Analogue aeromagnetic surveys of Great Britain for the Geological Survey (GSGB), subsequently digitised. Commercial Analogue survey of North Sea by Aerosurveys Inc, subsequently digitised by BGS. Commercial digital (+ one analogue) surveys off NW/N/NE of Britain by Huntings Geology and Geophysics and ESL, purchased outright by BGS. Local surveys, digital and analogue aeromagnetic (+ other methods) surveys for BGS and commercial companies. Data acquired over many years by different companies. Surveys vary from High Resolution helicopter covering a few square kms to regional surveys covering 1000s of square kms. Some data recorded analogue, subsequently digitised, other data full digital capture with GPS navigation. Approximately 75% of the bounding rectangle covered. Flight line separation varies between 2km and 0.4km, line spacing typically 2km over UK but 0.4km over Devon/Cornwall. Flight line separation for Aerosurveys/Huntings surveys vary between 6.4 to 15 km. Detailed surveys at various resolutions. Along line spacing varies, analogue data: digitised from 1:63 360 and 1:253 440 scale map sheets and digital surveys: Decca navigation, 305m asl (above sea level). Local helicopter surveys, analogue and digital recordings, various survey heights. HiRES survey, full digital data capture at 0.1 sec intervals, GPS navigation, 90m survey height.