Underwater GPS

[hydroslyder]

Does anybody know why they dont make an underwater GPS, I figured this would be something really kool, you would never have to worry about not finding a wreck, or the dive boat again.

Anyway just a thought.

Thanks

[jonnythan]

hydroslyder once bubbled...
Does anybody know why they dont make an underwater GPS, I figured this would be something really kool, you would never have to worry about not finding a wreck, or the dive boat again.

Anyway just a thought.

Thanks

Because the GPS signal won't reach you underwater ;)

The satellite signals just aren't strong enough.

[runvus4]

GPS works by getting singals from orbiting satellites. These signals can be blocked by overhead obstructions, such as tens of feet of water. When the signals are blocked, the GPS receiver cannot determine what it's location is.

[Stone]

If you want to find the boat, then you are talking about a "Neverlost" or "Eye Sea" beacon device.

[docmartin]

don't submarines use gps? of course their technology may not quite be in our price range.

[Boogie711]

Submarines only use GPS when they can trail an antenna. When they go into full 'stealth' mode, they not only can't receive a GPS signal, they can't communicate back and forth with Central Command.

Long story short - GPS won't work underwater. That's it, that's all.

[Mverick]

Best bet would be a WaterProof GPS.

That way, if it got doused on the boat it wouldn't short out the electronics.

Don't know if anybody makes a waterproof one though.

[norcaldiver]

try these:
http://www.magellangps.com/en/gpsAdventures/marine/

http://www.garmin.com/products/rino/

http://www.garmin.com/products/rino120/

[helpd desk snob]
I found these in about 3 seconds by going to yahoo and typing in "waterproof gps".
[/help desk snob]

[FallenMatt]

most of those gps units ar enot waterproof, just water resistant..
if i remember the specs, you can submerge the garmin gps receiver to only about 7 feet.

i've seen a DIY project somewhere on the web (it was a while ago , dont' remember the address now) where you put a gps receiver in a water tight englousure on the bouoy that you tow with you (dive flag).

i can imagine rigging a gps receiver with an external antenna and attaching it to float on the surface would work too..

the problem with gps signal is that it is EXTREMALLY weak.. something on the range of thousands times weaker than cell phone tower signal. you always need "line of sight" to the sky to get gps readings... probably just few inches of water would stop the singal to get to your underwater gps receiver....

[runvus4]

I figure the Navy has to have developed somehing to assist with undewater navigation. I was thinking along the lines of of ULF wave triangulation. The problem with that is that those waves travel at different speeds through waters with differing salt content which would make the system fairly inaccurate without a very large number of reference points. Also ULF waves have been linked in a corrolary (not causal) fashion with disruption to marine life.

[100days-a-year]

uhhh,Runvus ULF sound waves or ULF radio waves.Milatary has used ULF radio for decades to communicate with subs.ULF sound(a lond distance sonar form)has been implicated in beachings and deaths.It is a relatively new technology now mostly unneeded due to our far superior hunter/killer subs and some other toys we have.The EyeSea and similar are pretty cool ,but if you need that to know where you are in relation to the boat I'll pass on having you dive with me.

[runvus4]

I was talking about ULF sound waves as I know that those can penetrate the water on a trans-oceanic scale. I don't know enough about ULF radio waves... aside from what I've seen on sci-fi tv shows and in movies.... Whats the straight dope on the Eyesea?

[darkmoon3d]

Found this site doing a web search: http://www.wadespage.com/D800DS07RF00.shtml

I guess this might work as an alternative for underwater gps.

[gaudencio]

For me I still use the old and dependable compass nothing else. gps would be too expensive.
Jimmy T.

[DJ69]

The signal GPS's are using can't penetrate more then 50cm of water.
Other thing is the whole technolegy is based on sertin wave length's at special modelations and digital coding. (actually very similar to CDMA celphones). And the thing uses the fact that both the sat's are moving all the time, as well as the hand unit's (that's why is's more acurate then in motion then in standing).
So it's not that simple to modify.
Probably more simple is to create somthing new on the lines of the Neverlost but on larger scale, with 3+ larg beacons.....

If you ask me, when arriving to a new dive site, take a local guide for your first dives.

