Re: [gpsd-dev] Planning a 3.11 snap release

[Gerry Creager - NOAA Affiliate]

On Tue, Nov 26, 2013 at 12:38 PM, Eric S. Raymond <address@hidden> wrote:

Greg Troxel <address@hidden>:

> Also, let me know what kind of GPS receiver and antenna works for
> submarines.   I am actually curious how far under water it might work,
> but I bet it's at most a few meters.

Yes, I'm told you can get GPS signals several meters down.  The way these
nav sytems are designed is to nearly surface to get position fixes, then
dead-reckon using thrust calculations and accelerometers in deeper water.

Maybe. But not too deep. Were I to bet, I'd bet they come to periscope depth, and there's a GPS antenna atop the 'scope. Or, they release a tethered bouyant antenna.

 

Additionally, I'd bet money that the military uses lidar on seabed
features to tell how actual velocity differs from dead-reckoned. It's
what I'd do.

I've not heard of lidar at those depths, and I suspect the optical extinction is killer but I guess it's possible.

 

--
                <a href="" href="http://www.catb.org/~esr/" target="_blank">http://www.catb.org/~esr/">Eric S. Raymond</a>

-- 

Gerry Creager

NSSL/CIMMS

405.325.6371

++++++++++++++++++++++

“Big whorls have little whorls,

That feed on their velocity; 

And little whorls have lesser whorls, 

And so on to viscosity.” 

Lewis Fry Richardson (1881-1953)