最新刊期
卷 17 ， 期 2 ， 2013
- 摘要：Polarized reflectance of land surface is essential to remote sensing, despite the fact that the reflectance information received by polarimeter is always overwhelmed by atmospheric polarization effect, which is stronger than that of the land objects. Subtracting the atmospheric effect, therefore, is a bottleneck problem in the polarization remote sensing over land surface. Atmospheric neutral point, which refers to a position where the skylight is unpolarized, is introduced in this paper as a tool for separating the polarization effect between objects and atmosphere. The ground experimental results show that when observing the land surface from neutral point, the polarization effect of the atmosphere is reduced to zero and the polarization information of land surface is maximized. The results indicated the feasibility of using atmosphere neutral points for atmospheric correction over land surface.关键词：polarization remote sensing;neutral point;Atmospheric correction
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发布时间：2021-06-10 - 摘要：Current algorithms of endmember extraction basically need manually determining the number of endmembers, which is not conducive to automatically process. The paper puts forward iterative algorithm for automatic identification and extraction of endmember. First, we obtain the similarity threshold among pixels by statistical analysis, and determine the criterion of candidate endmembers. Then, the internal and external correlation judgments of candidate endmembers are done, and ill-conditioned matrix to circumvent judgment on endmember spectral set is conducted. Finally, the criterion of candidate endmembers is the end of the iterative conditions. When the hyperspectral image contains no candidate endmembers, the endmember spectral set is got and the numbers of endmembers are determined. Experiments show the effectiveness of this method, by which the error risk of sequential endmember extraction algorithm can be avoided, and the degree of automation is improved.关键词：hyperspectral image;mixed pixel;determining endmember number;endmember automatic extraction;iterative unmixing
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发布时间：2021-06-10 - 摘要：We propose a new method for extracting urban rivers from high resolution remotely sensed imagery in the frequency domain. Radial and angular samplings are used to analyze the magnitude spectrum （frequency spectrum） signature of the urban river after discrete Fourier transformation of the remotely sensed imagery into the frequency spectrum. The bilinear features of the urban river in high resolution remotely sensed imagery are divided into two parts: edge features and low frequency information. The frequency recognition marks of these two parts are retrieved based on the periodic texture frequency spectrum model and the spectrum energy discipline of ground objects. Meanwhile, arc ring two dimensional log Butterworth band-pass filter and two dimensional Butterworth low-pass filter are designed to extract edge features and low frequency information, respectively. The two extraction results can be used in extracting urban rivers effectively from highresolution remotely sensed imagery. Evaluation of the extraction results shows that the proposed algorithm is effective in extracting urban rivers from high spatial resolution remotely sensed imagery.
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发布时间：2021-06-10 - 摘要：This paper estimated HJ-1 land surface albedos in the Heihe region using the backup algorithm of Moderate Resolution Imaging Spectroradiometer（MODIS） Bidirectional Reflectance Distribution Function（BRDF）/Albedo product（method Ⅰ）,the Bayesian inference-based algorithm（method Ⅱ） and the Lambertian surface algorithm（method Ⅲ）.Compared inversed albedos with surface observations,statistical analysis results showed that:（1） The high resolution albedos from HJ-1 CCD data can provide spatial distribution of underlying surface as well as surface details.Different land cover types’ statistic values indicates that method Ⅰ and method Ⅱ capture similar results,with the absolute error of 0.01 and the relative error of 4% as compared with albedos from MODIS,while method Ⅲ has the absolute error of 0.03 and relative error of 13%.（2） The improvement in the albedo by method Ⅰ and method Ⅱ is almost independent to land cover types,capturing relative error between 2% and 8%;However,the temporal reliance of estimated albedo is more significant,and the improvement is more obvious in the maturity than in the dormancy.（3） Surface albedos estimated by method Ⅰ and method Ⅱ have better consistency with field observations.The root mean square errors are less than 0.05,and relative errors are less than 23%,while results of method Ⅲ are 0.069 and 36.3%,respectively.（4） The retrieval of albedos based on the prior knowledge may depend on the geometry of the sun and the observation,and thus depend on the season and the latitude,as well as sensor specifications.This study will provide significant understanding for space-borne albedo retrieval which lacks of sufficient multi-angular observations.关键词：HJ-1 satellite;MODIS;BRDF;albedo;Bayes;priori knowledge
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发布时间：2021-06-10 - 摘要：The Wishart classifier has the major issue of drastically favoring the intensity over the polarimetric information,so the weak backscattering targets such as water,road,bare soil and shadow in Polariemtric Synthetic Aperture Radar（PolSAR） image are hard to be made fine distinction.This paper proposed an unsupervised statistical classifier of the weak backscattering scatterers based on H-α target decomposition and hypothesis test.Likelihood ratio test is used as a distance measure to compare the similarity of a pixel and class centers.Pixels with small similarity are rejected according to the first type error and the distribution of the test statistics to reduce the effect on classification.The others pixels being not rejected are assigned to the class with the smallest statistics.The experiential results using E-SAR L band and Radarsat-2 C band quad polarimetric image demonstrate that this algorithm making advantage of the polarimetric information,improves the classification accuracy of the weak backscattering scatterers greatly.关键词：Polarimetric Synthetic Aperture Radar（PolSAR）;likelihood ratio test;weak backscattering scatterers;unsupervised classification.