[otobmark]

Our Navy still depends on inertial navigation which is updated by other means when possible (can't be jammed). Most long range (transatlanic etc.) aircraft also use inertial navigation (Supplimented w/ GPS, -civilian gps easy to jam). Subs can float an antenna to get a GPS fix. The VLF radio wavelengths are so long that it takes enormous time to send messages (extremely low bandwidth). I would guess that getting an accurate fix on source for triangulation would be difficult--I don't know. The inertial systems can be amazingly accurate, especially in something as stable as a sub. Perhaps a compact pocket size inertial system will someday be available. We used accelerometers in onboard telemetry in race cars and one trip around the track would draw a very accurate picture of the course. The sensor pack was not large and I could see the technology reaching personal size at some not too distant point.

[j-valve]

Has anyone ever taken their cell phone under with them in an enclosure while turned on? Do you still have cell signal?
If so you can probably get an Assisted GPS signal from your provider or even a fix from GPS One CDMA network if it's available in your area.

[SMan]

I did some looking around last fall. A company has a patent on a gps device for underwater use. I don't remember the company's name off the top of my head but I did find a pdf file of a flyer that talked about them demoing the product with a California dive club in the late 90's. The company did not have a toll free number and I did not feel like making a long distance phone about a product not out in the public. Their website still talks about the product. If I can find my information again I will post it.

S

[Braunbehrens]

j-valve once bubbled...
Has anyone ever taken their cell phone under with them

yeah, I make calls all the time while doing deco. It passes the time.

Seriously though, I've had my cellphone in my pocket before, so it was pressurized to about 150 fsw. Still works. I didn't get any calls while I was under ;)

Here is a link for UW gps:

http://www.underwater-gps.com/

If anyone is seriously interested in this, I recommend learning how to use a reel. It's cheaper and easier.

Before you learn that, learn how to navigate under water (admittedly a difficult skill, at least for me).

[jeremyrfoster]

Granted, GPS signal will not penetrate the water. Has anyone considered a surface receiver (similar to mounting a traditional receiver as I've heard mentioned) to the dive flag connected to a device that CAN penetrate water and sends the signals to a unit that the diver carries? I know this is a complex setup and would probably have to be commercially engineered.

We know that the satellite signals are very weak. The device I'm thinking of would basically act like a repeater... not only strengthening the signal, but also changing it to a different medium (ULF? Sonar?)

Jeremy

[Inspector#2]

About 3 years ago one of the LDS had a 2 or 3 piece set that I believe was a gps navigation set. The "floater" was the receiver for the gps. Somehow it communicated with a carried device the diver would have. Can't find it on the net anywhere but at one time it existed. If my memory is intact it was around $800.

Dave

Found a similar system but I don't remember the cable.

http://www.longbeachdive.com/product-concept-swich.htm

[Al Mialkovsky]

http://www.underwater-gps.com/Bouee-small.jpg
That is the buoy that you tow to use a gps underwater. You rich? It's a waste and I'm not a tow boat.:)

I am also a geocacher and have found underwater caches using a gps. But the coordinates took me to a site on the beach. From that spot I had to snorkle directly towards the northern tip of Lanai and when spotting the cache site from the surface drop down and log it.

King Kahekili (http://www.geocaching.com/seek/cache_details.aspx?ID=16119)

[kayakdiver]

have been using a simple approach for over 3 year
(published in Underwater Mag. nov/dec 02
info at http://groups.msn.com/divergps
**No power cable/antenna set-up is needed
I gain "updates"...Only as needed ...to keep an eye on the anchor position...and to mark points of interest
Problem? very....very....very..few divers will try something new
before they see scores of others using it.
I'm promoting this as an academic project
*Not a theory...used constantly with fantastic results

[pggeek]

I was thinking of putting in some underwater catches ;) Glad to see someone has done it.

Dam now I have to find a underwater case for my Garmin V. so I can swim to the spot, then dive to the catch.

Jason@programmergeek.com

[DA Aquamaster]

I have a Magellan sport track that is waterresistant to 10 ft. and accurate within 3 m or so under ideal conditions (when a WAAS sattelite is available). I will attach it to my dive float (it gets better reception if mounted upright) and tow it along on the dive. Assuming I keep the line tight it remains more or less above me and I can mark sites in a manner of speaking as long as I make a sharp 90 degree course change at the object and swim 50 ft or so from the object so that I can see clearly see it's location on the track after the dive. You can then scroll back along the track and mark the spot from the surface after the dive.

