Measuring magnetic history at Godrevy Point ... by Anthony Swan on June 12, 2015 fluxgate magnetometer GOD Godrevy Point Grid Magnetic Angle magnetic field magnetic north magnetic variation Ordnance Survey +
How do smartphones work out what direction they are pointing? by Ciaran Beggan on November 14, 2013 BGS Ciaran Beggan geomagnetism gravity field magnetic field NOAA smartphone Swarm True North WMM +