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发布时间：2021-06-10 - 摘要：Spatial data model is the basis of three dimensional cadastre. The paper analyzes the application demands of three d imensional cadastre and proposes a hybrid three dimensional spatial data model. The model consists of two sub-models: representing sub-model and calculating-analyzing sub-model. The former is used to represent the geometrical shape of property volumes, and the latter is used to support basic computing and spatial analysis. For the integration and transformation of two sub-models,we introduce the algorithm of Constrained Delaunay Tetrahedralization and the boundary extraction algorithm of TEN. To verify the feasibility of proposed model and algorithms,several typical cases of land space right from Shenzhen are used as test data. Experimental results show that the proposed model and algorithms are effective and feasible.关键词：spatial data model;three dimensional cadastre;property volume;constrained delaunay tetrahedralizations;simplcial complex;TEN
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发布时间：2021-06-10 - 摘要：The Chongming Eastern Beach continues to expand owing to sediment deposition from river basins and the nearby ocean. Since the 1960s, the eastern coastline of the beach has extended about 10 km seaward and more than 150 km2 of the tidal flat has been enclosed by embankments for reclamation. This study investigated the influence of these embankments on the evolution of the tidal flat. CORONA, Landsat and SPOT images covering Chongming Eastern Beach were collected to investigate the changing features of the tidal flat from 1965 to 2011.The results indicate that the extension of the flat accelerated after embankments were established. The rate of extension was greater in the first three years following construction; however, the average rate decreased as less sediment was transported from the river basin to the estuary. The construction of embankments also modified the direction of extension from north and northeast to southeast. The reflected tidal currents caused by embankments and the development of tidal creeks destroyed the vegetation cover outside the banks, leading to diffuse catchments that eventually transitioned to large areas of bare flat. This phenomenon repeated with embankments constructed at different times. The merging of the Tuanjiesha sandbank with Chongming Eastern Beach is meaningful for the study of new arising sandbank in the north channel.关键词：tidal flat reclamation;Chongming Eastern Beach;remote sensing;embankment;beach extension;vegetation degradation
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发布时间：2021-06-10 - 摘要：Three kinds of satellite infrared imagery from 2001 to 2009, namely, GMS-5, FY-2B, and FY-2C, were used to study the characteristics of convective cloud mergers in summer severe weather in the Huaihe and Yangtze River basin. In the 35 heavy rain and 43 hailstorm cases, the occurrence probabilities of cloud merger were 94% and 65%, respectively. The average cloud merging times were 11.6 and 1.9. In addition, five statistic factors, namely, distance of two clouds （Dis）, ratio of two cloud areas （Ar）, minimum of two cloud top bright temperature clouds （Tmin）, difference of two cloud top lowest bright temperature （dTmin）, and change of Tmin （ΔTmin）, were calculated and compared in the cases of hailstorm and heavy rain. Three similar points were found for the two kinds of severe weather. The quantities of the four factors comprised the main differences of the merging process in the two kinds of severe weather. Based on the combination of Tmin and dTmin, the cloud top temperature conditions and the statistic probabilities of occurrence with different Ar were analyzed. Finally, three indicators for severe weather forecasting were revealed with Dis and Ar factors.关键词：summer severe weather on Huaihe and Yangtze River Basin;convective cloud merger;satellite infrared imagery;heavy rain;hailstorm
