最新刊期
卷 13 ， 期 6 ， 2009
- 摘要：Accurate calibration is needed for Quantitative application of space-borne passive microwave radiometers. In this paper, the surface target which can be taken as the calibration reference target are studied, and the emission model was developed for the emissivity computation for these targets. It is found that in dense covered forest area, for 19-89GHz frequencies, microwave radiation brightness temperature can be calculated with an accuracy of 1K. For the frequency channel as low as 6 and 10 GHz, the desert area such as sahara can be taken as reference calibration target. And the established model accuracy in desert area is within 2K by using the NCEP reanalysis dataset as input.关键词：Microwave radiometer;calibration model;ground target
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发布时间：2021-06-10 - 摘要：In this paper,a land surface temperature data assimilation scheme is developed based on Ensemble Kalman Filter （EnKF） and Common Land Model version 1.0 （CLM）,which is mainly used to improve the estimation of the sensible and latent heat fluxes by assimilating MODIS land surface temperature （LST） products. Leaf area index （LAI） is also updated dynamically by MODIS LAI products. In this study,the relationship between the MODIS LST and the CLM surface temperature is determined and taken as the observation operator of the assimilation scheme. Meanwhile,the MODIS LST is compared with the ground-measured surface temperature,and the Root Mean Square Error （RMSE） is taken as the observation error. The scheme is tested and validated based on measurements in three observation stations （Blackhill,Bondville and Brookings） of Ameriflux. Results indicate that data assimilation method improves the estimation of surface temperature and sensible heat flux. The RMSE of sensible heat flux reduced from 81.5W·m-2 to 58.4W·m-2 at the Blackhill site,from 47.0W·m-2 to 31.8W·m-2 at the Bondville site,from 46.5W·m-2 to 45.1W·m-2 at the Brookings site. The RMSE of latent heat fluxes reduced from 88.6W·m-2 to 57.7W·m-2 at the Bondville site,from 53.4W·m-2 to 47.2W·m-2 at the Blackhill site. In addition,it is a practical way to improve the estimation of sensible and latent heat flux by assimilating MODIS LST into land surface model.关键词：MODIS land surface temperature products;common land model;ensemble kalman filter;sensible and latent heat flux
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发布时间：2021-06-10 - 摘要：With the rapid development of SAR missions,on-board SAR image processing is required. SAR could obtain much higher resolution images than ordinary radar,and it is very necessary to compress data before transmission,since the generated SAR data volume is much higher than the data bandwidth of the satellite downlink. In this paper,an efficient compression algorithm with accurate rate control is proposed based on SAR complex image characteristics. The algorithm applies an adaptive weighted quantizer on 2D-FFT coefficients,and then uses entropy encoder to code the quantized coefficients. Based on the es-tablished R-Q and MPE-Q statistical models,an accurate rate control is developed. We measure the compression performance with PSNR and MSSIM （Mean Structural Similarity） of the magnitude image and MPE （Mean Phase Error）. With four SAR complex images compressed at different ratios,the compression performance is analyzed and compared with other algorithms including JPEG2000,H.264,etc. Experimental results show that the proposed algorithm outperforms other algorithms,and the rate control obtains high accuracy.关键词：space-borne SAR complex image;rate control;image compression
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发布时间：2021-06-10 - 摘要：In rugged areas,topographic effects severely influence the spectrum characters of remote sensing image. Topographic correction is a necessary step to estimate real land surface situation from remote sensing images. As a kind of topographic correction methods,empirical approaches can hardly achieve desirable results. Existing physical topographic correction methods which are based on radiant transfer models require a considerable number of input parameters. Furthermore,the topographic correction and atmospheric correction are mixed,which cause inconvenience and instability. A simplified physical algorithm is proposed in this paper to overcome the disadvantages of existing algorithms. A ratio factor of diffuse irradiance on horizontal surface to solar direct irradiance is introduced. The algorithm only need solar geometry information and atmosphere model parameters as its input data,and is mainly concentrated on the removal of topographic effects. It can correct the apparent radiance of optical remote sensing images over rugged terrain to the apparent radiance without topographic effects. The algorithm was illustrated using a Landsat TM image.关键词：topographic correction;apparent radiance;physical model;aerosol optical depth （AOD）;6S
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发布时间：2021-06-10 - 摘要：In this paper,the retrieval of AOD （aerosol optical depth） over land surfaces from CCD （Charge Coupled Device） data of CBERS （China Brazil Earth Resources Satellite） 02B was studied. The inversive method is modified DDV （dark dense vegetation） algorithm:（1） based on the spectral data of vegetation and the characteristics of the CCD sensor,the relationship between blue and red band surface reflectances and the NDVI （Normalized Difference Vegetation Index） thresholds for dense vegetation （dark pixel） were worked out,and the atmospheric effect and its correction were also analyzed. （2） The LUT （look up table） for different bands was pre-computed using the 6S atmospheric radiative transfer code. （3） The AODs was retrieved through interpolating in LUT in accordance with radiances obtained by CCD,and the errors of this modified DDV method was also analyzed and discussed. Finally,the modified DDV method was successfully applied to Nanning and Beijing areas. The comparison of the retrieved AODs with those of MODIS shows a good agreement.关键词：remote sensing;CBERS02B;aerosol optical depth over land surfaces;dark dense vegetation
