基于双谱模型的被动微波遥感土壤湿度反演

利用随机粗糙表面的双谱散射模型计算了粗糙裸土壤表面的发射率,并建立了基于双谱模型的被动微波遥感的土壤湿度的人工神经网络反演方法.结果表明,基于双谱散射模型计算粗糙裸土壤表面发射率是可行的,利用人工神经网络反演方法,仅采用两个发射率的数据组合便可以反演出精度较高的土壤湿度值,且反演方法具有一定的抗噪性能.     

Passive microwave remote sensing system for soil moisture: somesupporting research

A review of the current understanding of passive microwave remote sensing of soil moisture and examples of potential applications are presented. The potential platforms for such a system are the Earth Observing System (Eos) platforms planned for the late 1990s. Some of the relevant results supporting the implementation of a soil moisture microwave sensor are discussed. These results include data interpretation, the minimal requirements for sensor system design, and applications in hydrology and water management     

Microwave remote sensing of soil moisture: elimination of textureeffect

In view of the influence of soil texture on microwave radiation, an attempt is made to eliminate the textural effects on the microwave reflectivity/emission. To determine the appropriate soil moisture parameter that minimizes the textural influences on microwave radiation from soils, soil moisture is expressed in terms of gravimetric and volumetric units and percentage of field capacity (M_fc ) and is plotted individually against the microwave reflectivity of soils. Only when soil moisture is in volumetric units are the textural influences significantly reduced. Therefore, a parameter, termed the critical water content (W_c), that takes into account the bound-water content of soils is used. An empirical relation between the interpolated values of W_c and the wilting point of soils has been developed. The soil water content above the W_c of each soil is considered as effective water M_eff     

星载微波辐射遥感的极化指数距平统计与土壤湿度分布

用辐射传输理论提出的地表微波辐射极化指数PI的定义,分别指出了土壤湿度、地面粗糙、植被层和大气层的各自影响.用DMSP SSM/I多时相6年的数据给出中国主要陆地19.35GHz通道的PI值月平均分布,表征土壤湿度的月变化,并获得中国主要陆地同季同月PI距平值△nPI的统计分布,展示了中国陆地土壤湿度变化的分布图,以及在干旱与水涝期间PI距平值的异常,用中国山西2001年5月的干旱和中国长江中游1998年8月水涝作了个例证明.这一理论方法可同样推广到有较低频率(如10.7GHz)的2002年5月发射的AMSR-E或中国风云系列卫星微波成像辐射计的通道,而获得土壤湿度分布更好的PI指数评估.在已知区域平均PI值与平均土壤湿度的条件下,可以定量反演该区域的土壤湿度,并用TRMMTMI实验数据进行了验证.     

Passive microwave remote sensing of forests: a model investigation

A model, based on the radiative transfer theory and the matrix doubling algorithm, is described and used to compute the emissivity e of forests. According to model simulations, the L-band emissivity trend versus forest biomass is more gradual than that of the backscatter coefficient. This gradual behavior is observed, in absence of leaves, also at C- and X-bands, while leaves anticipate saturation and make e higher in coniferous forests and lower in deciduous forests. Model results are successfully validated by some available experimental data. Operational aspects, concerning the potential of airborne and spaceborne radiometers in identifying forest type and estimating biomass, are discussed     

A multifrequency algorithm for the retrieval of soil moisture on alarge scale using microwave data from SMMR and SSM/I satellites

The sensitivity of microwave emission at different frequencies to soil moisture in bare and vegetated soils has been investigated using experimental data. Since the best frequency for the measurement of soil moisture (L-band) is absent in current satellite sensors, it is necessary to seek alternative solutions. An algorithm is proposed for the retrieval of soil moisture based on the sensitivity to moisture of both the brightness temperature and the polarization index at C-band, one that is able to correct for the effect of vegetation by means of the polarization index at X-band. The algorithm has been tested by using experimental data collected with airborne microwave radiometers on agricultural areas and validated by using the data sets of special sensor microwave/imager (SMM/I) and scanning multichannel microwave radiometer (SMMR). These research activities are planned in view of coming new satellites: AQUA (NASA) and ADEOS-II (NASDA), which will be launched by the end of 2001. These will have new generation microwave radiometers (AMSR-E and AMSR) onboard, which show much better characteristics with respect to the previous sensors, in particular an enhanced spatial resolution     

微波辐射计对月面特征参数的遥感理论模拟

根据现有的多通道被动辐射计技术，讨论微波辐射遥感月壤月岩特征参数的几个问题。由半空间非均匀温度、介电廓线分布的耗散介质的月壤模型与WKB方法，计算了月壤的多通道微波辐射传输的权重函数与相应的穿透深度。提出模拟多层月壤月岩的多层密集粒子介质辐射传输的一种建模，在各有关参数条件下计算了各通道的多层月壤月岩辐射亮度温度。并以此结果为理论观测，讨论了月壤厚度等参数反演可予以实施的方法。     

The main results of cloud and rain remote sensing by multichannel microwave radiometry

The basic results have been considered for multiwave remote sounding of the troposphere with clouds and rain from ground-based station in the zenith direction. The radio wave scattering by rain drops as well as variation of vapour content in the atmosphere during measurements are taken into account when processing of the experimental data. A separation of the complete attenuation in clouds with rain has been made over three components: due to vapour, cloud and rain. A relation is considered of millimeter and centimeter wave attenuation in clouds with rain between each other and with the rain intensity. A behaviour of the relation of attenuation structural functions is explained. The Diagnostic problems of millimeter wave attenuation are considered.     

