Aeromagnetic anomaly map of Finland

The Geological Survey of Finland (GTK) has carried out systematic aerogeophysical low-altitude surveys during the period 1972-2007. The flight altitude (main terrain clearance) has been 30-40 m with a nominal flight line spacing of 200 m. The standard flight lines chosen run North-South and East-West and follow the main geological trends. The distance between the measuring points along the survey lines has been 6-50 m. The geophysical parameters measured include Earth's magnetic field, the electromagnetic field and natural gamma radiation. Magnetic measurements determine the Earth's magnetic field strength (magnetic flux density), and the parameter obtained is the total magnetic intensity. The measurements have been made with one to three proton magnetometers until 1991 and thereafter with one or two cesium magnetometers. Most of the land area has been flown using two magnetometers.