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基于小波变换的图像压缩方法能在高压缩比的前提下保持好的重建图像质量,它的多分辨率特性与人类视觉系统非常相近,小波变换的编码技术被广泛地应用于遥感影像的压缩中。介绍了小波理论的相关知识,着重对嵌入零树小波、等级树分割、小波数据的形态学表示算法等方法进行了详细的论述,并对图像编码技术的发展方向进行了展望。 相似文献
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在ERDAS软件支持下,对ETM遥感影像数据的TM1—TM5,TM7与其全色波段TM8进行小波变换融合,对融合后的影像采用混合分类方法进行土地利用分类。并对其分类结果进行评价,总体精度达到95.43%,研究结果表明此方法可行有效。 相似文献
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介绍了小波图像的分解和重构方法以及小波融合过程。采用Symlet小波变换融合方法对西安地区鲸鱼沟水库的TM4、TM5子图进行单尺度二维离散小波变换融合,并进行水库的边缘检测。对图像通过TM4分解的低频图与TM5分解的高频图像融合再与TM4影像原图比较,融合图像提取细节效果明显优于TM4原图像。 相似文献
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随着多源遥感影像融合技术的成熟发展,如何提高高分辨率遥感数据的利用效益和使用质量已经成为影响其应用效果的瓶颈问题.针对QucikBird-2高分遥感数据光谱分辨率不足等问题,结合ASTER多光谱遥感数据,引入3种融合方法:主成分分析(PCA)融合、小波PCA融合和基于小波的IHS(色度、亮度、饱和度变换)融合,实现了对多光谱图像和高分辨率图像的融合,得到了多光谱高分辨率影像,使得在增强影像空间分辨率的同时也尽可能地保留了影像的多光谱信息.最后对3种融合方法的结果进行了定性和定量评价. 相似文献
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遥感技术的应用应贯穿区域地质调查的始终,要充分发挥遥感技术的先导与基础作用。在本研究区内.TM/ETM5、4、3波段组合为最佳波段组合,在常用的主成分变换法、乘积变换法、比值变换法、高通滤波法、小波变换法、IHS变换法6种融合方法中小波变换波段融合法为最佳融合方法。运用遥感影像更新区内的道路信息有助于提高填图效率和填图质量,以小波变换法融合全色波段的RGB(5,4,3)彩色影像为基础影像,其它彩色合成影像、单波段灰度影像等影像为辅助影像对区内岩石地层、构造进行了解译,运用复合法提取了本区的铁化和泥化蚀变异常,在野外地质路线观测过程中对解译的岩石地层、构造和提取的矿化蚀变都得到了较好的验证。遥感在区调过程中的道路更新、岩性识别、构造解译、矿化蚀变提取具有独特的优势。 相似文献
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通过经小波压缩降噪后的遥感影像,结合Bp神经网络进行遥感影像模式识别,与未经小波变换的BP神经网络进行遥感影像模式识别结果对比,总结出影像经小波变换后对于提高神经网络识别效率有很好效果。 相似文献
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基于形态小波的核磁共振测井信号去噪及现场应用研究 总被引:1,自引:0,他引:1
核磁共振测井中采集到的回波串信号十分微弱,而背景噪声很强,使信噪分离困难。为解决这一问题,引入了结合数学形态学的特征识别和小波分解的多分辨率分析特性的形态小波方法。讨论了方法的数据基础和应用步骤,并与小波软阈值方法处理结果进行了对比分析。实测数据处理结果表明:形态小波去噪方法具有良好的细节保留和抗噪声能力,去噪效果优于小波软阈值滤波方法;在消除测井信号随机噪声的同时,能很好地保留信号的波形和特征,在较低信噪比下仍可有效地提取测井信号的有用信息,提高了T2谱的反演精度。 相似文献
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Two-dimensional Conditional Simulations Based on the Wavelet Decomposition of Training Images 总被引:2,自引:1,他引:1
Scale dependency is a critical topic when modeling spatial phenomena of complex geological patterns that interact at different
spatial scales. A two-dimensional conditional simulation based on wavelet decomposition is proposed for simulating geological
patterns at different scales. The method utilizes the wavelet transform of a training image to decompose it into wavelet coefficients
at different scales, and then quantifies their spatial dependence. Joint simulation of the wavelet coefficients is used together
with available hard and or soft conditioning data. The conditionally co-simulated wavelet coefficients are back-transformed
generating a realization of the attribute under study. Realizations generated using the proposed method reproduce the conditioning
data, the wavelet coefficients and their spatial dependence. Two examples using geological images as training images elucidate
the different aspects of the method, including hard and soft conditioning, the ability to reproduce some non-linear features
and scale dependencies of the training images. 相似文献
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小波变换是近年来兴起的新的数学分支,并广泛应用于地震勘探领域。利用小波变换良好的局部化时频特性,可以很方便地将地震记录分解成不同的频道,分解后的各频道存在内在的分形规律。小波变换应用于煤田地震资料,提高其分辨率,具有重要意义 相似文献
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基于边缘特征的遥感影像小波变换融合法 总被引:4,自引:0,他引:4
如何将不同空间分辨率遥感影像合理有效地融合在一起,保持原始多光谱影像的光谱特性,提高影像的分类精度和空间分解力,这是遥感影像数据融合处理的热点研究问题。在对原始遥感影像进行小波变换的基础上,提取高空间分辨率影像边缘特征信息,并与原始多光谱影像进行了融合处理。以IRS、SPOT和ETM卫星影像为资料进行实验,结果表明,该方法在提高影像的空间分辨率的同时,能够很好地保持影像的光谱特性,尤其在空间分辨率差异较大的影像融合中,该方法在保持影像光谱特性方面要优于其他的融合方法。 相似文献
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Asok K. Sen 《Mathematical Geosciences》2009,41(1):43-49
Sedimentary records of Lake Edward in Central Africa from the late Holocene era exhibit submillennial-scale periodicities
