Re: [PSUBS-MAILIST] More on inertial guidancce

[SJSVOB@aol.com]

NMEA GPS serial data looks like the following:

$GPGGA,135150.00,3838.6729,N,09015.4367,W,1,03,4.2,156.3,M,,M,,*66

I can't remember what all the data is offhand, the latitude and longitude is 
obvious, 156.3 is the altitude, in there somewhere is the number of 
satellites currently tracking.  I might have taken that snapshot before my 
Motorola Encore GPS unit locked on to all the satellites available.

Ratheon has some modular components which communicate with one another using 
Ratheon's SeaTalk technology:
http://www.raymarine.com/products/index/instruments/index.html

Check out the ST80.  It has a dead reckonening mode.  I would think this 
system would be great for psubs.  When you lose the GPS satellites the system 
would probably just switch to dead reckoning mode.  I wonder how hard it 
would be to put the transducers outside the pressure hull and not have them 
get destroyed.

I was thinking it might be interesting to construct a device which would sit 
between the GPS unit and the SeaTalk network.  The device could accept NMEA 
info from a GPS, or create it's own information, and then send it through to 
the SeaTalk network.  That device could be capable of determining position 
based on the acoustic links being described in this thread.

You could add a 3-d bathymetric charting solution in there, but I don't think 
it would be capable of pinpointing your 3D position, only your position 
relative to the surface.  I don't think manufacturers of systems like SeaTalk 
envisioned them being taken to the depths.  For that additional "feature" you 
probably have to pay big time.

I'd be interested in discussing these ideas further?  Anyone have any reason 
to think this system would or wouldn't work?

Stephen Svoboda