最新刊期
卷 16 ， 期 3 ， 2012
- 摘要：The first Ku/Ka dual-frequency precipitation measuring radar field campaign was carried out successfully from September to October,2010 in China.Valuable data were obtained from this field campaign,including Ku/Ka dual-frequency airborne radar data and simultaneous observation data over land and sea as well as from spaceborne precipitation radar.Observation results of Ku/Ka-band precipitation measuring radar were presented.Point to point comparison of airborne radar data and vehicle-based X-band meteorological radar data was carried out,and quantitative indices were computed to indicate the observation consistency statistically.Comparisons of airborne radar data with TRMM PR data were made,in order to reveal precipitation measuring radar’s ability in detecting rainfall.Detection sensitivity and actual range resolution of airborne precipitation measuring radar were analyzed using observation data to validate Ku/Ka-band radar’s performance.关键词：precipitation measuring radar;field campaign;dual-frequency detection;performance analysis;data comparison
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发布时间：2021-06-10 - 摘要：Robust and efficient internal memory algorithm for vector map overlay is proposed.The algorithm employs the plane sweep idea improved from the traditional plane sweep algorithm to calculate the intersection points,by which all the special cases are handled properly.Then rings of the results are constructed by the intersection points and the information,and original rings with no intersection point are ignored or added to the result as outer rings（contour） or holes.All the generated rings have ID information,which simplifies the following two processes-finding the matching outer ring for each hole and attributes propagation.With this algorithm,we can determine all the intersection points for any overlay operation immediately,not by a one to one loop.We implemented the algorithm,and the comparisons with the one-by-one method（using spatial access method） demonstrated its efficiency.Besides,we implemented the whole function（including the algorithm and the necessary processes of reading data from and writing data to the disk）,and compared it with ESRI’s ArcGIS,by which correctness and efficiency of our approach are demonstrated.
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发布时间：2021-06-10 - 摘要：The accuracy of scene matching navigation system can be improved greatly when synthetic aperture radar （SAR） is used. However, geometric distortions of SAR real-time image, which are caused by terrain undulation and atmosphere turbulence etc, decrease the matching performance. By analyzing the causations of geometric distortion, a two-dimension separable correction method is presented, which corrects the distortion in azimuth direction by phase compensation along with the imaging processing, and leaves the distortion in range direction to the image post processing. In the end, an experiment was conducted based on three SAR real-time images of different terrains. Each of the images is simulated by digital elevation model （DEM） and orthography, and then corrected by three different methods. Based on the experimental results, some rules of the correction method selection are acquired.关键词：synthetic aperture radar （SAR）;image matching;geometric correction;Navigation
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发布时间：2021-06-10 - 摘要：Ideal knife-edge image and real remote sensing images were selected as the original image, and a series of degraded images were obtained through applying a various of radiation and geometric resampling operation on these original images. Then the MTF （modulation transfer function） evaluation was performed using the original image and all of degeneration images based on slant edge method. Experiments show that, in evaluating MTF of the imaging system, proper radiation resampling operation can be performed on the image for the visual effect, which will not affect the imaging system MTF, but the geometric resampling can seriously affect the MTF of imaging system.关键词：image quality assessment;modulation transfer function;knife-edge image;resampling
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发布时间：2021-06-10 - 摘要：Land surface temperature （LST） is a very important parameter controlling the energy and water balance between the atmosphere and the land surface. But when the sky is overcast, LST measurements are impossible with thermal remote sensing. Consequently, only cloudy-free measurements are useful, implying that the data set will be biased. Choosing the best spatial interpolation of land surface-the gradient plus inverse distance squared （GIDS） method, estimating LST under cloud cover is possible. An evaluation on LST estimation under cloud cover using GIDS in Jiangning study site of China Jiangsu province was tested in this paper with ETM+ and ASTER GDEMV1 data. The results showed that the GIDS can estimate LST smoothly with high accuracy. The error increased with cloud cover extent expanding, and the maximum of mean absolute error（MAE）, root mean squared error （RMSE） were less than 0.9℃ and 1.2℃, respectively. When the cloud cover extent was less than 100×100 pixel, the maximum error of MAE and RMSE were lower than 0.8℃ and 1℃, respectively. The accuracy of GIDS varied with the unclouded typical pixel, complexity of spatial constructer and land cover type of cloud cover. An important parameter, the standard deviation STD of Normalized Difference Vegetation Index（NDVI） for overcast, can index the uncertainty of GIDS estimated results and have same trend with MAE and RMSE. It can detect the estimated error extent and evaluate the estimated result linking to the denotation of STD of NDVI for spatial complexity and NDVI-LST negative correlation in cloudy condition. Therefore, care should be given to the GIDS estimated result before the application.关键词：cloud cover;gradient plus inverse distance squared （GIDS）;spatial interpolation;LST estimation;NDVI;reliability