in magnesium (Mg) and stable isotope compositions of endogenic calcite. Using multitaper spectral analysis, Russell et al. (Geology
31(8):677–680, 2003) detected a 725-yr cycle in the Mg data. We have analyzed the Mg data using a continuous wavelet transform and observed temporal
variations in the submillennial periodicities. These temporal variations can be discerned from a time-period representation
of the wavelet power spectrum by visual inspection. The multi-taper spectral analysis is based on the traditional Fourier
transform, which is a purely frequency domain technique, and therefore cannot detect temporal variability of the spectrum,
if any. In contrast, wavelet analysis offers a spectral-temporal approach by which both the dominant periodicities and their
time variations can be identified. In this regard, the results of our wavelet analysis extend those of Russell et al. (Geology
31(8):677–680, 2003). Our analysis reveals dominant periodicities around the 785-yr and 660-yr cycles, but these cycles persist over different
time spans within the late Holocene era. The 725-yr period identified by Russell et al. (Geology 31(8):677–680, 2003) with multitaper spectral analysis is very close to the average of the periods of these two cycles. For the purpose of accurately
reconstructing the climate history in Central Africa using Mg as a proxy, it would be important to take into consideration
the temporal variations of the submillennial periodicities. 相似文献
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Nestor A. Rivera S. Ray Jerry L. Jensen Andrew K. Chan Walter B. Ayers 《Mathematical Geology》2004,36(5):529-543
This study shows how wavelet analysis can be used on well log and drill core data to identify cyclicity in sedimentary sequences. Three possible methods for determining wavelength were investigated: the Morlet wavelet, the Fourier transform, and the semivariogram. When applied to several hypothetical signals similar to those observed in petrophysical measurements in hydrocarbon reservoirs, all three methods could identify the presence of cyclicity. Only the wavelet scalogram, however, gave a clear indication of when the cyclic element was present and where frequency changes occurred in the signal. To illustrate the wavelet analysis, we processed well log and core data from a well in the Ormskirk Sandstone and determined the wavelet coefficients for each zone and the wavelengths of the strongest cyclicities. The cyclicities observed corresponded well with sedimentary features of the formation (e.g., channels and channel sets). Also, ratios of the cyclicity wavelengths corresponded with ratios of the Milankovitch precession, obliquity, and eccentricity periods. This result is in agreement with other investigators, who have proposed that Milankovitch-driven climate changes exercised an important control on Ormskirk Sandstone deposition. 相似文献
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Current seismic tomographical models produce databases with increasing size and higher spatial resolution. Consequently, direct visual inspection and interrogation of the seismic database are becoming more and more an arduous and time-consuming task. Recently, it has been shown that feature extraction can be emphasized and simplified by the use local spectra extraction (LSE) obtained from Gaussian wavelet transform (Bergeron et al., 1999). For example, such a feature may be the subducting slab under Japan or a plume-like object beneath the transition zone under Iceland. A drawback of the LSE is that the physical space dimensionality is added by 1, thus increasing greatly the information content. Our approach is to assimilate and synthesize the set