THE AEROMAGNETIC SURVEY PROGRAM OF THE GEOLOGICAL-SURVEY-OF-CANADA - CONTRIBUTION TO REGIONAL GEOLOGICAL MAPPING AND MINERAL EXPLORATION

The aeromagnetic survey operations of the Geological Survey of Canada (GSC) began in 1946. utilizing a magnetometer in a bird system towed b y a Royal Canadian Air Force Anson. Subsequent early operations were c arried out by the GSC-operated Canso and Aero Commander aircraft. In 1 961, the GSC in-house survey team formed the nucleus of a contract sur veys group set up to monitor a new program established to complete the aeromagnetic mapping of the Canadian Shield in 12 years on a cost-sha ring basis with the provinces. Today, surveys are carried out under co ntract by light twin-engine aircraft such as the Cessna 404 and even, in some cases, single-engine aircraft that utilize compact computer-co ntrolled data acquisition and navigation systems and inboard magnetome ter installations. Early systems were capable of resolution of only a few nanoteslas (nT) compared to the current standard of 0.1 nT or less , and flight path positioning with 35 mm film and photomosaics or topo graphical maps was extremely challenging. Despite these limitations, t he careful selection of survey parameters and attention given to quali ty control have resulted in a world-class aeromagnetic data base that has contributed significantly to regional geological mapping and to mi neral and oil exploration in Canada. Concurrently, the GSC carried out research programs into the development of instrumentation and into pr ocessing, interpretation, and enhancement techniques. In 1968, the GSC acquired its own platform, a Beechcraft B80 Queenair, which was used to develop high-sensitivity techniques, and an inboard gradiometer sys tem, which was transferred to private industry in 1983. The GSC, in co operation with the Flight Research Laboratory of the National Research Council of Canada, has also conducted a program of research into magn etometry and navigation combined with aeromagnetic studies of the Arct ic since 1962.