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Sky Twilight Compass

After the last war the British and Americans became interested flying across the Arctic. Because of the long twilight of high latitudes, no heavenly bodies may be visible for direction or position checks for an extensive period.
New instruments had to be invented and new techniques to be developed.
The Pfund Sky-Compass (1948) is one of the most important inventions in this field, for it enables the navigator to measure the direction of the sun and to take course corrections from the sun when even it is below the horizon, by means of the polarized light in the sky. The Greenwich Grid system and the gyro compass are, of course, the basis of polar navigation, for the magnetic compass is useless over great areas around the North Magnetic Pole.
In 1949 non-stop flights from Fairbanks (Alaska) to Oslo (Norway) and from Bardufoss (Northern Norway) to Fairbanks were done. (Polar Route - North-West Passage to make History again: Practical Stages for Commercial Flights by Einar Pedersen)

In 1954 Scandinavian Airlines (SAS) began the first scheduled passenger flight between Copenhagen (Denmark) and Los Angeles, the world’s first Polar shortcut, the new route cutting the travel time between California and Scandinavia from 36 hours to 22 hours.
SAS made further improvements and used the Sky Compass for many years on their polar flights.

Gyro compass receiving its directive force from a gyroscope operated by electric motors.

Polar
                    route




 

My Sky Compass experiments



Web Links

Flightglobal 1992:
Polar Route - North-West Passage to make History again: Practical Stages for Commercial Flights by Einar Pedersen

Alasca Sciens Forum: Polar Navigation and the Sky Compass (1988)

Precision Astrolabe, Portuguese Navigators and Transoceanic Aviation

Air navigation in high latitudes

Non-conservative Rayleigh scattering in a finite atmosphere
I - Polarisation of skylight

An Analytical Model for Skylight Polarisation

Digital imaging of clear-sky polarization

Navigation im Nebel

Polarization singularities in the clear sky

A Sky Compass for Field Use

The Skylight Compass Card

Pye: Polarised Light in Science and Nature

How the clear-sky angle of polarization pattern continues underneath clouds: full-sky measurements and implications for animal orientation

Spottiswoode: Polarisation of light (1883)



Updated: 2009, Mar 28