Re: [PSUBS-MAILIST] Re: Snow White virus

["Sean T. Stevenson" <ststev@uniserve.com>]

How much room do you have in your sub?  As far as DR is concerned, I like to lay out a chart and use a pencil...  Assuming you have an electronic solution in mind, are you talking about a GPS unit 
or some sort of ECS?  Electronically I can see using a fluxgate compass and external knotmeter to provide NMEA info on course and speed, with the GPS overriding when the signal becomes 
available (when you are surfaced).  Adjustment for current would need to be made according to a tide/current atlas, but the information in these publications is generally surface oriented.  How much 
of a discrepancy will there be at depth?  As for staying out of the way of traffic - you're in a submarine... just who are you expecting to run into?

-Sean


On Thu, 01 Mar 2001 18:49:01 -0500, Michael B. Holt wrote:

>"Sean T. Stevenson" wrote:
>> 
>> Perhaps  you could explain exactly what your intent is...  DR
>> navigation while submerged with brief surface intervals to update
>> your position via GPS, or continuous submerged electronic navigation?
>
>Continuous would be good, but it's not necessary.
>
>> The latter can be accomplished by combining (correcting?) the NMEA
>> data from the GPS receiver with acoustic positioning of the receiver
>> relative to the sub.  DR can also be supplemented by inertial
>> navigation, although that can be a bit expensive. 
>
>Yeah, let's avoid "expensive."  Acoustic position of a buouy is
>a bit more complicated and expensive than I had in mind, too.
>
>What I had in mind is a DR track that was corrected by GPS
>checks every hour or so, depending on known currents and the
>like.  I don't expect this can be hard to do; it's probably
>already out there.  I would expect to find that sort of system
>built into high-end GPS units.
>
>> What sort of accuracy do you need?
>
>Just good enough to stay out of the way of traffic that can be
>expected.  It's not like I'd ever need to know where I was within
>ten feet.
>
>I suppose we'd have to call it Snow White navigation, now ....
>
>
>
>Mike