Assessing integration of intensity,polarimetric scattering,interferometric coherence and spatial texture metrics in PALSAR-derived land cover classification     

《ISPRS Journal of Photogrammetry and Remote Sensing》2014

Synthetic aperture radar (SAR) is an important alternative to optical remote sensing due to its ability to acquire data regardless of weather conditions and day/night cycle. The Phased Array type L-band SAR (PALSAR) onboard the Advanced Land Observing Satellite (ALOS) provided new opportunities for vegetation and land cover mapping. Most previous studies employing PALSAR investigated the use of one or two feature types (e.g. intensity, coherence); however, little effort has been devoted to assessing the simultaneous integration of multiple types of features. In this study, we bridged this gap by evaluating the potential of using numerous metrics expressing four feature types: intensity, polarimetric scattering, interferometric coherence and spatial texture. Our case study was conducted in Central New York State, USA using multitemporal PALSAR imagery from 2010. The land cover classification implemented an ensemble learning algorithm, namely random forest. Accuracies of each classified map produced from different combinations of features were assessed on a pixel-by-pixel basis using validation data obtained from a stratified random sample. Among the different combinations of feature types evaluated, intensity was the most indispensable because intensity was included in all of the highest accuracy scenarios. However, relative to using only intensity metrics, combining all four feature types increased overall accuracy by 7%. Producer’s and user’s accuracies of the four vegetation classes improved considerably for the best performing combination of features when compared to classifications using only a single feature type.  相似文献   

复杂地形下高密度激电法2.5维有限单元法数值模拟   总被引：1，自引：0，他引：1  

麻昌英  柳建新  刘海飞  郭荣文 《物探化探计算技术》2014,(4):405-409

目前三维有限元模拟计算量大,计算效率低,对计算机要求较高,2.5维模拟是三维问题的简化,较好地克服了上述问题。在高密度激电法模拟中,模拟的点数一般较大,要求程序计算效率高,因此对高密度激电法2.5维模拟研究是必要的。首先给出了2.5维稳定电流场的边值问题及对应的变分问题;为了能更好模拟复杂地形对极化率异常的影响,采用三角形网格,有利于模拟复杂地形又有利于将其应用于反演计算。推导了基于连续电性介质的2.5维稳定电流场的有限元法,利用等效电阻率法,编制了2.5维高密度激电法有限元模拟程序,计算了水平地形及起伏地形下的极化率异常模型,并验证了方法的可行性,分析得出了山谷地形比山脊地形对极化率观测的影响大的结果。  相似文献   

极化方位角补偿信息支持下的植被参数反演     

龙江平  丁晓利  汪长城 《测绘学报》2014,43(10):1051-1060

SAR图像中散射目标的散射矩阵受极化方位角(POA)的影响会改变散射体的散射特性,散射矩阵是极化干涉SAR (PolInSAR)估计不同极化状态下复相干性的基础。本文根据极化方位角产生机制,建立了多视情况下基于极化方位角补偿的极化干涉相干性估计模型,分析了极化方位角补偿对相干性估计方法和不同散射机制下相干性估计的影响程度,研究了基于三阶段法与极化方位角补偿的植被参数反演。利用L波段SIRC全极化SAR图像为实验数据验证极化方位角补偿对极化干涉相干性估计和植被参数反演的可行性。实验结果表明,极化方位角补偿能够改变不同极化状态相干性分布规律,提高相干直线拟合精度,改善植被参数反演的可靠性和合理性。  相似文献   

The Zeeman effect in the Sobolev approximation: applications to spherical stellar winds     

