AeroVmag: A new aero-towed vector magnetometer system

Magnetic fields are vectorial in nature, yet most geophysical surveys measure the amplitude of the fields, resulting in total field magnetic anomalies. This tradition is motivated mainly by the ease with which total field measurements can be conducted and the technical challenges involved in the acquisition of vector measurements. The quality of vector magnetometer systems depends mainly on the accuracy with which the orientation (i.e., pitch, roll, and yaw angles) is known. To overcome this challenge, triaxial vector magnetometers are commonly installed onto the platforms that carry these systems (e.g., ships and airplanes), which causes temporally varying magnetic contamination that is difficult to eliminate and quantify. We develop the first aero-towed vector magnetometer system, called AeroVmag, which can measure the three components of the magnetic field with negligible magnetic contamination induced by the carrying platform. The system contains a dual global navigation satellite system/inertial navigation system coupled with triaxial and scalar magnetometers. We test the system near the central Dead Sea Fault system in northern Israel, where we collected a dense grid of data approximately 110 m above the surface. We use crossover analysis to show that the system yields internally consistent data with noise levels of 15.6/44.5/14.0 nT for the north/east/vertical components, respectively. We show that these noise levels arise from the uncertainties related to the orientation of the towed bird, indicating that our processing scheme mitigates any other magnetic contamination or biases. The test survey results compare favorably with the existing sea surface total field anomalies and with the seismic reflection data, thus demonstrating the reliability of the system. The AeroVmag system can be towed by helicopters, fixed-wing aircraft, and heavy-lifting drones, providing obvious operational and economic benefits. Its applicability is expected to be highest in equatorial and regional surveys that study crustal-scale phenomena or when characterizing off-profile sources.