最新刊期
卷 ， 期 1 ， 2005
- 摘要：This paper presents an in-depth research on the effects of leaf biochemical concentrations on leaf spectra. Absorption features centered at 2100nm are focused on in this study because the spectra of predominant carbon containing and nitrogen containing components in leaf are different here apparently. Spectral changes due to different carbon or nitrogen concentrations at this waveband are examined with several samples and two rules are concluded by using continuum removed spectra. First, the spectral changes due to different carbon concentrations can be seen from 2030nm to 2050nm, where the continuum-removed spectra are nearly straight and their slopes are indicators to distinguish different carbon concentrations. Second, the spectral changes at 2054nm and 2172nm are good indicators to distinguish different nitrogen concentrations. Correlation analysis and stepwise regressions are employed to verify the relations of C:N ratio and continuum-removed spectra and the results are satisfactory.关键词：biochemical concentration;hyperspectral remote sensing;C:N ratio;continuum removal;band-depth norma-lization
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发布时间：2021-06-10 - 摘要：Based on the near infrared radiative transfer theory, the retrieval method of precipitable water vapor （PWV） with MODIS near infrared band data is analyzed under the simulation of radiative transfer model, MODTRAN. The effect of surface nonlinear reflective spectrum on PWV estimation is emphasized on. Both two bands ratio method and three bands ratio method are taken into account. The study indicates that the error due to the surface nonlinear reflective spectrum is very large if the reflectance ratio of water vapor band to atmospheric windows band is not equal to 1.The error is proportional to the ratio of transmittance ratio between these two bands. The ratio of band reflectance is calculated for hundreds kinds of surface material such as rocks, minerals, soils, vegetation and water in Johns Hopkins University spectral library. Most of the reflectance ratios have a considerable difference with 1.And the difference from 1 of two bands ratio method is smaller than three bands method. That indicates three bands method is predominant over two bands method. The coefficients used in three bands method is recalculated based on the spectral library. The result shows that their coefficients should be gained from the regression of whole spectral library and the sum of coefficients should be equal to 1.关键词：near infrared;water vapor retrieval;radiative transfer;MODIS;MODTRAN
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发布时间：2021-06-10 - 摘要：This paper researches on the methodology for brightness temperature component classification and temporal variations of these component values by an in situ experiment dedicated to maize canopy brightness temperature distribution. Results show the number of components and their brightness temperature values vary with time of day and biomass density. Three components of vegetation, sunlit and shaded soil could be identified at midday during the measuring period. When the canopy is highly co-vered, vegetation’s brightness temperature has a wider range, and the components are difficult to be distinguished. The interpretation of these phenomena will be conceived in the further research.关键词：maize canopy;classification;component brightness temperature
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发布时间：2021-06-10 - 摘要：It was said that the shape of a point target response is just a sinc function after formating in synthetic aperture radar（SAR） systems. But this idea is a mistake actually. The shape of a point target response can be closen as a sinc function shape under some limited conditions. For example, if the time-band width product of a chirp signal is large enough and the spectrum of the chirp signal is close to rectangular, the sequence is long enough to enable more energy of signal being kept down, and the sampling frequency is high enough to ensure less aliasing of the spectrum.Since the last shape is the modulus of a point target, the spectrum of the last shape is extended far away and the spectrum may have more aliasing, and any low-pass filters can not restore the signal satisfactorily. Usually, a liner-interpolation, which is a first-order hold low-pass filter（LPF）, is used to restore signal. It may have more errors than ideal LPF under lower sampling frequency. A higher sampling frequency may make the last shape of point target response more close to the shape of sinc function.Because the spectrum will be extended during the process of demodulation, it may result in aliasing. To change the complex image to modular image, the signal needs upsampling and a low-pass filter before demodulation, and downsampling after demodulation.Specially, more difference may be derived from a two-dimension sinc function shape for the shape of a point target response of a Squint Mode compared with a side-look SAR since its spectrum has more difference from rectangular than a side-look SAR.The reasons of the shape of a point target response differing from a sinc frunction are analyzed, and simulation results have been presented to support the analysis in this paper.关键词：synthetic aperture radar（SAR）;point target;low pass filter（LPF）;interpolation
