共查询到20条相似文献，搜索用时 296 毫秒
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A fast algorithm for recovering profiles of density and compressional (P) and shear-vertical (SV) wave speeds as functions of depth for the inverse seismic problem in a continuous layered elastic medium is obtained. This algorithm differs from previous fast algorithms for this problem since it requires only the compressional wave P-P reflection response at the surface of the medium, for three different slownesses or angles of incidence. Previous algorithms have required shear stress data in the form of the P-SV and SV-SV reflection responses, making them unsuitable for an ocean environment. This algorithm is thus much more suitable for reconstructing the ocean floor from pressure data taken in the ocean. The algorithm is exact, and it includes the effects of multiple reflections and mode conversions. A computer run illustrates the performance of the algorithm on synthetic data. 相似文献
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V. V. Tikhonov I. A. Repina M. D. Raev E. A. Sharkov D. A. Boyarskii N. Yu. Komarova 《Izvestiya Atmospheric and Oceanic Physics》2015,51(9):914-928
In this paper, a new algorithm for determining the concentration of the ice cover in Polar Regions by data of satellite microwave radiometry is considered. The technique of its construction is described in detail; it cardinally differs from the technique of creating present-day algorithms. The new algorithm demonstrates good results in determining the concentration of the ice cover in Polar Regions. The algorithm permits one not only to obtain maps of ice concentration, but also to determine areas of puddles covering the ice-cover surface in summer months. The algorithm is easy-to-use and requires no additional or fitting parameters. At the end of the work, advantages and disadvantages of the new algorithm are discussed. 相似文献
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The data of SeaWiFS (Sea-Viewing Wide Field-of-View Sensor), installed on SeaStar, has been used to generate SSC (suspended sediment concentration) of complex and turbid coastal waters in China. In view of the problems of the SeaDAS (SeaWiFS Data Analysis System) algorithm applied to China coastal waters, a new atmospheric correction algorithm is discussed, developed, and used for the SSC of East China coastal waters. The advantages of the new algorithm are described through the comparison of the restdts from different algorithms. 相似文献
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Using Signals, Underwater Sound (SUS) explosive charges as broad-band acoustic sources, a high-quality set of surface scattering strengths was measured throughout the Critical Sea Test (CST) experiments. These measurements were made for wind speeds ranging from ~1 to 18 m/s and covered grazing angles from ~5° to 30° and frequencies from ~60 to 1000 Hz. A new empirical algorithm was developed based on a multiparameter multidimensional nonlinear fit to all the SUS data from CST-1 through CST-7. This new algorithm returns the surface scattering strength for a given frequency, grazing angle, and wind speed. The new formulation explored the use of backaveraging the wind speeds in time (as opposed to using the instantaneous wind speed) to allow for the influence of processes driven by the wind history, In this paper, details of the development of this new algorithm will be discussed, comparisons with earlier prediction algorithms (the Ogden-Erskine and Chapman-Harris algorithms) will be made, and the important differences between the various CST SUS data sets will be highlighted and possible explanations offered. Finally, suggestions for further improvements to the algorithm are made 相似文献
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Dual-polarized ratio algorithm for retrieving Arctic sea ice concentration from passive microwave brightness temperature 总被引：1，自引：0，他引：1
We present a new algorithm for retrieving sea ice concentration from the AMSR-E data, the dual-polarized ratio (DPR) algorithm. The DPR algorithm is developed using vertically and horizontally polarized brightness temperatures at the same channel of 36.5 GHz. It depends on the ratio of dual-polarized emissivity, α, which is determined empirically at about 0.92 by remotely sensed brightness temperature in winter and used for the other seasons as well. The ice concentration retrieved by the DPR is compared with those by the NT2 and ABA algorithms. Since the main difference among these algorithms takes place in marginal ice zones, 17 marginal ice zones are chosen. The retrieved ice concentrations in these zones are examined by the ice concentration obtained by the MODIS data. The mean error, root-mean-square error and mean absolute error of the DPR algorithm are relatively better than those from the other two algorithms. The results of this study illustrate that the DPR algorithm is a more accurate algorithm for retrieving sea ice concentration from the AMSR-E brightness temperature, and can be used for operational purposes. 相似文献
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《Oceanic Engineering, IEEE Journal of》2009,34(4):516-525
