Airborne geophysics

The Earth’s magnetic field intensity was measured from an aircraft in spring 2008. The purpose was to study in particular the rock structures in areas covered by the sea.

 

The surveys were carried out from aircraft flying as low as at 30 metres. The plane flew in the Eurajoensalmi area along 5 to 10 km long measurement lines set about 50 metres apart. The sampling rate of the measurement instruments was several times a second which produces a sampling interval of few tens of meters along the line. The direction of the measurement lines was chosen on the basis of geological features. The measurement flights were organised by Geological Survey of Finland (GTK) and implemented in cooperation with the Finnish Aviation Academy.

The airborne measurements allow, for example, delineating boundaries of different rock types and detecting discontinuities in geological units caused by deformation zones in bedrock. Different rock types have different magnetic properties and the variation can be detected by measurements.

The area has been included in 1989 in Geological Survey of Finland national programme, using the same aircraft and survey techniques. A local helicopter survey on the Olkiluoto Island, one of the first carried out in Finland, was conducted by Suomen Malmi Oy in co-operation with a Canadian company Scintrex Ltd. The aim of the new survey in 2008 was to achieve better accuracy because the methods, positioning technology in particular, have advanced considerably in twenty years.