最新刊期
卷 ， 期 3 ， 2003
- 摘要：Canopy radiance in thermal infrared （TIR） band mainly comes from emission of canopy itself. This differs very much from the situation of visible and near infrared （VNIR） band, in which reflection plays the major role. How- ever, the sophisticated canopy model in visible and near infrared band are still instructive to thermal infrared researches. Some recent works extend results of canopy BRDF model, such as Hapke’s formula, to thermal infrared band through Kirchhoff’s law that directional emissivity of a surface equals 1 minus its directional-hemispherical reflectance. However, this in-direct approach is not convenient because using Kirchhoff’s law means to assume isothermal condition, but most natural surface is not isothermal. In this paper, we extend a typical canopy model in VNIR band, the SAIL model, to TIR band by adding terms of thermal emission in the radiation transfer equations. Analytic solution of the radiation transfer equations is derived. This enables us to directly simulate the emission and radiation transfer process inside the horizontal homogeneous canopy which is a good approximation to many kinds of crops. Leaf angle distribution （LAD） can be simulated discretely, and vertical canopy structure is also easily handled. Simulation of our model indicates that these factors play important role in directional signature of the canopy radiance. The model can also be used in some flexible ways, which enable it to act as basic modular in higher level TIR model. Here, we give two examples. In the first example, we use this model to calculate multiple scattering inside canopy and derive component effective emissivity. In the second example, the result of our RT model is adjusted by a row-structured GO model to simulate the real structure of winter wheat canopy as well as the footprint of radiometer. Comparison with field measured data indicates that the horizontal homogeneous assumption is also not valid in real cases, so the better choice is to integrate RT and GO model together.关键词：radiation transfer model;thermal IR remote sensing;directional thermal emission;effective emissivity
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发布时间：2021-06-10 - 摘要：Urbanization, stimulated by striking economic development, has been proceeded in China on a large scale and with striking rapidity in the past two decades. It is necessary to monitor and model urbanization process of China for its sustainable development. This paper presents a new light index for regional urbanization level estimation considering the light spatial distribution and intensity based on DMSP/OLS data, which was pre-processed by Japan National Institute of Environmental Studies. The correlation analysis between light index and composite urbanization index was carried out in province scale. The result shows that there is significant relationship between two indexes. The regression model for composite urbanization index estimation using light index was also developed with R 2 equal to 0.793. It suggests that light index is an effective and applicable index for regional urbanization analysis and monitoring. Through the analysis of light index change in China during 1992 to 1998, it is shown that the urbanization level in China is different from high level in East China to low level in West China, and urbanization level was improved largely during 1992 to 1998, especially in provinces of East China.关键词：urbanization;DMSP/OLS data;light index;China
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发布时间：2021-06-10 - 摘要：Accurate remotely sensed estimates of the chemical concentration of vegetation canopies provide a valuable aid to the understanding of ecosystem function and real-time agricultural decision-making. This is because many biochemical processes, such as photosynthesis, respiration and evapotranspiration are highly related to the biochemical concentrations such as chlorophyll, nitrogen, water and so on. Hyperspectral remote sensing images are providing an attractive way for biochemical estimates in a large scale promptly. In this study, investigation was designed to determine whether hyperspectral images of the airborne operative modular imaging spectrometer（OMIS）could be used to estimate foliar nitrogen concentration of wheat at a spatial resolution of 3m. OMIS image had 128 bands covering the V-TIR wavelength range, among which bands between 400nm and 2500nm accounting for 112 bands which were used in this paper. The images were acquired by the airborne OMIS in Xiaotangshan Area, Beijing, China, on April 26th, 2001 under a fairly clear weather. While the wheat leaves being sampled and measured foliar biochemistry, calibration was carried out synchronously. Red edge analysis and absorption feature analysis as well as stepwise regression analysis were utilized to determine the characteristic bands and parameters for the canopy-level nitrogen retrieval after accurate geometric correction and accurate image spectra rebuilt. The five concerned absorption features were centered around 675.8nm, 1175.8nm, 1409.1nm, 2078.2nm, 2295.1nm, which were selected according to the original image spectra shapes as well as some rational laboratory analysis results of dry materials. At last, the best estimation equation was applied to all the wheat pixels of the image so that a nitrogen concentration distribution map of wheat was obtained. As expected, the red edge slope（Srg）and area（Arg）could estimate the total foliar nitrogen（TN）fairly