水体叶绿素a浓度遥感反演方法研究进展

针对水体叶绿素a浓度反演问题,从反演所需的遥感数据源、主要研究区、主要研究单位以及反演模型4个方面,系统介绍了叶绿素a浓度遥感反演的发展现状,分析了现有水体叶绿素a遥感反演方法的优缺点,提出了目前存在的问题,并对水体叶绿素a浓度反演研究进行了展望。     

曹妃甸近海表层悬浮泥沙遥感定量监测研究

在曹妃甸近海水体实测光谱数据分析的基础上,与同步采集的水体悬浮泥沙浓度进行相关分析,选用合适的TM数据的遥感变量参数,根据2008年实测的四个剖面29个站点的海洋水色数据建立了水体悬浮泥沙浓度与TM数据对应的遥感定量反演模型,并用18个独立样本点进行了精度评价.研究结果表明:曹妃甸近海水体光谱曲线基本呈现单峰现象,敏感...     

长时序大范围内陆水体光学遥感研究进展

地球表面的江河、湖泊和水库等内陆水体是水资源的主要组成部分,由气候变化和人类活动所引起的内陆水体分布和水质时空变化等问题已成为各国科学家和政府关注的热点.相比常规实地采样监测手段,卫星遥感在长时序、大范围内陆水体监测方面具有重要优势.受到海洋水色遥感理论和方法的推动,同时也得益于内陆水体光学特性数据的不断积累,近年来内...     

Remote determination of chromophoric dissolved organic matter in lakes,China

Chromophoric dissolved organic matter (CDOM) strongly influences the water-leaving radiance from aquatic ecosystems. In most inland waters, the remote determination of CDOM absorption presents a central challenge due to their complex optical conditions. However, identifying the temporal and spatial variability of CDOM is fundamental to the understanding of aquatic biogeochemical dynamics. In the present study, semi-analytical and empirical modeling approaches were used to examine CDOM absorption in four, shallow, inland water bodies using the spectral bands and sensitivities of major satellite observational systems. Of the models examined, an empirical multiband model was found to provide the highest correlation with measured CDOM absorption. The spectral characteristics of the MERIS sensors yielded the best results with respect to the other available satellite sensors. High detrital load was observed to be a major impediment to estimating CDOM absorption, while lakes with elevated phytoplankton biomass did not present similar problems.     

Uncertainty analysis of remote sensing of colored dissolved organic matter: Evaluations and comparisons for three rivers in North America

The uncertainties involved in remote sensing inversion of CDOM (Colored Dissolved Organic Matter) were analyzed in estuarine and coastal regions of three North American rivers: Mississippi, Hudson, and Neponset. Water optical and biogeochemical properties, including CDOM absorption and above-surface spectra, were collected in very high resolution. CDOM’s concentrations (a_g(440), absorption coefficient at 440 nm) were inverted from EO-1 Hyperion images, using a quasi-analytical algorithm for CDOM (QAA-CDOM). Uncertainties are classified to five levels, in which the underwater measurement uncertainty (level 1), image preprocessing uncertainty (level 4) and inverse model uncertainty (level 5) were evaluated. Results indicate that at level 1, in situ CDOM measurement is significant with 0.1 in the unit of QSU and 0.01 in the unit of a_g(440) (m⁻¹). At level 4, surface wave is a potential uncertainty source for high-resolution images in estuarine and coastal regions. The remote sensing reflectance of wavy water is about 10 times of the truth. At level 5, the overall uncertainty of QAA-CDOM inversion is 0.006 m⁻¹, with accuracy R² = 0.77, k = 1.1 and RMSE_log = 0.33 m⁻¹. The correlations between uncertainties and other water properties indicate that the large uncertainty in some rivers, such as the Neponset and Atchafalaya, might be caused by high-concentration chlorophyll or sediments. The relationships among the three level uncertainties show that the level 1 uncertainty generally does not propagate into level 4 and 5, but the large uncertainty at level 4 usually introduce large uncertainty at level 5.     

