最新刊期
卷 ， 期 3 ， 2001
- 摘要：Snow cover extension and snow depth information may be useful indicators of regional and global climate change and of basinscale water storage in mountainous areas as well as snow disaster monitoring, forecasting and the loss assessment in pastoral areas. Thus, it is important to ensure that they are accurate and as free as possible of any known biases.\;Though it is practical to get snow extension from the visible and infrared remotely sensed data such as NOAAAVHRR, TM and the like, it is nearly impossible to get snow depth information from such data set. Passive microwave remotely sensed data such as SMMR and SSM/I make it possible to derive snow depth in a largescale area. Some algorithms have been developed to retrieve the snow depth from SMMR and SSM/I data, but those algorithms didn’t perform well in many studies.\;In this paper, using a revised Chang’s algorithm and SSM/I 37GHz and 19GHz horizontally polarized brightness temperature, we retrieved the snow depth distribution in QinghaiXizang （Tibet） plateau, assessed the results’ accuracy, and analyzed their error sources. It showed that the revised Chang’s algorithm described the general trend of snow depth of this area, in spite of overestimation in whole and large errors in local areas. The errors are mainly from the effects of the existence of frozen ground, depthhoar, vegetation cover and the lacking of considering the effects of the liquid water content of snow and the changing of shape and grain size of snow. The coarse spatial resolution of SSM/I remotely sensed data makes the retrieved snow depth hard to compare with the ones from ground observation, thus, makes it difficult to \{evaluate\} the accuracy. Some suggestions for further investigation were put forward at last.关键词：snow depth;passive microwave remote sensing;SSM/I data;results assessment
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发布时间：2021-06-10 - 摘要：This paper discussed the integration of model and GIS. It is shown that the integrated expression and the processes of the object state model, the object simulative model and the object analytic model are key issues for integration. An integration scheme based on metadata and metamodel is suggested. The characteristic of the derivation nets deducted from petri nets was analyzed and a new derivation+ nets was presented to express the evolution history of metadata and the adjustment of metamodel. Then an integration scheme based on derivation+ nets, which is used to express the data process flow, was proposed. As a result, a derivation+ net of the remote sensing classifier of BP neural nets is made to illustrate the strategy of the integration of model and GIS.关键词：GIS;petri nets;Integration;BP neural nets classifier
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发布时间：2021-06-10 - 摘要：Backscattering coefficients play on important role in active microwave remote sensing applications in oceanography. In general, the backscattering coefficients can be calculated from scatter models. But the results are different from the choice of ocean wave spectra that there exist some different forms under some similar wind conditions. Additionally, the models are due to the Gussian distribution of sea surface elevation, which exists only within very low wind condition. Thus model predictions are not faithful reproductions of radar cross section very often. The paper presents a method to calculate the backscattering coefficients with the use of two dimensional spectrum function of sea surface elevation with the prediction of non Gaussian distribution of the elevation and slope of wave surface. Th method does not use a single wave spectrum. The results are comparable with SIR C/X SAR data of South China sea.关键词：radar;spectrum function;sea surface;backscattering coefficients
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发布时间：2021-06-10 - 摘要：In this paper, we introduce the research background and key technical parameters of “Hangtian Tsinghua1” microsatellite. The scheme of onboard image intelligent processing, which includes cloud detection and image compression, is discussed in detail. Cloud detection is based on the cloud’s brightness character and we use gray threshold method to achieve image segmentation through the analysis of image histogram. Image compression method is a mend of Block Truncation Coding method that implements threelevel compression according to the activity of the image block. All onboard image processing tasks are fulfilled by the Transputer processor. The image processing work on the ground mainly including noise removal and image correction is discussed in the end.
