Re: [PSUBS-MAILIST] Once again

["Sean T. Stevenson" <cast55@telus.net>]

I was toying with the idea of a relatively low cost inertial navigation 
system using a 3DM-GX1 sensor from Microstrain.  Essentially, GPS would 
provide a position reference when surfaced, and the inertial system 
would take over once GPS position data is lost.  Of course, with an 
inertial system, error accumulates the more time elapses between GPS 
positions, but then some sort of hybrid GPS on a tether like you 
describe could limit that error to a maximum of the current submersion 
depth.  Realistically though, I think that sonar in conjunction with 
bathymetric maps are more reliable than electronic dead reckoning.

-Sean


George Slaterpryce wrote:

> Once again I come unto you the great PSubbers community with my 
> Thoughts, Musings and questions. Ye, Verilly... or something.
>
> First thought, Problem, location underwater. How to ascertain the 
> exact (or as near as exact) location of an object under water such as 
> a sub. Problem is I don't know how deep you can reliabley get a GPS 
> signal. So I thought of this solution that may not be the most elegant 
> but I think it would get the job done pretty well.
>
> GPS Bouy on a teather released form depth to the surface.
> You know the depth to the surface, so whatever line you released over 
> the depth would be your varience. From there you could get the GPS 
> location, calculate two more points on a circle path, then find the 
> center point of that, which would give you your GPS location. 
> (Illustration below)
>
> (or if you can't see them) 
> http://www.captovis.com/marine/designsketches/uwloco.png and 
> http://www.captovis.com/marine/designsketches/uwloco2.png
>
> Seem like a good idea to anybody else? comments? Detractions? 
> Improvements?
>
> George Slaterpryce






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