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发布时间：2021-06-10 - 摘要：Numerous geospatial computational models have been developed based on sound principles and published in journals or presented in conferences. However modelers have made few advances in the development of computable modules that facilitate sharing during model development or utilization. Constraints hampering development of model sharing technology includes limitations on computing,storage,and connectivity; traditional stand-alone and closed network systems cannot fully support sharing and integrating geospatial models. To address this need,we have identified methods for sharing geospatial computational models using Service Oriented Architecture （SOA） techniques and open geospatial standards. The service-oriented model sharing service is accessible using any tools or systems compliant with open geospatial standards,making it possible to utilize vast scientific resources available from around the world to solve highly sophisticated application problems. The methods also allow model services to be empowered by diverse computational devices and technologies,such as portable devices and GRID computing infrastructures. Based on the generic and abstract operations and data structures required for Web Processing Service （WPS） standards,we developed an interactive interface for model sharing to help reduce interoperability problems for model use. Geospatial computational models are shared on model services,where the computational processes provided by models can be accessed through tools and systems compliant with WPS. We developed a platform to help modelers publish individual models in a simplified and efficient way. Finally,we illustrate our technique using wetland hydrological models we developed for the prairie pothole region of North America.关键词：geospatial model;model sharing;distributed computing;geospatial interoperability
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发布时间：2021-06-10 - 摘要：Aimed at the uneven illumination phenomena in the remote sensing image,this paper puts forward an improved MASK dodging method based on wavelet. According to the process of MASK dodging method,this method proposed improves the modulus of wavelet self-adaptively and non-linearly in the process of the background image obtaining. Finally the experiments are given,which show that this improved dodging method can avoid the disadvantages of the method using mean in blocks as the modulus of wavelet directly,and they also show that this method in this paper can resolve the uneven illumination in remote sensing image. It can be applied in many cases.关键词：dodging method for Remote Sensing Image;MASK dodging method;wavelet transform;improved MASK dodging method
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发布时间：2021-06-10 - 摘要：The side-look imaging of SAR （Synthetic Aperture Radar） may result in the pockety density, so we can not get a satisfying result by using CFAR （constant false alarm rate） detection on the whole image. To improve the oil detection capability, we propose a new oil detection method based on edge detection in this paper. First, the AOI （area of interest） of oil is detected through radio edge detection, then an improved Weibull-CFAR detector is applied to the AOI. Comparing with the whole CFAR detection results, this detection method demonstrates better accuracy and efficiency on SAR images with pockety density, especially suitable for the oil detection of big images.关键词：synthetic aperture radar （SAR）;oil detection;constant false alarm rate（CFAR）;ratio edge detection （ROA）
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发布时间：2021-06-10 - 摘要：In this paper,we present a new InSAR phase filtering method based on optimal integration. The algorithms can preserve very well the phase details while at the same time smoothing out the noise. Firstly,we use statistical method to determine the number of windows used for the filtering. It is an empirical constant associated with coherence. Secondly,eight linear directional windows are singled out,within each window a filtering is performed,and at the same time the mean coherence for each window is calculated. The proposed filtering will linearly combine a certain number （which has been determined in the first step） of the eight directional windows. However,directional windows with smaller filtering standard deviation will be given priority. Finally,the new phase value is calculated in terms of the weighted mean value of chosen linear windows. In this step,optimal integration is used to determine the weight of each directional window. The proposed filter is adaptively implemented by altering the number of the linear windows selected for filtering according to the coherence. Strategy of using both linear windows and optimal integration makes great difference in the filtering and achieve a good tradeoff between phase noise suppressing and signal preserving. Experimental results with both simulated and real data sets show that the new filter reduces the noise effectively while still minimizing the loss of signals.关键词：optimal integration;direction smoothing;INSAR interferogram;edge preservation;adaptive filter
