共查询到20条相似文献，搜索用时 125 毫秒
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结合模平方的双树复小波变形监测数据滤波 总被引：1，自引：0，他引：1
针对变形监测数据的去噪问题,该文在分析离散小波变换去噪不足的基础上,提出了一种基于模平方的双树复小波变形监测数据滤波方法。该方法利用双树复小波变换的完全重构、近似平移不变性和较好的方向选择性等特点,通过最小尺度空间的小波系数得到噪声强度,并结合模平方处理法确定各层的阈值,经重构阈值处理后的各层小波系数即得到去噪后的信号;经算例,并与传统离散小波变换对比分析。结果表明:双树复小波变换的分解效果优于传统离散小波变换,能较好地表现出细节部分的频率信息,使变形信号的周期性变化特征更为明显。该方法去噪更彻底,进一步提高了消噪的精度和可靠性,可作为变形监测数据降噪处理的新方法。 相似文献
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在遥感影像融合中,IHS变换法与小波变换法具有互补性,文中把这两种方法结合起来,提出了一种基于IHS变换与小波变换的影像融合方法.通过对具体影像的实验证明,该方法是有效的,达到了预期的目的. 相似文献
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基于小波的GPS基线解算精化处理技术及其应用 总被引：7，自引：0，他引：7
采用小波技术对GPS信号进行处理,提出基于小波变换的周跳与粗差的探测.利用基于小波变换的小波滤波法对于提高GPS双差相位观测值的信噪比具有较好的效果,对其相位观测值进行小波滤波,消除或削弱多路径效应和各种观测噪声,使其观测值得以净化.这种方法对于缩小模糊度搜索空间及提高模糊度解的有效性有明显的作用,从而提高基线解算的精度. 相似文献
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基于小波变换和不变矩匹配的快速人体定位 总被引：1，自引：0，他引：1
人体定位是指在图片中确定行人位置的过程.为了提高人体定位的正确率和速度,提出了一种结合小波变换和不变矩匹配的定位方法.首先对图像进行小波变换,提取出图像小波系数;再根据行人模板的系数特征提取出不变矩模板;然后在小波域上通过不变矩匹配实现人体定位.该方法减少了待检区域,降低了计算代价.实验结果表明,该算法识别率达78.6%,测试结果比Oren等人提出的匹配方法提高了26.7%. 相似文献
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针对多光谱图像与全色图像的融合,提出了基于IHS变换和小波包变换的遥感图像融合新方法.该方法首先对多光谱图像作IHS变换得到3个分量:亮度I、色度H和饱和度S;其次利用小波包变换融合方法融合多光谱图像的亮度分量与全色图像,并用融合后的图像替代多光谱图像的亮度分量;最后作IHS反变换得到新的多光谱图像.实验分析表明,新方法的性能优于IHS变换融合方法、小波变换融合方法和基于小波变换与IHS变换融合方法,在保留多光谱图像光谱信息的基础上,增强了融合图像的空间细节表现能力. 相似文献
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介绍了基于小波包变换和距离特征选取的影像融合方法：首先对多光谱影像做IHS变换;其次对多光谱影像的亮度分量和全色影像做小波包变换并分别采用加权平均法和距离特征选取法融合低频部分和高频部分;最后通过小波包重构和IHS逆变换得到最终的融合影像。以ERDAS8．5软件自带的影像文件为例对这种方法进行了实验,并利用信息熵等标准与其他融合方法进行了比较,实验结果表明该方法能得到更好的融合效果。 相似文献
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基于IHS变换和小波变换的遥感影像融合 总被引：18，自引：0，他引：18
在遥感影像融合中，IHS变换法与小波变换法具有互补性，文中把这两种方法结合起来，提出了一种基于IHS变换与小波变换的影像融合方法。通过对具体影像的实验证明，该方法是有效的，达到了预期的目的。 相似文献
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This paper introduces a new method for GPS signal acquisition, which is based on the repeatability of successive code phase
measurements and the M-of-N search algorithm. The performance of the proposed method in terms of probability of signal detection
is similar to that of traditional methods, except that the calculation of the probability of detection does not rely on the
noise distribution or the Carrier-to-Noise ratio (C/N0). The code phase repeatability-based method is presented along with equations for probability of detection and probability
of false detection. If the distribution of the noise is known, it also provides an estimate of the C/N0. The proposed method is illustrated for coherent and non-coherent acquisition and C/N0 estimation. 相似文献
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A wavelet-extreme learning machine for low-cost INS/GPS navigation system in high-speed applications
The combined navigation system consisting of both global positioning system (GPS) and inertial navigation system (INS) results in reliable, accurate, and continuous navigation capability when compared to either a GPS or an INS stand-alone system. To improve the overall performance of low-cost micro-electro-mechanical systems (MEMS)-based INS/GPS by considering a high level of stochastic noise on low-cost MEMS-based inertial sensors, a highly complex problems with noisy real data, a high-speed vehicle, and GPS signal outage during our experiments, we suggest two approaches at different steps: (1) improving the signal-to-noise ratio of the inertial sensor measurements and attenuating high-frequency noise using the discrete wavelet transform technique before data fusion while preserving important information like the vehicle motion information and (2) enhancing the positioning accuracy and speed by an extreme learning machine (ELM) which has the characteristics of quick learning speed and impressive generalization performance. We present a single-hidden layer feedforward neural network which is employed to optimize the estimation accuracy and speed by minimizing the error, especially in the high-speed vehicle and real-time implementation applications. To validate the performance of our proposed method, the results are compared with an adaptive neuro-fuzzy inference system (ANFIS) and an extended Kalman filter (EKF) method. The achieved accuracies are discussed. The results suggest a promising and superior prospect for ELM in the field of positioning for low-cost MEMS-based inertial sensors in the absence of GPS signal, as it outperforms ANFIS and EKF by approximately 50 and 70%, respectively. 相似文献
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Metop-GRAS in-orbit instrument performance 总被引：2，自引：1，他引：1
