最新刊期
卷 18 ， 期 3 ， 2014
- 摘要：We propose an available method to generate land surface shortwave albedo at a 30 m spatial resolution in eight-day i nterval. The method uses at least one pair of fine-resolution remote sensing images（ e. g.,Landsat data） and coarse-resolution r emote sensing albedo products（MODIS albedo） to estimate the 30 m albedo on the date when the MODIS albedo is given without Landsat data. When MODIS albedo time-series is given,the time-series of a 30 m resolution albedo can be estimated. The method consists of three main steps:（1） generating fine-resolution shortwave albedo images based on Landsat ETM + data.（2） generating coarse-resolution shortwave albedo images based on MODIS albedo products.（3） using STARFM model to blend spatial i nformation from fine-resolution shortwave albedo images and temporal information from coarse resolution shortwave albedo i mages to estimate high spatio-temporal resolution albedo. Comparison with actual ETM + albedo shows that the predictions are of reasonable accuracy,and maintain a high level of spatial detail. For the problem of degrading estimation accuracy in the STARFM model for heterogeneous r egions,this study presents an improvement by introducing the idea of mixed pixel decomposition. In u sing this method the predicted albedo shows bigger correlation coefficients and smaller deviations with actual ETM + albedo for heterogeneous regions.关键词：surface albedo;Landsat;MODIS;data fusing;high spatio-temporal resolution
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发布时间：2021-06-10 - 摘要：The Leaf Area Index（LAI） is essential in the remote sensing of vegetation,and is widely used in quantitative remote sensing products. LAI products should be validated to enable their effective applications in various fields. In this study,the indicators and methods of LAI product validation were investigated,and a process for LAI product validation was established. The grassland in Xilinhot,Inner Mongolia of China was selected as the study area. Landsat TM data and ground measurements were used to build the Normalized Difference Vegetation Index（ NDVI）-LAI model. Then,the "true"LAI reference for validation was established. The MODIS LAI product was also validated in this study according to the reference LAI and the proposed model. In addition,the sources of error in the MODIS LAI product were analyzed. Results showed that the MODIS LAI product（ i. e.,MOD15A2） in the study area was overestimated by approximately 25%. Among the factors that affected the error,the difference in LAI remote sensing models was the most dominant,leading to an overestimation of 44. 2% in the MODIS LAI model. Meanwhile,image quantitative difference exerted a significant influence,causing an underestimation of approximately 16. 2%. In addition to these two factors,the scale effect produced an underestimation of 3. 1%,including an underestimation of 2. 4% from the scale effect of the NDVI-LAI model,and an underestimation of 0. 7% from the scale effect of NDVI.关键词：Leaf Area Index（LAI）;MODIS LAI products;validation;scale effect
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发布时间：2021-06-10 - 摘要：To identify the type of noise in an Interferometric Syntheic Aperture Radar（InSAR） interferogram and facilitate more effective data processing,especially for interferogram filtering based on wavelet transform,we developed a novel method for identifying the noise type and estimating the noise level. This method combines wavelet transform with logarithmic transformation and includes an in-depth analysis of the characteristics of interferogram wavelet coefficients from the viewpoints of energy distribution and statistical interpretation. First,we investigated the energy distribution characteristics of low-frequency subband wavelet coefficients before and after the logarithmic transformation to identify the noise type of the interferogram. On this basis,the noise level could be estimated using high-frequency subband wavelet coefficients. From the analysis results of this study,we conclude that the noise type of the InSAR interferogram is additive noise,the high-frequency coefficients show a Gaussian distribution,and the noise level can be estimated by a high-frequency subband on one scale. These results provide further scope for noise analysis and p rocessing of InSAR interferograms based on wavelet transform.关键词：INSAR interferogram;noise;wavelet coefficient;energy
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发布时间：2021-06-10 - 摘要：The Global LAnd Surface Satellite Products System（GLASS） albedo product provides a gap-filled shortwave albedo map with high temporal resolution through which the occurrence of snow and rain and the variation of vegetation status can be d etected.The GLASS albedo is retrieved with the Angular Bin（AB） algorithm,which can estimate the shortwave albedo from a single observation of reflectance. To assess the accuracy of this albedo product,FLUXNET observations were used to calculate the actual surface albedo as the true value to validate the high-spatial resolution albedo derived from Landsat Thematic Mapper（TM） imagery at30 m by the AB algorithm. The Landsat TM albedo was then aggregated to 1 km resolution and was compared with the GLASS albedo at 1 km. The absolute error of the GLASS albedo is less than 0. 0163,which demonstrates itsreliabilityfor most a pplication requirements.关键词：albedo validation;GLASS;TM;scaling;FLUXNET