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Several, although not all, wind–wave gages are equipped with sensors capable of detecting sea-level oscillations within the tsunami frequency band. The present paper looks at the algorithms to be implemented in the software of these gages in order to automatically perform the real-time detection of a possible tsunami within recorded signals. In particular, a new algorithm is proposed and tested. The first part of the paper concentrates on the algorithms' characteristics, implementation strategies and basic testing. First of all, the situations in which wind–wave measurements are either essential, or useful for real-time tsunami detection are discussed. In the second place, already existing algorithms are recalled, specifying their characteristics and fields of application. Then, the characteristics of the new proposed algorithm – mainly based on an infinite impulse response, time domain filter – are illustrated and analyzed. Performance and efficiency of the considered algorithms are compared using synthetic time series. The second part of the paper discusses the algorithms' use in the framework of Tsunami Early Warning Systems (TEWS), testing them in actual cases. 相似文献
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Detection in the presence of reverberation is often difficult in active sonar, due to the reflection/diffusion/diffraction of the transmitted signal by the ocean surface, ground, and volume. A modelization of reverberation is often used to improve detection because classical algorithms are inefficient. A commonly used reverberation model is colored and nonstationary noise. This model leads to elaborate detection algorithms which normalize and whiten reverberation. In this paper, we focus on a more deterministic model which considers reverberation as a sum of echoes issued from the transmitted signal. The Principal Component Inverse (PCI) algorithm is used with this model to estimate and delete the reverberation echoes. A rank analysis of the observation matrix shows that PCI is efficient in this configuration under some conditions, such as when the transmitted signal is Frequency Modulated. Both methods are validated with real sonar surface reverberation noise. We show that whitening has poor performance when reverberation and target echo have the same properties, while PCI maintains the same performance whatever the reverberation characteristics. Further, we extend the algorithms to spatio-temporal data. We propose a new algorithm for PCI which allows better echo separation. This new method is shown to be more efficient on real spatio-temporal data 相似文献
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Cycle Slip Detection and Ambiguity Resolution Algorithms for Dual-Frequency GPS Data Processing 总被引：13，自引：0，他引：13
This article investigates the problem of cycle slip detection and ambiguity resolution using dual-frequency GPS data. Several algorithms are proposed and described. F or cycle slip detection, three L1/L2 observable combinations have been integrated to formulate a new algorithm for cycle slip detection. For ambiguity resolution, both widelane and narrowlane ambiguity resolution algorithms are presented, but the focus is on the narrowlane ambiguity resolution. Numerical results are included to evaluate the performance of the proposed algorithms, which have shown that cycle slips can be effectively detected and the narrowlane ambiguities can be resolved almost instantaneously after successful determination of the widelane ambiguities. 相似文献
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《Oceanic Engineering, IEEE Journal of》2009,34(3):262-268
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叶绿素荧光遥感算法为探测近岸海域二类水体叶绿素浓度开辟了新途径．基于大连湾及邻近海域的实测数据,本文研究了海水叶绿素浓度的荧光遥感算法．结果表明：随着海水叶绿素质量浓度的增高,荧光峰出现显著的红移现象,叶绿素质量浓度与荧光峰波长存在着正相关关系．此外,基于MODIS、MERIS及GLI传感器荧光波段建立的荧光基线高度算法较差,不适用于该研究海域．选择680、685、690、695、700、705nm作为荧光峰波长建立的荧光基线高度算法,随着选定波长的增大,该算法拟合的相关性逐渐增高,最大相关系数（R2）可达0．91;而以实测荧光峰波长建立的荧光基线高度算法最佳,乘幂函数拟合优于线性拟合,拟合方程为P（chl）=3．167×10^5 FLH^1.45（R2=0．93）．本研究为新一代海洋水色卫星传感器的开发、建造提供了科学依据,并为已有高光谱传感器在叶绿素荧光遥感反演方面的应用打下了基础． 相似文献
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端元提取是混合像元分解的基础,也是高光谱遥感的研究热点。对于特定区域的高光谱图像应该使用哪种端元提取算法,需要对各种端元提取算法进行客观地评价。作者针对黄河口湿地CHRIS高光谱图像,使用了重建图像与原图像的均方根误差、有效端元数量两个指数对PPI、N-FINDR、VCA、OSP、IEA和SISAL六种典型的端元提取算法进行了评价。结果表明,SISAL算法重建误差最小,仅有其他算法误差的10%~28%;OSP算法识别了具有物理意义的6种有效端元,多于其他算法识别的地物类型,而SISAL算法识别的端元缺乏物理意义。 相似文献
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This study compares five primary productivity algorithms for Korean waters. Five algorithms are in the form of vertical generalized production models: One algorithm is for gross primary production and four are for net primary production. The five algorithms were evaluated using 117 in situ primary production datasets observed by 20 cruises from 1994 to 2011 in Korean waters (East Sea, Yellow Sea, East China Sea, and Yeosu Bay). The results show that the regionally-tuned variants give better results than the original formulation. We recommend, among the tested algorithms, YSVGPM (Yellow Sea Vertically Generalized Productivity Model) for gross primary productivity algorithm and Kameda-Ishizaka algorithm for net primary productivity algorithm for estimating primary production in Korean waters. 相似文献
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Huffman与LZW算法在海洋观测浮标通信数据压缩中的应用研究 总被引：2，自引：2，他引：0
在现有两种比较主流无损压缩算法基础上(Huffman算法和LZW算法),根据海洋观测浮标采集的观测数据特点,比较两种压缩算法的优缺点,并通过布放在西太平洋海域的一套观测浮标数据进行数据验证。结果表明,使用Huffman算法和LZW算法分别对海洋观测浮标数据进行压缩,两者的压缩率都基本可达50%左右甚至更低,Huffman算法压缩率较优,而LZW算法复杂度较优。通过分析,可证明这两种无损压缩算法都能有效地提高深远海通信效率和降低通信成本,同时也提高了科学观测数据的安全性和保密性,可根据实际情况选择在深远海观测浮标数据通信中应用。 相似文献
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水体透明度(Secchi Disk depth,SDD)是水环境监测的重要参数,遥感技术对于监测水体透明度具有重要的应用前景。本文旨在分类和比较当前用于监测水体透明度的算法,并提出未来研究的方向,以推动水环境监测技术的进一步发展。文章对目前检索水体透明度的算法进行分类和比较。其中,经验算法、半分析算法和机器学习算法是目前研究的主要方向。通过分析算法特性和优缺点,提出未来研究的重点和方向。经验算法基于透明度与光谱数据、叶绿素a浓度等的相关性,半分析算法基于水下能见度理论,机器学习算法则基于更优的数据特征学习能力。不同算法具有各自的适用范围和限制。未来的研究应该着重于整合多源遥感数据,改进QAA (quasi-analytical-algorithm),深入分析光学参数与水体透明度的关系,将机器学习算法应用到水体透明度模型的建立中,以建立具有高精度、适用性广的反演模型。 相似文献