最新刊期
卷 ， 期 1 ， 1997
- 摘要：PhysicalBRDFmodelsareusuallyverycomplexanddifficulttoinvert Weusuallyneedtoemploya prioriknowledgeinthisorthatway ,fixsomeparametervaluesandinvertsomeothers Usuallymostofusagree thatnon -sensitiveparametersshouldbefixed Buttherehasnotbeenanyconsen -susonhowtodefinethe sensitivityofaparameterininversion LiandStrahler ,LiandWangalsosuggestedthatonlythosethemostsen sitiveandmostuncertainparametersshouldbeinvertedbyusingasubsetofobservations Buttheyfailedtospell outhowtodeterminesuch“mostsensitiveandmostuncertain” parametersandhowtofindsuchasubsetofob servations ThislackingofconsensusandquantitativerulesmakesinversionofphysicalBRDFmodelsacase -by -case“trick”oran“artbutscience” WetriedtodevelopageneralframeworkforBRDFmodelinversion Itisbasedonaccumulationofknowl edgeandaninversionstrategywhichwecalledMulti-stage ,Sample -directionDependent,Target-decisions （MSDT） Presently ,ourknowledgeinclude :1)DTM ;2 ) previousland -coverclassification ;3)seasonalchange patternoftheseland -covers ;4 )rightmodelforeverytypeoflandcovers ;5) physicallimitations （ornone） ofeachparameterineachmodel;6)abestguessofeachparametervalueandtheuncertaintyofsuchguess . OurMSDTinversionstrategyisbasedonanUncertaintyandSensitivityMatrix （USM ）ofparametersat givendirections/bandsofobservations Itsdefinitionissomehowanalogoustothepartialderivativematrixused inNewtonmethodsforminimization ,buttherearethreesignificantdifferences :suchguess 1)Theuncertainty oftheinitialguessistakenintoaccount ;2 )Itislessdependentontheinitialguess ;3)Allelementshavethe sameunitandthereforequantitativelycomparable AnexampleofUSMfromLi -StrahlerGOMSmodeland ASASsamplingwillbepresented ,anditisobviousfromthematrixwhatparametershouldbeinvertedfirst , andwhatsubsetofobservationsshouldbeused AnotherexampleofUSMfromSAILmodelandhemispherical samplingisalsopresented ComparisonbetweeninversionerrorsofusingdifferentsubsetsofsamplesshowUSM couldbeahelpfulconceptinBRDFinversion关键词：Bidirectional reflectance;inversion;uncertainty;sensitivity;Target-decision
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发布时间：2021-06-10 - 摘要：Based on sensitivity of the direct solar short radiation on the aerosol property,a so called wide band extinction method is proposed to determine the 0 75μm aerosol opitical depth using th eradiation,and its accuracy is analyzed according to numerical simulations and comparative measurements As shown in numerical simulations using Junge and LOWTRAN aerosol size distributions,the depth solution error of <5% can generally be expected if a typical Junge distribution of v *=3 is taken instead of true distribution The method is tested in comparative observations with the result that aerosol optical depths measured by pyrheliometer conform well with those by sunphotometer As far as total 1267 sets of comparative experiments are concerned,the standard deviation is 10 5%,and the deviation of the mean optical depth only-0 7% Monthly mean or yearly mean result would have much better accuracy The present method is used in determining 0 75μm aerosol optical depths from the direct solat radiation detected by the phyrheliometer over 10 sites in China during 1980—1994 The 10 sites are meteorological observatories of Beijing,Shenyang,Wulumuqi,Germo,Keshi,Zhengzhou,Wuhan,Shanghai,Kungming and Guangzhou Some conclusions are: （1） Except Shenyang,aerosol optical depths over other 9 sites have an increasing trends with the annual increasing rates changing from 0 0008（Germo）to 0118（Beijing） （2） Pinatubo vocalnic eruption in 1991 had very great influence on aerosol optical depth Compared to that before 1990,the aerosol optical depths in 1992 over the ten sites increased obviously from 0 041 to 0 295 （3） In Wuhan,Beijing,Shenyang,Guangzhou and Zhenzhou cities,aerosol pollution was rather seriousq The total means of the aerosol optical depths during 1980—1994 were all more than 0 4,and especially in Wuhan,0 551 Germo and Kunming were relatively clear,and in particular in Germo it was only0 1687 （4） In the five sites of Kunming etc in the southern of Yellow River,the aerosol optical depths were relatively big in spring Except Wulumuqi,in the sites in the northern of Yellow River,they were relatively high in spring and summer and low in autumn and,inWulumuqi and Shenyang,they were comparatively high in winter关键词：atmospheric aerosol;Optical depth;Wide band extinction;Aerosol size distribution
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发布时间：2021-06-10 - 摘要：After an introduction of the development and the trend of dynamic monitoring of the soil moisture based on the NOAA-AVHRR remote sensing data,the paper gives a full and particular account of soil moisture retrieving method Based on the study of energy exchange at airsoil interface,the parameters of thermal equation are divided into 3 parts:micrometeorological parameter,soil physical parameter and soil surface temperature parameter;from which an improved method of retrieving soil surface thermal inertia from satellite data is developed Results are given at the end of this paper关键词：Soil moisture;Thermal inertia;NOAA-AVHRR data