R. Ignace  K. G. Gayley 《Monthly notices of the Royal Astronomical Society》2003,341(1):179-191

Modern spectropolarimeters are capable of detecting subkilogauss field strengths using the Zeeman effect in line profiles from the static photosphere, but supersonic Doppler broadening makes it more difficult to detect the Zeeman effect in the wind lines of hot stars. Nevertheless, the recent advances in observational capability motivate an assessment of the potential for detecting the magnetic fields threading such winds. We incorporate the weak-field longitudinal Zeeman effect in the Sobolev approximation to yield integral expressions for the flux of circularly polarized emission. To illustrate the results, two specific wind flows are considered: (i) spherical constant expansion with   v ( r ) = v _∞  and (ii) homologous expansion with   v ( r ) ∝ r   . Axial and split monopole magnetic fields are used to schematically illustrate the polarized profiles. For constant expansion, optically thin lines yield the well-known 'flat-topped' total intensity emission profiles and an antisymmetric circularly polarized profile. For homologous expansion, we include occultation and wind absorption to provide a more realistic observational comparison. Occultation severely reduces the circularly polarized flux in the redshifted component, and in the blueshifted component, the polarization is reduced by partially offsetting emission and absorption contributions. We find that for a surface field of approximately 100 G, the largest polarizations result for thin but strong recombination emission lines. Peak polarizations are approximately 0.05 per cent, which presents a substantial although not inconceivable sensitivity challenge for modern instrumentation.  相似文献   

郑州市南郊地热井勘探     

李天生  范文  张文玉 《河南国土资源》2000,(1)

本文简要介绍了郑州市水文地质和地热地质条件 ;分析解释了在郑州市芦邢庄进行地热井定位勘探时取得的激电测深资料 ;确定了具体的地热钻探井位 ,给出了该井成井后的实际水温、水量等参数  相似文献   

The sensitivity of EGRET to gamma-ray polarization     

John R. Mattox 《Experimental Astronomy》1991,2(2):75-84

A Monte Carlo simulation shows that the EGRET gamma-ray telescope aboard the GRO satellite does not have sufficient sensitivity to detect linear polarization, even for 100% polarized gamma-ray sources. This is confirmed by analysis of calibration data. Several data selection techniques suggested to enhance polarization sensitivity have been evaluated and found to not significantly improve sensitivity.NRC/NAS RESEARCH ASSOCIATE  相似文献   

Polarization observations of four southern pulsars at 1560 MHz     

Wu Xin-ji  R. N. Manchester  A. G. Lyne 《Chinese Astronomy and Astrophysics》1991,15(4)

We present some interesting results from the mean pulse polarization observations of four southern pulsars made at the Australian National Radio Astronomy Observatory, Parkes, using the 64-m telescope in June and July, 1988. The 2 × 16 × 5 MHz filter system from Jodrell Bank has proved excellent in de-dispersing the pulse signals and measuring their polarization properties. We give the data for the four pulsars in some detail and discuss their spectral behaviour.  相似文献   

Polarization transfer in a pulsar magnetosphere     

S. A. Petrova 《Monthly notices of the Royal Astronomical Society》2006,366(4):1539-1550

Propagation of radio waves in the ultrarelativistic magnetized electron–positron plasma of a pulsar magnetosphere is considered. The polarization state of the original natural waves is found to vary markedly on account of the wave mode coupling and cyclotron absorption. The change is most pronounced when the regions of mode coupling and cyclotron resonance approximately coincide. In cases when the wave mode coupling occurs above and below the resonance region, the resultant polarization appears essentially distinct. The main result of the paper is that in the former case the polarization modes become non-orthogonal. The analytical treatment of the equations of polarization transfer is accompanied by numerical calculations. The observational consequences of polarization evolution in pulsar plasma are discussed as well.  相似文献   

'Notches' in the average profiles of bright pulsars     

Maura A. McLaughlin  Joanna M. Rankin 《Monthly notices of the Royal Astronomical Society》2004,351(3):808-812

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The effect of rotational gravity darkening on magnetically torqued Be star discs     

J. C. Brown  D. Telfer  Q. Li  R. Hanuschik  J. P. Cassinelli  A. Kholtygin 《Monthly notices of the Royal Astronomical Society》2004,352(3):1061-1072

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