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发布时间：2021-06-10 - 摘要：Surface albedo significantly affects the balance of surface energy and variation of global climate. Previously,surface a lbedo products have achieved significant success; however,many problems remain,such as low temporal resolution and missing data. Based on the observation data of uniform sites and MCD43B3 production of MODIS,this article verifies three algorithms and their products that arrive separately from a surface albedo production called Global LAnd Surface Satellite（ GLASS）: AB1（ABD01）,AB2（ABD03）,and STF（ABD06）. Then,we analyze and compare the improvement in quality between the initial and f inal products of GLASS. The result shows that the product ABD06 has the best matching with ground observation data,where the RMSE is 0. 050 and R2is 0. 9. In addition,compared with MCD43B3’s surface albedo product,the best consistency is also observed for ABD06,which is supported by the largest number of valid data among the three different products（ ABD06 is 5507,ABD01 is 4290,and ABD03 is 3296）,and the RMSE is better than 0. 03,while R2is 0. 9. Therefore,ABD06 is suitable for the production of long time series’ surface albedo products. The statistical result for a large amount of data also shows that with up to80% of the d ata coming from GLASS’s three products,we can satisfy the accuracy requirement for the deviation between the climate model of the surface albedo and products（0. 02—0. 05）.关键词：surface albedo;MODIS;FLUXNET;time series;GLASS
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发布时间：2021-06-10 - 摘要：Long time series Global LAnd Surface Satellite（GLASS） Leaf Area Index（LAI） product（1981—2012） is generated from time-series MODIS and AVHRR reflectance data using general regression neural network method. This study assesses the performance of the GLASS LAI product in two ways:（1） by comparing the spatial and temporal characteristics of the GLASS LAI product with those of other moderate-resolution LAI global products and（2） by comparing the GLASS LAI values with ground measurement data. The results show that the GLASS LAI product achieved a good consistency with the MODIS and CYCLOPES LAI products at the global scale,although with differences in magnitude of LAI values. The largest differences occur between the GLASS and CCRS LAI products in high northern latitudes and close to the equator,followed by differences between the GLASS and MODIS LAI products and the GLASS and CYCLOPES LAI products. The GLASS and MODIS LAI products have more complete temporal trajectories than the CYCLOPES LAI product,while the GLASS and CYCLOPES LAI products have more continuous and realistic trajectories than the MODIS LAI product. The GLASS LAI product maintains reasonable profiles in c ontrast to the MODIS LAI product,which shows dramatic fluctuations,particularly during the growing seasons. Compared with 20 ground-measured LAI reference maps at 17 sites,the GLASS LAI product shows lower uncertainty,with an R-square of 0. 76 and RMSE of 0. 51,than the MODIS and CYCLOPES LAI products.关键词：Leaf Area Index（LAI）;GLASS;validation;MODIS;long time series
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发布时间：2021-06-10 - 摘要：Relative radiometric correction of remote sensing images is a basic data preprocessing technique used to eliminate r adiometric problems in images such as non-uniformity,stripe noises,and defective lines. Over the past 30 years,numerous relative radiometric correction methods and algorithms have been developed. This situation brings up three questions.（1） What are the differences and relationships among these methods?（2）What are the characteristics of each method?（3） How is a suitable method selected? To answer these questions,the methods are first classified into three categories: calibration-based,scene-based,and c omprehensive methods. Second,the mathematical models of the three categories of methods are provided in the new classification system. Then,each method is introduced and compared with the others. Third,the applicability of the methods is comprehensively analyzed according to the following aspects: non-uniformity characteristics,geometric characteristics,sensor calibration,and the comprehensive characteristics of images. Suggestions on selecting a suitable method are provided,and an example of image correction is demonstrated. Finally,the research tendency and several existing problems of relative radiometric correction are analyzed.The computer criteria for signal and noises,the evaluation system,and the influence on subsequent absolute corrections require f urther studies.关键词：relative radiometric correction;calibration-based relative radiometric correction method;scene-based relative radiometric correction method;comprehensive relative radiometric correction method;applicability analysis
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发布时间：2021-06-10 - 摘要：Speed Up Robust Features（SURF） is an improvement of Scale Invariant Feature Transform（SIFT）. When it is used to match remote sensing images,SURF can significantly increase matching speed,but slightly decrease matching accuracy. Thus,a r emote sensing image matching method based on Non-Subsampled Contourlet Transform（NSCT） and SURF is proposed in this paper. First,the remote sensing image to be matched and the reference image are decomposed by NSCT. Two corresponding l ow-frequency images are obtained. Then,to reduce the influence of high-frequency noise on matching results,two low-frequency images are inputted to the SURF algorithm to obtain pre-matching results. Finally,to solve the error matching problem of the SURF algorithm,the parameters of the transform model are solved by pre-matching results,and the mismatching is eliminated by using the random sample consensus algorithm. A large number of experiments were conducted,and the results show that compared with the SIFT and SURF algorithms,the proposed algorithm improves the matching speed,as well as the matching accuracy,and exhibits good performance in terms of resisting rotation,noise,and brightness changes.关键词：remote sensing image matching;Scale Invariant Feature Transform（SIFT）;Speed Up Robust Features（SURF）;Non-Subsampled Contourlet Transform（NSCT）