It at least lets you know where to park the boat on the next dive but is not of any use in navigating once you are underwater.

I don't see why a housed GPS would not work as long as you used a remote antenna on the surface and ran the wire down to you on (or as) your flag line. You would need to keep it tight though to keep the float above you. (lets see... $300 for the GPS, REALLY big $ for the custom Ikelite housing...)

[jplacson]

DA Aquamaster once bubbled...
I don't see why a housed GPS would not work as long as you used a remote antenna on the surface and ran the wire down to you on (or as) your flag line. You would need to keep it tight though to keep the float above you. (lets see... $300 for the GPS, REALLY big $ for the custom Ikelite housing...)

You have to understand how a GPS receiver works to begin with... but with your idea of keeping a tight line to the surface..you're kidding right? Not even a metal rod could hold a straight line up at depth... unless you only plan to dive down to 10 feet or so... or have a metal tube that's about 10' in diameter. Any length of cable, wire, rope will be towed behind you...no matter how tight you get it.

Now back to how GPS receivers work... running A remote antenna will work... IF a GPS only used ONE antenna. The only way an idea like that would work is the way UnderWater GPS works... the buoys have GPS receivers each... then each buoy must relay it's position down to the underwater GPS, which must then recalculate it's position based on it's relative position to the bouys (at least 3 must be used for proper triangulation) then adjust to calculate proper GPS position based on buoy positions.

You're idea of running an antenna relay would work... IF you ran 12 (a modern GPS receiver has a 12-channel parallel antenna...meaning it can track 12 satellites for positioning... and MUST have a MINIMUM of 4) lines to the surface... and have separate relays for each antenna... but that wouldn't give you YOUR position, it would give you the position of the buoy or floating antenna.

[jeremyrfoster]

Wait a minute, John. I realize that modern GPS's have arrays of antennas, but they are packaged in a single unit... are they not? You can purchase an antenna (array) for your car/boat that you slap on the roof as a single unit. It's not like you have to have 4 wires going from your receiver unit to your roof.

[jplacson]

Actually the antenna extension has 12.

And when you do attach the antenna to your car or boat... the GPS display tracks the BOAT/CAR... not the unit itself anymore... the GPS will track the point where the satellite signals hit the antenna... not the unit that calculates it.

Now I think it's kind of pointless to have a GPS system that doesn't track your location...and just tracks a floating buoy don't you? You're better off with a normal buoy and buy a NeverLost system to find your way back.

Accurate GPS readings will be off since the floating antenna relay will ALWAYS trail behind you... or to your side...or whichever direction the current takes it... not to mention potential snag problems... cuz unlike a guideline, which doesn't move... you will HAVE to drag this antenna buoy around to get your position right? Since the GPS is tracking the buoy/relay and not you. If you go to the UnderwaterGPS site, you'll see that this is basically what they do... except they deploy 3 - 4 relays at different locations to act like satellites themselves... then teh GPS calculates based on triangulations from the 3-4 buoys.

trailing a non-fixed antenna relay will give you very inaccurate locations readings... maybe as far as a 60 foot radius... or at BEST 25 foot radius if WAAS is available.

[Charlie99]

jplacson once bubbled...
You have to understand how a GPS receiver works to begin with...

... IF a GPS only used ONE antenna.

... IF you ran 12 (a modern GPS receiver has a 12-channel parallel antenna...meaning it can track 12 satellites for positioning... and MUST have a MINIMUM of 4) lines to the surface... and have separate relays for each antenna... but that wouldn't give you YOUR position, it would give you the position of the buoy or floating antenna. Even a 12 channel GPS has 1 and only 1 antenna. The GPS system uses code division multiplexing where the different satellites are detected using correlation techniques similar to that of the CDMA celluar system. A single coaxial cable is sufficient to connect the antenna with the main GPS unit.

[jeremyrfoster]

Charlie99 once bubbled...
Even a 12 channel GPS has 1 and only 1 antenna.

Now that sounds right! Thanks, Charlie99.

[Don Burke]

Submarines use mast mounted antennas for GPS, including periscope mounts. Yes, it is normally a single antenna, although some precision machines will use two to better pick up the two frequencies used. No one has been able to make a trailing wire work reliably at those frequencies.

LORAN, on the other hand, will penetrate a few inches of seawater. The wire and masts just below the surface will pick up the 100 kHz signals to some extent.

