FLYMÅLING

NGU conducted an airborne geophysical survey in Forollhogna area, in Rennebu, Midtre
Gauldal and Holtålen municipalities in Trøndelag County, and Tynset, Tolga and Os
municipalities in Innlandet County, as part of NGU’s general airborne mapping program. The
data acquisition in Forollhogna area was carried out from June 23rd to July 20th, 2021.
This report describes and documents the acquisition, processing and visualization of the
acquired datasets and presents them in maps. The geophysical survey consists of 8214 linekm data, covering an area of 1609 km2, flown from the base near Orvos (Flight 1-38) and from
the base near Frigården (Flight 39).
The NGU modified Geotech Ltd. Hummingbird frequency domain EM system supplemented
by an optically pumped Cesium magnetometer and the Radiation Solutions 1024 channels
RSX-5 spectrometer mounted on a AS350-B3 helicopter were used for data acquisition.
The data collected were processed at NGU using Geosoft Oasis Montaj software. Raw total
magnetic field data were corrected for diurnal variation and leveled using Geosoft microlevelling algorithm. Radiometric data were processed using standard procedures as
recommended by International Atomic Energy Association (IAEA).
EM data were filtered and leveled using both automated and manual levelling procedures.
Apparent resistivity was calculated from in-phase and quadrature data for three coplanar
frequencies (880Hz, 6.6kHz and 34kHz), and for two coaxial frequencies (980Hz and 7kHz)
separately using a homogeneous half space model.
All data were gridded using cell size of 50x50 meters and presented as 40% transparent
grids with shaded relief on top of topographic maps.

Marine Base Maps for the Coastal Zone (Marine grunnkart i kystsonen) is a project aimed at producing user-oriented maps of the Norwegian coastal zone with a special focus on the seabed. In 2020, three coastal sites were permanently declassified to allow the acquisition of new types of datasets and the development of new methods to produce marine base maps. One of these sites is the seabed surrounding the Fjøløy and Klosterøy islands situated 25 km north of Stavanger. This report introduces the datasets that were acquired on this site between 2020 and 2022 for the purpose of method development. These include three airborne LIDAR surveys (including one from an Unmanned Aerial Vehicle), three airborne photography surveys leading to three orthophoto imageries, one airborne hyperspectral imagery survey, two multibeam sonar surveys (including one using Unmanned Surface Vessels), and a new set of ground-truth data from a variety of sensors including video transects, water sampling, and spectrometry. This report also summarizes pre-existing and relevant datasets on this study site, and introduces the preliminary methods developed to produce marine base maps from these datasets, whether from the contractors or the collaborators leading the project

NGU conducted an airborne geophysical survey in Røros, Trøndelag county as part of
NGU’s general airborne mapping program in 2020.
This report describes and documents the acquisition, processing and visualization of the
acquired datasets and presents them in maps. The geophysical surveys consist of 2584 linekm data, covering an area of 523 km2 flown between June 15th to June 22nd, 2020.
The NGU modified Geotech Ltd. Hummingbird frequency domain EM system supplemented
by an optically pumped Cesium magnetometer and the Radiation Solutions 1024 channels
RSX-5 spectrometer mounted on a AS350-B3 helicopter was used for data acquisition.
The survey was flown with 200 meters line spacing, azimuth 90o
. Average speed was
95 km/h, and average height clearance of the EM bird was 47 m and 77 m for the
spectrometer.
Collected data were processed at NGU using Geosoft Oasis Montaj software. Raw total
magnetic field data were corrected for diurnal variation and levelled using standard levelling
algorithm. Radiometric data were processed using standard procedures recommended by the
International Atomic Energy Association (IAEA).
EM data were filtered and levelled using both automated and manual levelling procedures.
Apparent resistivity was calculated from in-phase and quadrature data for three coplanar
frequencies (880 Hz, 6.6 kHz and 34 kHz), and for two coaxial frequencies (980 Hz and 7 kHz)
separately using a homogeneous half space starting model of 1000 ohm-m.
All data were gridded using cell size of 50x50 meters. Magnetic and radiometric data is
presented as 40% transparent grids with shaded relief on top of topographic maps. EM data is
presented as 30% transparent grids on top of topographic maps.

Aeromagnetisk kart over Norge 1:250 000

Aeromagnetisk kart over Norge 1:250 000

Aeromagnetisk kart over Norge 1:250 000

Det ble foretatt en geofysisk måling fra fly over et ca. 120 km2 stort område rundt Løkken. Det ble fløyet med en profilavstand på 400 meter og en høyde over bakken på 160 meter. Det ble målt magnetisk med et flux-gatemagnetometer og elektromagnetisk med et måleutstyr bygget av Geofysisk Malmleting. Resultatene er gjengitt som kart med en fotomosaikk i målestokk 1: 20 000 som grunnlag.

Målingene ble utført i 1959 og var nærmest en test av utstyret. Prosjektleder I. Aalstad.

Et område av ca. 65 km lengde fra Tvedestrand til Langesundsfjorden, fra kysten og ca 20 km inn i landet ble dekket med magnetiske målinger fra fly. Flyhøyden ble holdt på 500 fot og profilavstand var 500 meter. Resultatet er gjengitt som magnetiske kart i målestokk 1:25 000. Som topografisk grunnlag er benyttet en flyfotografisk mosaikk.