well（R 2=0.656, 0.643 respectively）. The absorption depths and absorption areas of the three absorption features centered around 670nm, 1175nm and 1409nm were effective estimators of wheat foliar nitrogen concentration（R 2=0.7447, 0.7569 and 0.7073 respectively, n=43）. The new developed spectral indices, NDVI（NRCA 1175.8, NRCA 733.9）and NDVI（dr745, dr699.2）were the best estimators of TN（R 2=0.8145 and 0.769 respectively）. The values of the nitrogen concentration distribution map ranged from 1.8% to 6.5%, which was quite consistent with those of field measurements（2.8%-6.3%）. The distribution agreed highly with the growth status distribution. Therefore to some extent, the estimation equation was validated. So it’s possible, feasible and time-saving to estimate foliar nitrogen concentration at a large scale by using hyperspectral remote sensed images.关键词：high spectral;image spectra;nitrogen;stepwise regression;spectral feature;mapping
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发布时间：2021-06-10 - 摘要：The problems of pixel mixture are the main obstacles of quantitative remote sensing. In this paper, we classify the problems of pixel mixture into two groups: mixture in class and mixture between classes. and focus our study on the former. The key problem of subpixel unmixing is to determine the component spectra. Many methods have been developed to determine the component spectra. However, most of these methods base on the assumption that pure component signatures can be found from the image itself. Obviously, this assumption is not correct for pixel mixture in class. In this paper, a new method to combine hyperspectral and multiangular data together to retrieve subpixel information is introduced. This method begins from the definition of the component signatures and tries to get a priori information from the data itself, so it′s more likely to acquire the "pure" endmember spectra and the subpixel information extracted by this method is more reliable than some other ways. To demonstrate the result of this method, we use BOREAS （the Boreal Ecosystem-Atmosphere Study） data to extract component signatures and the corresponding areal proportions in SSA（Southern Study Area）OJP（Old Jack Pine）site. The result is encouraging.关键词：subpixel unmixing;GOMS model;inversion;Multiangular remote sensing;hyperspectral remote sensing
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发布时间：2021-06-10 - 摘要：Thermal and "Speckle"noise is an obstacle to get digital elevation model（DEM） from the interferogram by 2-D unwrapping of interferogram phase. An adaptive filtering method for synthetic aperture radar（SAR）interferometric phase images is presented in this paper. Based on sixteen directional masks, which are the enlarged Prewitted edge masks, the fringe direction can be determined. Then those pixels on the same direction is filtered by average phase filtering method to generate filtered phase value. In fact, the change of interferogram phase is a gradual change. The pixel’s direction can be selected from the neighbouring directions of the preceding pixels in order to avoid too many computation about the directions of the present pixel. This method is useful, especially for tightly packed fringes. The method can be carried out easily. Using interferograms generated by SIR-C/X-SAR repeat-pass, its effectiveness is tested.关键词：interferometric synthetic aperture radar;interferometric fringe;phase noise filtering;edge detection
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发布时间：2021-06-10 - 摘要：In order to meet the needs of marine fishery agencies, an operational GIS & RS application system for marine fishery in East China Sea has been developed. RS,GIS,CBR,Database/Data warehouse,and GPS technologies have been integrated in this system. Because there are fuzzy,dynamic,three dimension characters in the marine environment,traditional GIS can not meet the needs. For the spatial-temporal dynamic change character of fishing ground,and there is not robust math model for forecasting, Case-based reasoning technology has been applied. For the operational character,layer-map-atlas hierarchy based data organizing method has been put forward and applied,and template is also applied for layer making. Expert system and model base management technologies have been integrated for fish stock access. An extent spatial ER methods is presented for dynamic marine fishery data concept modeling. The vector primitives （face,edge,vertex and volume） are introduced into 3D raster structure in order to express and analyze three dimension marine fishery data. This system can nowcast and forecast fishing ground of East China Sea for every week,and access fish stock of East China Sea for every fishing season,and this system also can be served for marine fishery management,eg. fishing boat tracing.关键词：remote sensing;geographic information system;marine fishery;case-based reasoning
