最新刊期
卷 ， 期 6 ， 2002
- 摘要：Polarimetric SAR Interferometry （Pol-InSAR） represents the current culmination in microwave remote sensing technology, it is a new earth observation technology that integrated the Polarimetric SAR and Interferomteric SAR. In this paper, the basic principal and physical mechanism of Pol-InSAR, data processing and the difference between conventional InSAR and Pol-InSAR, and several hot application scopes are discussed in detail. At last, the existing problems and prospective of Pol-InSAR are also discussed.
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发布时间：2021-06-10 - 摘要：A common problem encountered in biomass estimation from radar image is the terrain effects appeared in radar images. Topography changes the local radar incidence angle, determines the surface area to be illuminated by a image pixel. In addition,the underlying terrain influences the spatial structure of vegetation layer.It is a complex task to correct or reduce this unwanted fluctuation in radar backscattering due to topography. In general, both high-quality digital elevation model （DEM）and the dependence of backscattering of various land covers on topography are required.The radar backscatter model introduced in this paper simulates radar backscattering from vegetations on various slopes. The backscattering-slope relationships derived from simulation, and a DEM forms the basic for a model-based radar terrain effect correction method. If the multi-band or multi-polarization radar data exist, model simulation can help to infer the topographic information from one channel of radar image, and then use it to correct other channels.关键词：backscatter model;radar imagery;terrain effect;biomass
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发布时间：2021-06-10 - 摘要：During recent years, theoretical modeling and field experiments have established the fundamentals of active microwave remote sensing as an important tool in determining physical properties of soil. But, its application to hydrologi-cal and agricultural sciences has been hampered by natural variability and the complexity of the vegetation canopy and surface roughness that significantly affect the sensitivity of radar backscattering to soil moisture. Vegetation cover will cause an under-estimation of soil moisture and an over-estimation of surface roughness when we apply the algorithm for bare surface soil moisture estimation to vegetation covered regions.A polarimetric SAR backscatter measurements, by using eigenvalues and eigenvectors of the covariance matrix, can be decomposed into three components based on the scattering types:an odd number of reflections,an even number reflections , and a cross-polarized scattering power. This decomposition technique allows us to obtain the estimation of single and double reflection components of backscattering coefficients for VV and HH polarization.In this study,we evaluate the usage of the decomposition theory in application of estimating soil moisture for vegetated surface with the temporal fully polarimetric L-band SAR measurements. Using the decomposed scattering measurements from JPL/AIRSAR image data, we evaluated their usage to reduce the vegetation effect on estimation soil moisture under configurations of a single-frequency （L-band）and multi-pass with a same incidence. The results indicate the decomposition technique can be used to estimate the soil moisture change and their magnitudes for vegetated surface, it provide a powerful tool for monitoring surface soil moisture, especially with the moderate vegetated surface.关键词：decomposition technique;polarimetric radar;soil moisture;vegetated surface
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发布时间：2021-06-10 - 摘要：This paper presents the experimental measurements of the complex dielectric constants in two groups of soil samples using the microwave network analyzer. One group is the laboratory prepared soil samples with different moisture and salinity contents. We evaluated real parts and imaginary parts of dielectric constants as a function of microwave frequency , salinity, and water content. The real part is strongly affected by the soil moisture, whereas the frequency and the salinity of soils have little influence on it. The imaginary part is strongly affected by salinity at low frequencies（f< 5GHz） .When f< 2GHz the imaginary part decreases with the increment of frequency; whereas, at higher frequencies it tends toward a constant. The longer wavelength band, such as L-band, has better sensitivity to soil salinity than shorter wavelength. Another group of soil samples were cllected in the Jilantai Salt Lake area. The measurements are well agreed with the group one. Then we analyze the simultaneous pass RADARSAT image at the Jilantai Salt Lake area. The correlation coefficient between the backscattering intensity values of the RADARSAT image and the real parts of the salt soil is 0.23 , whereas the correlation coefficient for the imaginary part is 0.66. That indicates the backscattering coefficient of the radar image well correlated with the salinity of salt-affected soil.This study provides an experimental basis for future soil salinity monitoring using microwave remote sensing.关键词：soil salinity;dielectric constant;microwave remote sensing
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发布时间：2021-06-10 - 摘要：Based on the basic principal of ploarimetric SAR interferometry（Pol-InSAR）and coherent scattering model, the inversion algorithm of vegetation parameters based on Simulated Annealing Algorithm is presented. First, the basic principal of Pol-InSAR and the two-layer coherent scattering model taken into account the scattering of surface and vegetation are discussed. Then, the basic theory of Simulated Annealing Algorithm and the inversion model based on Simulated Melt-Annealing Algorithm are discussed. At last, utilizing the complex single Sinclar matrix data of spaceborne SIR-C L-band , on October 9 and 10, 1994, the inversion of vegetation parameters is implemented. Comparison of the result of inversion with field measurement data indicates that the inversion algorithm can obtain the height of vegetation with good accuracy .关键词：polarimetric SAR interferometry;coherent scattering model;simulated melt-annealing algorithm;parameter inversion