Classification of multispectral remote sensing data using aback-propagation neural network

The suitability of a back-propagation neural network for classification of multispectral image data is explored. A methodology is developed for selection of both training parameters and data sets for the training phase. A new technique is also developed to accelerate the learning phase. To benchmark the network, the results are compared to those obtained using three other algorithms: a statistical contextual technique, a supervised piecewise linear classifier, and an unsupervised multispectral clustering algorithm. All three techniques were applied to simulated and real satellite imagery. Results from the classification of both Monte Carlo simulation and real imagery are summarized     

微波遥感在岩土工程中应用的基础实验研究

由电磁辐射理论知道,物质的微波辐射是热能激发组成物质分子的转动态能级跃迁辐射出的电磁波。在等温过程加载的条件下,对岩石和混凝土进行了２ｃｍ、３ｃｍ、１０ｃｍ３个波段以及水平和垂直两种极化状态的实验,得出岩石和混凝土的微波辐射能量随压力变化面变化的实验结果,实验了不同岩性岩石和不同强度混凝土共计４０个试件,无一例外。变化规律是：在２ｃｍ和１０ｃｍ波段微波辐射能量随压力增加而增加,在３ｃｍ波段微波辐射     

Virtual sensors: using data mining techniques to efficiently estimate remote sensing spectra

Various instruments are used to create images of the earth and other objects in the universe in a diverse set of wavelength bands with the aim of understanding natural phenomena. Sometimes these instruments are built in a phased approach, with additional measurement capabilities added in later phases. In other cases, technology may mature to the point that the instrument offers new measurement capabilities that were not planned in the original design of the instrument. In still other cases, high-resolution spectral measurements may be too costly to perform on a large sample, and therefore, lower resolution spectral instruments are used to take the majority of measurements. Many applied science questions that are relevant to the earth science remote sensing community require analysis of enormous amounts of data that were generated by instruments with disparate measurement capabilities. This work addresses this problem using virtual sensors: a method that uses models trained on spectrally rich (high spectral resolution) data to "fill in" unmeasured spectral channels in spectrally poor (low spectral resolution) data. The models we use Are multilayer perceptrons, support vector machines (SVMs) with radial basis function kernels, and SVMs with mixture density Mercer kernels. We demonstrate this method by using models trained on the high spectral resolution Terra Moderate Resolution Imaging Spectrometer (MODIS) instrument to estimate what the equivalent of the MODIS 1.6-/spl mu/m channel would be for the National Oceanic and Atmospheric Administration Advanced Very High Resolution Radiometer (AVHRR/2) instrument. The scientific motivation for the simulation of the 1.6-/spl mu/m channel is to improve the ability of the AVHRR/2 sensor to detect clouds over snow and ice.     

A sensitivity analysis of soil moisture retrieval from the tau-omega microwave emission model

The potential of the /spl tau/--/spl omega/ model for retrieving the volumetric moisture content of bare and vegetated soil from dual-polarization passive microwave data acquired at single and multiple angles is tested. Measurement error and several additional sources of uncertainty will affect the theoretical retrieval accuracy. These include uncertainty in the soil temperature, the vegetation structure, and consequently its microwave single-scattering albedo, and uncertainty in soil microwave emissivity based on its roughness. To test the effects of these uncertainties for simple homogeneous scenes, we attempt to retrieve soil moisture from a number of simulated microwave brightness temperature datasets generated using the /spl tau/--/spl omega/ model. The uncertainties for each influence are estimated and applied to curves generated for typical scenarios, and an inverse model used to retrieve the soil moisture content, vegetation optical depth, and soil temperature. The effect of each influence on the theoretical soil moisture retrieval limit is explored, the likelihood of each sensor configuration meeting user requirements is assessed, and the most effective means of improving moisture retrieval indicated.     