of local spectra by using two proxy quantities: the spatial distributions of the local maxima of the L2-norm, E-max, and the associated local wavenumber, k-max. We propose to test this new computer vision method with two types of noisy synthetic data in order to emphasize the basic strengths and features of this novel method. We show that even if the signal to noise ratio is very low (less than 1dB), the presence of a slab and a plume or columnar structure can be detected in the k-max spatial distribution. The E-max proxy detects background fluctuation modulated by the sharp peaks in the spatial patterns. Without any a-priori knowledge, we cannot perceive these subtleties by a direct visual inspection of the raw data set. With our numerical experiments, we have developed a database of synthetic patterns, as in a dictionary, which can prove to be useful for the geophysical community for comparing with new local tomographic models. Examples of this operation can be viewed on the web. The P1200 tomographical model from Zhou (1996) is also analyzed and zoomed “in” with wavelets. Most prominent of this geophysical example are the significant depth extent of the plate-tectonic boundaries around Asia and the signature of the megaplume under the East African rift.Electronic supplementary material Electronic supplementary material is available for this article at and accessible for authorised users. 相似文献
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We discuss here the issues faced by earth scientists in analyzing and visualizing large datasets over a GRID-like setup from a client-server perspective. We approach this problem by using a remote, web-based visualization and data analysis framework, called WEB-IS, and by employing second-generation wavelets as a means for reducing the amount of data transferred and for extracting coherent features in complex geophysical flows and surface faulting patterns. As an example, we describe how onboard processors on satellites can function as a server for beaming down extracted information to the client computer on the ground, thus exemplifying WEB-IS as a viable middleware on a GRID network for geosciences.Reviewed by: Prof. I.D. Clemens, Prof. L. Hanyk 相似文献
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We describe a new approach for simulation of multiphase flows through heterogeneous porous media, such as oil reservoirs.
The method, which is based on the wavelet transformation of the spatial distribution of the single-phase permeabilities, incorporates
in the upscaled computational grid all the relevant data on the permeability, porosity, and other important properties of
a porous medium at all the length scales. The upscaling method generates a nonuniform computational grid which preserves the resolved structure
of the geological model in the near-well zones as well as in the high-permeability sectors and upscales the rest of the geological
model. As such, the method is a multiscale one that preserves all the important information across all the relevant length
scales. Using a robust front-detection method which eliminates the numerical dispersion by a high-order total variation diminishing
method (suitable for the type of nonuniform upscaled grid that we generate), we obtain highly accurate results with a greatly
reduced computational cost. The speed-up in the computations is up to over three orders of magnitude, depending on the degree
of heterogeneity of the model. To demonstrate the accuracy and efficiency of our methods, five distinct models (including
one with fractures) of heterogeneous porous media are considered, and two-phase flows in the models are studied, with and
without the capillary pressure. 相似文献