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发布时间：2021-06-10 - 摘要：The rapid development of economy and explosive growth of population have caused large decrease of water resources and vegetation coverage in the earth so that soil exhaustion, land desertification and salination become worse and worse, especially in arid to semi-arid area. It is very difficult to carry out the truth ground inventory and monitoring using the routine methods due to large and wide terrain and poor natural environments. Remote sensing technology has the ability of rapid information acquisition of large land expansion, and will supply useful information for monitoring the surface features in these regions. In recent years, imaging radar interferometric technique with its all weather, day and night capabilities, can generate the digital elevation model （DEM） and monitor surface change using amplitude and phase information from radar signal. So it has become a potential tool to acquire more resource and environmental information. The repeat-pass interferometry acquires two images by using one antenna for repeat passes over the same area at two different times. The two images can be used for further information extraction only while they have somewhat coherence.Arid to semi-arid landscapes are characterized by its sparse vegetation cover and lower soil moisture, and make the scattering origination in the radar image mainly from the surface. The coherence of the radar data acquired by repeat-pass interferometry is generally high, even for a long acquisition time intervals. However, the geometric changes from the surface can be generated with the time. These changes may originate from vegetation growth and erosion caused by wind or water. Any change can be detected by the decrease of coherence, hence the decorrelation of interferometric data can supply the basis for surface change monitoring.This paper presented the results of discrimination and classification of surface land types in Kashi test site, Xinjiang Province of northwestern China using the repeat-pass interferometric data, acquired by European Resource Satellite 1 and 2, based on the interferometric coherence estimation. Six types of land were discriminated and classified, including bare soil, salina, bush, bare rock/Gobi, marsh and water body. Then the backscatter and coherence characteristics of these land types were analyzed, and the relationship between coherence and surface features in arid and semi-arid area was also discussed. Finally, the temporal decorrelation model was made, and will supply the theoretical support for monitoring surface change in arid and semi-arid area using interferometric data.关键词：interferometry;arid to semi-arid area;surface features;monitoring
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发布时间：2021-06-10 - 摘要：The backscattering coefficients calculation is carried out with variable ocean wave spectrum and SAR image models. The results are not comparable with others because of variable spectrum. The present paper gives an equivalent spectrum to calculate the backscattering coefficients calculation of surface of internal wave. Finally, the calculation results are comparable with the SIR-C/X-SAR images of internal wave of South-China Sea.关键词：internal wave;SAR image;backscattering
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发布时间：2021-06-10 - 摘要：The study simulates the radar backscatter coefficients of rice using developed microwave backscatter simulated model, and analyze the interaction between microwave electromagnetic wave and rice crown within a rice growth cycle. The emphasis is paid attention to the effects of rice physical parameters to the rice backscatter coefficient and the law as polarization variation. The data include the rice physical parameters measured in field and Radarsat-SAR remote sensing multi-temporal images acquired at the same time around Zhaoqing test site, Guangdong province.The comparison between Radarsat-SAR observation results and the backscatter simulated model results shows that rice backscatter characteristic varied as the physical parameters variation in the rice growth cycle, and that the variation law is different with the polarization modes. It provides theoretical support for multi-temporal and multi-polarization SAR remote sensing technology application to rice monitoring and production estimation.关键词：SAR;rice;backscatter coefficient;time domain analysis;model simulation
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发布时间：2021-06-10 - 摘要：Surface parameters inversion by using Polarimetric SAR includes the inversion of the soil surface permeability , correlation length and RMS height. The retrieval of scattering parameters can be viewed as a mapping problem from the domain of measured signals to the range of surface/medium characteristics that quantify the observed medium. To date, parameter inversion has been based largely on empirical models. Empirical models have usually avoided the nonuniqueness problem by limiting the validity of the model to a single parameter and a narrow range. This limit on the range of validity requires that multiple empirical models be created-one model for each parameter. In this study, the Spaceborn Imaging Radar SIR-C data at L and C band was used to perform the inversion of bare surface parameters. A BP neural network based on IEM model was developed to carry out the inversion, and a test method was also developed. The combination of a scattering model （IEM） and NN makes it possible to perform inversion with higher accuracy and in real time. Backscat-tering coefficients computed from the model inverted surface parameters was proved to be good, compared with the real backscattering coefficients from radar image.关键词：IEM model;polarimetric SAR;neural network;surface parameters inversion
