最新刊期
卷 ， 期 5 ， 2004
- 摘要：Ionospheric effects on linear FM rectangular envelope signals of space-borne SAR are considered in this paper. Two kinds of effects due to the ionosphere are presented and the relative formulas are derived, including compressed pulse shift and second phase error. It can be seen that the compressed pulse shift is proportional to total electron content （TEC） and inverse proportional to the square of signals frequencies,and that the second phase error is proportional to TEC and the square of signals bandwidth while in inverse proportional to the square of signals frequencies at the same time. The ionospheric effects at P, L, C bands are also investigated by comparison based on the formulas derived above. The result shows that signals at P-band will be severely affected by the ionosphere. The effects will be obvious at L-band if the signals have a large bandwidth or TEC values are high. At C-band, ionospheric effects are neglectable.关键词：SAR;ionosphere;phase error
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发布时间：2021-06-10 - 摘要：To extract quantitative information from the remote sensed imagery accurately, atmospheric correction that decoupled the surface spectral signature and the aerosol scattering effect is a necessary step. There are several models to describe the multiple bouncing between the surface and atmosphere. But when viewing only from a single direction, we can’t get the enough information such as the albedo of surface to decouple the surface signature and aerosol scattering from these models, so a lambert surface has to be assumed and large error may be introduced in the atmospheric correction when the ground is non-lambertian. This paper describes the atmospheric correction algorithm of AMTIS for the VIS/NIR bands. The algorithm is based on a BRDF Loop approach and MODTRAN4.1 is applied to calculate the atmosphere parameters used in the atmospheric correction. The parameters used to decouple the multi-bouncing effect such as direct-hemisphere albedo and hemisphere-direct albedo are estimated in the loop process. The BRDF model for calculating albedo is a kernel driven model. To accelerate the atmospheric correction, all the atmospheric parameters used in this algorithm are pre-computed with MODTRAN4.1 and saved in the Look-up Table. Pri-or knowledge is used in the retrieval of kernel-driven model when the prior multi-angle sampling is not enough. The atmospheric correction result is validated using the synchronous ground experiment. The atmospheric correction result shows that this algorithm can wipe off the atmospheric smoothing effect and the BRDF shape of ground surface is reversed effectively.
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发布时间：2021-06-10 - 摘要：The multi-channel microwave radiometer （RAD） on-aboard SZ-4 spacecraft, was launched at the end of 2002, the first space-borne microwave radiometer in China. Due to lack of in-orbit calibration, the measurements have to be quantatively evaluated before applications. In the paper, we put forward a vicarious external calibration method for solving the problem. The method is to re-calibrate all RAD channels using the two type of targets with known microwave radiation characteristics on the surface of the Earth. The first target was global open ocean. We collected synchro 252 sea surface truths with RAD from NDBC buoys combined with radiosonde profiles from nearby islands, as well as geophysical products of TMI （TRMM Microwave imager） ,including sea surface temperature, wind speed , water vapor contents, and liquid water contents. After calculation using our radiative transfer equation developed for RAD, we got a synchro oceanic parameter database for RAD brightness temperature calibration. The warm end we chose was Amazon Rain Forest. We obtained 8 profiles for two stations within 50 km from the RAD nearest overpasses. The brightness temperatures were derived from applying a simpled emissivity model and atmospheric absorption model. We compared the re-calibrated brightness temperatures of RAD with those from SSM/I within 0.5 degree of latitude and longtitude and within 2 hour of RAD overpasses above global open ocean. We found there exited a good consistency between those equivalent channales of RAD and SSM/I, i.e., 19.35GHz and 37.0 GHz. The correlation coefficient of the channales are 74.4% and 60.1% repectively for vertical and horizontal polarization of 19.35GHz. The poor correlation in 37GHz channels may contribute to the path differences of them since the incidence angles of RAD is 42.6 degree, while SSM/I 53.3 degree. We also compared brightness temperatures of RAD with measurements from a ground based microwave radiometer employed in the Nanhai experiment carried in February, 2003. The largest discrepancies also showed in those of 37GHz. In general, due to the insuitable location of ground test and poor sync time, and only few provable measurements for comparisons with the temperatures of RAD were made.关键词：SZ-4;Microwave radiometer;vicarious external calibration
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发布时间：2021-06-10 - 摘要：The hyperspectral remote sensing plays more and more important roles in Remote Sensing area. Correspondingly its application becomes wider and wider. Some new hyperspectral airborne and space borne sensors provide us more choice to use such data. Hyperspectral database system is very important in improving the research in remote sensing theory, quantitative study, and applications. This paper aims to analyze the characteristic of hyperspectral data and provide a standard storing rule for the hyperspectral data set in the relation database system with practice of database system development. The hyperspectral data set include the spatial, spectral and other properties data. Three storing models in Oracle database platform are also displayed here, and compared with the practical application. Finally their advantages, shortcomings and the choosing conditions are analyzed.关键词：hyperspectral data;database;store;Oracle
