共查询到20条相似文献，搜索用时 15 毫秒
1.
基于多波段分析的无阈值自动光谱角制图分类法 总被引：2，自引：0，他引：2
对光谱角制图分类法进行改进,主要方法是在原影像的6个波段基础上,加入了K-L变换的前3个波段、K-T变换的3个波段(亮度、绿度和湿度)以及NDVI(归一化植被指数)信息将图像波段数增加至13个,增强了地物之间的光谱区分度(即类间方差);得到光谱角度图像后,提出一种无需阈值的地类确定方法,减少了人工参与,提高了判别精度和处理效率。 相似文献
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土壤电导率 (Electrical conductivity, EC)是评价土壤盐渍化的重要指标。通过实测新疆艾比湖湿地自然保护区土壤EC及可见光—近红外光谱数据,利用波谱响应技术模拟Landsat 8 OLI、Sentinel 2、Sentinel 3卫星的宽波段数据。构建宽波段模拟数据及其5种预处理后的三维光谱指数 (Three-dimensional spectral index, TDSI),采用梯度提升回归树算法 (Gradient boosting regression tree, GBRT) 建立3种卫星土壤EC估算模型,并比对加入TDSI后模型精度的变化。结果表明：在不同土壤EC条件下,3种卫星具有相似的光谱趋势,均在红、近红外波段附近反射率较高;TDSI与土壤EC相关性基本均在0.4以上,最大程度保留了与土壤EC敏感度高的红、绿、蓝、近红外、短波红外波段信息;GBRT对于土壤EC估算能力表现突出,3种卫星对土壤EC的最佳预测精度R2分别为0.831、0.847、0.903,在加入TDSI后,R2分别提高至0.835、0.857、0.935,综合分析发现,Sentinel
3对土壤EC估算效果最佳 (R2=0.935,均方根误差RMSE=2.986 mS·cm-1,赤池信息准则AIC=57.500)。通过利用波谱响应技术结合TDSI深度挖掘波段间的协同信息,采用GBRT验证了不同卫星对土壤R2的估算效果,二者相结合可以有效提升模型预测精度,为干旱区土壤盐渍化定量监测与防控提供有利指导。 相似文献
3.
Statistics and geometry of the eigenspectra of three-dimensional second-rank symmetric random tensors 总被引：1，自引：0，他引：1
Geoscientists have undertaken mapping of the Earth's crustal strain (or stress) fields using a great variety of field data. The output can be represented by a 3-D second-rank symmetric random strain tensor. The random principal strains-land rotations of the random tensor are frequently computed. The accuracy is calculated using a first-order approximation. The distribution aspects of the random principal strains and rotations have received almost no attention in Earth Sciences. A first-order approximation of accuracy may not be sufficient if the signal-to-noise ratio is small, as is often the case for geodetically derived random strain tensors. Therefore, the purpose of this paper is to investigate the distribution and estimation problems of the general 3-D second-rank tensor equation GΛG T = T , where T is a given 3-D second-rank symmetric random tensor, Λ a diagonal (3 × 3) random eigenvalue matrix, and G a (3 × 3) random orientation matrix, which is also orthogonal. Λ and G are to be estimated (or solved) from T . If some eigenvalues coincide, additional conditions are imposed on the eigenvectors so that they can be chosen uniquely. The joint probability density function (pdf) of the random eigenvalues and rotations will be worked out, given a joint pdf of the elements of random tensors T. Because the rotations are of special interest in Earth Sciences, we shall also derive the joint marginal pdf of random rotations. The geometry of eigenspectra will be studied. The biases of random eigenvalues and rotations will be derived, which have been neglected in the past. They can be very crucial in interpreting the pattern of a derived strain field, however, when applied to a real Earth Science problem. The variance-covariance matrices will be computed using a second-order approximation. 相似文献
4.
天山北坡中东段天然草地光谱植被指数特征 总被引：8，自引：0，他引：8
据１９９２－１９９４年天山北坡中东段各种主要天然草地类型混合牧草群落光谱观测资料,牧草产量资料分析发现,天然草地牧草产量与光谱被指数都具有季节变化特征,呈现出低到高,再由高到低的变化规律;天然草地光谱植被指数可以较了地反映牧草产量的年际变化和不同类型天然草地的产量差异,由于降水等自然条件的影响,牧草产量的年份,光谱植被指数也高,牧草产量低的年份,光谱植被指数也低。 相似文献
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分析新疆北疆部分地区若干种矿物、岩石在可见～近红外波段内光谱曲线,结合其化学成份、矿物成份、结构构造等特点,总结了0.4μm～2.4μm间火成岩、变质岩的光谱变化特征,并从其化学成份上对这些变化特征予以分析,得出火成岩光谱特征与化学成份相关、变质岩光谱特征与母岩关系密切的结论。 相似文献
6.