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发布时间：2021-06-10 - 摘要：Strong speckle noise of SAR interferogram is a great obstacle to phase unwrapping. In order to obtain a more accurate topographic model, a noise filtering step must be performed before the unwrapping of phase. In this article, we propose to filter this noise with a multi-resolution analysis of the interferogram, the real part and the imaginary part of the interferogram are processed seperatively. Several different probability density function are modeled with the Pearson system of distributions, then the wavelet coefficients of the noiseless data are estimated with a Bayesian model, maximizing the posteriori probability density function. The result is compared to that of three other methods and shows that the proposed method is powerful to interferogram speckle noise reduction, as well as it can preserve fine details in the interferogram that are directly related to the ground topography and maintain phase values distribution.关键词：SAR interferogram;Stationary wavelet transform;Maximum A Posterior;filtering
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发布时间：2021-06-10 - 摘要：To smooth coherent speckle noise and preserve edge information in SLC SAR images as precise as possible, a new algorithm called all direction auto-adaptive dynamic window filtering method based on coherent speckle statistic characteristic and analysis of spatial filtering algorithms for SAR image, is developed in this paper. For every processing pixel the filtering window is divided into mutually exclusive all direct sub-windows according to the complexity of image texture and edge existence. Local relative standard deviation is used to determine whether local filtering window area is homogeneous. Kuan filter and a 3 x 3 directive operator are incorporated to process the SAR image. The proposed method can auto-adaptively modulate its filtering window size and selection of filtering pixels. The developed method is applied to a single-look ERS SAR image. Experimental result shows that the performance of the method is satisfactory in both speckle suppression and preservation of image details.
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发布时间：2021-06-10 - 摘要：The Speckle in SAR images disturbs SAR image application. In the past 20 years numerous methods to reduce speckle in SAR images have been proposed. Although these methods can effectively reduce speckle in SAR images, they blur edge and texture information. In this paper, SAR image speckle suppression is analyzed from the view of mathematical physics. In fact, SAR image speckle suppression is an inverse problem. The essence SAR image speckle suppression is found by analyzing the speckle statistical distribution and the common speckle filters. It is important for developing the method, which can effectively reduce speckle in SAR images and can preserve edge and texture information.关键词：SAR;speckle
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发布时间：2021-06-10 - 摘要：The introduction of polarimetry to SAR interferometry makes it possible to improve the interferometric measurement resolution of the under-vegetation terrain and to estimate the height of vegetation targets. This paper introduces a new algorithm of polarimetric SAR interferometry, which can greatly improve the precision of the measurement. The coherent model of vegetation is used as the input of the polarimetric interferometric SAR system to get the simulation data, and the data is used to analysis and test the presented algorithm.关键词：SAR;interferometric SAR;polarimetric SAR;polarimetric SAR interferometry
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发布时间：2021-06-10 - 摘要：Soil moisture is a highly variable component in land surface hydrology and plays a critical role in agriculture and hydrometeorology. It also plays an important role in the interactions between the land surface and the atmosphere, as well as the partitioning of precipitation into runoff and ground water storage. Two basic microwave approaches are used to measure soil moisture, one is passive which is based on radiometry and the other is active and uses radar. Both approaches utilize the large contrast between the dielectric constant of dry soil and water. Two systems are complementary. The passive microwave systems include frequent coverage, low data rates, and simpler data processing, but with poor resolution . In the case of the active microwave systems, the advantages include high resolution, but this comes at the expence of higher data rates and more complex processing. In this study, we showed the estimation of soil moisture with vegetation cover integrated passive and active microwave data.A total backscattering amoumt for a vegetated surface include volume, surface, and surface-volume interaction scattering terms. The direct volume scattering is considered to be controlled mainly by vegetation; surface scattering term is controlled by soil dielectric component and roughness. The backscattering model here is based on without surface-volume interaction scattering terms. Im attempt to use active microwave remote sensors in estimation of soil moisture, we are mainly facing two major problems: effects of surface roughness and vegetation cover. For a given sensor, we assume the roughness under the condition of no change during data acquisitions. The main problem for retrieval surface dielectric properties is separate the volume scattering item from total backscattering.With the time-serial soil moisture map from L band passive microwave radiomerty, the Electronically Scanned Thinned Array Radiometer （ESTAR）at Southern Great Plains 1997（SGP’97）, we calculated the surface reflectivity with 800m resolution. The volume scattering items at 800m resolution can be derived using multi-temporal resample calibration Radarsat SAR and surface reflectivity data. Weighting the ratio of NDVI at different resolution from NOAA/ANHRR and TM, the surface reflectivity wity 50m resolution can be estimated according to the total backscattering and volume scattering , then soil moisture be mapped at 50m resolution. The deriving results showed the same trend of soul moisture change comparing with the field measurement.关键词：backscattering;reflectivity;soil moisture;vegetation
