|Polar compasses have followed a well defined and straightforward line of development which conforms closely to the state of the art development; more so perhaps, than most other instrument development. It has, of course, long been known that the earth’s magnetic field is either unreliable or unusable as a directional reference in the polar regions, and the need for suitable substitutes has been ever present. True heading can and has been measured by use of the pelorus for determination of the bearing of the sun by day and stars by night, and applying this value to the computed azimuth of the celestial body. This method is slow and generally may involve on-the-spot computation. The pelorus has been superseded in aircraft by the astrocompass which is simply a pelorus built around a mechanical analogue computer and hence gives true heading directly. In the interest of simplicity, the original astrocompass was quite crude and inaccurate. Recently developmental models have been made of precise instruments, precision being obtained by better optics and more accurate scales.
|NAVIGATION: Journal of the Institute of Navigation, Volume 4, Number 3
|136 - 138
|Cite this article:
|Burka, Samuel M., "POLAR COMPASSES", NAVIGATION: Journal of The Institute of Navigation, Vol. 4, No. 3, 1954, pp. 136-138.
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