This aeromagnetic survey was carried out by Geo Data Solutions GDS Inc. from January 12, 2018 to March 16, 2018. The data were recorded using split-beam cesium vapour magnetometers mounted in the tail booms of a Beechcraft King Air and a Piper Navajo. The nominal traverse and control line spacings were 400 m and 2400 m, and the aircraft flew at a nominal terrain clearance of 150 m. Travers lines were oriented N45°E with orthogonal control lines.

This map of the first vertical derivative of the magnetic field was derived from data acquired during an aeromagnetic survey carried out by Fugro Airborne Surveys during the period April 17, 2006 to August 26, 2007. The data were recorded using a split-beam cesium vapour magnetometer (sensitivity = 0.005 nT) mounted in the tail boom of a Cessna Caravan aircraft. The nominal traverse and control line spacings were, respectively, 800 m and 2 600 m, and the aircraft flew at a nominal terrain clearance of 250 m. Traverse lines were oriented N30degreesE with orthogonal control lines. The flight path was recovered following post-flight differential corrections to the raw Global Positioning System data and inspection of ground images recorded by a vertically-mounted video camera. The survey was flown on a pre-determined flight surface to minimize differences in magnetic values at the intersections of control and traverse lines. These differences were computer-analysed to obtain a mutually levelled set of flight-line magnetic data. The levelled values were then interpolated to a 200 m grid. The International Geomagnetic Reference Field was not removed from the magnetic total field. The first vertical derivative of the magnetic field is the rate of change of the magnetic field in the vertical direction. Computation of the first vertical derivative removes long-wavelength features of the magnetic field and significantly improves the resolution of closely spaced and superposed anomalies. A property of first vertical derivative maps is the coincidence of the zero-value contour with vertical contacts at high magnetic latitudes (Hood, 1965).