Further by downloading this data the user acknowledges that they agree with the NERC data policy (), and the following conditions:

1. To cite the data in any publication as follows:

Jordan, T., Lowe, M., Robinson, C., Reed, T., & Toomey, R. (2024). Processed aeromagnetic line data flown from Rothera station with a Windracers Ultra UAV (2023/24 season) (Version 1.0) [Data set]. NERC EDS UK Polar Data Centre. https://doi.org/10.5285/4bcc9b4e-fab5-46cd-aac3-56c28e61cff1

2. The user recognizes the limitations of data. Use of the data is at the users' own risk, and there is no warranty as to the quality or accuracy of any data, or the fitness of the data for your intended use. The data are not necessarily fully quality assured and cannot be expected to be free from measurement uncertainty, systematic biases, or errors of interpretation or analysis, and may include inaccuracies in error margins quoted with the data.

Methodology:

The magnetic sensor was mounted in the payload bay door of the Ultra, meaning the sensor sat ~1.5 m behind the payload bay when the door was closed. This location was chosen as other areas far from the core electronic systems and engines, such as wing tips and tail, housed electronically activated control surfaces, which would likely generate unacceptable levels of noise. Magnetic data was collected with a GEMSys GSMP-35U UAV magnetometer. Data were logged at 10 Hz, and included GPS derived time and position, total magnetic field (nT) as well as x, y and z fluxgate magnetometer information and roll, pitch, heading information from a small Inertial Navigation System (INS) mounted on the aircraft floor.

A magnetic base station, deployed close to Rothera Station, was used to correct for diurnal variations of the magnetic field. Prior to use the base station values were subject to the following corrections: i) DC correction to remove steps, associated with adjusting the base station support. A DC correction allows application of a uniform correction of a set value across the dataset ii) The base station data was detrended by a polynomial trend order of 8 to remove residual trends and the absolute average total field value. Iii) The data was then filtered by a mean filter with a window width of 40 (10 minutes) to remove residual high frequency noise. The base station data is also provided here for reference.

The raw airborne magnetic data was initially cleaned by manually removing extreme outliers and spikes. Next the magnetic data was filtered with a statical mean filter with a window width of 10 (1 second). Magnetic compensation was applied to account for adjustments of the UVA in term of aircraft roll, pitch and yaw, based on data from a triad of fluxgate magnetometers, also de-spiked and filtered at 1 second. Compensation was carried out in the software Aeromagnetic Compensation Postprocessing Application from GEMSys.

After compensation the total field magnetic survey data was corrected for the core field using the 2020 IGRF model, implemented in the Geosoft Oasis Montaj software. The magnetic data was levelled against ADMAP-2. Levelled ADMAP-2 data include a magnetic survey flown perpendicular to the SWARM survey. The ADMAP data was flown on two different altitudes at 2440 m and 1220 m. Therefore all data from SWARM and ADMAP-2 were upward continued to a constant altitude of 2440 m. Iterative levelling combined with removal of large outliers at the cross tie was applied until a satisfactory result (no artifacts in flight lines direction) was achieved. The levelled magnetic product was subtracted from the upward continued line data consisting of ADMAP-2 and SWARM data to obtain the levelling coefficients. Those coefficients are subsequently added to the SWARM line data at the original altitude. In doing so, the SWARM survey is levelled against ADMAP-2, while retaining the higher resolution that is achieved by a significant lower altitude.

Data collection:

Sensor(s): GEMSys GSMP-35U UAV magnetometer

Platform(s):UAV - Windracers Ultra TD-02

Data quality:

After levelling the crossover error was 37.7 nT.

Data has 2 km line spacing. Along track resolution may be higher, but is limited by the distance to the nearest magnetic sources (>500 m).