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发布时间：2021-06-10 - 摘要：Remotely sensed Land Surface Temperatures （LSTs） usually have low spatial resolutions. Downscaling is an effective technique to enhance the spatial resolutions. Current methods for downscaling remotely sensed LSTs were summarized. Using satellite data, we made an inter-comparison among three typical methods, including the Normalized Difference Vegetation Index （NDVI） method, the Pixel Block Intensity Modulation （PBIM） method, and the Linear Spectral Mixture Model （LSMM） method. We further designed an index, Co-Occurrence Root Mean Square Error （CO-RMSE）, for measuring the textural similarity in inter-comparisons. Results indicate that （1） the performance of the NDVI method is most affected by the season, followed by the PBIM method; （2） the performance of the LSMM method is most influenced by the spatial resolution; the NDVI method has an advantage over the PBIM method at high resolutions, while at low resolutions, the performance of the PBIM method is better than that of the NDVI method; （3） these three methods are suitable for areas with combination of vegetation and bare ground, areas with varied topography and albedo, and areas with distinct LST differences in different classes, respectively; （4） the NDVI method is the easiest to implement, while the LSMM method is the most difficult. Further analysis showed that scale factor is the key issue to the LST downscaling and it needs to be carefully selected regarding the season, spatial resolution, land cover, application and the operability.关键词：land surface temperature;downscaling;scale factor;CO-RMSE
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发布时间：2021-06-10 - 摘要：Basing on the shipboard measurements obtained during the 24th CHINARE campaigns and radiance of AIRS, we get the initial value from the statistical regression according to latitude-based classification. The atmospheric CO2 vertical profile was computed by line-by-line radiative transfer model using the temperature from AMSU and radiance from the thirteen selected AIRS channels. The results were compared with measurements from WDCGG,which show the accuracy change with latitude and relative errors are 0.31%、1.17% and 2.63% from low to high latitude respectively. The results were compared with CO2/AIRS from NASA, which show the relative errors are 1.11% and 1.07% respectively.关键词：Southern Ocean;line-by-line integration;radiative transfer model;atmospheric infrared sounder;atmospheric CO2 concentration
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发布时间：2021-06-10 - 摘要：This paper gives a detailed review of IceBridge mission, including the on-board multiple sensors employed, the collected data, and the different levels of products. The on-board multiple sensors can be divided into five types: digital camera, lidar altimeter, radar, gravimeter, and auxiliary equipment. Prospects of research based on IceBridge data are described in four aspects: three-dimensional mapping of snow or ice, changes in glacier elevation and estimates of mass balance, detection of changes in sea ice thickness and distribution, and calibration and validation of satellite remote sensing observations. IceBridge will undoubtedly enhance the understanding of polar changes under global warming.关键词：IceBridge;lidar;gravimeter;Antarctica;Arctic;airborne remote sensing;global change
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发布时间：2021-06-10 - 摘要：We derived Melt Extent（ME） and Melt Index（MI） of snowmelt in Antarctica from 1978 to 2010 using satellite passive microwave SMMR and SSM/I data. A modified ice sheet snowmelt detection method based on wavelet transform was developed to determine and characterize melt occurrences. Annual ME and MI data were used to analyze temporal variation in features of snowmelt in Antarctica from 1978 to 2010.In addition, we analyzed variation in snow melt from 2000 to 2010 for comparison; this decade has experienced the greatest changes in global climate. Furthermore, we divided Antarctica into four analysis regions based on the complexity of spatio-temporal variations of snowmelt. We discovered that snowmelt in Antarctica exhibited different temporal patterns in East Antarctica and West Antarctica. The snowmelt in West Antarctica changed dramatically during the first analysis period, while the variations of snowmelt in East Antarctica were more moderate, even appearing to decrease. In addition, we found a positive correlation between variations of snowmelt and variations of temperature in Antarctica, which suggests that temperature changes influenced snowmelt.关键词：Microwave radiometer;Antarctica;snowmelt;Wavelet;patio-temporal variation