Estimating canopy water content using hyperspectral remote sensing data

Hyperspectral remote sensing has demonstrated great potential for accurate retrieval of canopy water content (CWC). This CWC is defined by the product of the leaf equivalent water thickness (EWT) and the leaf area index (LAI). In this paper, in particular the spectral information provided by the canopy water absorption feature at 970 nm for estimating and predicting CWC was studied using a modelling approach and in situ spectroradiometric measurements. The relationship of the first derivative at the right slope of the 970 nm water absorption feature with CWC was investigated with the PROSAIL radiative transfer model and tested for field spectroradiometer measurements on two test sites. The first site was a heterogeneous floodplain with natural vegetation like grasses and various shrubs. The second site was an extensively grazed fen meadow.     

Examining human heat stress with remote sensing technology

Heat stress as an environmental hazard which can seriously affect productivity, health, or even survival of individuals has long been studied. Despite the endeavors that have been made to address the issue quantitatively with various heat stress indices, they are often measured at scatter sites. This research devotes to revealing human heat stress within continuous space with remote sensing technology. The study began with the retrieval of dry-bulb temperature from land surface temperature (LST) with empirical models. As wet-bulb temperature was calculated from dry-bulb temperature and relative humidity, discomfort index (DI) as an indicator of heat stress was revealed for the study area at 1 km spatial resolution for three summer days. Results indicated that DI can be derived within continuous space with remotely sensed data, and its spatial distribution can be dramatically affected by relative humidity. Further comparison between DI and LST indicated that LST as a widely utilized indicator of surface thermal condition fails to address human heat stress as environmental factors such as relative humidity are not taken into account.     

基于水体光学分类的二类水体水环境参数遥感监测进展

二类水体主要包括内陆及近岸水体,受浮游植物、悬浮颗粒、有色可溶性有机物等多种因素影响,光学特性复杂多变,难以建立统一的水环境参数遥感定量估算模型.针对水体的光学特征,进行水体光学分类,进而反演水环境参数的方法,不仅能够提高参数估算精度,而且便于模型在同类水体中推广应用.水体光学分类方法主要包括基于固有光学特征的光学分类...     

A three-band semi-analytical model for deriving total suspended sediment concentration from HJ-1A/CCD data in turbid coastal waters

The accurate assessment of total suspended sediment (TSM) concentration in coastal waters by means of remote sensing is quite challenging, due to the optical complexity and significant variability of these waters. In this study, three-band semi-analytical TSM retrieval (TSTM) model with HJ-1A/CCD spectral bands was developed for the retrieval of TSM concentration from turbid coastal waters. This model was calibrated and validated by means of one calibration dataset and three independent validation datasets obtained from three different turbid waters. It was found that the TSTM model may be used to retrieve accurate TSM concentration data from highly turbid waters without the spectral slope of the model requiring further optimization. Finally, the TSM concentration data were quantified from the HJ-1A/CCD images after atmospheric correction using the dark-object subtraction technique. Upon comparing the model-derived and field-measured TSM concentration data, it was observed that the TSTM model produced <29% uncertainty in deriving TSM concentration from the HJ-1A/CCD data. These findings imply that the TSTM model may be used for the quantitative monitoring of TSM concentration in coastal waters, provided that the atmospheric correction scheme for the HJ-1A/CCD imagery is available.     

跨时空观下的遥感应用新视野

遥感是一门应用性极强的现代地球信息学科,在总结分析遥感学科理论发展与遥感应用新特征基础上,进行遥感学科发展与应用理论探索,是推动遥感学科与应用迈上新台阶的重要任务。本文通过对现有遥感学科组成及分类体系的分析,首先提出了一种基于方法论的遥感学科分类新方法,在分析遥感应用中普遍存在的跨时空特征基础上,从遥感应用新视野提出了跨时空遥感的理论,最后结合典型案例剖析了跨时空遥感的应用。跨时空遥感理论的建立顺应遥感学科发展的需要,遥感应用时空观的提出对今后遥感应用具有参考价值。     

Estimating the Great Lakes net radiation using satellite remote sensing and MERRA reanalysis

ABSTRACT

The net all-wave radiation of the Great Lakes (GL) is a key to understanding the effects of climate change on the GL. There is a high possibility of underestimating the net all-wave radiation of the GL when using existing methodologies with inputs from near-shore and land-based meteorological data. This study provides the first technique to estimate net all-wave radiation over the GL from July 2001 to December 2014 using a combination of data from satellite remote sensing, reanalysis data sets, and direct measurements. The components of the surface radiation budget estimated from the proposed method showed good statistical agreement. The instantaneous net radiation estimated by our methods was compared with the in situ measurements from June 2008 to April 2012 (Stannard Rock Lighthouse: SR) and September 2009–April 2011 (Spectacle Reef Lighthouse: SP). The comparisons from SR and SP also showed strong statistic agreement (R²?=?0.74 and 0.7; RMSE?=?9.26 and 10.60?W?m^?2 respectively). Monthly spatial variations of net shortwave radiation varied with cloud cover and surface albedo while net longwave radiation varied with the temperature difference between the water surface and the atmosphere.     

