Receiver noise correction in semi-airborne transient electromagnetic method with an electric source

Abstract

Semi-airborne transient electromagnetic method (SATEM) has been widely used in geophysical investigations. This method uses a grounded-wire to transmit the source signal and installs the receivers on an aircraft so that the data with a large depth of investigation can be acquired efficiently. However, the instability of aircraft when collecting the data will introduce the non-geological factors that distort the recorded data sets, which further affect the precision of the investigation result greatly. The researching of the mechanism and the correction method of these factors, including geometric effect, geomagnetic effect and mutual inductance effect between transmitter and receivers, is of great significance to the SATEM method. Thus, we proposed a thorough scheme to suppress noise generated by the non-geological factors of the SATEM configuration. We first derived the formulas for calculating the mutual inductance coupling between transmitter and receiver. The formulas of the geometric noise and geomagnetic noise that are affected by the roll, pitch, and yaw of the aircraft are further derived to analysis the influence interval of the motion noise. Then a hybrid correction scheme that uses a two-stage strategy to correct the receiver noise is put forward. The results show that the geomagnetic field and the mutual conductance contribute more noises than the geometric effect. The geomagnetic field will distort the data at all time channel, while the effect of the mutual inductance mainly focused on the early time channels. A field example demonstrated that the proposed method could well suppress the non-geological noise and improving the signal to noise ratio.