The GRAS instrument on the Metop-A satellite provides more than 600 radio occultation measurement profiles per day. The instrument
is characterized by its wide antenna coverage, high signal-to-noise ratio and an ultra-stable clock reference. The conventional
dual-frequency tracking of GPS signals is under dynamic atmosphere conditions complemented by open loop tracking with sampling
of the signal at a 1 kHz rate, providing an unprecedented view of the signal spectral environment. This paper presents the
instrument performance as derived from analysis of in-orbit measurement data. We show that the noise figure is low enough
to enable mapping of external radio noise variations over the earth’s surface. An error propagation model is presented to
relate instrument characteristics to bending angle performance. This model is also used to illustrate the relation between
filter bandwidth, resolution and measurement noise. The Doppler model, guiding open loop measurements, is found to be accurate
to better than 20 Hz with a possibility for improvement to 10 Hz. The high performance at low altitudes enables the presence
of surface reflections at the −20-dB level to be identified in more than 50% of the occultations. The potential performance
improvements for next generation receivers are discussed. 相似文献
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将复共线性对参数估计危害的度量结果与截断奇异值估计相结合,提出了基于信噪比检验的双截断奇异值估计。利用信噪比检验,根据每个参数最小二乘估计信噪比估值的大小将待估参数分为受复共线性危害较大和较小的两部分,并对这两部分参数的截断奇异值估计进行不同强度的截断。对受复共线性危害较大的部分参数,使其截断参数相对较小,对受复共线性危害较小的部分参数,使其截断参数较大。这种精细化的处理在有效降低参数估计方差的同时减少了偏差的引入。将基于信噪比检验的双截断奇异值估计应用于GEO卫星定轨仿真算例中,实验结果表明,新方法的解算精度较高。 相似文献
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针对复小波双变量滤波模型仅考虑小波复系数实部,忽略了系数的虚部,导致信号相位噪声的增加而影响滤波效果的问题,提出基于复小波变换的复数域双变量模型干涉图滤波算法。该算法将双变量贝叶斯估计算法从实数域推广到了复数域,用噪声复系数概率密度函数刻画了小波复系数实部与虚部的相关性,根据小波分解复系数来估计噪声方差和信号方差,建立了复小波复数域双变量滤波模型,求得了干涉图复系数的贝叶斯估计。试验结果表明,本算法对干涉图噪声有较强的抑制能力,保留了干涉图的边缘及细节信息,滤波性能优于传统的实数域复小波双变量滤波、Goldstein滤波、单小波滤波和最优化融合滤波方法。 相似文献
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Adaptive GPS/INS integration for relative navigation 总被引：1，自引：0，他引：1
Je Young Lee Hee Sung Kim Kwang Ho Choi Joonhoo Lim Sebum Chun Hyung Keun Lee 《GPS Solutions》2016,20(1):63-75
Relative navigation based on GPS receivers and inertial measurement units is required in many applications including formation flying, collision avoidance, cooperative positioning, and accident monitoring. Since sensors are mounted on different vehicles which are moving independently, sensor errors are more variable in relative navigation than in single-vehicle navigation due to different vehicle dynamics and signal environments. In order to improve the robustness against sensor error variability in relative navigation, we present an efficient adaptive GPS/INS integration method. In the proposed method, the covariances of GPS and inertial measurements are estimated separately by the innovations of two fundamentally different filters. One is the position-domain carrier-smoothed-code filter and the other is the velocity-aided Kalman filter. By the proposed two-filter adaptive estimation method, the covariance estimation of the two sensors can be isolated effectively since each filter estimates its own measurement noise. Simulation and experimental results demonstrate that the proposed method improves relative navigation accuracy by appropriate noise covariance estimation. 相似文献
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Carlos López-Martínez Xavier FàbregasLuca Pipia 《ISPRS Journal of Photogrammetry and Remote Sensing》2011,66(5):597-607
This paper addresses the problem of speckle noise on single baseline polarimetric SAR interferometry (Pol-InSAR) on the basis of the multiplicative-additive speckle noise model. Considering this speckle noise model, a novel filtering technique is defined and studied in terms of simulated and experimental Pol-InSAR data. As demonstrated, the use of the multiplicative-additive speckle noise model does not lead to a corruption of the useful information but to an improvement of its estimation. The performance of the algorithm is analyzed in terms of the physical parameters retrieved from the filtered data, that in this work correspond to the forest height and the ground phase. In case of experimental data, the retrieved forest height is compared and validated against Lidar ground truth measurements. 相似文献
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针对北斗B1C信号在低载噪比情况下跟踪精度低的问题,提出一种基于扩展卡尔曼滤波（EKF）的北斗B1C信号数据/导频联合跟踪方法.通过构建数据/导频双通道联合跟踪模型,增加对B1C信号利用率,并在联合跟踪模型的基础上引入扩展卡尔曼滤波器,削弱传统跟踪环路中鉴别器和环路滤波器带来的跟踪误差,进一步提高跟踪环路对低载噪比信号的跟踪性能.仿真结果验证:在低载噪比情况下,相比于传统单导频通道跟踪、单导频扩展卡尔曼跟踪和联合跟踪,该方法可以有效提高跟踪精度. 相似文献