Designing Service Architectures for Distributed Geoprocessing: Challenges and Future Directions

In this paper we study the feasibility of using services offered by a Spatial Data Infrastructure as a basis for distributed service oriented geoprocessing. By developing a prototype we demonstrate that a Spatial Data Infrastructure facilitates rapid development of applications that solve typical problems for an existing risk management application. The prototype provides users with a distributed application that enables the assessment of fire damage areas based on land cover data in a given area. The services involved in the application include: Web Feature Services, Web Map Services, a Gazetteer Service, a Catalogue Service, and Geoprocessing Services. We present the architecture of the application and describe details about implementation‐specific issues. We conclude that current OGC specifications provide a sound basis for developing service oriented architectures for geographic applications; however, in particular for geoprocessing applications, we question the feasibility of the use of Web Feature Services as data sources for larger amounts of data and call for further research in this direction.     

锡林浩特草原区域MODIS LAI产品真实性检验与误差分析

本文研究了LAI产品真实性检验的指标和方法,建立了LAI产品真实性检验的流程,将遥感产品真实性检验误差分解为模型误差、数据定量化差异和尺度效应3个方面。以内蒙古锡林浩特草原为研究区,结合实测数据和Landsat TM数据建立NDVI-LAI模型,得到LAI验证参考"真值",据此"真值"按照本文的流程对MODIS LAI产品进行验证,分析了研究区MODIS LAI产品真实性检验的误差来源。研究表明,该研究区的MODIS LAI(MOD15A2)产品相对高估约25%。各个误差因素中,LAI遥感模型差异对于结果影响最大,MODIS LAI模型高估了该区域草地LAI(高估约44.2%);数据定量差异的影响也比较大,MODIS地表反射率数据与Landsat TM地表反射率数据的差异造成了约16.2%的低估;尺度效应的影响较小,造成约3.1%的低估,其中NDVI-LAI模型的尺度效应带来2.4%的低估,NDVI数据的尺度效应造成约0.7%的低估。     

高光谱目标探测的进展与前沿问题

针对高光谱目标探测问题的主要挑战,将高光谱目标探测的进展与前沿问题分为两个方面进行综述。基于信号检测理论的方法如结构化背景的约束能量最小化方法、非结构化背景的自适应一致性余弦评估器等,是高光谱目标的探测经典算法;随着统计模式识别与机器学习领域中新技术的出现,一些数据驱动的目标探测方法逐渐成为了高光谱目标探测的前沿问题,如核方法、稀疏表达方法等。概述了两类方法的特点,比较了各自的优势和不足,并展望了高光谱目标探测未来的发展趋势。     

不透水面产品在重庆地区的验证

以国家地球系统科学数据中心发布的不透水面数据产品为基础,利用地理国情数据中地表覆盖分类提取的不透水面成果进行重庆地区精度验证,并与兴趣点数据(Point of Interest,POI)、夜间灯光数据进行相关性和空间重叠度分析.结果表明:不透水面产品在重庆地区验证情况较好,不透水面产品与地理国情不透水面耦合性较高,能够较为准确地反映城市建设状况,全市不透水面产品有71.61％以上位于地理国情不透水面范围内;不透水面产品面积与POI核密度、夜间灯光亮度具有正相关性,但相关系数不高,且空间分布具有一定差异.通过不透水面产品在重庆地区验证分析,能够对未来不透水面提取优化研究提供基础支撑.     

试论中国NSDI建设的若干问题

国家空间数据基础设施(National Spatial Data Infrastructure,简称NSDI)是"数字地球"的基础.要发展中国数字地球及其应用,就必须加大NSDI的建设力度.文中主要从(地球)空间数据框架、空间数据标准、空间数据交换网络和空间数据协调管理机构4个方面,介绍了中国NSDI的有关进展,分析了其中存在的一些问题,讨论了发展方向.     

