Analysis and preprocessing of geomagnetic signals based on morphological filter and Hilbert-Huang transform

In geomagnetic navigation, in order to get accurate measurement values of geomagnetic field, various kinds of noises must be eliminated beforehand. Through analyzing the characteristics of the noises in the geomagnetic measurement signals, this paper presents a new method that combines morphological filter and Hilbert-Huang transform(HHT) .The data is processed firstly using morphological filter to eliminate the influence of the instantaneous strong pulses, then the processed data is decomposed using empirical mode decomposition (EMD) method, and the two-dimensional Hilbert frequency-time spectrum is achieved. The characteristics of the noises in the signal are analyzed, and a threshold is decided according to the decomposition results; the decomposed components are low-pass filtered on main intrinsic mode functions (IMFs), finally a reconstruction is carried out to get the preprocessed signal. An experiment on the actually acquired data was carried out to verify the presented method, and the result shows that this method can effectively process and eliminate the noises in geomagnetic measurement signals.