MEMORANDUM
To: Members And Friends
NFB R&D Committee
From: T. V. Cranmer, Director of Research
Subject: Compass
Date: January 31, 1995
A few days ago Mr. Chong suggested development of a "non-magnetic"
compass should be added to our list of research priorities. I take
this suggestion to mean that the compass should not employ a
magnetic needle or similar mechanical means of seeking north. A
flux gate compass does not rely on a magnetized element, and the
guys at Smith-Kettlewell have produced a working model of a flux
gate device with audible tones that indicate orientation with
respect to the Earth's magnetic field. Even though this device
does not use a needle magnet, it still suffers inaccuracies
resulting from local distortion of the geomagnetic field induced by
large metal structures and some electronic equipment.
Thinking of these matters reminded me of the laser gyroscope made
by Honeywell exhibited at the meeting of the Global Positioning
systems group of the IEEE where I recently presented a paper. This
high-tech replacement for the old mechanical gyros features long
term stability. That is, it does not process. It seems reasonable
to assume that this gyro could be set on north and thereafter
detect changes in orientation. Even though it is not suppose to
process, you might want to recalibrate every hundred years or so,
or every time your battery ran down--which ever came first.
The laser gyroscope is now used in sophisticated guidance devices
on the ground and in space. No doubt it could be used to produce
an exquisite orientation device for the blind. The barrier to
building such a device is likely to be economic rather than
technical.
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