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发布时间：2021-06-10 - 摘要：Based on the national large scale land use/land cover vector data （1∶100000）, we produced 1 km resolution grid cell data set in which each type of land use/land cover is represented as area percentage. From the 1 km grid cell data set, 1 km grid data with one unique attribute in each grid is built and then a series of grid data sets with 4 km, 8 km and 10 km spatial resolution are derived using maximum area attribution decision law and the centric attribute decision law separately. As to the derived data sets with different scale and scaling up method, we analyzed the distribution of error in area of each type of land use/land cover type. In addition, we explored the relationship between the error in area and physiognomy types. The result shows that: 1) 1 km grid data decrease the real residential area and constructive land （more than 60% of the total real area is lost）, while the forestry land and dry farming land are increased; 2) the difference between real area and the computed area from grid data is compatible with the land use/land cover complicacy; 3) the errors from scaling up data with maximum area law increase when scale increases, while the errors with centric attribute law randomly distributes when scale changes; 4) physiognomy types can impact on the errors distribution significantly when using the maximum attribution law in scaling up. For instance, the area of paddy land and dry farming land in mountain area and hill area will decrease obviously when it is scaled up, which differs significantly from that in other area with other types of physiognomy. However, physiognomy has little effect on the error distribution with centric attribution law when the grid data is scaled up.
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发布时间：2021-06-10 - 摘要：Synthetic Aperture Radar （SAR）, as a kind of active remote sensors, is a system that can scan and image earth surface objects in a high resoution using its EM wave. Ever since the late of 1970s, SAR as a way of earth observation has progressed to the space borne stage. However, to utilize SAR image product adequately and efficiently, we often need to locate accurately an arbitrary pixel, which is corresponding with the target on the earth surface. Taking Radarsat 1 as an example, this paper first briefly describes the multi level, multi type traits as well as the product format of SAR image. After comparison of several location methods of remote sensing image, R D theory is proved to have its advantage as the footstone of absolute pixel location model of SAR image. In developing pixel location model, the dilemma of employing direct coordinates transformation is pointed out and two practical location algorithms based on R D theory are presented. The test results betrary that the relative position location algorithm can achieve a high accuracy no less than the similar research till to now in the world. The iteration location algorithm can also achieve a high accuracy permitted in the technical document of RSI Co. and therefore has a certain practicability.关键词：SAR;pixel location;R D theory;Doppler;location precision
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发布时间：2021-06-10 - 摘要：This paper is to investigate empirically the accuracy effects of photogrammetric point determination （PPD） using digital aerial stereo images with different level of JPEG compression as well as the suitability of adopting JPEG standard to compress digital aerial images. A pair of aerial blackwhite photos with 1∶8000 scale taken from a city proper was selected and scanned at a resolution of 25μm. We measured 18 image points with ISDM （Image Station Digital Mensuration） of Intergraph digital photogrammetric workstation and performed the bundle adjustment by single model with WuCAPS\-\{GPS\} （Wuhan GPSsupported bundle block adjustment） developed by the authors. In processing various JPEG compressed images with Q factors from 1 to 100, the accuracy of the 3D coordinates of photogrammetric points was assessed and compared. The empirical results have shown that, when the compression ratios are under 10, the visual quality of JPEG compressed images is excellent and the accuracy of manual image mensuration is not influenced in essence. Although the significant differences of 3D coordinates of pass points are found in the bundle adjustment with different JPEG compressed images, the resulting accuracy of PPD will also meet the requirement for most photogrammetric applications. Therefore, a compression ratio of 10 could be recommended for photogrammetric point determination.关键词：JPEG compression;interior orientation;relative orientation;absolute orientation;bundle adjustment;accuracy
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发布时间：2021-06-10 - 摘要：The spatial and spectral decorrelation are important steps in the compression of multispectral remote sensing image. To obtain better decorrelation effect, in this paper, the vector quantization is employed into the compression of multispectral remote sensing image in order to decorrelate the spectral vectors corresponding to the same objects. Then the classified KL transform is used to reduce the spectral correlation of quantization error image. Finally, the prediction tree is adopted to reduce the spectral correlation of structure and the spatial correlation of the eigenimages. The experimemtal results show that satisfactory compression effect, has been achieved using the methods introduced in this paper.关键词：vector quantization;classified KL transform;Prediction tree
