载激光雷达气溶胶数据辅助的近岸浑浊水体大气校正研究

提出了一种星载激光雷达CALIOP气溶胶数据辅助的MODIS/Aqua水色数据大气校正方法,并在长江口及其邻近浑浊水体区域进行了实验。通过与实测光谱数据的对比分析说明,本文方法能在一定程度上避免如近红外波段离水辐亮度为零的假设的不合理性,摆脱对实测数据的依赖,有效地反演离水辐亮度,修复SeaDAS软件中短波红外-近红外联合大气校正算法中短波红外波段引起的产品的条带问题。     

应用MODIS数据反演河北省海域叶绿素a浓度

为了建立更加合理、准确的叶绿素a遥感反演模型,利用地物光谱仪测定了河北省海域水面的光谱反射率,分析了光谱反射率与实测叶绿素a浓度之间的关系.在此基础上,通过MODIS数据各波段及波段组合的反射率与实测叶绿素a浓度的相关分析,确定第1波段(B1)为最佳反演波段,建立了应用B1反演叶绿素a浓度的遥感模型,并对模型精度进行验证.结果表明:该模型相关系数为0.66,反演结果均方根误差为0.48 mg/m3,模型精度优于SeaDAS的OC3标准经验算法;该模型反演河北省海域表层水体的叶绿素a浓度有较好的效果.     

水稻叶片不同光谱形式反演叶绿素含量的对比分析研究

通过对常优1号和武粳15两个品种水稻叶片的反射率R、lg(1/R)、反射率一阶微分（FD）和反射率归一化（BN）等光谱形式的测量和计算，分析了叶片光谱不同变化形式与叶绿素含量的相关关系，建立了统计方程，并进行了比较与评价，同时，对反演方程的最佳波段选择进行了探讨。结果表明，叶绿素含量与反射率一阶微分光谱方程的相关性最强，而采用lg(1/R)的光谱形式能够提高遥感反演叶绿素含量的效果。经验证，两个水稻品种叶绿素含量的模拟值与实测值的复相关系数R2分别达到0.641和0. 818。     

基于遥感数据的积雪信息提取:以新疆北疆为例(英文)

This paper proposes an applicable approach for snow information abstraction in northern Xinjiang Basin using MODIS data. Linear spectral mixture analysis (LSMA) was used to calculate snow cover fractions (SF) within a pixel, which was used to establish a regression function with NDSI. In addition, 80 snow depths samples were collected in the study region. The correlation between image spectra reflectance and snow depth as well as the comparison between measured snow spectra and image spectra was analyzed. An algorithm was developed for snow depth inversion on the basis of the correlation between snow depth and snow spectra in the region. The results indicated that the model of SF had a high accuracy with the mean absolute error 0.06 tested by 26 true measured values and the validation for snow depth model using another dataset with 50 sampling sites showed an RMSE of 1.63. Our study showed that MODIS data provide an alternative method for snow information abstraction through development of algorithms suitable for local application. Supported by the National Natural Science Foundation of China (No.70361001).     

基于神经网络的二类水体大气修正

大气修正是海洋水色遥感中的关键技术之一。近海二类水体大气修正面临两个挑战：浑浊水体造成NIR大气修正波段的离水辐射明显大于零;近海上空存在较强吸收性的气溶胶。本文针对HY-1A CZI,在辐射传输模拟的基础上建立了基于神经网络技术的二类水体大气修正算法,可以由波段1-4的TOA反射率和三个角度反演得到离水反射率、气溶胶光学厚度等参数。利用模拟数据进行了算法的性能评估,并开展了卫星数据处理试验。结果表明,除了在非常浑浊的水体,反演结果基本合理。     

Atmospheric Correction Over Coastal Turbid Waters of Bay of Bengal Using OCEANSAT-I Ocean Colour Monitor (OCM) Data

