Re: [PSUBS-MAILIST] More on inertial guidancce

["Paul Suds" <paul_suds@hotmail.com>]

I would think that it would be very easy to determine distance from the ship 
mathematically. The distance from the ship at a point directly below the 
ship and on the same horizontal plane as the sub could be easily determined 
based on the distance from the ship to the sub (hypotenuse), and the 
distance of the sub to the surface of the water (adjacent side). The sub 
would then be at the opposite side distance, from the point directly under 
the ship on the same horizontal plane as the sub. Acoustically, and using a 
differential amp, you could determine the distance from the surface of the 
water and from the ship. Is this how the tracker works?  You'd have to 
figure in a Z coordiante to complete this algorithm though, otherwise you 
would end up with a location anywhere in a 360 degree radius of the ship. 
I'm sure the acoustics would be collimated in degree or radians to give you 
that last variable. This is quite simple when you think about it. I have 
experience with lasers thickness devices based on reflectance times and 
refractive indexes times and the associated electronics, but I have no 
experience with the ultra or sonic transducers used for this purpose. What 
frequency do these transducers usually operate at. Are they modulated in any 
way, and do they use doppler or just time differnce for distance?
Suds
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