An equivalent source method for removal of attitude-induced responses in drone-towed magnetic scalar gradiometry data

• Published in: Geophysical Journal International
• Main Authors: Petersen, Jacob Thejll, Kolster, Mick E., Rasmussen, Thorkild M., Døssing, Arne
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2023
• Subjects: Electromagnetic theory; Magnetic anomalies; Modelling and interpretation; Inverse theory; Crustal structure; Drone-towed magnetic surveying; Equivalent source method; Northern Sweden
• Online Access: https://orbit.dtu.dk/en/publications/dec4288b-bf9a-4895-98a1-9f31951d4b9a; https://doi.org/10.1093/gji/ggac404; https://backend.orbit.dtu.dk/ws/files/297862901/ggac404.pdf

Drone-towed scalar field gradiometry surveys conducted in windy conditions or under self-excited oscillations generate attitude-induced responses that can hinder the geological interpretation. Here, we present a gradiometric equivalent source method (GESM) to remove these attitude-induced responses by interpolating and continuing the measured gradiometry data to new idealized pseudo-sensor positions free of any attitude deviations. In addition, we present transverse horizontal difference (THD) data from a precisely positioned drone-towed horizontal gradiometry survey collected in Nautanen, northern Sweden. Analysing the Nautanen survey's positional data revealed that the gradiometer system exhibited directional-dependent yaw deviations with periods of unpredictable attitude deviations. Based on synthetic THD data created using the Nautanen survey's positional data, these deviations manifest as line-to-line striping and short-wavelength oscillations in the THD maps. Applying GESM to the synthetic THD data removes these attitude-induced THD responses with satisfactory accuracy compared to the true THD values. Furthermore, on the actual THD data collected in Nautanen, applying GESM improved the continuity of anomalies, significantly improving the interpretation of the data. The results suggest that applying GESM to drone-towed gradiometry surveys, given precise attitude information via an onboard GNSS-IMU system, maintains high quality even when surveying in windy conditions or in high-gradient areas. The results suggest that including GESM in the data processing of drone-towed gradiometry surveys, given precise positional information via an onboard GNSS-IMU system, ensures high-quality geological interpretation even in windy conditions or in high-gradient areas.