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发布时间：2021-06-10 - 摘要：In order to combat the developing trend of eco-environment degradation, a series of national environmental projects have been carried out in frail ecological zone since 1998. The construction measures adopted by the projects include handing farmland back to forestland or grass land, protecting nature forestry from deforestation, planting sheltering forest, conserving soil and water, and so on. To evaluate the effect of the projects on eco-environment, five sites in different eco-environmental zones were selected as study areas to monitor the change of land cover over 1997—2002. Through analyzing the change of land cover, it suggests that as a result of national environmental projects, the eco-environment is rehabilitating gradually except for the study area of East-northern China. The sheltering forestry has increased 1479 hm2, farmland has increased, and forestland and grassland decreased in the region of the case site located in East-northern China. In the region of the case site located in the north of Beijing, the total area resulted from the construction project is 51492 hm2, farmland has decreased, and forestland and grassland have increased. In the region of the case site in the north part of Shanxi Province, the total area resulted from the construction project is 11115 hm2, farmland has decreased, and forestland and grassland have increased. In the region of the case site located in the middle part of Gansu Province, the total area resulted from the construction project is 17437 hm2, farmland has decreased, and forestland and grassland have increased. In the region of the case site in Sichuan Province, the total area resulted from the construction project is 65347 hm2, forestland has increased, and farmland and grassland have decreased.关键词：RS;GIS;eco-environment;dynamic monitoring
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发布时间：2021-06-10 - 摘要：We developed a sea surface emissivity model and atmospheric model for special frequencies and incidence angles of RAD. After simulated brightness temperatures being received by RAD main beams at SZ-4 spacecraftat levels, some statistical algorithms of retrieving sea surface temperatures, wind speeds, volume water vapor contents and volume liquid waters of cloud above the global ocean were developed. The retrieval results were compared and validated with those from global NDBC （National Data Buoy Center） buoys, radiosondes, and other space-borne microwave radiometer products.关键词：microwave radiometer;geophysical parameter retrieval;validation
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发布时间：2021-06-10 - 摘要：Target detection is the first stage of automatic target recognition（ATR）. A rapid Constant False Alarm Rate （CFAR） detection algorithm is proposed in this paper. This detection algorithm is based on Rayleigh clutter distribution assumption and is composed of two stages: a horizontal CFAR and a vertical CFAR. The superposition of the reference windows of adjacent pixels is used to speed up the estimation of clutter mean, and the characteristic of clutter distribution is used to speed up the estimation of clutter variance. The standard variance characteristic of target data is used to reduce false alarm rate. A weighted counter filter is used to eliminate the sparse bright pixels, and the connected regions whose area is within a certain bound are detected as region of interest. Experiment using the MSTAR pubic data set shows the power of this approach in SAR target detection.
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发布时间：2021-06-10 - 摘要：A novel method is presented for ship detection in synthetic aperture radar （SAR） images, which is based on the constant false alarm rate （CFAR） technique and considers the probability density function of sea clutter as Gaussian distribution. All possible ship targets are detected using an overall threshold, which is calculated using the analytic formula. Then a statistic filter is used to eliminate the false ship pixels. This method avoids complicated iteration, calculation of shape parameters and dichotomy threshold, and therefore its accuracy and computation speed are improved, which are demonstrated by the results.In the paper, the main ATR techniques for ship detection in SAR images are reviewed, which include the window filter method, self-adapting threshold method, pdf （probability density function） method and PNN （Probability Neural Network） mo-del. A novel method is then presented, which is based on CFAR technique and Gaussian distribution of sea surface clutter. In this method, CFAR operator is given based on Gaussian distribution （normal distribution）, and the statistic filter is introduced to eliminate the false ship pixels, finally the framework of the method is described. The X-SAR and ERS SAR images are used for the algorithm test. Parameters such as detection threshold, computation time, number of detected targets and target pixel numbers are chosen as parameters for comparison with other methods. Results and comparison show that the new method proposed in this paper has advantages of high accuracy and computation speed.关键词：SAR;CFAR;ship detection;gaussian-distribution