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发布时间：2021-06-10 - 摘要：A method is presented for combining GPS and GLAS data to produce a high-quality DEM. First, the GLAS data was transformed so that it could be combined with GPS data to produce a DEM. An algorithm was selected to locate GLAS points and the GPS points covered by GLAS footprints were highlighted. Comparison of the two types of data indicates that the maximum and minimum mean height differences are 1.118 m and 0.997 m, respectively, with a stable standard of about 5—6 cm. The maximum and minimum values became 0.405 m and 0.284 m after rectification by ellipsoid transformation. Detailed components of the error are also discussed. Next, sparse GPS data were extracted as feature points along the GPS measurement profile using a revised angle limitation method. Finally, a DEM was produced for the Dome-A using processed GPS data and transformed GLAS data. 1199 of the GPS points and 53 of the GLAS footprints were used to validate the DEM, with 5 cm and 12 cm as the mean and absolute maximum, respectively, of residuals. Additionally, three other DEMs were produced using original GPS data, original GPS data and GLAS data, and processed GPS data. The DEM produced with processed GPS data exhibited better accuracy than that produced from original GPS data according to comparison of contours and residuals of check points, confirming the importance of the GPS process.关键词：Dome-A;ICESat;GLAS;GPS;DEM
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发布时间：2021-06-10 - 摘要：The significant decline of Arctic sea ice under global warming, especially in summer, plays an important role in global and regional climate change, and affects global and regional ecosystems. Here, the spatio-temporal variations of Arctic sea ice and their causes were analyzed based on satellite microwave AMSR-E data for June 2002 through February 2011. The results showed that the extent of Arctic sea ice decreased by 82800 km2 annually, decreasing most rapidly in summer. The rate of decrease in summer for the period 2002—2011 was more than twice that of 1979—2006; moreover, sea ice concentration also decreased. The sea ice conditions were heavy in 2003 and 2004, while 2007 experienced a minimal sea ice area. Perennial sea ice decreased approximately 30% between 2002 and 2011 with decreases occurring in the Beaufort Sea, Chukchi Sea, East Siberian Sea, Laptev Sea, Kara Sea, and over the vast area from these marginal seas to the Arctic Ocean. Increases in seasonal sea ice occurred in regions where perennial sea ice decreased. The sea ice area has a significant negative relationship with the annual average temperature, and the decrease trend will continue with global warming intensification.关键词：Arctic sea ice;concentration;extent;area;spatio-temporal variation;AMSR-E
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发布时间：2021-06-10 - 摘要：The AMSR-E satellite data and in-situ data were applied to retrieve sea surface air temperature （Ta） over the Southern Ocean. The in-situ data were obtained from the 24th —26th Chinese Antarctic Expeditions during 2008—2010. First,Ta was used to analyze the relativity with the bright temperature （Tb） from the twelve channels of AMSR-E, and no high relativity was found between Ta and Tb from any of the channels. The highest relativity was 0.38 （with 23.8 GHz）. The dataset for the modeling was obtained by using in-situ data to match up with Tb, and two methods were applied to build the retrieval model. In multi-parameters regression method, the Tbs from 12 channels were used to the model and the region was divided into two parts according to the latitude of 50°S. The retrieval results were compared with the in-situ data. The Root Mean Square Error （RMS） and relativity of high latitude zone were 0.96℃and 0.93, respectively. And those of low latitude zone were 1.29 ℃ and 0.96, respectively. Artificial neural network （ANN） method was applied to retrieve Ta.The RMS and relativity were 1.26 ℃ and 0.98, respectively. The air-sea interaction over the Southern Ocean is so strong and unstable that it increases the retrieval difficulty and affects the accuracy of the results.关键词：AMSR-E;sea surface air temperature;ANN;multi-parameters regression method
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发布时间：2021-06-10 - 摘要：<正>1引言目前雾霾监测的主要手段是利用PM2.5在线测量,获得观测点处的空气污染状况,然而对于面区域以及大气环境中雾霾产生、发展和消散过程的3维立体监测能力有限,卫星遥感能够有效弥补其关键环节,提供面覆盖的观测能力。卫星遥感通常能够获得整层大气颗粒物（气溶胶）的参数,例如气溶胶光学厚度（AOD）表征大气柱中气溶胶颗粒物整体消光能力。卫星遥感能够实现在不破坏大气
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发布时间：2021-06-10 - 摘要：<正>国际数字地球会议（International Symposium on Digital Earth）是国际数字地球学会（International Society for Digital Earth）的系列会议。第八届国际数字地球会议（The 8th International Symposium on Digital Earth）将于2013年8月26-29日在马来西亚古晋市（Kuching）举办。会议由马来西亚工艺大学（Universiti Teknologi Malaysia）承办,以
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发布时间：2021-06-10
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