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发布时间：2021-06-10 - 摘要：Shuttle Imaging Radar C and X-band Synthetic Aperture Radar mission（SIR-C/X-SAR） is an international cooperation program in radar for Earth observation There are 13 countries including China participated in this program SIR-C/X-SAR has three bands-L,C,X,polarimetry and interferometry imaging capability,the L and C band have polarization mode of HH,HV,VH,VV,and X band is only with VV polarization mode This paper introduces the China SIR-C/X-SAR program,its progress and achievements since its begining at six years ago While the shuttle flow over China,the Chinese scientists carried out the real time experiments including the spaceborne-airborne-ground data collection and sand layer penetration experiment Volcanos up to 5600m at sea level is discovered by SIR-C/X-SAR in Kunlun Mountains The lithological and structural features underneath vegetation cover is detected A segment of Great Wall in a desert region of the Ming and Sui dynasty has been identified,even part of the wall buried by Sand The prelimenary results of oceangraphy and urban study is also introduced and theinterferometry technology for generating DEM is presented关键词：Spaceborner adar;SIR-C/X-SAR;Target detectionn
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发布时间：2021-06-10 - 摘要：The dielectric constant of a board simulating the medium in half space is measured in the laboratory using the space wave method including the metal-scaling method and the dual polarization method The experiment is performed in X frequency range,the amplitudes and the phases of the received fields are measured simultaneously The dielectric board consists of paraffin,plaster and graphite First,the scattered fields by different Fresnel zones in the board are calculated by Kirchhoff formula It is concluded that the area larger than 10 Fresnel zones can be approximately regarded as infinitely large The thick of the board is determined by the attenuation coefficient of the elctromagnetic waves After repeatedly measuring the dielectric constants in the waveguide for different prescriptions,the weight ratio in the board is chosen as paraffin:plaster:graphite=2 38:1:1 8,in which case the attenuation is desired The thickness and the area of the board are chosen as 10cm and 135cm×105cm The experiment frequency is 9 965GHz,the 3dB half width of the wave bean is 9°。The microwave receiver（Atlanda 1780） receives the phases and amplitudes of the reflected fields in the specular direction In the metal-scaling method,transmitting and receiving are performed in a same polarization,the reflection coefficient of the medium is obtained by comparing the phases and amplitudes of the fields reflected by the medium board and a metal board,then the permittivity is deduced from the reflection coefficient The incident angle is adopted as 15°in the metal-scaling method,the measurements indicate that the results using parallel polarization is better than that using vertical polarization In the dual polarization method,however,the incident angle is taken to be 60°,a wave with both vertical and parallel polarizations is transmitted by an inclined horn,the amplitude and the phase of the reflected field in the specular direction is received for each polarization respectively A simple formula to deduce the dielectric constant from the amplitude ratio and phase difference of these two polarizations is given in the paper The measurements indicate that the result of dual polarization method agree well with that of the matal-scaling method using parallel polarization The measured result of the long sample method in the waveguide has a little difference（less than 20%）with their results,which originates from the inevitable difference between the sample part and the whole board From the contrast with the long sample method in the waveguide,it is found that our metal-scaling method is intrinsically a long sample method in the free space The paper also gives the corresponding formulas for the waveguide to the free space The paper analyses the errors of the phase measurement in the metal-scaling method which mainly come from the flatness of the metal board and the stability of the instruments In the experiment the real part of the permittivity is not sensitive to the phase error,the imaginary part only have a relative error of the same order with the phase error,thus the results of the experiment are rather stable,which verifies the feasibility of the phase method Both the metal-scaling and the dual polarization methods have the advantages that the measurements and the inverse formulas are simple and the results are stable But for the purpose of on-site measuements,the dual polarization method is better关键词：Space waves;Long samples;Dielectric constnat;Phase method;Specular reflection;X freqency range
