 Check out the bookstore at IRBS.com |
|
|
|
|||||
|
||||||
Subject: Re: Digital Sextant
From: Vic Fraenckel (vfraenc1@XXX.XXX)
Date: Tue Apr 02 2002 - 08:41:30 EST
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@XXX.XXX
KC2GUI www.windsway.com
Home of the WindReader Electronic Theodolite
Read the WIND
|