The transient electromagnetic method has a maximum depth because of continuous attenuation by transmission of electromagnetic signal in underground.
由于电磁信号在地下传播时不断衰减，瞬变电磁测深法有一个最大探测深度。
2
A filtering method based on wavelet transform with local maximum value was discussed. The method could distinguish signal from the noise according to the different features of scale change.
We have derived the formulas for wavelet coefficients of the fractal signal and white noise separately on the basis of which the maximum likelihood method is used to estimate the fractal parameter.