Validation of MODIS Vegetation Continuous Fields for monitoring deforestation and forest degradation: two cases in Mexico

This study assesses whether MODIS Vegetation Continuous Fields percent tree cover (PTC) data can detect deforestation and forest degradation. To assess the usefulness of PTC for detecting deforestation, we used a data set consisting of eight forest and seven non-forest categories. To evaluate forest degradation, we used data from two temperate forest types in three conservation states: primary (dense), secondary (moderately degraded) and open (heavily degraded) forest. Our results show that PTC can differentiate temperate forest from non-forest categories (p = 0.05) and thus suggests PTC can adequately detect deforestation in temperate forests. In contrast, single-date PTC data does not appear to be adequate to detect forest degradation in temperate forests. As for tropical forest, PTC can partially discriminate between forest and non-forest categories.     

试论中国NSDI建设的若干问题

国家空间数据基础设施是“数字地球”的基础。要发展中国数字地球及其应用,就必须加在ＮＳＤＩ的建设力度,文中主要从（地球）空间数据框架,空间数据标准,空间数据交换网络和空间数据协调管理机构４个方面,介绍了中国ＮＳＤＩ的有关进展,分析了其中存在的一些问题,讨论了发展方向。     

利用分离性测度多类支持向量机进行高光谱遥感影像分类

提出了一种基于变换域离散度排序的高光谱图像快速压缩算法。该算法针对高光谱数据在Hadamard变换域的特性,自适应地选择有利的排列顺序,将变换域光谱矢量的各维度按照离散度进行重新排序,不仅使光谱矢量的大部分能量和差异集中在低维部分,而且把高信噪比的分量调整到低维空间,并据此构造出高效的码字排除不等式,最后结合LBG(Linde Bazo Gray)聚类算法,通过矢量量化快速完成高光谱图像的编码。在不同压缩比下进行实验,结果表明,本文提出的高光谱图像压缩算法能在保证良好的图像恢复质量的前提下,大幅度降低计算复杂度,实现快速压缩。     

基于MODIS数据的中国陆面制图：方法软件和数据产品

本文介绍一个自动处理MODIS 1B数据并生产覆盖全中国陆面产品的软件系统。该算法改进了LAI（MOD15）,土地覆被分类（MOD12）,云检测（MOD35）,陆面反射率（MOD09）和气溶胶（MOD04）产品。这些算法的输入数据都是本地获取的参数,能够有效降低其带来的不确定性。产生的部分新产品是NASA标准产品中没有的,包括森林火烧迹地和PAR。数据处理系统运行于中国科学院资源与环境数据中心。     

利用POLDER数据验证MODIS BRDF模型参数产品及Ross-Li模型

将MODIS BRDF模型参数产品(MCD43A1)模拟的近红外波段反射率与从POLDER-3/PARASOL BRDF全球数据集中筛选的9961个像元的BRDF观测数据进行对比,验证了MCD43A1所采用的RossThick-LiSparseR BRDF 模型(Ross-Li模型)拟合二向反射的能力。结果表明,Ross-Li模型总体上可以有效地模拟地物的二向反射,所有像元的近红外波段反射率模拟值与POLDER-3观测数据之间的R²达到0.943,RMSE为0.016,模拟反射率比POLDER-3数据总体偏低5.2%。但Ross-Li模型明显低估了热点反射率,热点模拟结果比POLDER-3数据平均偏低14%,模拟值的R2为0.824,RMSE为0.07。热点反射率模拟误差与地表覆盖类型有关,针叶林热点反射率模拟值偏低最严重,其次是阔叶林、草地与农田,灌木与裸地热点反射率模拟值偏低相对较小。通过修正Ross-Li模型中的体散射核,可以明显改善热点反射率的模拟效果(R²＝0.839,RMSE＝0.043)。Ross-Li模型对天底、暗点等特征方向反射率的模拟较为准确。Ross-Li模型的模拟精度随太阳天顶角和观测天顶角的增大而降低。对于农田与草地而言,Ross-Li模型的模拟精度随NDVI的增加而降低;但在森林与灌木覆盖条件下,当NDVI约为0.5时,Ross-Li模型的模拟效果最差。     