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发布时间：2021-06-10 - 摘要：From the regionality viewpoint,this paper discussed the methods of built-up landcover change monitoring by remote sensing in large-scale regions. The methods of extracting built-up land-cover change information were generally discussed. The benefits and accuracy of 3 classification methods of MLC,frequency-based contextual classification with gray-level vector reduction, and ANN were compared in the test classification. The tests proved that the highest accuracy of classification method was the ANN,the kappa index was 0.6625. However,it need a long time to train the neural net,and the classification results didn’t have a significant improve than the other two methods. Frequency-based contextual classification considered the neighborhood pixels information,but the classification result depended on the window size greatly,it’s not easy to select a good window size for every kinds of land-cover. According to the test results,we selected the MLC to classify the TM imageries of the Pearl River Delta. With the expert knowledge,the computer classification results were improved based on GIS. The final results showed that the built-up land-cover of urban area changed greatly during 1988-1998 The buili-up land-cover area was only 556.08 km 2 in 1988,and increased to 1497.61 km 2 in 1998. Both core-oriented development and road-oriented development of the built-up land-cover were significant in the Pearl River Delta. During the study period,66.87% of the new built-up land-cover was in the 1 kilo-meter buffer of the main roads. But the general spatial structure kept relatively stable,83.46% of the built-up land-cover in 1988 was in the inner ring,and it was 84.18% in 1998. Finally,the results show that the built-up land-cover change destroyed the high quality soils greatly.关键词：Pearl River Delta;built-up land-cover change;monitoring by remote sensing
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发布时间：2021-06-10 - 摘要：The idea of synthetic integration for extracting and analyzing the geological information is put forward and discussed. Three integration modes, of hierarchical identification using various scales of remote sensing, of discrimination methods and techniques for minerals and rocks, and of spectral identification tree based on spectral frature of minerals and rocks, are primarily established. Of all, minerals or mineral assemblages discrimination are emphasized. Two combination analysis models for geological application, which are based on the single mineral identification and on the mineral assemblage identification using remote sensing, are established. It is most potential for extracting information of alteration and mineralization, and analyzing the geological environment. Both the gold deposit of Chicheng-chongli in Hebei Province and Cuprite district are as test areas, which used technique combination of both the synthetic integration and combination analysis models for geological application. The potassic altered mineral assemblage, which are strongly related to the genetic source for gold deposit, are extracted from Chicheng-chongli area in Hebei Province. The seven Mineralization and Alteration spots are extracted and confirmed. The geological genetic are analyzed effectively according to the intergrowth minerals which are discriminated using AVIRIS data at Cuprite district in U.S.A..关键词：synthetic integration technique;mineral analysis models;hyperspectral remote sensing
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发布时间：2021-06-10 - 摘要：This paper introduces the methods of compiling the land-cover map of Northwest China（with an area of approximately 3,100,000 km 2）using SPOT4-VEGETATION data sets and the validation techniques using high spatial resolution TM images. Based on the spectral reflectance, NDVI（Normalized difference Vegetation Index） and NDWI（Normalized Difference Water Index）time series data sets from SPOT4-VEGETATION, the land-cover map of Northwest China is compiled by applying the ISODATA unsuperviesd classification method. In order to evaluate this land-cover map’s accuracy, 47 sampling units are selected from the whole mapping region. Each sample has a 25km×25km unit and evenness distribution as well as high heterogeneity. With the assumption of the TM interpretation in the 47 sampling units as the true land cover condition, we calculated every land cover type and its area percentage existing in every sampling unit in the SPOT4-VEGETAION map and the TM interpreted map, respectively. According to the statistical results, the land-cover classification system of the SPOT4-VEGETATION is modified,the sampling statistical histogram of the validation results in every province is established and the regression coefficient value is also calculated respectively. The validation results show that the land cover mapping of Northwest China using SPOT4-VEGETATION data sets and the ISODATE method can get an improving accuracy attributing to the high quality of SPOT4-VEGETATION data products and the effective method of spectral index combination of NDVI and NDWI. The reasons that reduce or impact the landcover classification accuracy mainly derive from two aspects:one is attributed to different landcover classes with same spectral characteristics, and the other is due to the mixed pixel problem. TO the former, adding some auxiliary information data such as DEM can reduce the possibility of misjudgment; to the later, the methods of mixed pixel decomposition and sub-pixel mapping may be good ways to increase the land cover classification and mapping accuracy.关键词：land cover mapping;SPOT4-VEGETATION data set;ISODATA method;validation on remote sensing classification;Northwest China