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发布时间：2021-06-10 - 摘要：A data-based mechanistic （DBM） modeling approach is used to model the statistical relationship between time-series reflectance and leaf area index （LAI）. This relationship model is referred to as LAIDBM model. Moderate Resolution Imaging Spectroradiometer （MODIS） data products are utilized as example data to implement DBM modeling and validation. LAI field measurements from the Bigfoot project were used to further validate LAIDBM model. The results show that LAIDBM model provid a very good explanation of the relationship between time-series reflectance and LAI. The LAI estimated by LAIDBM model is better than MODIS LAI in terms of data quality and continuity.关键词：leaf area index;time-series;MODIS;data-based mechanistic （DBM）
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发布时间：2021-06-10 - 摘要：This paper takes fully polarimetric SAR data as study object to analyze the change detection technology. As the coherency matrix C3 or covariance matrix T3 of fully polarimetric SAR data follows a complex Wishart distribution. First, the likelihood-ratio parameter is built by a test statistic based on Wishart distribution to represent change features. Then the initial change information is extracted by the expectation maximization （EM） iterative algorithm based on a general Gaussian distribution. Finally, the change information is generated by optimizing the initial change information using probability relaxation iteration algorithm considering the context information. The method can extract change information automatically as well as produce change result of almost speckle noise free by integrating a series of filtering operations, including incoherent average, initial classification, optimizing classification. The validity of the method is demonstrated by comparison with traditional logarithm ratio method.关键词：fully polarimetric SAR;change detection;likelihood-ratio;minimum error rate Bayesian criterion;probability relaxation iteration algorithm
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发布时间：2021-06-10 - 摘要：As hyperspectral remote sensing image is easily interfered by noises, a denoising method of hyperspectral remote sensing image based on Nonsubsampled Contourlet Transform （NSCT） and Kernel Principal Component Analysis （KPCA） is proposed. First, hyperspectral image of each band is decomposed by NSCT to acquire the coefficients which are processed by KPCA. The proper principal components are selected for KPCA reconstruction according to noise features. Finally, the denoised image is obtained by performing inverse NSCT. Experimental results show that the proposed method can suppress noise interfer- ence in hyperspectral remote sensing images, and preserve the useful information of original data more completely.关键词：hyperspectral remote sensing;image denoising;NSCT;KPCA
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发布时间：2021-06-10 - 摘要：Change detection is the process of analyzing changes of surface features with multi-temporal remote sensing imagery of the same area. Hyperspectral remote sensing images contain abundant spectral information for accurate change detection, which, regrettably, is not fully taken into account by existing approaches. In this paper, a hyperspectral change detection method based on Independent Component Analysis （ICA） is investigated. The difference image is analyzed by skew-based ICA. The change of a single feature can be obtained and then the change is extracted from each abundance image. Experiment results dem- onstrate that the ICA-based hyperspectral change detection performs better than other traditional methods with a high detection rate and a low false detection rate.关键词：hyperspectral remote sensing image;change detection;ICA;skew;difference image
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发布时间：2021-06-10 - 摘要：A new microwave humidity sounder （MWHS） developed and built by CSSAR was deployed in China in May, 2008. The sounder is part of a suit of instruments onboard FY-3 satellite, which measures brightness temperatures from 3 double-sideband channels centered at （183.31±1）GHz, （183.31± 3）GHz and （183.31±7）GHz. Atmospheric emission in these regions is primarily due to water vapor and influences of liquid water. Measurements were compared with simulations obtained using forward radiative transfer equation. The comparison of brightness temperatures showed that the measurements agreed well with model simulations. Humidity profiles were retrieved using back propagation neural network （BP-NN） algorithm and other methods. The results show that humidity profiles derived using back propagation algorithm best agreed with the profiles from radiosonde datasets. Second, compared to the humidity retrievals by AMSU-B retrieval model, root-mean-square （RMS） of relative humidity was comparable with those of AMSU-B in a range of 15% to 25%, and RMS of water vapor density was smaller than 1 g/m 3 . Therefore, it can be used for retrieving atmospheric humidity profiles for operational applications. Meanwhile, the paper firstly uses Mexican hat wavelet function into BP-NN, and the results show that it is comparable with BP-NN. Most importantly, Mexican hat wavelet function can reach convergence quickly and avoid of easily getting stuck in local minima.关键词：FY-3;microwave humidity sounder;humidity profiles;neural network;rootmean-square
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发布时间：2021-06-10 - 摘要：This paper presents a new algorithm for the automatic registration of airborne LiDAR data with aerial images using building corner features as registration primitives. First, three-dimensional building outlines are directly extracted from LiDAR points and building corner features which consist of two orthogonal straight lines are obtained by the regularization of three-dimensional building outlines. Straight lines are also extracted from every aerial image. Second, the building corner features are projected onto aerial images and corresponding image corner features are determined using the similarity measures. Lastly, the exterior orientation parameters are refined by bundle adjustment using the corner points of corner features as control points. Iteration strategy is adopted to obtain optimal results. The main advantage of the proposed algorithm is that the three-dimensional building outlines are extracted directly from LiDAR points without transforming LiDAR points into range image or intensity image, and therefore there are no interpolation errors. The experimental results show that the proposed algorithm can obtain more accurate results in comparison with the registration method based on LiDAR intensity image.关键词：airborne LiDAR;aerial imagery;registration;line;corner
