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Omega Navigation in the Shadow of Antarctica

Published online by Cambridge University Press:  21 October 2009

R. Barr  and
K. B. Young
R. Barr
Affiliation:
Physics and Engineering Laboratory, DSIR, Wellington, New Zealand
K. B. Young
Affiliation:
Royal New Zealand Air Force, Whenuapai, New Zealand
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Extract

1. INTRODUCTION. Very-low-frequency radio waves were used to implement the Omega navigation system because of their low attenuation (2–4 dB/1000 km) when propagating globally in the waveguide formed between the Earth and the ionosphere. However, it became apparent in the early seventies, throughout the period when the majority of the stations of the Omega network were commissioned, that VLF signals propagating over permafrost or glacial ice could suffer anomalously large attenuations, of greater than 20 dB/1000 km, especially during the daytime. In the Northern Hemisphere problems have arisen with the heavy attenuation of Omega signals propagating over the Greenland ice sheet. In particular a very bad region for Omega coverage occurs around Winnipeg in Canada (the ‘Winnipeg Hole’). In this area Omega North Dakota suffers from ‘near field’ effects, Omega Liberia is contaminated by trans-equatorial modal effects and Omega Norway is removed by the attenuation of its signals when crossing the Greenland ice-cap. There have even been discussions on the feasibility of constructing extra VLF transmitters in Canada to alleviate this problem.

Type
Research Article
Information
The Journal of Navigation , Volume 42 , Issue 2 , May 1989 , pp. 236 - 247
Copyright
Copyright © The Royal Institute of Navigation 1989

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References

REFERENCES

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