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发布时间：2021-06-10 - 摘要：Dramatic change of the grayscale in aerial images,such as high-brightness region and large areas of shadow,leads to a grayscale distortion phenomenon in dodging images. This study improves the method of background image generation in the Mask dodging algorithm and enhances the quality of background image by using an expansion and engulfment algorithm. The dodging experiment on an aerial image,which includes high-brightness rooftop,high-brightness water,and large areas of shadow,shows that the improved algorithm obtains better result than other current Mask dodging algorithms. The approach eliminates the grayscale distortion problem among the high-brightness and shadow regions effectively and enhances the texture details among the dark regions apparently.关键词：aerial image;Mask dodging;expansion and engulfment algorithm;background image;shadow
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发布时间：2021-06-10 - 摘要：We study the coldest vicarious calibration method for the Jason-2 Microwave Radiometer（JMR）. We simulated the o bserved value of the global minimum brightness temperature for three JMR channels using the microwave radiation transfer theoretical calculation model. Using 2008 to 2012 Jason-2 geophysical data record data products for global earth observations of brightness temperature,we establish a statistical model for identifying the coldest brightness temperature series. We then set up a spectral analysis model,according to the annual change characteristics,to remove the annual harmonic from the coldest brightness temperature series. Using the linear fitting method,the annual harmonic is removed and then extrapolated to the theoretical minimum brightness temperature,to calculate the annual drift of the JMR instrument.关键词：vicarious calibration method;radiative transfer model;harmonic analysis;Instrument drift;calibration
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发布时间：2021-06-10 - 摘要：Land Surface Temperature（LST）,widely recognized as one of the key indicators that influence the environment and ecological system,is involved in many land surface processes. It is regarded as an effective way to measure the LSTs at global and regional scales using the thermal sensors onboard satellite platforms. Many researchers have conducted studies and developed algorithms to retrieve LST from the thermal infrared imageries observed by sensors onboard different satellite platforms. For the sensors provided with one thermal band,such as Landsat TM /ETM +,CBERS,and HJ-1B,the single-channel（or mono-window） methods have been proposed as empirical models. However,the surface emissivity and atmospheric parameters（e. g.,water vapor content） that are not readily accessible to common users are indispensable when these empirical models are implemented. The quantitative applications of these methods will consequently be limited to some extent. To overcome this problem,a new approach called Multi-Temporal and Spatial Information-Based Single Channel（MTSC） is proposed,which is based on the spatial and temporal information obtained from multi-temporal images. The HJ-1B is considered as an example,owing to its frequent revisit. The preliminary results demonstrate that the HJ-1B surface temperature results retrieved by the MTSC method are spatially consistent with MODIS surface temperature products（both for land and sea surfaces）. Compared with the MODIS product,the LST is overestimated about 1 K and the sea surface temperature is overestimated about 0. 5 K for the HJ-1B. The HJ-1B results retrieved by the MTSC method show more details with spatial integrity. Finally,followed by the in-depth analyses and discussions,some possible ways to improve the MTSC method are also suggested,including determining the similar pixels,modifying the objective function for optimization,and initializing the parameters adaptively. The MTSC method could be more perfect in view of its retrieval accuracy and practicability for common users,given that these improvements are made.关键词：spectral similarity;radiative transfer equation;land surface emissivity;atmospheric correction;MOD11
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发布时间：2021-06-10 - 摘要：Improving the inversion accuracy of soil moisture by optical and passive microwave remote sensing data is an important task to develop quantitative remote sensing. Based on the Soil Moisture Experiment in 2002（ SMEX02） data set,the relationship between the surface soil moisture and the L-band soil emissivity was analyzed. We also discussed the influence of vegetation on soil microwave radiation and deduced a new soil moisture inversion algorithm that takes L-band soil emissivity and Normalized Difference Vegetation Index（NDVI） as independent variables. The SMEX02 experimental data indicates that the correlation b etween the soil moisture and the L-band soil emissivity decreases rapidly with the increase in NDVI. The verification result shows that the new algorithm developed in this paper has higher inversion precision than the empirical algorithm for the surface soil moisture covered by crop canopy. In relative terms,the inversion RMSE increased from 0. 053 to 0. 047 for H polarization and from 0. 0452 to 0. 0348for V polarization. The R2variable increased from 0. 70 to 0. 81 and from 0. 79 to 0. 86 for H and V polarization,respectively.关键词：soil moisture;passive microwave remote sensing;SMEX02 experiment;synergistic inversion
