最新刊期
卷 ， 期 4 ， 2000
- 摘要：On the basis of presenting the status quo of space technologies and major national and international activities related to data policies, this paper analyses the characteristics of the existing data policies, and issues of sharing space data and its ethical challengess. Six key actions in the worldwide are suggested.关键词：Outer space;Data policy;Ethics
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发布时间：2021-06-10 - 摘要：The existing operational models limited by their pure empiricism are unable to be applied to microwave frequencies, and the physical model of wind velocity retrieval represented by two scale model are limited by their over simplifications. This paper establishes a wind velocity retrieval model which combines the merits of both theoretical soundness of physical models and the practical applicability of operational models. This paper presents a method for short wind generated wave spectrum based on analyses of existing microwave scattering data at widely varying frequencies. Such short wind generated wave spectrum has been proved very effective in improving the retrieval level and generality of the retrieval models. A new practical wind velocity retrieval model is then formed by using such short wind generated wave spectrum. Comparisons among the computed results based on the present model and those based on other models as well as backscattering measurements are presented in this paper. It is shown that the present model can be successfully applied to a wide range of radar frequencies （0.428—34.4 GHz） and is able to predict the asymmetry of upwind and downwind directions. The agreement between the model predictions and the measurements is satisfactory.关键词：the spectrum of short wind generated waves;Bragg scattering;normalized radar cross section （NRCS）;friction velocity;microwaves frequency
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发布时间：2021-06-10 - 摘要：A method of establishing experimental models of mic row ave radiometric characteristics for extended targets is introduced in this paper . Microwave radiometric characteristics are represented by brightness temperatur e. A large amount of antenna temperature data is obtained through the repeated m easurement of the targets under different conditions and at different time. Appa rent temperature is obtained from antenna temperature through the inversion of t he integral equation. The brightness temperature is obtained from apparent tempe rature by eliminating the scattered radiometric temperature. The formula of brig htness temperature for the targets with respect to incident angle and surface ph ysical temperature are established through twodimensional curvefitting of brig htness temperature. Comparing the experimental model established by this method with the semiempirical formula （theoretical model） of water brightness temperat ure, it is found that they are very close in the range of surface temperature （4 \35℃） covered by the measurement and measuring angle 20°\65°. The experimen tal models established with this method for concrete road, asphalt road, and cru shed stone road are also presented.关键词：extended target;microwave radiometric characteristics;brightness temperature;experimental model
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发布时间：2021-06-10 - 摘要：Monte Carlo method has been widely used to simulate t he BRDF value of vegetation canopy in the field of visible remote sensing. This paper discusses how to use Monte Carlo method to simulate the thermal radiant di rectionality of the continuous vegetation. Based on two preconditions: the loca l thermal equilibrium is satisfied and emissivities do not change with temperatu re, the component effective emissivities of winter wheat and soil had been calcu lated by Monte Carlo method which can describe the transfer process of photon. T hen the radiance L（θ） of non-isothermal mixed pixel can be calculated acco rding the following model:L（θ）=ε e1（θ）·L b（T 1）+ε e2（θ）·L b（T 2）The simulated result were well proved by measured radiance in the field of Yuche ng Station of CAS in Shandong province.关键词：Monte Carlo method;radiant directionality
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发布时间：2021-06-10 - 摘要：In order that NO images can provide abundant macrosc opic information and at the same time ensure detailed information of certain pre cision, this article puts forward a set of methods. Its experimental area is Jil in province in northeast China. Based on NO image data of 1998 and latest TM i mage data, a calibration was done with high resolution satelliter data to impro ve the forest area estimation derived from low resolution satellite data. Meanwh ile fractal geometry theory is lead applied to analyze spatial structure chara cters of remote sensing images. Spatial distribution and shape of land blocks i n the image are quantified with the method of fractal dimension. It is helpful t o get more and useful information from remote sensing images.关键词：spatial structure characters;Fractal;primary unit;s econdary unit
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发布时间：2021-06-10 - 摘要：In the Chinese Arctic scientific expedition during Jul y to September, 1999, a set of digital images by helicopter remote sensing are o btained. With high ground resolution of 30 cm, these images can be used to analy ze detailed sea ice parameters. In this paper, a method for determining the thr eshold value is adopted to separate ice and water. A ratio of radiance is de fined as the ratio of the ice element number that with large difference compared with the neighbor element over the total element number with the same radiance value. By the result, not only ice edge and ice concentration are accurately cal culated, but some new parameters are also chosen to present the status of sea i ce. Ice area is a parameter to give the area of each ice to show the size of ice. Sea ice is divided into five types by its area size to show the ice dis tribution ratio in different types. As many big ice packs consist of small ice pieces crowded each other, a new parameter called breaking degree is propos ed to express the complexion degree of ice shape. These parameters can be used t o distinguish ice size in a big ice, which can greatly affect vessel navigation and air-ice-ocean heat exchange. By combining these parameters, people can get more information of sea ice for its concentration, area of big ice and broken degree of ice pack. It seems that these parameters are useful in the studies in ice melting process and interaction between atmosphere and ocean water. These pa rameters are hardly determined by satellite imagery. The method can be used to c alculate water’s area, and complexion degree of water regions to express lead, l ane, polynya, etc. The methods can be used in sea ice analysis for either polar ice or the ice in Bohai Sea.关键词：airborne remote sensing;digital image;sea ice;Arctic
