Equivalent source inversion to homogenise magnetic airborne surveys in Antarctica flown on irregular flight lines, line spacing, heights and decades.

Magnetic data collection in Antarctica is commonly carried out using airborne platforms, which allow to cover large spatial areas. Airborne surveys in Antarctica have been conducted since the 1950s as part of international and collaborative efforts. A challenge in creating a homogenous magnetic data compilation for Antarctica arises from heterogeneity in data collection through the decades, for example from different flight lines spacing, different observation height and long time period between surveys. Traditional data processing is performed manually or semi-automated which is time consuming due to the factors described above.

Equivalent source technique is a powerful tool to automate the data processing to combine irregular airborne surveys on different observation heights and time periods. The magnetic field data from different airborne surveys can be represented by a set of equivalent sources that accurately reproduce the input data. The magnetic forward response of the equivalent sources can be calculated at any height making upward / downward continuation obsolete and allowing a uniform observation height between surveys. Furthermore, the magnetic field can be calculated on a regular grid, removing irregular flight lines from airborne data compilations. Combining the equivalent source method with despiking-, wavelet filtering-, IGRF/DGRF correction- and weighted distance base station correction routines allow a fully automated processing workflow to create a harmonised magnetic compilation containing irregular airborne surveys with decreased noise.

We present a test case in East Antarctica to highlight the potential of an automated processing workflow to harmonise magnetic airborne data without biases arising from manual processing. Here, we utilise ICECAP data (2009-2017) and RAE data (1956-1960) as well as the ADMAP data compilation grid as prior. The next step is to use ADMAP line data to create a fully automated homogeneous continent wide Antarctic magnetic data compilation under the SCAR ADMAP working group umbrella.