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发布时间：2021-06-10 - 摘要：The method of plot experiment with field application was used in this research. The variations of rice foliage and canopy spectra with corresponding biochemical concentration field-measured in jointing,heading and filling stages were analyzed. Through the analysis of absorption characteristic and vegetation index,the best spectral features for rice nitrogen and chlorophyll concentration estimation were obtained. Based on the Hyperion image of Jiangyan,we built the models of rice canopy nitrogen and chlorophyll estimation. At last,rice canopy nitrogen and chlorophyll concentration were retrieved from Hyperion image and their distribution maps were obtained. The results showed that:（1） Nitrogen concentration can be retrieved accurately using the area of absorption feature centered at 670nm based on band depth normalized to band depth （BNC） analysis; （2） Based on reversional normalized spectrum,NDVI using 560nm and 670nm was strongly correlated with chlorophyll concentration.关键词：hyperspectral remote sensing;rice;Hyperion;nitrogen;chlorophyll
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发布时间：2021-06-10 - 摘要：Phenological information of paddy rice is important for area extraction and growth monitoring. The purpose of this study is to detect the major phenological stages of paddy rice over China using remote sensing data. Time-series Terra moderate-resolution imaging spectroradiometer （MODIS） Enhanced Vegetation Index （EVI） was smoothed with the low pass Fourier and wavelet filtering methods,then the stages of transplanting,beginning of tillering,heading,and maturation were obtained according to their characteristics. The paddy rice stages in 2005 derived from this study were significantly positive correlated and consistent with the statistical data （P < 0.05）,and most of the absolute errors were less than 16 d. The methods presented in this study could be applied in other years,as well as the ability to generate the growth stages of other crops.关键词：remote sensing;MODIS;EVI;paddy rice;growth stage;phenology
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发布时间：2021-06-10 - 摘要：The cloud cover is an important factor which lowers the remote sensing image quality,so real-time automatic cloud detection and effective rejection of high cloud coverage pictures are of prime importance. In this paper we proposed a high performance and high accuracy algorithm of cloud detection which combines two different analytical techniques:the spectrum threshold comparison and the texture analysis. These two approaches discriminate the image from different visions. A structure of the discrimination tree is proposed to improve the accuracy and to accelerate the detecting procedure,which defines the rule how to use these two methods properly. The cloud detection results gained by this algorithm are well satisfied. And the structure of the discrimination tree promotes the operating efficiency on average. We also proposed an advanced approach to calculate the fractal dimension value,which is about five times faster than the original approach. The cloud detection algorithm has been applied to the data processing system of China-Brazil Earth Resources Satellite-2B. The experimental results show that this algorithm can satisfy the demand of error rate:the false alarm rate is lower than 5% and the missed detection rate is lower than 10%.关键词：satellite remote sensing image;cloud detection;fractal dimension calculation;gray level co-occurrence matrix;structure of the discrimination tree
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发布时间：2021-06-10 - 摘要：Supervised classification in remote sensing imagery is receiving increasing attention in current research. In order to improve the classification ability,a lot of spatial-features （e.g.,texture information generated by GLCM） have been utilized. Unfortunately,too many features often cause classifier over-fit to a certain features’ character and lead to lower classification accuracy. The traditional feature selection algorithms have an unstable classification performance which depends on the number of training samples. This study presents a rough set based ensemble remote sensing image classifier （briefly denoted as RSEC）. It partitions feature set into a lot of reducts,and constructs training subset by utilizing these reducts. Each training subset trains an artificial neural network （ANN） classifier; the decisions from all the base classifiers are combined with a voting strategy. This approach can reduce input features to a single classifier,and it can avoid bias caused by feature selection. The RSEC classifier has been compared with the direct ANN method and the traditional feature selection method. It can be seen from the result that RSEC has better classification accuracy and more stable than the others.关键词：ensemble classifier;rough sets;artificial neural network;feature selection
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发布时间：2021-06-10 - 摘要：The long time series vegetation trends （LTSVT） research based on remote sensing in large area is the core field of vegetation ecology and an important direction in the global change study. AVHRR,SPOT VGT and MODIS are currently the main data resources of LTSVT research. With volumes of remote sensing data,the analysis and evaluation methods for LTSVT study emerged as an urgent issue. Algebra calculation,Fourier transformation,PCA analysis,wavelet transform,linear trend analysis （LTA）,correlation analysis （CA）,etc.,are the main methods. After the assessing and grouping of the methods,we focused on comparing the LTA and CA,which were well accepted methods,with the newly introduced Sen+Mann-Kendall method. Our review showed Sen+Mann-Kendall had a strong strength of errors resistance and was not constrained by the data statistical distribution.关键词：long time series vegetation trends LTSVT;evaluation methods;Sen+Mann-Kendall
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