novice
Posts: 90
Joined: Tue Aug 07, 2012 2:55 pm

The Concept Of Apparent Wander?

Tue Jan 08, 2013 6:32 pm

Abstract:

"If the DI instrument is fitted with a latitude nut, it produces an opposite error to the earth's rotation (i.e., 15 x sin latitude in degrees per hour) to give an adjusted heading. If, however, the aircraft was moved away from the latitude at which the lat nut was set, then error, either positive or negative, would arise because the degree of apparent wander varies with latitude; i.e., it increases toward the poles."

Basically i'm wondering why it increases towards the poles, i understand that apparent wander is a change in orientation of the gyroscopes spin axis due to the rotation of the earth. Is it because as the DI is aligned to true north, true north is changing quicker at higher latitude?

Thanks
 
WingedMigrator
Posts: 1770
Joined: Wed Oct 26, 2005 9:45 am

RE: The Concept Of Apparent Wander?

Thu Jan 10, 2013 12:16 am

I know nothing about this equipment, but the physics can easily be guessed at...   

At zero latitude, the gyro spin axis is aligned with the earth's rotation axis and is thus unaffected.
At the pole, the gyro spin axis is normal to the earth's rotation axis and changes by 15 deg/hour.

For an observer fixed on the earth's surface the direction of true north changes in inertial space, and does so faster at higher latitude.
 
novice
Posts: 90
Joined: Tue Aug 07, 2012 2:55 pm

RE: The Concept Of Apparent Wander?

Sun Jan 13, 2013 1:17 pm

Thanks for the explanation 'WingedMigrator'   

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