Peiliang Xu 《Geophysical Journal International》1999,138(1):1-24
The random principal eigenvalues and random eigenvector parameters have been routinely estimated from second-rank symmetric (SRS) random tensors and geophysically interpreted in the Earth Sciences. Statistical inference of random eigen-values and random eigenvector parameters has almost always been made as if they were normally distributed. The practical validity and applicability of the assumption of normal distributions for random eigenvalues and random eigenvector parameters has not yet been checked, however. Statistical inference of random eigenvalues and random eigenvector parameters should be based on their joint probability density function (pdf) derived from that of the original random tensor. We shall extend the work of Xu & Grafarend (1996a , b ) to the case of constrained SRS random tensors in this paper. All the relevant Jacobians for n -D unconstrained and 3-D constrained SRS tensors have been obtained. We then propose three pdf models for original SRS random tensors, which cover the commonly used Gaussian and Laplace pdfs and include pdf models for positive definite random material tensors. The pdfs of the random eigenvalues and random eigenvector parameters have been worked out. It is shown that the pdfs of the random eigenvalues and random eigenvector parameters are significantly different from the commonly used Gaussian pdf model. Deviatoric stress tensors and double-couple seismic moment tensors have been simulated to show the applications of the developed theory. The simulations have additionally indicated that Fisher's pdf model for directional data is not representative of the random rotations of constrained SRS random tensors. 相似文献
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The use of FFT techniques in physical geodesy 总被引：20，自引：0，他引：20
9.
Jeffrey Park Craig R. Lindberg David J. Thomson 《Geophysical Journal International》1987,91(3):755-794
We present a new method for estimating the frequencies of the Earth's free oscillations. This method is an extension of the techniques of Thomson (1982) for finding the harmonic components of a time series. Optimal tapers for reducing the spectral leakage of decaying sinusoids immersed in white noise are derived. Multiplying the data by the best K tapers creates K time series. A decaying sinusoid model is fit to the K time series by a least squares procedure. A statistical F -test is performed to test the fit of the decaying sinusoid model, and thus determine the probability that there are coherent oscillations in the data. The F -test is performed at a number of chosen frequencies, producing a measure of the certainty that there is a decaying sinusoid at each frequency. We compare this method with the conventional technique employing a discrete Fourier transform of a cosine-tapered time-series. The multiple-taper method is found to be a more sensitive detector of decaying sinusoids in a time series contaminated by white noise. 相似文献
10.
In Part I of this paper, we derived a set of data tapers designed to minimize the spectral leakage of decaying sinusoids immersed in white noise. Multiplying a long-period seismic record by K of these tapers creates K time series. A decaying sinusoid is fit to these K time series in the frequency domain at a number of chosen frequencies by a least-squares procedure. The fit is tested at each frequency using a statistical F -test. In Part I, we demonstrated that the multiple-taper method is a more sensitive detector of decaying sinusoids than the conventional direct spectral-estimate.
In this paper, we present a number of extensions to the multiple-taper method. We explain how the technique can be modified to estimate the harmonic components of records containing gaps. We discuss how sinusoids at frequencies between FFT bin frequencies can be detected, and how this method can be combined with conventional multi-station stacking procedures. 相似文献
In this paper, we present a number of extensions to the multiple-taper method. We explain how the technique can be modified to estimate the harmonic components of records containing gaps. We discuss how sinusoids at frequencies between FFT bin frequencies can be detected, and how this method can be combined with conventional multi-station stacking procedures. 相似文献
11.
植被高光谱特征分析及其病害信息提取研究 总被引：4，自引：0，他引：4
高光谱(hyperspectral)遥感是20世纪末地球观测系统中最重要的技术突破之一。根据植被高光谱数据的植被冠层光谱反射特征和诊断性光谱吸收特征,利用光谱连续统去除法,探讨光谱一阶微分反射比(FDR)和从连续统去除的光谱吸收特征中获得的波段深度(BD)、连续统去除后微分反射比(CRDR)、波段深度比(BDR)和归一化波段深度指数(NBDI)等光谱特征参量。结合多时相的条锈病小麦PHI航空高光谱影像,分析条锈病对小麦光谱的影响及其光谱特征,并运用光谱特征参量和波谱角制图(SAM)技术监测和识别小麦条锈病。 相似文献
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F. K. Boadu 《Geophysical Journal International》2000,141(1):227-240
A new numerical approach to the solution of waves propagating in a fluid-saturated medium, using Biot's theory as a foundation, has important implications for oil reservoir management and earthquake prediction. A numerical scheme is developed using an exponential transformation that explicitly treats the petrophysical and fluid properties of the medium within the framework of a generalized model. The scheme accounts for wave dissipation and velocity modifications. The numerical solution is used to perform numerical experiments to study the dynamic behaviour of waves in a fluid-saturated medium at well-logging frequencies (15 kHz). The results from the numerical experiments indicate that the degree of saturation by a high-viscosity fluid (HVF) such as oil, the temperature and the porosity of a medium strongly influence the spectral power distribution, frequency content and the velocity of waves propagating through the medium. An increase in HVF saturation causes enhanced attenuation of the low-frequency components, and increases the seismic velocity. An increase in porosity, however, enriches the low-frequency components and decreases the seismic velocity. A spectral quantification procedure is suggested and used to obtain information about the petrophysical and fluid properties of the medium from the spectral characteristics of the transmitted waveform. The procedure involves segmentation of the energy or power distribution of the transmitted waveforms into specified energy bands. The energy or power in these bands is then estimated. The extracted quantification variables are found to have strong correlations with the degree of HVF saturation, and the temperature and the porosity of the medium. 相似文献
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Tatiana Quarta Maurizio Fedi & Angelo De Santis 《Geophysical Journal International》2000,140(2):311-323
An analysis of the field scaling power spectrum yields useful information about the source distribution, but it is uncertain whether deterministic, random, fractal or mixed approaches have to be used for the interpretation. To this end, the scaling properties of potential field spectra are analysed for a number of different source models of geological interest. Besides the models of Naidu (purely random sources) and Spector and Grant (gross block statistical ensembles) we consider other types of density and magnetization distributions with spectral exponents in the fractal range, such as a single homogeneous body with a random white source distribution. Spectral slopes in the fractal range are obtained.