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发布时间：2021-06-10 - 摘要：The remote sensing mechanism and spectral characteristics of water bodies and other objects in SPOT 4 imagery were analyzed. Due to the similar infrared spectral response feature of water bodies to those of the objects under the mountain shadows in the imagery, thresholding for infrared bands is not suitable for the extraction of water bodies. The decision tree algorithm including several classifiers was put forward, which can extract water bodies effectively and easily. The terrain information and geometric features such as perimeter, area, and shape, which are frequently used in visual interpretation, can be used to classify water bodies into subclass. The decision tree algorithm including several classifiers associated with terrain and geometric information was developed to classify water bodies. Jiangning county of Jiangsu Province was selected as a case study area, SPOT 4 （XI, 1999.1） and contour data of the area were used as information sources, the results after applying the proposed approach were satisfactong.关键词：water bodies;decision tree algorithm;spatial structure
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发布时间：2021-06-10 - 摘要：The vertical column abundance of atmospheric NO 2 was measured with ground based solar spectra and a reference extraterrestrial spectrum in the visible wavelength range of 430—450 nm. The vertical column abundance and its variations of NO 2 in the region of Hefei were obtained from the measuremental data from the November to the end of December of 1999. The variation trends basically coincided with the surface density of NO 2 measured independently with conventional instruments on the ground. The instruments, principles of measurement and some of results were introduced.关键词：NO 2 column abundance;measurement;atmospheric pollution;solar spectra
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发布时间：2021-06-10 - 摘要：Rice is one of the main grain crops in our country. The rice planting area and yield could affect argicultural development and economic stability in China. For NOAA has a lower spatial resolution, the result is that most AVHRR pixels contain a mixture of land cover classes which influence the accuracy of classification. Methods for unmixing the mixed pixels have been used in a range of studies and the accuracy of the analyses has often increased. However, there are many problems in these methods. For instance, because sometimes the same objects have different spectra, or the same spectra represents different objects, so identifying the land cover classes successfully is very difficult by only relying on spectra data and obtaining end member spectra is another problem. In this paper, an alternative approach, the artificial neural network which makes no assumption about the nature of the mixing and does not require end member spectra, is presented. We select five factors （NDVI, temperature difference, soil type, landuse type and DEM）, which have important effect on the distribution of rice planting, as the nodes of input layer to classify the image. The planting areas of early rice in Hubei province are obtained.关键词：mixed pixel;Artificial neural Network;rice planting area
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发布时间：2021-06-10 - 摘要：Insect migration panorama was always regarded as a ‘black box’ before radar entomology was borne in 1968. Comprehensive and intensive studies have been undertaken in UK, USA, Australia and China since then. Although many new phenomena and their mechanisms in the process of insect migration have been revealed by radar and the technique’s utility for insect migration research is clearly established, it is, however, the complexity of the equipment and labor intensive nature of the data analysis procedures in radar entomology that form a giant obstacle to apply the technique to become a practicable and economic proposition for routine and long term monitoring. The development of the ZLC configuration enable radar entomology entering a new era. The current emphasis on short term, and intensive studies on emigration events will be replaced by long term monitoring and to the detection of immigration events. Fully automatic, unattended operation, with immediate analysis and processing of the observations and full dissemination of reports within 24 hours, will hopefully let the outbreak forecasting of migratory insect pests to be operational. The characteristics of the ZLC radar and its prospects of application in China are reviewed. Developing a VLR network in China and combining with the GIS technique will produce an operational surveillance system for migratory pest outbreaks. Possible applications include monitoring the side effect of large scale pesticide spraying, comparing insect diversity in different environment, and monitoring the effects of environmental change such as deforestation or varying pollution levels.
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发布时间：2021-06-10
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