基于复合分界指标和 CEEMD-WT 的 GNSS 滑坡监测坐标时间序列降噪方法

GNSS Landslide Monitoring Coordinate Time Series Noise Reduction Methods Based on Composite Divisional Indicator Index and CEEMD-WT

  • 摘要: 针对完备集合经验模态分解 (Complementary Ensemble Empirical Mode Decomposition,CEEMD) 技术难以有效分离全球导航卫星系统 (Global Navigation Satellite System, GNSS) 变形监测序列中的高频变形信号,以及难以去除低频形变信号中夹杂的监测环境振动噪声等问题,提出了一种基于 CEEMD、 小波变换(Wavelet Transform, WT) 和复合分界指标相结合的滤波降噪方法,并利用 4 组仿真数据和真实滑坡场景下的监测坐标序列进行试验。首先,对原始时间序列进行 CEEMD 分解, 并计算每个本征模态函数 (IntrinsicMode Functions,IMF) 分量的复合分界指标 T 值;然后,寻找第一个局部极小值 T 对应的第 m 层 IMF 分量,将前 m-1 层 IMF 分量作为纯噪声进行剔除;再进一步,根据 T 值的大小将剩余 IMF 分量分类为保留信号和待处理信号,并利用 WT 方法对待处理信号进行二次降噪处理;最后,将处理后信号与保留信号以及趋势项进行信号重构,得到最终降噪结果。真实滑坡数据实验结果表明, 与 WT、 基于标准化绝对矩均值和基于相关系数的 CEEMD 方法相比, 所提方法能够保留相对高频的滑坡变形信号, 同时能够有效去除低频形变信号中夹杂的振动噪声。经过该方法去噪后,其 E、 N、 U 方向的均方根误差分别为 1.13 mm、 1.63 mm和 2.22 mm,与上述三种方法相比,降噪效果分别提升了 21%、 17%、 12%, 此外,该滤波方法可有效提升滑坡监测预警的准确率。

     

    Abstract: Objectives: Aiming at the problems that Complementary Ensemble Empirical Mode Decomposition ( CEEMD) is difficult to effectively separate out the high-frequency deformation signals in the global navigation satellite system ( GNSS) deformation monitoring sequences, as well as the difficulty of removing the vibration noise of the monitoring environment that is interspersed in the low-frequency deformation signals, a filtering and noise reduction method based on the combination of CEEMD, wavelet transform ( WT) , and composite partitioning indexes is presented. Methods: First, CEEMD of the original sequence is performed and the T-value of each Intrinsic Mode Functions ( IMF ) is calculated. Second, the mth layer IMF component corresponding to the first local minima T is searched for, and the first m-1 layers of IMF components are rejected as pure noise. further, according to the magnitude of the T-value, the residual IMF components are classified into retained signals and to-be-processed signals, and the processed signals are secondly noise reduced using the WT method for secondary noise reduction of the signal to be processed, Finally, the processed signal is reconstructed with the retained signal and the trend term to obtain the final noise reduction result. Results: From the simulation experiments with real data experiments on landslides:( 1)The T-value has better signal retention ability and noise suppression compared to the noise reduction effect of the WT-based, mean standardized absolute moment -based and correlation coefficient-based CEEMD methods, and the method has the best SNR value and RMSE in the four sets of simulated data experiments.( 2) After denoising with this method, its root mean square errors in E, N and U directions are 1.13 mm, 1.63 mm and 2.22 mm, respectively, which are 21%, 17%, and 12% better than the noise reduction effect of the WT-based, mean standardized absolute moment -based and correlation coefficient-based CEEMD methods, respectively.( 3) The scheme in this paper has maintained the red warning after the first red warning was issued at 04:00 on 3 October, and compared to the moments when the first three schemes erroneously issued red warnings, it only issued orange warnings, and the change in the displacement rate of this scheme was also the smoothest of the four schemes, with the warning level not dropping to blue.Conclusions: The proposed method can not only retain the relatively high-frequency landslide deformation signals, but also effectively remove the vibration noise interspersed in the lowfrequency deformation signals, and can be applied to the de-noising of monitoring sequences of landslide scenarios, and the filtering method can effectively improve the accuracy of landslide monitoring and early warning, and avoid causing casualties and waste of resources.

     

/

返回文章
返回