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发布时间：2021-06-10 - 摘要：Fronts in the Bohai sea are detected based on BJ-1 small satellite data using a gravitation model. We select the red band as the experimental band due to the characters of small satellite data. In addition,the fronts south of the Bohai Bay and east of the Liaodong Bay are chosen as experimental areas because they are both eligible for front detection. In the experiments,a linear stretch and band computation are first applied to data in order to protrude front information. The stretch intervals are set according to histograms. Then,utilizing a gravitation model,the fronts can be extracted from preprocessed data,and the results show that fronts can be successfully extracted from BJ-1 small satellite data usingthe gravitation model. The detected fronts are continuous and obvious. Compared with traditional front detection algorithms,the proposed algorithm can not only detect continuous and conspicuous fronts,but can also suppress noises.关键词：BJ-1 small satellite;model of universal gravity;front detection;Bohai
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发布时间：2021-06-10 - 摘要：In this study,forest background reflectivity was retrieved based on a four-scale model in Jiagedaqi District,northeastern China by using the bidirectional reflectance distribution function product from moderate resolution imaging spectroradiometer. The seasonal variation of forest canopy Bidirectional Reflectance Distribution Function（ BRDF） and background reflectivity were then observed. The results showed that:（1） in the study area,the characteristics of bidirectional reflectivity of the mixed and coniferous forests are similar. In summer,the BRDF of the broadleaf forest was lower than that in the coniferous forest and the mixed forest in the red band,with the opposite trend in the near-infrared band. The BRDF of different forest types presents obvious seasonal variation,especially in the deciduous forest area.（2） The background reflectivity in the red band was low,ranging from 0 to 0. 1 in the study area. The background reflectivity in near-infrared band was mostly more than 0. 3 with high spatial variation.（3） The trends of the seasonal variation of background reflectance in different forest types were similar. However,the amplitudes of the seasonal variation in different forest types differed: the variation of background reflectance of the broadleaf forest was the largest,especially in the near-infrared band.关键词：MODIS BRDF;northeastern China forest;background reflectance;four-scale model
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发布时间：2021-06-10 - 摘要：Regionalization of the urban thermal environment is the technical basis for alleviating the conflict between urban socioeconomic development and the thermal environment based on partition management. In this paper,we constructed a regionalization model for the urban thermal environment.（1） Moderate Resolution Imaging Spectroradiometer land surface temperature products from four seasons were standardized and classified for characterizing the spatiotemporal pattern of the urban thermal environment in2008.（2） A comprehensive evaluation system of the urban thermal environment was constructed and the principal components were identified by using the spatial principal component analysis method.（3） A self-organizing mapping neural network was used for spatial regionalization of the urban thermal environment. The results show that the distribution levels of the urban heat island are clearer during the nighttime than during the daytime and the high-temperature zone has the higher aggregation degree in summer than in the other seasons. The composition of the underlying surface directly affects the urban thermal environment. The principal components affecting the urban thermal environment include vegetation coverage,geomorphology,urban construction scale,and anthropogenic heat emission. The Beijing metropolitan area was divided into seven urban thermal environment zones,and specific measures and suggestions were proposed for improving the urban thermal environment based on the multiple formation mechanisms of the urban thermal environment in each zone.关键词：thermal environment;regionalization;spatial principal component analysis;Artificial neural Network;Beijing
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发布时间：2021-06-10 - 摘要：<正>经研究决定"第十九届中国遥感大会"将于2014年9月20-23日在西安市召开。本届大会由中国遥感委员会主办,北京空间机电研究所、中国宇航学会空间遥感专业委员会、中国遥感应用协会光学遥感专业委员会共同承办。会议旨在交流近年来国内遥感领域在理论、技术与应用等方面的最新进展,展示遥感技术最新成果。大会同期将举行第八届中国青年遥感辩论会、遥感科技创新展、中国遥感影像艺术展、遥感科普文化周等活动。
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发布时间：2021-06-10 - 摘要：<正>针对全球叶面积指数（LAI）产品存在的数据缺失、不连续和不确定性较大等问题,北京师范大学全球变化数据处理与分析中心（http://www.bnudatacenter.com/）发布了1981年-2013年的全球GLASS LAI产品。该产品利用"多输入-多输出"的广义回归神经网络反演算法,将一年的MODIS或AVHRR地表反射率数据作为输入,一次性输出获得一年的LAI产品。GLASS LAI产品具有空间完整、时间序列平滑连续等特点,且精度优于MODIS和GEOV1等全球LAI产品,可以很好地反映全球植被的物候变换规律。基于该产品的部分研究成果请见本期"陆表遥感数据产品的分析研究"
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发布时间：2021-06-10
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