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RE: [PSUBS-MAILIST] Once again

Sorry that I haven't responded sooner as we have had a power outage for most of the day on the facility where I reside.


Not familiar with the Microstrain 3DM-GX1.  It appears that it is a 3-degree of freedom unit and for proper navigation 6-degrees of freedom are required…3 gyros (with low drift) and 3 accelerometers.  You can review the IMU 6-DOF v2 unit at www.sparkfun.com that I briefly glanced over.  They do not provide drift information and this is critical for determining the accuracy of your dead-reckoning.  If the drift of this unit isn’t bad, it still has to be integrated into a nav package and the mathematics aren’t inconsequential…major matrix manipulation.


I believe that there are sonar units that will provide SOG information but haven’t looked into the matter for some time.


Jay K. Jeffries

Andros Is., Bahamas




-----Original Message-----
From: owner-personal_submersibles@psubs.org [mailto:owner-personal_submersibles@psubs.org] On Behalf Of Sean T. Stevenson
Sent: Saturday, April 08, 2006 11:15 AM
To: personal_submersibles@psubs.org
Subject: Re: [PSUBS-MAILIST] Once again


Jay - how do the specifications of the $300 sensor you were looking at

compare to the Microstrain 3DM-GX1? Also, can an off-the-shelf sonar be

used to provide speed-over-ground?