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Dan Allen wrote:
| I wonder what kind of silicon sensors exist that act as artificial
horizons,
| and what kind measure angles, and how accurately?  The digital compasses
| recently referred to are accurate to 2 degrees.  For a sextant the angle
| needs to be measured to a few seconds of arc to be competitive.

In discussing the Digital Sextant, one must NOT confuse a digital compass
with the method of measuring altitude. A sextant is NOT used to measure
azimuth so to quote the accuracy of a digital compass module as an argument
against the possibility of building a Digital Sextant clouds the issue. I
have personally used digital optical encoders that can measure an angle to
360/4096 degrees = 0.088 degrees = 5.27 minutes. The encoder resolves 360
degrees into 4096 counts. While this does NOT come close to what would be
needed to make the Digital Sextant, it is a device I am familiar with. There
exists encoders that have even higher resolution.

There also exists a integrated circuit device (Analog Devices ADXL202) which
can measure it's own relationship to the the earth's gravitational field and
who's output is a measure of the angles it makes with the gravitational
field in two axes.  I have used this device as well..

I have interfaced both devices to a microcontroller with ease and made
useful measurements with them. Perhaps a Digital Sextant is not so far
fetched after all!

Vic
________________________________________________________

Victor Fraenckel - The Windman                 vfraenc1@nycap.rr.com
KC2GUI                                                      www.windsway.com

      Home of the WindReader Electronic Theodolite
                               Read the WIND

   

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