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发布时间：2021-06-10 - 摘要：Since SAR sensors have limited bandwidths, this leads to slow responses to sudden changes （ smearing sharp edges） . Thus, it is difficult to detect edges in SAR images. A new edge detection method is developed to detect edges in SAR images in this paper. There are two steps to accomplish it. First, the local area is segmented into one bright area and one dark area. Second, the boundary of the bright area and the dark area is regarded as the edge, and the edge is identified based on intensity variety. Application of this method to SAR images has shown that the method can effectively detect edges.关键词：edge detection;image segmentation
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发布时间：2021-06-10 - 摘要：By transmitting signals with large bandwidth and utilizing the relative motion between the radar and the objects to be imaged, synthetic aperture radar（SAR） can produce high-resolution images of targets or scenes of interest. Now, SAR imaging technology has been widely used in many military and civilian applications, such as battlefield awareness, environment monitoring,and city planning. Today, over thirty SAR systems have been put into operation and more are being built around the world. However,most of them can only produce two-dimensional（2-D）SAR images. In practice, 3-D SAR images and 3-D target feature extraction are needed for many applications. The 3-D features of a target scatterer include the radar cross-section （RCS） ,the 2-D location （range and cross-range） and the height（the third dimensional parameter）of the scatterer.Very few papers have discussed the 3-D target feature extraction problem. A popular approach to extract the 3-D target features is interferometric SAR（IFSAR） , which uses a pair of vertically displaced antennas to obtain coherent and parallel measurement apertures. IFSAR can be used to measure the height but has no resolution capability along the height dimension since it only provides two vertical parallel apertures. Hence IFSAR is only a 2.5-D imaging system. Moreover, in IFSAR, the height measurement involves the troublesome phase unwrapping procedure. Recently, Knaell proposed a new idea for the extraction of 3-D target features, which is based on curvilinear SAR（CLSAR） . Unlike the conventional SAR or IFSAR, whose flight trajectory is a straight line, the flight path of a CLSAR system is curve-shaped. CLSAR can be used to form synthetic apertures both in the azimuth and in the height dimensions. Hence CLSAR has resolution capability in the height dimension and the height ambiguity problem encountered in IFSAR is avoided.There are two challenging issues associated with CLSAR. First, the flight path of CLSAR cannot be controlled or measured accurately and the autofocus task here is more complicated than the conventional SAR systems. Second, the aperture of a CLSAR is like a sparse array. The spread function of a point scatterer has high sidelobes and hence the images obtained with conventional Fourier analysis have artifacts. We must carefully devise the feature extraction algorithm so that meaningful features can be extracted.Recently,Wu et al . have proposed a unified robust autofocus algorithm for the conventional 2-D SAR and ISAR imaging. In this paper,we have successfully extended them to the simultaneous autofocus and 3-D target feature extraction via CLSAR. The new algorithm is a parametric approach but is based on a flexible data model and a robust parameter estimation algorithm. The aucofocus is achieved by enhancing the focusing of the dominant scatterers of the target. The advantages of the new algorithm over existing autofocus algorithms include: 1) selecting the dominant scatterers of a target automatically in the 3-D image domain, 2) eliminating the necessary condition of a target containing well isolated or very dominant scatterers, 3) combining the phase and radar cross section information from the selected scatterers optimally by minimizing a nonlinear least squares cost function, and 4) avoiding the burdensome phase unwrapping step, The new approach can be used to significantly improve the estimation accuracy of the target features. Numerical examples are provided to illustrate the performance of the proposed algorithm.关键词：synthetic aperture radar;curvilinear synthetic aperture radar;motion compensation;feature extrac-tion
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发布时间：2021-06-10 - 摘要：The experiment of land clutter measurement, which was implemented at X-band, VV polarization in an outfield , is summarized. This paper includes the description of microwave measurement system, measurement principle and measurement contents. The results and analysis of backscattering coefficients are provided. The measured terrain consists of dry lawn fields, exposed soil, green wheat fields.关键词：land clutter;radar equation;Backscattering coefficient
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发布时间：2021-06-10 - 摘要：Interferogram images derived from spaceborne synthetic aperture radar system exhibit artifacts due to noise and atmospheric effects,which may mitigate the accuracy of the result DEM. In this paper,we present a method to combine uncorrelated topographic profiles generated by multi-temporal interferometric SAR data,this weighted combination is carried out in wavelet domain, which estimates the distortion power,of noise and atmosphere and improves the accuracy of final DEM with interferofram images of Shangyi area, Hebei province as test data.