Space-borne ocean-colour remote sensor-detected radiance is heavily contaminated by solar radiation backscattered by the atmospheric air molecules and aerosols. Hence, the first step in ocean-colour data processing is the removal of this atmospheric contribution from the sensor-detected radiance to enable detection of optically active oceanic constituents e.g. chlorophyll-a, suspended sediment etc. In standard atmospheric correction procedure for OCEANSAT-1 Ocean Colour Monitor (OCM) data, NIR bands centered at 765 and 865 nm wavelengths were used for aerosol characterization. Due to high absorption by water molecules, ocean surface in these two wavelengths acts as dark background, therefore, sensor detected radiance can be assumed to have major contribution from atmospheric scattering. For coastal turbid waters this assumption of dark surface fails due to the presence of highly scattering sediments which causes sufficient water-leaving radiance in NIR bands and lead to over-estimation of aerosol radiance resulting in negative water leaving radiance for λ < 700 nm. In the present study, for the turbid coastal waters in the northern Bay of Bengal, the concept of spatial homogeneity of aerosol and water leaving reflectance has been applied to perform atmospheric correction of OCAEANSAT-1 OCM data. The results of the turbid water atmospheric correction have also been validated using in-situ measured water-leaving radiance. Comparison of satellite derived water-leaving radiance for five coastal stations with in-situ measured radiance spectra, indicates an improvement over the standard atmospheric correction algorithm giving physically realistic and positive values. Root Mean Square Error (RMSE) between the in-situ measured and satellite derived water leaving radiance for wavelengths 412 nm, 443 nm, 490 nm, 512 nm and 555 nm was found to be 1.11, 0.718, 0.575, 0.611 and 0.651%, respectively, using standard atmospheric correction procedure. By the use of spatial homogeneity concept, this error was reduced to 0.125, 0.173, 0.176, 0.225, and 0.290 and the correlation coefficient arrived at 0.945, which is an improvement over the standard atmospheric correction procedure.     

利用小波分形维数确定水稻光谱分辨率特征尺度

采用1维离散小波HAAR、DB4、SYM4对LOPEX 93数据库中的6条水稻反射光谱曲线进行10层小波分解。利用小波近似系数重构信号,采用步长行走法计算重构信号的小波分形维数。研究各尺度下小波分形维数、小波细节系数方差、小波细节系数信息熵、小波近似系数重构方差的特征。结果表明水稻光谱曲线具有分形特征,分形计算中相关系数值均大于0.9证明分形计算的有效性。4个参数的尺度特征揭示了水稻光谱曲线特征尺度转折点出现在尺度6,当水稻光谱分辨率小于64 nm,才能较好地反映光谱曲线峰谷细节特性。通过田间实测18条水稻光谱,计算各尺度的两种植被指数及植被指数与叶绿素的相关系数,进一步证明这一结论。     

叶片辐射等效水厚度计算与叶片水分定量反演研究

在分析叶片水分对叶片反射率光谱影响的基础上,结合叶片内部水、干物质、叶绿素等光谱吸收系数曲线特征,分析了975nm波长水气吸收特征处叶片与光线相互作用原理,并利用Beer定律和945nm,975nm波长光谱反射率差值,推导了975nm波长辐射等效水厚度REWT的计算公式。由于表面反射、杂散射光、非均匀介质和叶片内部多次散射等因素,光在叶片内部的辐射传输不能直接用Beer定律描述,且利用Beer定律计算的REWT与叶片等效水水厚度EWT之间会有较大的偏差。论文设计和获取了多植物、不同水分梯度的叶片光谱获取试验数据,整理和分析了欧盟Lopex93数据,利用这两组独立数据和论文提出的REWT计算公式,比对验证了975nm波长叶片REWT和叶片EWT的统计模型,结果表明：由于光在叶片内部的多次散射,REWT是EWT的3.3倍左右。论文研究结果一方面为叶片EWT定量遥感探测提供了一种快速、简单且有较强通用性的计算方法和模型,另一方面,探测叶片REWT和EWT的定量关系,有助于了解叶片内部的光辐射传输情况,特别是间接了解近红外波段叶片内部的多次散射情况。     