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发布时间：2021-06-10 - 摘要：In this paper, a BG algorithm to enhance the spatial resolution of microwave radiometer is introduced. The main principle of the BG algorithm is as follows. A higher resolution image can be obtained using the linear combination of the adjacent measurements if the density of the measurement is larger than that of the instrument. The principle is also suitable for other microwave remote sensing sensors. The tunable parameter referenced from the study of Stogryn is introduced in this paper, which it can balance the tradeoff between the spatial resolution and the system sensitivity, and prevent increasing the flicker noise of the image too serious when high spatial resolution is pursued. Simulated images of microwave radiometer at 20, 50, and 90GHz were enhanced. The rate of spatial resolution enhancement depends on the density of the sampling.关键词：BG algorithm;Microwave radiometer
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发布时间：2021-06-10 - 摘要：The volume of image data generated by airborne and spaceborne remote sensing mission have been increased dramatically. The efficient lossless compression is urgent. A hyperspectral image comprises a number of bands, each of which represents the intensity of return from an imaged scene received by a sensor at a particular wavelength. Since the reflectance of the earth’s surface and atmospheric absorption are wavelength dependent, the brightness vector formed in the spectral domain for each pixel will have a similar form. The relationship between type of ground and spectral response means that a hyperspectral image can be considered as a group of brightness vectors. Therefore VQ（vector quantization） an the ideal candidate for compression. If VQ is used to compress image losslessly, both the codevector index and the quantization error image should be sent to channel. The amount of codevector index is invariable, consequently, it is important to reduce the error image’s average information amount, i.e. entropy, if we want to improve the coding efficiency. In this paper, a new VQ lossless compression method based on an information distortion measure is proposed. Using this new measure to match codevector, i.e. quantize vector, the coding efficiency can be improved without increasing complexity. Experimental results show that the entropy of the error image using VQ based on information distortion measure is about 0.05bpp （bits per pixel） lower than that on Euclidean square error measure.关键词：vector quantization;distortion measure;Lossless compression;hyperspectral image
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发布时间：2021-06-10 - 摘要：Base-band digital signal generator is an essential device in Synthetic Aperture Radar （SAR）. It plays an important role in satisfying the development of multi-resolution and multi-mode of SAR system. With the digitization of SAR signal processing, base-band digital signal generator has substituted for SAW devices, and functioned as a part of the digital linear frequency modulator （chirp）, which generates various sending signals for the radar. Facing more and more complicated SAR systems, in the meanwhile, developers must deal with testing and validation problems of the system. So it’s necessary to develop a device that can help developers to validate the functions of SAR sub-assemblies, and digital signal generator just functions as a test device for the base-band signal processing devices of the radar. The author first introduces the functions of high-speed digital signal generator developed for SAR system, then analyses the principle and design process of linear frequency modulation signals, and discusses on the test function of the signal generator. The performance, composition and design scheme of a high-speed base-band digital signal generator is presented according to the above two functions.关键词：synthetic aperture radar（SAR）;base-band;digital signal generator;linear frequency modulation signal
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发布时间：2021-06-10 - 摘要：The application and research of spatial information are generally considered as a challenging problem due to the excessive voluminousness, complexity of processing and difficulty in sharing of spatial data. As a novel web-based infrastructure and technology system of spatial information, Spatial Information Grid （SIG） integrates and extends information grid technology, spatial information system, web services and etc. To implement sharing and integration of spatial information, SIG takes service as its technical core, and establishes a unified and intelligent platform to acquire store, organize, distrbute, analyze, aggregate, and apply, spatial information. Based on the given basic definitions of SIG, the technical ingredients and research contents are proposed. Then, a system architecture of SIG is proposed and built. Moreover, some key technologise, of SIG, such as spatial data sharing and spatial analyzing services are studied and elaborated. Hences, the system framework and technical foundation of SIG are formed and SIG research is promoted into a new stage.关键词：Spatial information SIG;service;spatial data sharing;spatial analyzing &processing service