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发布时间：2021-06-10 - 摘要：Based on the SIR-C L-band fully polarimetric SAR data of hotan area of Xinjiang Province,on October 9 and 10, in 1994,first,the basic principles of polarimetric SAR interferometiy measurement and data processing scheme are de-tailedly discussed. Then, three optimized coherence map related to three scattering mechanism are obtained by Cloude optimization algorithm. Furthermore, the strong dependency of interferometric coherence on the polarization and the coherence signatures of land cover related to three scattering mechanism are analysied, the inferometric phase corresponding to highest coherence map is useful in DEM extraction, the lowest coherence map is useful in identification of land cover. At last, based on the data correlation analysis of optimized coherence coefficient, backscattering coefficient and polarimetric entropy, making use of optimized coherence, polarimetric entropy and backscattering coefficient data, Identification and classification of land cover is implemented and evaluated. The good result is obtained.关键词：polarimetric SAR interferometry;optimized coherence;identifcation and classification
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发布时间：2021-06-10 - 摘要：In the field of map production, flood surveillance, and change study of lakeshore, the lake shoreline must be detected. A new method is explored in this paper, which can detect the lake shoreline in SAR images. Using this method, The edge points are detected by Mallat’ s Wavelet-based edge detection method firstly, and then the Gradient Vector Flow Active Contour Model is used to connect the edge points. The result of the experiment shows that method presented in this paper can restrain the interference of speckle noise, and detect the lake shoreline precisely.关键词：SAR image;speckle noise;wavelet;edge detection;active contour model;lake shoreline
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发布时间：2021-06-10 - 摘要：Subordinate fault is the direct production of crust deformation, It has rich information of structure deformation . The forming and evolution of subordinate fault can lead to break up of the rocks and speed up the weathering of the rocks. Transformed subordinate faults have many types and are of complex patterns, they are important subject of structure study, and also they are the important study base of ground surface stability. In this paper, we use the airborne L-SAR image of Hong Kong, and select the weak-information of subordinate faults by processing the image, set up the model of transform deformation, in order to analyze the structure background of unstability ground surface of study area. The NE faults are the main faults in study area, their dextral movement formed a series of subordinate shear plane R , P, R’ and related transformed faults. They are represented as weak information of lineation in radar image and related to the development of micro-geography. By selecting and enhancing the weak information, we made the deformation frame of subordinate faults. Together with field investigation, we found that there are EW and NEE trans-tension faults in Ma-An-Shan area, and the EW faults are the transformed faults of NEE faults. Most of these faults are related to the landslide, and are the main geological factors of Ma-An-Shan landslide.关键词：radar geology;subordinate faults;transformed structures;stability of ground surface
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发布时间：2021-06-10 - 摘要：Using shuttle imaging radar SIR-C data, the authors studied the distribution and formation of shallow layer ground-water in China-Mongolia boundary. The following results are obtained: 1. The bright yellow belt on the composite SIR-C imagery （R: L-HH,G:L-HV, B:C-HV）shows the distribution of shallow groundwater, as a result of radar volume scatter and backscatter caused by shallow groundwater level, and well-growing vegetation and sand solidification along sand-dune. 2. Landform varies from gentle to steep in China-Mongolia boundary of the research area, it is caused by normal fault. The Up-block in China relatively fall. This forms a favorable condition for water storage. 3. Radar remote sensing has the capability of penetrating dry sand and soil, and captures surface and subsurface moisture information, and possesses the sensitivity of reflection roughness or micro-topography of ground surface and the crown layer of vegetation. It has a great advantage for remote sensing study in arid region. Radar remote sensing has been one of the useful means in prospecting for shallow layer underground water in arid area.关键词：radar remote sensing;shallow-ground-water;ground-water enrichement belt;Ejin county
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发布时间：2021-06-10
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