[PSUBS-MAILIST] Underwater Navigation

Sat Aug 31 21:40:02 EDT 2019

Hi Alan, when I dove with Hank in the Gamma at Flathead lake, I used a
navonics program on my phone. Pinned our gps locatation before the dive.
Checked our general heading. At that moment I had a detailed map of what
was below us. Upon nearing the surface the phone reaquired the signal and
pinned our current locatation. Which I could see our distance traveled, and
the time of the dive duration. Most of the time we traveled in a relative
straight line, but sometimes we circled back on our own cloud of dust. That
being said,  hank also tows a buoy line with trawler floats. I'm thinking
that if the buoy line could be a carrier of the gps locator it could be
fairly cheap system with a decent tracking system. The navonics system had
some nice features im looking into. At least I would would know where im
at.  If i could transmit that to the surface vessel on the same buoy line,
so would they.

Just a thought.
David

On Sat, Aug 31, 2019, 4:06 PM Alan via Personal_Submersibles <
personal_submersibles at psubs.org> wrote:

> River,
> thanks for that, you obviously know this stuff.
> A few more thoughts have come to mind on my system, appreciate your
> thoughts.
> We could use 3 or 4 off the shelf transducers from a depth sounder system,
> hung 10 meters below buoys. Each having their own electronics enclosure,
> with GPS & electronics to transmit the GPS data acoustically to the
> submarine.
> The submarine transducer receives the signals which are analysed for their
> distance & GPS position then trilaterates it's GPS position based on these
> &
> it's depth. This GPS position is fed to the off the shelf boat chart
> plotter so we
> can visualise our position on a bathymetric chart, & chart our dives,
> logging way
> points of interest. We can also print out data on return.
> The subs GPS coordinate can be transmitted to all the buoys ( in case one
> is closer
> than the others) and this can be transmitted to the support boat.
> The cost would be 4 buoys, 5 transducers, batteries, maybe 5 arduinos or
> Similar, & a chart plotter. ( & hours of electronics & coding)
> I like the idea of transducers hung under the water as there is less
> chance of
> the signal being obstructed than with a seabed based system.
> It could be a plug & play system that could be shared among subs.
> Alan
>
>
>
> > On 1/09/2019, at 9:45 AM, River Dolfi via Personal_Submersibles <
> personal_submersibles at psubs.org> wrote:
> >
> > That type of system, with several transponders with known location
> communicating with the submersible is known as a "Long Base Line" system,
> or LBL. That was the state of the art before GPS. Typically, dynamically
> positioned drilling rigs would hold themselves on position based on
> feedback from LBL transponders installed on the seafloor (often by manned
> submersible) providing more reliable and accurate positioning than Loran C
> was capable of. Now you would just use GPS.
> >
> > Today, Universal Short Base Line (USBL) systems are more common. A
> surface mounted hydrophone unit transmits an activation ping to an smart
> beacon attached to the undersea item to be tracked. Upon receiving the
> activation ping, the beacon transmits a timestamp and a depth back to the
> surface hydrophone. Using a reference speed of sound in water, the total
> travel time of the signal, , bearing of the signal, and the depth reported
> by the beacon, the topside unit can calculate the relative position of the
> subsea beacon (or multiple beacons) which can be interfaced with a GPS
> receiver on the topside unit, and provide a UTM coordinate and depth for
> the subsea item to be tracked.
> >
> > This is all fine and good for tracking an ROV, where the operator and
> the surface unit are at the same location. Navigating a sub using a USBL
> system requires specialized acoustic modems to transmit the UTM data back
> down to the submersible, and then some type of computer to display it all.
> >
> > There is no need to mention how ludicrously expensive (and heavy, and
> complicated, and delicate) all of this equipment is.
> >
> > One of the biggest unresolved problems on Psubs is navigation, inertial
> navigation and anything acoustic based is entirely too finnicky and
> complicated.
> >
> > I think the most practical navigation tools available to amateur
> submariners would be a basic heading indicator (magnetic or airplane gyro
> compass) and some of the really nice commercially available
> fishfinder/sonar units available.
> >
> > The bathyscaphe crews in the 60's used to sink a number of labelled 55
> gallon drums filled with concrete in a grid pattern around the projected
> dive area. If you can locate yourself within the grid of barrels using
> sonar, you have a reference frame to navigate from.
> >
> > I propose creating a series of sonar reflectors anchored to the
> sea-floor. Attached to the anchor could be a trawl float with a specific
> number or pattern of sonar reflectors attached. Think of day markers on a
> ship. Each reflector station could be located, and identified, by a
> fishfinder at a moderate distance. The position of the sub could be fixed
> by knowing heading, bearing to a specific reflector station, and the
> approximate distance to the station.
> >
> > Galvanic timed releases can be obtained for cheap, and used to retrieve
> the trawl floats and sonar reflectors after a predetermined period of use.
> >
> > A typical PSub outing could be covered by 3-4 sonar reflector stations,
> and there is no need to standardize on expensive equipment.
> >
> > -River J. Dolfi
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>
>
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