Dynamics of chromophoric dissolved organic matter in Mandovi and Zuari estuaries — A study through in situ and satellite data

The spatial and temporal distribution of absorption of chromophoric dissolved organic matter at 440 nm (a_CDOM (440)) in the Mandovi and Zuari estuaries situated along the west coast of India, has been analysed. The study was carried out using remotely sensed data, obtained from the Ocean Colour Monitor (OCM) on board the Indian Remote Sensing satellite — P4, together with in situ data during the period January to December 2005. Satellite retrieval of CDOM absorption was carried out by applying an algorithm developed for the site. A good correlation (R=0.98) was obtained between satellite derived CDOM and in situ data. Time series analysis revealed that spatial distribution of CDOM has a direct link with the seasonal hydrodynamics of the estuaries. The effect of remnant fresh water on CDOM distribution could be analysed by delineating a plume in the offshore region of the Zuari estuary. Though fresh water flux from terrestrial input plays a major role in the distribution of CDOM throughout the Mandovi estuary, its role in the Zuari estuary is significant up to the middle zone. Other processes responsible for feeding CDOM in both the estuaries are coastal advection, in situ production and resuspension of bottom settled sediments. The highest value of a_CDOM(440) was observed in the middle zone of the Mandovi estuary during the post-monsoon season. The relation between a_CDOM(440) and S (spectral slope coefficient of CDOM) could differentiate CDOM introduced in to estuaries through multiple sources. The algorithm developed for the Mandovi estuary is S=0.003 [a_CDOM(440)^−0.7091] while for the Zuari estuary, S=0.0031 [a_CDOM(440)^−0.777], respectively.     

内陆水体藻蓝蛋白遥感反演研究进展

藻蓝蛋白(PC),作为蓝藻的标志性色素,通常被用作进行蓝藻水华遥感监测的标志物.近年来,内陆水体水质恶化,富营养化加剧,藻华频发,PC遥感反演研究越来越受到关注.本文从PC光学特性、反演算法开发、卫星传感器应用等方面难点及干扰因素,综合梳理了过去30 a PC遥感反演研究的发展历程和趋势,以期理解国内外相关研究的新思路...     

Application of Aqua MODIS sensor data for estimating chlorophyll a in the turbid Case 2 waters of Lake Erie using bio-optical models

There is considerable interest in accurately estimating water quality parameters in turbid (Case 2) and eutrophic waters such as the Western Basin of Lake Erie (WBLE). Lake Erie is a large, open freshwater body that supports diverse ecosystem, and over 12 million people in the mid-western part of the United States depend on it for drinking water, fisheries, navigational, and recreational purposes. The increasing utilization of the freshwater has deteriorated the water severely and currently the lake is experiencing recurring harmful algal blooms (HABs). Improving the water quality of Lake Erie requires the use of robust monitoring tools that help water quality managers understand sources and pathways of influxes that trigger HABs. Satellite-based remote sensing sensor such as the moderate resolution imaging spectroradiometer (MODIS) may provide frequent and synoptic view of the water quality indices. In this study, data set from field measurements was used to evaluate the performance of 14 existing ocean color algorithms. Results indicated that MODIS data consistently underestimated the chlorophyll a concentrations in the WBLE, with the largest source of errors from dissolved organic matter and xanthophyll accessory pigments in this data set. Most of the global algorithms, including OC4v4 and the Baltic model, generated near-identical statistical parameters with an average R² of ~0.57 and RMSE ~2.9 μg/l. MODIS performed poorly (R² ~0.18) when its NIR/red bands were used. A slightly improved model was developed using similar band ratio approach generating R² of ~0.62 and RMSE ~1.8 μg/l.     