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发布时间：2021-06-10 - 摘要：Soil moisture is a very important variable in hydrologic cycle and exchange of matter and energy near ground boundary. It was investigated by the means of remote sensing due to a number of reasons. In this study, under experimental conditions, relationship between hyperspectral data and soil surface moisture has been investigated. Correlation between soil surface moisture for nine soil samples and four sets of spectral data of them （prototype reflectance, absorbance, the first-order derivative of reflectance and the first-order derivative of absorbance） was analyzed. We found that it has no obvious correlation between soil surface moisture and prototype reflectance and absorbance for all samples, while absorbance has higher correlation than reflectance. The first-order derivative of reflectance and the first-order derivative of absorbance have the obvious correlation near wavebands 1844 nm, and the first-order derivative of absorbance reflectance has more obvious correlation than the first-order derivative of reflectance. We choose these bands with high square of correlation coefficient to creat liner regression forecasting equation. Another nine soil samples were used to verify the precision of estimation equation. Results show that the first-order derivative of absorbance has the capability to estimate soil surface moisture of the four sets of data. It shows the great potential to estimate soil surface moisture within a large area for different soil types.关键词：soil moisture;hyperspectral;derivative spectra;reflectance
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发布时间：2021-06-10 - 摘要：Composite scene of row crops induced an unavoidable error in ground observations due to the use of wide field of view （FOV） in the measurements. The measurements vary with sample size and position, detector height and view direction, and bias due to project principle, which is called FOV effect. This study focused on the estimation of FOV effect on the measurements of maize canopy directional brightness temperature （DBT） using a computational geometric 2D model. The model was developed to simulate the fractional variations of canopy brightness temperature components. In this research, the maize canopy was classified into three brightness temperature components: sunlit soil, shaded soil and vegetation, each component has a unique brightness temperature value. The simulation results revealed that the errors caused by wide FOV have complex features due to canopy geometry and measurement geometry. Generally, vegetation fraction is always over counted in the nadir, errors increase dramatically with the decrease of detector height as well as the enlargement of sample size, and the deviation of the error corresponding to sample position is small. In oblique view, the errors are limited to a low level due to the compensation effect. The best approach to reduce this kind of error is to set the detector to a higher altitude as the model suggested.关键词：ground measurement;FOV effect;maize canopy;directional brightness temperature
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发布时间：2021-06-10 - 摘要：In the past few years, there has been a growing interest in the development of automatic change detection techniques for the analysis of multi-temporal remote sensing images. This paper introduces a method for multivariate change detection, which is based on the canonical correlation analysis and the orthogonal transformation. Differing from traditional multivariate change detection schemes such as the principal component analysis （PCA）, this method takes two co-registered multivariate or multi-spectral satellite images covering the same geographic area typically acquired at different times as a whole random sample, and transforms two sets of random variables into a new set of random variates by using canonical transformation. To overcome the problem of lacking automatic techniques for discriminating the changed and unchanged pixels in the difference image, we propose an automatic technique based on the Bayes theory for the analysis of difference image. It assumes that the difference magnitudes comply with normal distributions. An automatic method for selection of the decision threshold that minimizes the overall change detection error probability is investigated. To perform an unsupervised estimation of the statistical terms that characterize these distributions, an iterative method based on the Expectation-Maximization （EM） algorithm is also presented. The experimental results show the fact that the presented method is exactly creditable and effective in multivariate change detection of remote sensing satellite data.关键词：change detection;bayes rule of minimum error;expectation maximization algorithm;decision threshold
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发布时间：2021-06-10 - 摘要：The maximum likelihood classification （MLC） is one of the most popular methods in remote sensing imag classification. Because the maximum likelihood classification is based on spectrum of objects, it cannot correctly distinguish objects that have same spectrum and cannot reach the accuracy requirement. In this paper, we take an area of Fengtai District of Beijing as an example and discuss the method of combining texture of high-resolution image with spectrum to improve the accuracy of TM image information extraction. Firstly, analysis of the textures of the in high-resolution imags is made by using texture analysis of Gray Level Coocurrence Matrices and selecting statistic index. Then threshold is selected and the optimal threshold is obtained according to entropy. Objects that have same spectrums such as vegetation land and cultivated land are distinguished using image segmentation in virtue of the optimal threshold. Finally, the find result is obtained through combining image segmentation with original classification. The finat result is compared with the classification results based on spectrum only or texture only. The result indicates that the objects with same spectrum are distinguished by using texture analysis in image classification, and the combination improves more than spectrum only or texture only in classification accuracy.关键词：maximum likelihood classification;Texture analysis;Gray Level Coocurrence Matrices;thresholding
