Fróðskaparrit - 01.01.1971, Side 14

22
Magnetic Anomalies Around The Faeroe Islands
Hydrographisches Institut; I want to thank the institutions
mentioned above for their very valuable cooperation.
Presenting the measurements and their interpretation I want
to emphasize that it has been a reconnaissance survey, which
has given more hints than facts; to give a complete inter-
pretation of the magnetic anomalies around the Faeroe Islands
a much denser net of measurements is required.
Survey Operations
Fig. 1 shows the sailing routes where the magnetic total
field was measured. The survey ship was “Ole Rømer” a 65
tons wooden cutter. The navigation was done in the classical
way, every ten minutes bearings were taken to outstanding
landmarks; as survey lines never were far from the islands,
good landmarks were always to be found, and the navigation
uncertainty is believed to be within 200 metres.
Total geomagnetic field intensity measurements were ob-
tained by an ELSEC Proton Magnetometer Type 592. The
magnetic readings were taken on strip chart recorder, where
for practical reasons a full scale value of 2000 was used, which
means that the measurements were obtained with a uncer-
tainty of 20 gammas.
Due to hard weather the speed of “Ole Rømer” varied (from
5 to 30 km/hour). The lack of digital recording and the
mentioned speed variation make it very difficult and laborious
to present the measured profiles in a proper way.
No attempts have been done to remove the main geomagne-
tic field from the total intensity data. This task was not found
necessary as I do not want to present a contour map of the
magnetic data. A contour map would be quite unrealistic due
to the great distance between the profiles.
In the profiles presented corrections for the daily geomag-
netic variations have not been applied as the daily variations
measured north of Tórshavn in Hoyvík usually had wave-
lengths of several hours and amplitudes of less than 200
gammas during the survey.