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发布时间：2021-06-10 - 摘要：With the nonlinearity of bi-directional mirror scan, motion of spacecraft and attitude variability, the model of the line of sight and Projection for Landsat 7 are very complex, and it cost much time during systematically geometric correction. In order to solve this problem, a method to simplify the model and speed up the calculation process is introduced. Image distortion is decomposed into nominal distortions and perturbation caused by seven deviations from nominal motions including one mirror-scan component, three spacecraft-motion components and three attitude components. The nominal mirror scan is selected as an estimated linear model. The nominal spacecraft motions are selected as three forecast orbit components. Three nominal attitudes are all selected as zero. The nominal line of sight can be calculated in advance which cost a great amount of time, and real-time calculation will cost only a little part of time. The whole process is modeled in detail. A new method is introduced in this paper when only partial components can be described. At last, through the analysis in theory and the experiments with real data, the speed and precision of the model are discussed, and the model is validated.关键词：Landsat 7;geometric calibration;line of sight;distortion;perturbation
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发布时间：2021-06-10 - 摘要：With the launch of NASA’s Terra satellite and Moderate Resolution Imaging Spectroradiometer （MODIS）,operational Bidirectional Reflectance Distribution Function （BRDF） and albedo products are now providing new opportunity to scientific community.The MODIS BRDF/Albedo algorithm makes use of a semiempirical kernel-driven bi-directional reflectance model to lnverse the albedo by multiangle remote sensing data acquired within 16 days. These products include directional hemispherical albedo （black-sky albedo）,bihemispherical albedo （white-sky albedo）, Nadir BRDF-Adjusted surface Reflectance （NBAR）, model parameters describing the BRDF,and extensive quality assurance information. There has been some validation result for this work,but further validation based on field measurement is also needed to widen application.This work aim to compare the albedo acquired by albedo meter in meteorological station and inverted by field measurement and air-borne MAR data using Kernel-driven model with that of MODIS.The initial validation result is also given in this paper.关键词：albedo;multi-angle remote sensing;inversion;kernel-driven model
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发布时间：2021-06-10 - 摘要：The high precise method that automatically rectifying and registering the multi-source remote sensing imagery which are from different sensors with different resolutions and taken from different times, is presented in this paper. First of all, the image to be registered is roughly rectified by using the polynomial model. Then, the feature points are extracted automatically, which are distributing evenly on the roughly rectified image. Guided by the extracted feature points, the common points to be used in automatic registration are obtained by using the pyramid-layered template matching technique. Finally, both the geo-refe-rencing image and the image to be precisely registered are divided into a number of triangular regions by constructing the Triangulated Irregular Network （TIN） on them, and the high precise rectification and registration can be fulfilled on each triangular region one by one.关键词：multi-source remote sensing imagery;image registration;image rectification;TIN
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发布时间：2021-06-10 - 摘要：It is a key problem to analyze quantitatively the correlations between remote sensing data and chlorophyll-a comcentration for measuring the chlorophyll-a content with remote sensing method and technology. Two field campaigns were made in March and June 2003, respectively. Reflectance spectra were measured with a portable FieldSpec FR spectroradiometer （ASD Inc.）. Water samples for chlorophyll-a measurement were collected at the same time guided by some related standards of China. The features of the spectral reflectance were analyzed in detail with peak height, trough depth, area surrounded by peak, distance from peak to trough and peak shoulder width. And the same result as others is to discover the most important features near 682nm and near 706nm. The regressive linear/nonlinear fitting model were developed respectively between chlorophyll-a concentration and other factors as follows: 1st, the ratio of reflectance near 706nm to reflectance near 682nm （R706/R682）;2nd, the ratio of reflectance near 706nm to reflectance near 572nm （R706/R572）;3rd, the first derivative of reflectance near 690nm （R’694）;4th, the position of reflectance peak near 706nm（λmax706）;5th, the distance from reflectance peak near 706nm to trough near 682nm （Dpeak706-682）;6th, the area surrounded by reflectance peak near 706nm （Apeak）; and 7th, the height of reflectance peak near 706nm （Hpeak706）. By comparison of R2,average error and RMS error respectively, the results show that R706/R682, exponential fitting degree R2 with 0.9199, λmax706, linear fitting degree R2 with 0.9038 can denote chlorophyll-a content and they are better to predict chlorophyll-a concentration of water-body near Meiliang bayou in Taihu. The position of reflectance peak near 706nm is the most sensitive factor to denote chlorophyll-a concentration by comparison of distance from reflectance peak to absorbance value, height of reflectance peak and area of reflectance peak. It is very important to predict chlorophyll-a content for the bands near 572nm, 682nm and 706nm.关键词：spectral feature;chlorophyll-a;taihu lake;RS
