[PSUBS-MAILIST] Underwater Navigation

Sun Sep 1 14:28:13 EDT 2019

 David, I wish that I had had the Navonics program loaded on my phone at the Flathead Expedition.  It would have been very helpful for documenting the dives and also to follow Sean Stevenson's direction who was SOC for the R300.  What happened several times is that he would position the tender over a dive site and give me a heading and a description of the topography.  On several occasions I ended up missing the feature they were directing me to.  If I would have had the application on my phone and used it like you did with Hanks dives, I think it would have made it easier to follow directions as we would be looking at the same topography map of the dive site.
I have since downloaded the app and will use it for my next dive.
Cliff

    On Saturday, August 31, 2019, 08:41:07 PM CDT, David Colombo via Personal_Submersibles <personal_submersibles at psubs.org> wrote:  

 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
> _______________________________________________
> Personal_Submersibles mailing list
> Personal_Submersibles at psubs.org
> http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles

_______________________________________________
Personal_Submersibles mailing list
Personal_Submersibles at psubs.org
http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles

_______________________________________________
Personal_Submersibles mailing list
Personal_Submersibles at psubs.org
http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://www.whoweb.com/pipermail/personal_submersibles/attachments/20190901/e12baa04/attachment-0001.html>