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Date: Tue, 01 Jan 2008 15:49:33 -0500
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From: "rtitsworth" <rtitsworth@mindspring.com>
References: <list-2626169@logan.com>
Subject: First dumb question of the year...
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Happy new year,

So, I was sitting around thinking silly thoughts (when I probably should
have been building) and it occurred to me that gyroscopic instruments
essentially attempt to maintain a constant reference frame (in space) from
which to measure changes in attitude, heading, etc.  So, over time,
shouldn't the rotation of the earth cause the gyro to indicate a change
(error) relative to earth's horizon.  i.e. An attitude indicator in an
airplane sitting on the equator and facing west (or east) should
progressively pitch up (or down) at about 15 degrees per hour
(360deg/24hrs).  That's a bunch.

Likewise, the attitude indicator of a south (or north) facing airplane on
the equator would indicate a roll at the same rate.  Likewise, the DG of an
stationary airplane sitting at the north (or south) pole would react
similarly.  Likewise, at all other latitudes and orientations a mix of the
above effects would seem to be at play.

Hmmmm.  Any insights?

For BrentR, AHRS work differently (by measuring and integrating changes in
accelerations over time???), but it seems they would ultimately be subject
to the same effect?

Rick Titsworth