The Use of Relative Velocity Corrections in Carrier Alignments
NAVAL AVIONICS FACILITY INDIANAPOLIS IN INDIANAPOLIS
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The accuracy of an alignment of an inertial navigation system on a moving ship depends on the accuracy of the reference velocity available. The sensor obtaining this reference velocity is almost always located away from the navigation system being aligned suggesting that a relative velocity correction would be helpful. This is true when the sensor sees inertial velocity. When the source is an EM log which does not see inertial velocity, a relative velocity correction can either improve or degrade the reference velocity depending on the location of the source and the nature of the turn. With the appropriate data on how a ship turns it might be possible to find an empirical equation that could be used to correct EM log velocities to inertial velocities regardless of the nature of turn. The report gives the equations for making a relative velocity correction when the sensor is an inertial source, and also discusses the envelope of conditions under which these same corrections are helpful when the sensor is an EM log.