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发布时间：2021-06-10 - 摘要：The paper studied the variational process of leaf area index （LAI）, leaf chl orophyll density （CH.D） and Hyperspectral data with growing period. The correla tion between the hyperspectral data and LAI, CH.D of rice was also analyzed. Sp ectral derivative technique was used to suppress the effects of low frequency sp ectral noises on background （such as Soil and so on）. The derivatives of relfect ance spectrum can enhance the correlation and improve the precision of predictin g LAI and CH.D. Results show that the derivatives of reflectance spectrum and CH .D more markedly correlate with LAI at some wavelength; CH.D is more av ailable to express crop canopy spectral information than LAI.关键词：spectral derivatives;LAI;CH.D;regression analysis
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发布时间：2021-06-10 - 摘要：Operational Modular Imaging Spectrometer （OMIS） is a new type of airbome remote sensor. It has 128 spectral bands ranging from visibl e to thermal infrared wavelength. Its application fields include geography, agri culture, forest and ocean etc. For the convenience of the wide use of OMIS Data and the instrument improvement, quantitative evaluation of OMIS data is indispen sable. Signal-Noise-Ratio（ SNR ） is an important evaluation scale. According to R. E. Roger’s view, for a complex instrument such as AVIRIS, it is not reasonabl e to assume that the noise included is random and not correlative, especially in visible spectral bands. In this paper, through the analysis of the noise charac ters in OMIS data the authors point out that the noise mixed in OMIS data is a k ind of additive noise and not correlative. Based on athrough analysis of the fou r available SNR estimation methods, a conclusion can be drawn that the spati al a nd spectral decorrelation method is the most reasonable one for OMIS data. The e xperimental results are also presented. It is also pointed out that after radiom etric correction, the SNR of the acquired data can effeciently reflect the SNR character of the remote sensor.关键词：operational modular imaging spectrometer;signal-nois e-ratio;geostatistical method;semivariance function;decorrelation
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发布时间：2021-06-10 - 摘要：In this paper we propose a new method for multispec tr al image data compression based on Karhunen-Leove Transformation （KLT）/Wavelet Transformation （WT） and VQ with Spectral Feature Coding（SFCVQ）. After KLT is app lied to multispectral image data for exploiting the spectral correlation, the Wa velet Transformation （WT） is used for the transformed multispectral image data t o remove spatial redundancy. Then the SFCVQ is designed to compress every spectr al image data. A higher compression performance is obtained. Experimental result s shows that in comparison of the methods of KLT/WT/SFCVQ with KLT/KLT/VQ, under the condition of the same Compression Ratio （ CR ）, the Peak Signal to Noise Ratio （ PSNR ） is not varied apparently, while the compression speed increase s 30folds, or 5folds compared with the KLT/WT/FSVQ, and the total compression pe rformance has a great enhancement.关键词：KLT;wavelet transformation;vector quantization with spectral feature coding;data compression
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发布时间：2021-06-10 - 摘要：Land cover change detection is an important applica ti on field of remotely sensed data In this paper, a new method for vegetation chan ge detection based on multitemporal Landsat TM images is introduced. Results of its application in vegetation change detection of Dunhuang Qasis show positive a spects of this method Color composition of multitemporal TM data gives an obviou s view of vegetation change in the stady area. Color components from color space transformation can be used for quantitative analysis of vegetation change. Hue and Saturation components indicate types and intensity of changes respectively. Lightness component shows general NDVI distribution over the study period. This new method can be easily applied to other change study fields.关键词：vegetation cover;change detection;color composition and color space transformation
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发布时间：2021-06-10 - 摘要：A new way of multiprincipal component analysis is proposed. The image processin g technology of information reextraction focuses on the special objects based o n the original remote sensing data being processed by some conventional methods. Meantime, it is a way to process comprehensively different remote sensing data with different spatial resolutions and spectral ranges. The application of the m ethod has shown good result for extracting geological structure information in w est Qaidam Basin of China.关键词：remote sensing image processing;multiprincipal component analysis;geological structure information
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发布时间：2021-06-10 - 摘要：The paper describes the techniques of error minimiz at ion. In the paper, the error is divided into three types: theoretical error such as errors created in the projection from the earth’s surface to a plane coordin ate system and in digitizing maps, errors in the procedure of creating thematic d ata from TM images and errors due to the spatial resolution of TM images. Three different methods are adopted in respect to the three types of error mentioned above. To minimize error created due to the TM image’s spatial resolution, a ser ies of sampling methods are applied and discussed in detail in the paper. Accord ing to the analysis on the effects of the error minimization methods, especially the sampling methods, there is about 30% cut off from the gross area of farmlan d, and the net area of each land use type is much more close to the actual data.关键词：natural resources;GIS and RS;area summarization;sample
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发布时间：2021-06-10 - 摘要：More and more GPS receivers are onboard low-orbit sat ellites for orbit determination, which can be applied to remote sensing, meteoro logy and sea surface altitude determination. The method of ambiguity resolution for relative orbit determination with carrier phase is proposed. Some criteria a re developed to identify correct ambiguities. With the method, the accuracy of c a rrier phase-based relative orbit determination may attain the order of a few de cimeter from the results calculated by using data collected from GPS/DR onboard TOPEX/POSEIDON.关键词：GPS;relative orbit determination;sigma method;ambig uity
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发布时间：2021-06-10 - 摘要：To analyze positional accuracy of geographical line s in GIS, this paper begins with a discussion on the representation and positional errors of linear features. We make a clear distinction between digital lines in spatial databases and continuous lines in the natural world. Using algorithms f or generating continuous curves from digital lines in GIS, we develop several er ror band models for continuous curves and derive numerical relationships for est imating errors of line length. Examples are provided to show the visualization o f error bands of geographical curves and the use of error equations of line leng th.关键词：geographical line;positional error;Visualization
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发布时间：2021-06-10
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