We also study the effects of important natural sources, such as salt domes and sedimentary basins, representing them with simple Gaussians or combinations of Gaussian signals. The same spectral slopes as for gravity signals generated by 3-D fractal source distributions are found for them. Hence the power law decay of the field is not a characteristic only of fractal source models.
If a 3-D fractal source distribution is assumed a priori , a way of verifying the goodness of the model is to examine the whitened field at source level. The probability that the whitened field derives from a random white population is estimated for synthetic and real anomalies by applying the usual statistical tests. 相似文献
We also study the effects of important natural sources, such as salt domes and sedimentary basins, representing them with simple Gaussians or combinations of Gaussian signals. The same spectral slopes as for gravity signals generated by 3-D fractal source distributions are found for them. Hence the power law decay of the field is not a characteristic only of fractal source models.
If a 3-D fractal source distribution is assumed a priori , a way of verifying the goodness of the model is to examine the whitened field at source level. The probability that the whitened field derives from a random white population is estimated for synthetic and real anomalies by applying the usual statistical tests. 相似文献
17.
沙坡头地区气候变化特征及其功能谱分析 总被引：3，自引：0，他引：3
论文探讨了沙坡头地区气候要素的年际、年内变化特征,并采用功能谱分析方法,定量分析了气温、降水的周期性变化规律,得出气温年际变化具有８．４ａ、３．５ａ和２．８ａ的周期规律;降水年际变化具有８．４ａ、５￣６ａ、３．５ａ和３ａ的周期性规律。采用交叉功能谱分析方法研究了气温与降水协同变化机制、周期性及其对人工植被的影响,得出降水和气温组合因子具有１０．５ａ、８．４ａ、３．５￣３．８ａ的波动周期。为气候资源 相似文献
18.
面向土地利用动态遥感监测的成像光谱数据处理技术研究 总被引：1，自引：1，他引：0
成像光谱数据具有较高光谱分辨率,在类别细分方面具有一定的优势。该文针对成像光谱数据特点,研究与成像光谱数据特征相适应的土地利用动态遥感监测技术,包括边缘辐射纠正技术、影像融合技术和异常光谱检测技术,该方法在试验区应用中取得了良好效果。 相似文献
19.
谱段设置是资源卫星传感器设计的关键技术之一。该文针对土地资源管理对资源卫星光谱分辨率的需求。详细分析了收集和采集的主要土地利用/覆被光谱数据的特征，从主要地物的光谱可分性出发，提出了满足土地资源管理需要的资源卫星传感器谱段设置方案，并利用机载成像光谱数据进行波段优选和在轨资源卫星数据的模拟验证，分类对比研究表明，该优化谱段模拟图像土地利用／覆被分类效果好于TM和CBERS-1影像。 相似文献
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Evaluation of Landsat-7 ETM+ Panchromatic Band for Image Fusion with Multispectral Bands 总被引：9，自引：0，他引：9
The Landsat-7 ETM+ panchromatic band is taken simultaneously with multispectral bands using the same sensor system. The two data sets, therefore, are coregistered accurately and the solar illumination and other environmental conditions are identical. This makes ETM+ Pan advantageous to SPOT Pan for resolution fusion. A spectral preserve image fusion technique, Smoothing Filter-Based Intensity Modulation (SFIM), can produce optimal fusion data without altering the spectral properties of the original image if the coregistration error is minimal. With TM/SPOT Pan fusion, the technique is superior to HSI and Brovey transform fusion techniques in spectral fidelity, but has slightly degraded edge sharpness as a result of TM/SPOT Pan coregistration error because SFIM is sensitive to coregistration accuracy and temporal changes of edges. The problem is self-resolved for ETM+ because there is virtually no coregistration error between the panchromatic band and the multispectral bands. Quality fusion imagery data thus can be produced. 相似文献