Fusion of RADARSAT-2 and multispectral optical remote sensing data for LULC extraction in a tropical agricultural area

In this study, we investigated the performance of different fusion and classification techniques for land cover mapping in Hilir Perak, Peninsula Malaysia using RADAR and Landsat-8 images in a predominantly agricultural area. The fusion methods used are Brovey Transform, Wavelet Transform, Ehlers and Layer Stacking and their results classified into seven different land cover classes which include (1) pixel-based classifiers (spectral angle mapper (SAM), maximum likelihood (ML), support vector machine (SVM)) and (2) Object-based (rule-based and standard nearest neighbour (NN)) classifiers. The result shows that pixel-based classification achieved maximum accuracy of the optical data classification using SVM in Landsat-8 with 74.96% accuracy compared to SAM and ML. For multisource data classification, the highest overall accuracy recorded for layer stacking (SVM) was 79.78%, Ehlers fusion (SVM) with 45.57%, Brovey fusion (SVM) with 63.70% and Wavelet fusion (SVM) 61.16%. And for object-based classifiers, the overall classification accuracy is 95.35% for rule-based and 76.33% for NN classifier, respectively. Based on the analysis of their performances, object-based and the rule-based classifiers produced the best classification accuracy from the fused images.     

湖泊遥感研究进展与展望

湖泊遥感作为一门新型交叉学科,是湖泊科学和遥感科学的重要分支.本文探讨了湖泊遥感科学的研究对象、内容和方法,通过梳理国内外总体研究进展,总结出湖泊遥感的5个发展趋势:(1)关注问题,从兴趣导向发展到问题导向;(2)观测手段,从地基遥感/中分辨率卫星发展到高分辨率/高光谱/无人机;(3)算法算力,从单机版经验/机理模型发...     

中分辨率成像光谱仪的海冰密集度遥感反演

海冰信息在船舶运输、天气预报和全球气候预测等领域都起着重要作用.一直以来微波遥感是卫星监测海冰密集度的主要手段,目前基于可见光遥感的中分辨率海冰密集度产品还较少,其中只有NOAA发布了相关业务化产品,但其所采用的算法对低密集度海冰反演准确性仍存在提升空间.本文在Liu提出的算法基础上进行改进,提出了最邻近像素法确定纯冰...     

中国高光谱遥感的前沿进展

高光谱成像技术具有光谱分辨率高、图谱合一的独特优势,是遥感技术发展以来最重大的科技突破之一。中国的高光谱遥感发展与国际基本同步,在国家和省部级科研项目的支持下,解决了高光谱遥感信息机理、图像处理和多学科应用等方面多项世界性难题,有效解决了高光谱遥感理论研究与多领域应用中的关键技术瓶颈,实现了在农业、地矿、环境、文物保护等多领域的成功应用,产生了显著的社会经济效益。本文回顾了中国高光谱遥感技术的前沿研究进展,总结分析了取得的主要创新性成果。     

光学遥感影像智能化处理研究进展

随着对地观测技术的发展,海量遥感影像不断传输到地面。传统的遥感信息处理方法在处理效率、精度上的不足,限制了遥感信息的挖掘及利用,亟需发展智能化方法满足遥感影像处理的需求。受自然界中生物进化机制的启发,基于进化计算的遥感影像智能化处理方法具有以下特点:(1)拥有全局优化能力,对目标函数的优化能力更强;(2)具有自组织、自学习的特点,能够从遥感数据本身学习,不依赖数据分布等先验信息;(3)拥有处理多目标问题的能力,同时考虑多个目标函数而不需要人工确定它们之间的权重。因此,智能化遥感信息处理方法能够在海量遥感影像中有效地提取适用于不同应用目的的信息。本文主要介绍智能化遥感信息处理方法的典型应用包括遥感影像智能化分类(监督分类、聚类)、遥感影像亚像素信息提取(高光谱影像混合像元分解、亚像元制图),并讨论了遥感信息智能化处理方法的发展方向。     

多源遥感数据管理与远程处理集成实现

针对目前对多源遥感影像数据管理与远程处理的集成应用研究较少的现状,文章基于FTP、关系数据库和空间数据库引擎设计多源遥感影像数据及其元数据与快视图数据的一体化管理方案,基于Web Service与PCI-EASI设计遥感影像远程处理服务,并对多源遥感影像数据管理与远程处理功能进行集成,通过综合运用FTP和Web Service技术,提高了数据管理效率和应用的灵活性。最后以"粤港澳水质遥感监测系统"为例,实现了对多源遥感影像数据的有效管理及水质监测业务的系统化,验证了研究成果的可行性和实用性。