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发布时间：2021-06-10 - 摘要：With Land satellite data of fifteen years combining aero data, this paper analyzed and studied 15 years’ dynamic change of water resources using types and water quality by remote sensing technique and field investigation in Taohu and Gehu Lake of Taihu drainage area. The used water resources types were divided into purse net area for breeding fish, fish pool surrounded, bottomland used, inning farm and natural lake by remote sensing approach. The actual area of different using types and density of purse net in some period were calculated with GIS approach. For the purse net of breeding fish in lake bringing a lot of economical benefits in recent years, purse net area and natural lake area have been changed rapidly for about 15 years. There was no purse net area in 1980s. In 1994, the ratio of purse net area to total lake area is 15% in Gehu Lake, and 27% in Taohu Lake. However, the ratio rapidly increased up to 78.8% in Gehu Lake, and up to 83.8% in Taohu Lake in 1998. This ratio greatly exceeds that of logical purse net area to total lake area, which should be less than 20%. Multi-spectral remote sensor can inspect and survey the dynamic change of purse net density at any time, so that the results may avoid false area data that are caused for the personal sake. Excessive density of purse net for breeding may cause aquatic plants decreasing greatly. This paper analyzed 15 year’s occupied proportion change of the aquatic plants by remote sensing approach in Taohu and Gehu lakes. 1980s, the proportion of aquatic plants occupid area to total lake area is more than 50% in Gehu Lake, and is more than 75% in Taohu Lake. In the mid-1990s, a lot of aquatic plants were cut down. There are a few aquatic plants in Gehu natural lake area protected. In 1998, only about 5% proportion of aquatic plants occupid area existed in the middle of Taohu Lake. Most space of the lakes could be used as purse net for breeding fish. This case brought on that the utilized value of the lakes by way of drinking, tour and aquatic animals and plants resources declined greatly. Furthermore, the content of nitrogen and phosphorus in the lakes was increased due to the effect of purse net of breeding fish. Pollution and eutrophication in the local lakes tend to be serious. It is effective that water environment indicators such as the concentrations of suspended substance and chlorophyll-a can be obtained by the use of multi-spectral remote sensing technology being applied to Taihu Lake and Dianchi Lake. However, the ability to inverse water environment under complex water quality or ecological conditions is limited with multi-spectral remote sensor owing to the wide wave band width. It could be a trend that hyper-spectral or super-spectral remote sensing technology is applied to complex water environment.关键词：water resources using types;purse net of breeding aquatics;remote sensing analysis;Taihu lake area
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发布时间：2021-06-10 - 摘要：Liquid water content（LWC）of precipitating cloud is of vital importance in monitor severe storms and weather modification, also for research and application of climate change and water cycle within the ocean-land-atmosphere system. It is well known that passive microwave techniques have been used in global precipitation remote sensing with preliminary success, but for remote sensing of LWC it is still a challenging task. In this paper, the precipitating cloud models are established by using combined cloud dynamic model and the real observation data and verified with the real observation data obtained during TOGA COARE IOP. Based on these cloud models the numerical simulation study were made with vector radiative transfer model. It is found that the radiance of the channel 6.9GHz（v or h）is very sensitive to the column liquid water content of the precipitating cloud, the brightness temperature Tb monotonously increase with LWC; The brightness temperature difference of v and h channels of 6.9GHz, ΔT b（=T bv-T bh）, is the best for remote sensing of LWC over ocean, ΔT b monotonously decrease with LWC, and the influence of different cloud type to ΔT b-LWC is small; On the contrary, the brightness temperatures are very insensitive to the ice water content of upper part of precipitating cloud, it means that ice water content of the precipitating cloud is almost without contribution to the total water content（TWC）of precipitating cloud. Simulation results indicate that the channel of 6.9GHz on Satellite-borne radiometer can be used to estimate column liquid water content of precipitating cloud, for operational use we have to do the investigation of the retrieval accuracy in more details, especially to verify by real observation data.关键词：space-borne microwave remote sensing;liquid water content of precipitating cloud;radiative transfer model
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发布时间：2021-06-10 - 摘要：A review of research works concerning remote sensing of land surface evapotranspiration and energy fluxes was presented, and problems and difficulties in this field were outlined. It is pointed out that parameters retrieved from remotely sensed data are crucial for accurate simulation of land surface energy fluxes. As to the model, a two-layer representation of canopy-soil system is a good choice both for theory precision and application convenience in the field of remote sensing. The methodology of linkage between remote sensing data and land surface model is to be innovated and more remotely sensed data to be integrated in future works.关键词：Review;Remote sensing;Land surface evapotranspiration
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发布时间：2021-06-10
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