HJ-1A/B卫星CCD影像辅助的MODIS水色大气校正产品质量改进

针对我国近岸高浑浊水体区域MODIS短波红外波段大气校正产品中存在的信号饱和及条带问题,利用神经网络模型,采用准同步的HJ-1A/B卫星CCD影像及实测遥感反射率数据对MODIS/Terra水色遥感大气校正产品进行了质量改进。改进后结果与MODIS/Terra遥感反射率产品相比,平均相对误差为13.3%,信号饱和区域修复结果与实测数据各波段平均相对误差为28.2%。结果表明,该方法在保证结果精度的情况下,能有效地修复MODIS/Terra水色波段因为信号饱和而产生的数据空白区域,同时也能较好地解决MODIS/Terra大气校正产品中的条带问题。     

NASA MODIS海冰产品评价分析——以辽东湾海冰监测为例

NASA开发的MODIS海冰产品可提供全球范围的海冰分布和冰表温度信息,但将其直接用于局地和区域海冰监测时,其精度还有待进一步验证.以辽东湾冬季海冰监测为例,对MODIS海冰产品进行了分析,发现该产品将区域内绝大部分海冰标识为云.根据NASA的海冰算法,利用反射率和冰表温度(Ice Surface Temperatur...     

一种新的基于MODIS的地表含水量模型构造与验证

考虑到水的光谱反射特性，提出了一种新的统一地表含水量指数（SWCI）模型，并通过国家气象局降雨量和台站土壤水对应数据进行了验证。本方法能较好地反映地表的含水量值及其变化，可用于大范围且快速的土壤水遥感监测。     

地面和机载多角度观测数据的反照率反演及对MODIS反照率产品的初步验证

MODIS的反照率产品采用半经验的二向性反射核驱动模型算法(AMBRALS),对16天累积观测的多角度遥感数据进行反演。产品的应用需要相关研究的地面观测数据进行验证。主要研究基于地面气象台站用反照率表观测的反照率数据、地面和机载多角度遥感数据通过AMBRALS算法反演得到的反照率,与MODIS相应的地面反照率产品做比较的降尺度验证方法,并提供对MODIS反照率产品的初步验证结果。     

Validation of MERIS Case-2 Water Products in Lake Taihu,China

Three artificial neural network (ANN) processors available as plug-in modules for the Basic ERS & ENVISAT (A)ATSR and MERIS Toolbox (BEAM) were validated in Lake Taihu, China. Mean deviations of reflectance derived from Lakes\Boreal and Lakes\Eutrophic were 10-90%, while reflectance from the FUB-WeW processor showed larger errors. All processors showed underestimates of chlorophyll a (Chl-a), total suspended matter (TSM), and phytoplankton pigment absorption, while particulate scattering values were severely overestimated. None of the readily available MERIS processors is currently able to separate atmospheric and water-leaving radiance over Lake Taihu, while the retrieval of phytoplankton biomass through ANN processors shows promise.     

基于波谱知识库的MODIS叶面积指数反演及验证

目前用物理模型反演叶面积指数普遍存在缺少先验知识的状况，如何获得准确的先验知识是遥感走向应用的一个关键环节。中国典型地物标准波谱数据库就是结合国家重大行业中的应用需求，研究制定地物波谱获取与分析的技术规范和数据标准，建立典型地物标准波谱数据库。从波谱数据库提取模型反演所需要的先验知识，实现了基于SAIL模型的MODIS数据（经过几何纠正与大气纠正）叶面积指数的反演。另外，基于TM数据，对MODIS混合像元进行了分解，用纯像元的叶面积指数与实测数据进行对比验证，同时，反演结果与NASA的LAI产品也进行了对比，结果表明基于波谱库的先验知识可以有效的提高叶面积指数的反演精度。     

Validation of MODIS integrated water vapor product against reference GPS data at the Iberian Peninsula