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发布时间：2021-06-10 - 摘要：The Spaceborne Image Radar （SIR-C） onboard the space shuttle Endeavor acquired interferometric synthetic aperture radar （INSAR） data over Mt Kunlun,NW China,during its second flight In this paper,DEM acquisition of test site using SIR-C INSAR data was demonstrated The main procedure included coregistration of data,remove of flat terrain effect and phase unwrapping using DCT technique The results show more details than the existing topographic map The precise correction and analysis have to be done in the further work关键词：INSAR;SIR-C;DEM
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发布时间：2021-06-10 - 摘要：The paper presents some results of vegetation spectral identification,classification and biomass mapping by hyperspectral imaging spectrometry in Poyang Lake wetland,China The study focuses on how to retrieve canopy biophysical characteristics and how to identify vegetation types from hyperspectral image effectively The main approaches are as follows ①Retrieval of apparent surface reflectance from imaging spectrometer imagery,based on Multiheigh technique;②Derivative spectral analysis and biomass estimation;③Wetland vegetation identification and classification based on spectral waveform matching关键词：Imaging spectral;Derivative spectral analysis;biomass;Spectral match and identification of vegetation
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发布时间：2021-06-10 - 摘要：Crop area estimation is one of main application fields of remote sensing The paper focuses on the operational methods for rice area estimation,in which TM data are used to extract the basic rice planting area in a given year 1992,and NOAA AVHRR data are used to predict the change tendency of the rice planting area The basic area data need to be updated for every rice growth period upon the availability of TM data Three methods are presented to extract the base rice area They are:（1） visual interpretation with interactive adjusting on the screen;（2） interactive automatic classification with manual eliminating of the non-rice pixels on the screen;（3） automatic classification with GIS overlay and spatial analysis They can be combined to increase the reliability and the accuracy of rice planting area extraction The SAVI data profile from NOAA AVHRR are merged into a multi-bands image which is classified for predicting the tendency of the change The methods are used to estimate the early rice area in Hubei province of China in 1994 The results are acceptable关键词：rice;Area estimation;Remotc sensing;Operationalization
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发布时间：2021-06-10 - 摘要：Starting from the question what the integration of GPS,RS and GIS is,the main tasks to be investigated in the integration of GPS,RS and GIS and their theory and key techincs are described in this paper The different integration possibilities are discussed briefly关键词：remote sensing;Global positioning systems;Geographic information systems;Integration
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发布时间：2021-06-10 - 摘要：Data modeling and management are active areas in GIS research This paper presents an integrated data model——extended relational model,which underlies the GIS software—GEODBMS is abased GEODBMS manages spatial data including graphics and attributes through a single relational DBMS Its storage model employs the overlapping quadtree ,an improved quadtree,as the spatial index structure to facilitate spatial data querying with an extended SQL GEODBMS’s data management functions ensure secure data access and provide recovery and concurrency control for transactions in multi-user environment关键词：Extended relational data model;Extended SQL;Overlapping quadtree;Data recovery;Concurrency control
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发布时间：2021-06-10 - 摘要：Based on the classification of Holdridge’s Life Zone on climate-vegetation relationship and the support of Geo-information system,the basic patterns of Holdridge’s Life Zone in China under the current climate regime were studied in the first part of this paper,then the changes of spatial pattern,area and spatial distribution of Holdridge’s Life Zone of China were brought forward under 2×CO 2 scenarios based on simulating results of GCMs such as GFDL,GISS and OSU.It is possible that the available atea for forestry should tend to decrease in result that boreal moist forest in North China area are shrank westward,but boreal rain forest and cool temperate rain forest in Southwest China are expanded By the comparison of patterns between Holdridge’s life zone and China’s current vegetation,the author considers that there are some problems from naming of life zone and limiting of climatic indexes so that the patterns of Holdridge’s life zone are different from one of China’s vegetation Therefore,with the use of Holdridge’s Model,the modification to the model will be necessary according to the real natures of the researched region In addition,it is suggested that the connections of Geo-information system and thematic models should improve the development of global change studies关键词：Holdridge’s life zone model;Global climate change;Geo-information system
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发布时间：2021-06-10
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