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发布时间：2021-06-10 - 摘要：Aerosol is an important index in atmosphere monitoring. Disadvantages exist when monitoring aerosol from HJ-1 data by dark dense vegetation （DDV） or contrast reduction algorithm. In this paper, based on the algorithm which was developed by Hsu, et al.（2004）, the deep blue algorithm is applied to CCD/HJ-1. First, the database of land surface reflectance is built from MODerate-resolution Imaging Spectroradiometer （MODIS） spectral reflectance product. Second, after analyzing relationship between CCD camera reflectance and MODIS, the reflectance of MODIS are corrected to CCD camera of HJ-1. Third, aerosol optical depth （AOD） is retrieved from apparent reflectance in the first band of CCD/HJ-1. Finally, AODs over Beijing area are retrieved from December 2008 to October 2009, and the results are validated by ground-based measurement of Beijing station in the PHOtométrie pour le Traitement Opérational de Normalisation Satellitaire （PHOTONS） network included in the worldwide Aerosol Robotic Network （AERONET）. The validation and discussions show that, when AODs are greater than 0.5, the accuracy of deep blue algorithm can satisfy the aerosol monitoring using HJ-1 data, and aerosol model can greatly influence the results.关键词：aerosol;HJ-1;deep blue;AERONET/PHOTONS
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发布时间：2021-06-10 - 摘要：Multispectral false color composite（FCC） images are widely used in interpretation of linear structures,which are directional because of the restriction of tectonic stress field.However,when the satellite image illumination cannot match the directions of linear structures,the structural features are less visible and their interpretations cannot be clearly recognized.Therefore,the paper brings out a new technique based on directional illumination simulating from digital elevation models（DEMs） to enhance multispectral images,which can enhance the structure lineaments by exchanging the traditional illumination model to the optimum illumination perpendicular to the targets,and allow the interpretation of the directional structure lineaments by using certain direction illumination.The paper interprets the fault-related lineaments by remote sensing image in southern segment of Longmen Mountains thrust belt,and the accurate identification of faults is the key to understanding tectonic structure for future work in oil and gas exploration.关键词：multispectral false color composite（FCC）;illumination;digital elevation model;fault interpretation
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发布时间：2021-06-10 - 摘要：High-solution multispectral imagery is attractive to various users and can be collected with a group of Charge-Coupled Device（CCD） cameras on board low-altitude Unmanned Airship（UA）.Due to imperfect system integration and inherent nature of UA,however,the registration of High-solution multispectral imageries from UA are subjected to several challenges.In this paper,a low-cost multispectral imaging system composing of four CCD cameras is described as well as its potential issues to registration operation are summarized.After that,Fast Fourier Transformation（FFT） induced multispectral imagery Cross-Correlation Matching technique is developed to automatically generate high-precision tie pints for overlapped UA imageries.Next,Homograph joint estimation based on the Least Square adjustment is described in detail to align multispectral imagery acquired at each exposal and "leveled" Thin Plate Spline（TPS） transformation is established to register multispectral imagery sequences as well.Finally,experiments of registering high-solution multispectral imageries collected from low-altitude unmanned airship are implemented with proposed approaches and valuable conclusions are conducted.关键词：multimodal registration;Fourier-Mellin transform;thin plate spline;unmanned airship
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发布时间：2021-06-10 - 摘要：In order to evaluate the clustering accuracy of different distance measure methods for vegetation index time-series data,we make a comprehensive comparison among six distance measure methods（Euclidean distance,spectral information divergence,spectral angle cosine,kernel spectral angle cosine,correlation coefficient and spectral angle cosine-Euclidean distance） based on the MODIS Enhanced Vegetation Index（EVI） time-series data in China by selecting 468 test pixels across 55 vegetation types and a test region.The test results indicate that the correlation coefficient method shows the lowest clustering accuracy.However,the spectral angle cosine-Euclidean distance method which captures both the curve shape and the amplitude features of the vegetation index time-series data shows the highest clustering accuracy among the six methods.Both the Euclidean distance method which is only sensitive to the spectral brightness and the spectral angle cosine method which is only sensitive to the curve shape perform an inferior clustering accuracy not only in distinguishing different land cover types but also in the regional application.Although the kernel spectral angle cosine method does not show high clustering accuracy in the test at the point level,it shows better performance in the regional application.The spectral information divergence method has a modest performance in the test both at the point level and at the regional level.关键词：vegetation index;clustering;distance measure;discrimination degree;MODIS;EVI
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发布时间：2021-06-10
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