Hydrometeorological data extension for the Sudan-Sahel zone of WestAfrica using satellite remote sensing

Conventional techniques for assessing and investigating water resources in the Sudan and Sahel zones of West Africa, which are subject to frequent and prolonged droughts, are often difficult to implement. Satellite remote sensing coupled with available ground truth data from a limited number of rain gauge locations provides an alternative means of hydrometric data extension within the zone. Monthly and seasonal rainfall estimates, based on a database derived from Meteosat infrared data, are determined. Rain gauge data are regressed on five-day maximum surface temperatures and cold cloud occurrences. A linear model is used for dry month estimates. Values of the coefficient of determination vary from 0.55 to 0.69 for the monthly model, and the value is 0.83 for the seasonal model     

A combined modeling and multispectral/multiresolution remote sensing approach for disaggregation of surface soil moisture: application to SMOS configuration

A new physically based disaggregation method is developed to improve the spatial resolution of the surface soil moisture extracted from the Soil Moisture and Ocean Salinity (SMOS) data. The approach combines the 40-km resolution SMOS multiangular brightness temperatures and 1-km resolution auxiliary data composed of visible, near-infrared, and thermal infrared remote sensing data and all the surface variables involved in the modeling of land surface-atmosphere interaction available at this scale (soil texture, atmospheric forcing, etc.). The method successively estimates a relative spatial distribution of soil moisture with fine-scale auxiliary data, and normalizes this distribution at SMOS resolution with SMOS data. The main assumption relies on the relationship between the radiometric soil temperature inverted from the thermal infrared and the microwave soil moisture. Based on synthetic data generated with a land surface model, it is shown that the radiometric soil temperature can be used as a tracer of the spatial variability of the 0-5 cm soil moisture. A sensitivity analysis shows that the algorithm remains stable for big uncertainties in auxiliary data and that the uncertainty in SMOS observation seems to be the limiting factor. Finally, a simple application to the SGP97/AVHRR data illustrates the usefulness of the approach.     

热红外联合被动微波重构裸土区地表温度时间序列数据算法

在进行一定区域地表温度时间序列的研究中,常遇到由于天气原因造成的温度数据缺失问题,针对这一突出问题,在分析土壤发射率数据库的基础上,提出了一种裸露地表晴空时段热红外、微波亮温数据与非晴空时段微波亮温数据相结合来获取时间序列中缺失的地表温度数据的算法.此算法不仅解决了被动微波进行地表温度反演过程中下垫面发射率难以确定的问...     

Estimation of bare surface soil moisture and surface roughnessparameter using L-band SAR image data

An algorithm based on a fit of the single-scattering integral equation method (IEM) was developed to provide estimation of soil moisture and surface roughness parameter (a combination of rms roughness height and surface power spectrum) from quad-polarized synthetic aperture radar (SAR) measurements. This algorithm was applied to a series of measurements acquired at L-band (1.25 GHz) from both AIRSAR (Airborne Synthetic Aperture Radar operated by the Jet Propulsion Laboratory) and SIR-C (Spaceborne Imaging Radar-C) over a well-managed watershed in southwest Oklahoma. Prior to its application for soil moisture inversion, a good agreement was found between the single-scattering IEM simulations and the L-band measurements of SIR-C and AIRSAR over a wide range of soil moisture and surface roughness conditions. The sensitivity of soil moisture variation to the co-polarized signals were then examined under the consideration of the calibration accuracy of various components of SAR measurements. It was found that the two co-polarized backscattering coefficients and their combinations would provide the best input to the algorithm for estimation of soil moisture and roughness parameter. Application of the inversion algorithm to the co-polarized measurements of both AIRSAR and SIR-C resulted in estimated values of soil moisture and roughness parameter for bare and short-vegetated fields that compared favorably with those sampled on the ground. The root-mean-square (rms) errors of the comparison were found to be 3.4% and 1.9 dB for soil moisture and surface roughness parameter, respectively     

基于遥感数据挖掘的智能地理信息系统设计

为了有效实现地理信息一体化管理,设计并实现一种基于遥感数据挖掘的智能地理信息系统。通过数据管理模块对空间数据库中的不同类型的地理数据进行管理和调度,在需要时可对地理信息数据进行可视化处理,同时融入真实场景中;利用三维处理模块对简单的三维图形进行描绘,代替实际地理环境中的地物,将其与真实场景融合;通过场景控制模块对虚拟物体和真实场景进行配准,基于当前现场场景判断所需从数据库提取的信息和显示的内容;依据网络传输模块链接系统的服务端和客户端,实现通信。软件设计过程中,对基于遥感数据挖掘的智能地理信息系统进行了详细地分析,并给出遥感数据挖掘的实现过程以及系统部分程序代码。实验结果表明,所设计的系统具有很高的实用性和可靠性。     

基于区域协同遥感观测的海上应急救援业务增强系统设计

目前我国正大力推进区域协同遥感观测系统的建设,针对海上应急救援应用中存在的海上搜救体系的协调性有待提升、海上救助装备的数量有待增加和性能有待改善以及海上搜救应急反应速度有待提高等问题,提出利用区域协同遥感观测技术,建立海上应急救援业务增强系统,实现天空地海协同搜寻、海上救援态势评估、海上目标漂移预测等功能,以提高海上遇险对象搜寻效率,同时提高海上救助调度能力,险情和救助情况信息获取及时、准确,基本实现跨部门、跨区域的业务协同。