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发布时间：2021-06-10 - 摘要：The famed Great Wall of China stretches some 3,000 kilometers （1,850 miles）. High-resolution satellite remote sensing provides cheap and quick data resources for delineating the Great Wall. In this paper, the remote sensing mechanism and spectral characteristics of the Great Wall segment in remote sensing imagery were analyzed. Due to the similar spectral response feature of Great Wall to road and sand, threshold for bands is not an effective method for the extraction of Great Wall. Thus, A gray-slope algorithm is introduced, which can extract Great Wall information effectively and easily. Due to the extensive destroy to the Great Wall, it is only 1 or 2 pixels wide in IKONOS imagery. And the gray level between Great Wall and other objects around it is very different, that is, the change of gray level along Great Wall is greater than that of road and sand. Based on these two characteristics and bands threshold, the gray-slope method makes road and sand separated from the Great Wall easily. Yulin County in Shan’xi Province is selected as a case study area, and IKONOS imagery is used as a data source. The result is satisfied when this method is applied to identify the Ming Great Wall submerged in the Maowusu desert. However, the universality of this algorithm needs to be tested further in other areas as the spatial characteristics and spectral response of Great Wall may vary.关键词：Great Wall;remote sensing;information extraction;gray-slope method
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发布时间：2021-06-10 - 摘要：In this paper, a method based on NDVI-Ts space is proposed for Chinese land cover classification. The ten days composite ch4 and ch5 light temperatures for 1995 were used to estimate land surface temperature with split window method. Then the monthly land surface temperature and NDVI were produced with the maximum value composite from the 10-day composite Ts and NDVI. With the monthly Ts and NDVI, the monthly NDVI-Ts spaces were created. And pixel vector direction in the NDVI-Ts space was described with NTVA （Normalized Temperature Vegetation Angel）. Principal Components Analysis （PCA） was used to compress the 12 monthly NTVA images and three Principal Components were extracted. Fuzzy K-mean algorithm in clustering was used with the three Principal Components, summation of monthly NDVI and accumulated >0℃ Ts image to produce China land cover classification map. The result revealed that remarkable improvement for land cover classification can be reached with the combination of NDVI and land surface temperature..关键词：land cover classification;NDVI;Ts;NTVA
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发布时间：2021-06-10 - 摘要：Spectral reflectance of rice canopies with different nitrogen treatment was measured over an entire growing season and eight spectral indices such as RVI, NDVI, PVI etc were calculated. Based on the biological mechanism of yield formation, relationships of these vegetation indices to yield and its components were analyzed. The results showed that it was limited to predict yield with vegetation index from single or multiple developing stages. However, the dynamic curve of Leaf Area Nitrogen Index （product of LAI by leaf nitrogen content on dry weight basis） can well track the process of yield formation. Due to the close relationship with the vegetation index, Cumulative Leaf Area Nitrogen Index （CLANI, the area below the curve） was used to derive a model named VI-CLANI-Yield model for rice yield estimation. The comparison of the present model with the LAD-Yield model and complex VI-Yield model indicated that the yield estimation accuracy was best for VI-CLANI-Yield model with average relative error of 0.075. This suggests that VI-CLANI-Yield model would be a practical and effective approach for rice yield forecasting.关键词：rice;vegetation index;leaf area nitrogen index （LANI）;yield;yield components;forecasting model
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发布时间：2021-06-10 - 摘要：Radar image scene matching is an important means on navigation and location of aeroplane, due to its all-weather imaging capability. However, because of radar side looking and terrain undulation, the real objects distorts and displaces when radar scene is imaged. It impacts the matching precision between a radar image and the reference one. In this paper, based on the way of scene imaging, the analogy real-radar image （image one） is made from reference image firstly. And the impact of terrain undulation is introduced into the real-radar image one by rectification with DEM data. Then the real-radar image （image two） is produced, which contains the impact of terrain undulation. In the experiment, two types of the analogy real-radar images of the same area are matched with the reference one. The matching results are compared, and the difference of matching result is used to analyze the practical influence of terrain undulation on radar scene matching. At last, the article draw a conclusion——the imaging characteristic of actual surface object is a main factor that affects matching, and the terrain undulations just have influenle on matching only when it combined with object feature.关键词：scene matching;horizon-range projective imaging;reference image;">
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发布时间：2021-06-10
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