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发布时间：2021-06-10 -
A Method for Tracing Run-length Outline to Implement Vectorization of Raster Graphics and Image Data
摘要：An effective method of vectorization in which both raster graphics and image data are converted into polygon features through tracing the run-length outline is developed. It is an important aspect in GIS to extract thematic vector information from remote sensing images and the resultant spatial analysis such as spatial overlay and spatial diffusion ,which can be simplified in the raster data structures needs a powerful support of efficient vectorization technique. The run-length codes of raster have the characteristics of storing high precision image, containing the horizontal difference information, easy access, rapid conversion, operability and moderate compression ratio where these features are well shown in the paper. The concept of‘up neighbor run-length’and ‘down neighbor run-length’ is well defined and the efficient algorithms for seeking vertical neighbor run-length for vertical tracing are developed in this paper. The adaptation of vectorization technique based on run-length outline enhances computer’s ability and efficiency of handling large scale and high precision complex raster data. The result of the program test indicates that this method has stronger adaptability and weaker sensitivity to large scale and complex raster data. It is proved to be flexible and practical, as it can extract not only the arc links with topo-relation but also integral borders. This method could be widely used for raster-type geographical spatial analysis and also remote sensing images processing.关键词：run-length codes;vectorization;up neighbor run-length;down neighbor run-length- 149
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发布时间：2021-06-10 - 摘要：Aerosol is a key factor to understand uncertainties in the study of atomosphere radiation equilibrium and climate change, and Asia dust is an important source of aerosol. In addition, dust detection is the first step to monitor dust disaster and study dust aerosol. Some detection methods using brightness temperature and apparent reflectance had been presented. In this paper, the thermal infrared temperature difference △T（T 11μm-T 12μm） is investigated as a possible method for detecting dust outbreaks. Previous research indicates that ΔT is always bigger than 0 due to vapor absorption difference in thermal infrared bands （T 11μm and T 12μm） when aerosol optic thickness τ 0.50μm is less than 1.0. However, when radiative properties of the winter dust aerosol is incorporated into SBDART atmospheric radiative transfer model, atmospheric radiation calculations indicate that the temperature difference ΔT over land surface will decline below 0 as optic thickness τ 0.50μm of dust aerosol increases to more than 1.7. This is due to the reason that the imaginary part of the complex refractive for dust aerosol at 11μm band is bigger than that at 12μm band, which causes thermal infrared absorption at 11μm band is bigger than that at 12μm band. The feasibility of dust detection using this technology is demonstrated by comparing satellite observations and surface observations of meteorological stations in one serious event of spring dust that occurred in North-East China on April 7, 2002.关键词：NOAA-AVHRR;dust detection;thermal infrared temperature
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发布时间：2021-06-10 - 摘要：Although the integrated technique of management for Mason pine caterpillar have developed a systemic research for about half a century, it is still unable to meet the demand of forestry sustainable development with social and economic development. The monitoring and management system of forest insects and diseases based on "3S" and internet technology have already been established in many countries. However it is still in very preliminary stage and far from being perfect in our country at present. In this paper, we utilize remote sensing of data Qianshan county, Anhui province and primarily discuss the correlation between the occurrence and development of pine caterpillar and terrain, roads with residential areas in virtue of spatial analysis functions of GIS such as overlay, proximity and spatial statistics analysis. Dynamic change information of pine caterpillar among different years is also compared. Finally this article educed various factors influencing pine caterpillar and master space-time spatial expansion rule of pine caterpillar. It is beneficial to early forecast and prevention of pine caterpillar. The result has validated some empirical knowledge, such as geographic distribution and developing process of pine caterpillar. It shows the feasibility of forecasting pine caterpillar quantitatively and orientationally by using GIS.关键词：geographic information system（GIS）;mason pine caterpillar;forest diseases and insects;spatial expansion;spatial analysis
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发布时间：2021-06-10
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