AIRBORNE GEOPHYSICS

/ WRITTEN BY MARIE-ANDRÉE DUMAIS

The Geological survey of Norway (NGU) has carried out airborne geophysical surveys since 1958.

Initially, magnetic measurements were acquired with a towed-magnetometer from a fixed-wing aircraft covering both onshore and ofshore regions of Norway and its continental shelf. In 1972, a program for higher resolution helicopter-borne geophysics was started with the aim to densify the coverage and including other geophysical methods. Additionally, the fxedwing acquisition continued with more instrumentation possibilities.

Today, a typical airborne acquisition includes magnetic, electromagnetic and radiometric measurements. The target survey height is 60 m above the ground. NGU owns several geophysical instruments and equipment certifed for airworthiness. Thus, the instrumentation and the survey design are adjusted to the geological target requirements. Reports and geophysical data are available and can be downloaded from the NGU website (www.ngu.no).

During the last 50 years NGU has carried out high resolution airborne surveys for bedrock mapping, mineral and petroleum exploration, and environmental studies both in Norway and in neighbouring countries. Examples of environmental applications are the mapping of man-made Caesium deposition, weakness zones in the bedrock and Radon hazards.

NGU is the central national institute for knowledge of the bedrock, mineral resources, superfcial deposits, Quaternary Geology and groundwater of the mainland of Norway. Apart from the oil industry, NGU is the largest environment for geology and geophysics in Norway.

AIRBORNE SURVEY COVERAGE ONSHORE AND NEARSHORE

Fixed-wing aircraft

Rotary-wing aircraft