In this work, the water vapor product from MODIS (MODerate-resolution Imaging Spectroradiometer) instrument, on-board Aqua and Terra satellites, is compared against GPS water vapor data from 21 stations in the Iberian Peninsula as reference. GPS water vapor data is obtained from ground-based receiver stations which measure the delay caused by water vapor in the GPS microwave signals. The study period extends from 2007 until 2012. Regression analysis in every GPS station show that MODIS overestimates low integrated water vapor (IWV) data and tends to underestimate high IWV data. R² shows a fair agreement, between 0.38 and 0.71. Inter-quartile range (IQR) in every station is around 30–45%. The dependence on several parameters was also analyzed. IWV dependence showed that low IWV are highly overestimated by MODIS, with high IQR (low precision), sharply decreasing as IWV increases. Regarding dependence on solar zenith angle (SZA), performance of MODIS IWV data decreases between 50° and 90°, while night-time MODIS data (infrared) are quite stable. The seasonal cycles of IWV and SZA cause a seasonal dependence on MODIS performance. In summer and winter, MODIS IWV tends to overestimate the reference IWV value, while in spring and autumn the tendency is to underestimate. Low IWV from coastal stations is highly overestimated (∼60%) and quite imprecise (IQR around 60%). On the contrary, high IWV data show very little dependence along seasons. Cloud-fraction (CF) dependence was also studied, showing that clouds display a negligible impact on IWV over/underestimation. However, IQR increases with CF, except in night-time satellite values, which are quite stable.     

MODIS MAIAC高分辨率气溶胶光学厚度产品在干旱区的适用性研究

The Multiangle Implementation of Atmospheric Correction (MAIAC) is a new generic algorithm applied to MODIS measurements to retrieve Aerosol Optical Depth (AOD) over land at high spatial resolution (1 km). It is expected to have good potential in improving the AOD inversion of dark and bright surfaces of land. The high spatial resolution of the MAIAC retrievals enhances the capability to distinguish aerosol sources and determine subtle aerosol features. Retrieval of satellite aerosol properties is therefore often challenging due to considerable seasonal variations in surface reflectance and aerosol properties. To date, MAIAC AOD over arid regions under data-scarce environments has been evaluated. Considering these uncertainties, a systematic effort was made to evaluate the MAIAC AOD over arid areas using Aerosol Robotic Network (AERONET) ground-based AOD from 2000 to 2019. Considerable MAIAC-AERONET AOD matchups demonstrate the capability of MAIAC to retrieve AOD over varied ground surfaces and temporal scales. We employed a broader perspective and evaluated MAIAC performance under varying aerosol loading, aerosol types, surface coverage, and viewing geometry. The results show that (1) MAIAC performed well over various temporal scales, including monthly, seasonal and annual scales. Although underestimation is prevalent, MAIAC AOD in the spring and winter months correspond to the highest and lowest retrieval accuracies, respectively. (2) MAIAC performed well over four different typical land surface land surfaces, showing the highest retrieval accuracy over grassland, yet it slightly overestimated AOD. Construction land is most affected by the aerosol model, and farmland is strongly disturbed by surface reflectance and underestimated most obviously (Below EE = 46.5%). (3) The accuracies of the MAIAC AOD observations of Terra and Aqua are similar; R2 is more than 0.75, but both are underestimated, especially for Aqua. In general, MAIAC’s ability to provide AOD at high spatial resolution appears promising over arid areas and is expected to be helpful to study the characteristics of fine aerosols in arid areas and promote the study of local air quality. © 2023 Science Press. All rights reserved.     

Comparison of MODIS fPAR Products with Landsat-5 TM-Derived fPAR over Semiarid Rangelands of Idaho

While validation of the MODIS fPAR product is well behind that of the LAI product, it is recently receiving more attention. In this study, MODIS fPAR and Landsat-5 TM-derived fPAR (TM fPAR) were calculated and quantitatively compared using imagery from 2005 to 2008 for the semiarid rangelands of Idaho, USA. fPAR change maps were calculated between active growth and late-summer senescence periods. Accuracy of the MODIS fPAR and TM fPAR were determined indirectly by incorporating field-based measurements of above-ground forage biomass and percent ground cover from a variety of sites (n = 442).