Mapping of Marine Chl-a and Suspended Solid Concentration Using OCM-2 Sensor

Chlorophyll-a (Chl-a) and Suspended Solid Concentration (SSC) shows the productivity of water and their surrounding environment. These parameters can be effectively estimated through several remote sensing techniques. From the recent reports on the Gulf of Thailand, it is found that Chl-a and SSC are increasing in coastal areas due to changing environment caused by variations in the global carbon cycle, climate change and water pollution linking to anthropogenic conditions such as high population density and rapid urbanization in neighbouring coastal areas deteriorating the coastal and marine environment. Various models are evaluated in this study for estimation of marine Chl-a and SSC by employing Ocean Colour Monitor-2 sensor of Oceansat-2 satellite for Northern Gulf of Thailand. The retrieval of Chl-a and SSC by the atmospheric correction of visible bands from 400 to 700 nm to attain normalized water-leaving radiances and then a suitable algorithm is applied. The In-situ reflectance values of sea waters are measured using the ASD spectroradiometer. The reflectance values of the spectroradiometer are correlated for the same day atmospherically corrected satellite reflectance and the analysis offers high correlation R² 0.73. Satellite derived, Chl-a and SSC are correlated with observed in situ Chl-a and SSC. This analysis offered better correlation of R² 0.86 and 0.85 respectively with the algorithms of Chl-a and SSC.     

Assessing Metal-Induced Changes in the Visible and Near-Infrared Spectral Reflectance of Leaves: A Pot Study with Sunflower (<Emphasis Type="Italic">Helianthus annuus</Emphasis> L.)

The aim of this study was to monitor changes in leaf spectral reflectance due to phytoaccumulation of trace elements (Cd, Pb, and As) in sunflower mutant (M5 mutant line 38/R4-R6/15-35-190-04-M5) grown in spiked and in situ metal-contaminated potted soils. Reflectance spectra (350–2500 nm) of leaves were collected using portable ASD spectroradiometer, and respective leaves sample were analyzed for total metal contents. The spectral changes were quite noticeable and showed increased visible and decreased NIR reflectance for sunflower grown in soil spiked with 900 mg As kg^?1, and in in situ metal-contaminated soils. These changes also involved a blue-shift feature of red-edge position in the first derivatives spectra, studied vegetation indices and continuum removed absorption features at 495, 680, 970, 1165, 1435, 1780, and 1925 nm wavelength. Correlograms of leaf-metal concentration and reflectance values show highest degrees of overall correlation for visible, near-infrared, and water-sensitive wavelengths. Partial least square and multiple linear regression statistical models (cross-validated), respectively, based on Savitzky–Golay filter first-order derivative spectra and combination of spectral feature such as vegetation indices and band depths yielded good prediction of leaf-metal concentrations.     

SO2污染环境下水稻导数光谱与生理生化指标的相关性研究

通过田间开顶式小区熏气试验,研究在SO2急性伤害条件下水稻冠层导数光谱与叶片含硫量、叶液pH值以及叶绿素含量的相 关性。分别选择分蘖期和抽穗期显著相关的波段(分蘖期： 689 nm、584 nm、570 nm; 抽穗期： 689 nm、584 nm、585 nm)建立 预测叶片含硫量、叶液pH值及叶绿素含量的回归模型,并分别用拔节期和灌浆期相应导数光谱反射率检验模型预测精度。结果表明 ,由分蘖期建立的回归模型估测拔节期叶液pH值以及叶绿素含量与实测值之间相关系数分别为0.884和0.630; 由抽穗期建立的回 归模型估测灌浆期的叶片含硫量、叶绿素含量与实测值之间相关系数分别为0.659和0.768,均通过显著检验。