DOI: 10.5285/eb6bf8df-ea87-4c3c-8f27-33fa8d5ac663
title: Processed line aeromagnetic data over the Thwaites glacier region (2019/2020 season)

description: Aeromagnetic data provides important constraints on the sub-surface geology of a region. This dataset contains aeromagnetic line data collected by the British Antarctic Survey during the second aerogeophysical survey carried out as part of the International Thwaites Glacier Collaboration (ITGC). Data were collected using a caesium magnetometer system, and have been corrected to total field values following the approach laid out by the SCAR ADMAP working group (https://www.scar.org/science/admap/about/). In total 8688 km of data is presented, of this ~6052 km was collected in the main survey area, while other data was collected on input transit flights. The aircraft used was the BAS aerogeophysicaly equipped twin otter VP-FBL. Data are available as an ASCII table (.csv). The Thwaites 2019/20 aerogeophysical survey was carried out as part of the BAS National Capability contribution to the NERC/NSF International Thwaites Glacier Collaboration (ITGC) program. Data processing was supported by the BAS Geology and Geophysics team.
description: Raw line aeromagnetic data from the December 2019 ITGC airborne survey were initially corrected for the regional geomagnetic field (IGRF), and compensated for aircraft motion. Compensation coefficients were calculated from a calibration flight flown ~500m above the Lower Thwaites Glacier field camp during the previous season, and are therefore not optimal. The dataset may benefit from a low pass filter to remove residual noise due to aircraft dynamic motion. Diurnal variations in the magnetic field were recorded at 30 second intervals using a base station at Lower Thwaites Glacier field camp. Base station corrections were calculated by subtracting the local mean base station value across the survey from the recorded base station values. The base station corrections were then filtered with a 30 minute filter to ensure short wavelength signals, likely only seen at the base station, were not transferred to the airborne dataset. No base correction was applied to any of the transits, or initial calibration flights. An additional Tip Tank correction was made to remove the offsets induced by aircraft operational procedures such as pumping fuel. This correction is generally restricted to turns and transits, as data quality is worse during these times, and users may wish to consider discarding this data. DATA FORMAT: Data are provided in ASCII file format (.csv). The data set includes the following channels: FlightID: Sequential survey flight number from T1 to T17. x: coordinate (m) Polar stereographic true scale -71 y: coordinate (m) Polar stereographic true scale -71 Lon: Longitude DDD.DDDDDDDD Lat: Latitude DD.DDDDDDDD Height_WGS1984: Elevation on the WGS1984 ellipsoid (m) Date: Date YYYY/MM/DD Time: Time (GPS) HH:MM:SS.SSSSS MagR: Raw total field magnetic data (nT) MagC: Compensated total field magnetic data (nT) RefField: IGRF correction (nT) TCorr:Tip correction (nT) MagRTC: Mag after IGRF, compensation and tip correction (nT) Bcorr: Base station correction with 30 minute mean filter (nT) MagBRTC: Mag after all corrections (nT)
description: Data was collected using the BAS aerogeophysically equipped twin otter VP-FBL. Magnetic data was collected using wing tip mounted Scintrex CS-3 High Sensitivity Cs magnetometers. Only data from the magnetometer with the lowest noise characteristics is reported here. Data was recorded at 10 Hz on a PicoEnvirotec logging system. Additional base station information from proton procession magnitomiters set up as base stations and recording 1 sample every 30 seconds was used during data processing.
description: After the basic processing presented here the standard deviation of the crossover errors within the ITGC survey was 14.83 nT. The line spacing for the survey is variable between 5 km and 10 km. Line data is generally designed to interleave with existing AGASEA data. The provided data is sampled at 10Hz, which equates to a 6m along track sample spacing. A ~1Hz sinusoidal signal is recognised in the data, and application of 3 second (18 m) low pass filter is therefore recommended. The true usable resolution of this dataset is proportional to the depth to source, which is typically 750 to 1500 m.