For diver navigation, those hand-held gadgets show some promise. I think they need considerably more development before they become more than a get-home beacon.

For deep submersibles, a field of transponders is set, surveyed, and used for local navigation. It's pretty time consuming.

With the advances in electronics, there should be a way to have beacons on the surface with GPS input so the field would be self surveying. The system would work much like an audio version of LORAN with the beacons also sending updates to the diver units so the varying positions of the beacons could be accounted for.

Anybody got a few million burning a hole in his pocket so we can do some R&D? :)

xxxxxxxxxxxx

I've seen the waterproof box that you put a handheld GPS in so you can send it to the surface from time to time. That strikes me as clumsy. I'd prefer to leave the GPS on the surface and have a link to a display the diver could hold. The link could be audio or even fiber optic, since the diver would have to tow the buoy around by something anyway. If the horizontal trail distance was an issue, the dive could pull the line as close to vertical as practical for relatively precision readings when needed.

This one would be much cheaper, but dragging that buoy doesn't have much appeal unless you are required to drag a marker anyway.

[JGB560]

Ok there is something called false GPS that one of the posts mentioned here. Its basically a GPS receiver mounted in a buoy. Attached to the buoy is a hard wired waterproof display that a diver carries showing the receivers position. The buoy is towed by a diver. It is called false GPS because it gives the position of the buoy, not the diver. The error is dependant on the amount of line from the float (buoy) to the diver and his vertical position from the center of the buoy. For deep dives in strong currents such as a tide or rip current it could be 100ft or more. The GPS satalites are sending (transmitting) there RF signal (1.5 GHz signal) down through free space ( line of site). The GPS uses multiple signals from several satalites to calculate its position. Now the first reason that regular GPS doesn't work underwater is because the 1.5 GHz signal is a high frequency radio wave. These waves do not penetrate solid or liquid media (water) very well. This is why your older 900MHz phones works a little better in your house then the 2.4Ghz phones even though the reverse is true ouside. However lower RF can penetrate solids and shallow water better. The navy uses ULF (ultra low frequency) comunication from ships to subs for this reason, but the sub still has to come up to a shallower depth (150ft or so) and float a buoy with an antenna. The second reason is that the system is data hungry in the sence that data is contiounsly be transmitted from the satalites.
There is a system being developed that uses acoustic waves (SONAR) that solves both of these problems using the GIB technology. First because sound travels 4 times faster in water then air, sound waves can move more easily through water. The GIB system uses multiple surface SONAR buoys in each major body of water. Second the sonar signals are sent from the buoy to the receiver only when a request for data is called for by the receiver, thus eliminating the continous downlink of data. And the data to individual receivers is time or frequency multiplexed. This allows for a large number of receivers to gather there individual positional data with out any signal conflicts.

[MaxAlegraD]

GPS underwater is something very far from reality mainly because of the error that is intrinsic to the GPS system + the error generated by using solutions such as attaching the GPS unit to line and letting it float.

Normally GPS units generates errors in measuring positions in the range of a minimum of 9ft. My experience has been between 18-45ft avarage.

Well to get coordinates of a wreck or some place that you want to return that error is ok.

If we add to that an error based on the depth and strong currents we can end up with errors above 60ft very easy.

If an avarage error of 60ft if ok than go for it ! You have a new toy in your gadget list for underwater exploration. But remember that when you plot the coordinates of the map you can get wrong reading on any direction (N,S,W,E). The map can get really messy.

For those who need more precise readings only the use of a single coordinate and the use of a fixed GRID can help. By doing that you reduce the error sampling by simply adjusting the coordinates of your grid to the base coordinate. Something like a Differential GPS.

[ba_hiker]

military uses inertial navigation for many things including subs. it predates gps by several decades. it does not require an outside refrence, just a precise knowledge of where you start, in precise measurements of the directions and distances traveled. gps is used to get the starting position.

the precise distance and direction measuring insterments used to be very complected and expensive, but now are being built on a few chips (mems).

[IslandHopper]

You should be able to get a used INS out of an old "retired" 727 ... get someone to make a housing for it and take it under with you.

Of course that old (read "affordable") model will probably require a housing the size of your kitchen sink and weigh on the order of 100 lbs .... but you'd have accurate underwater nav !!!!
... of course, the read-out simply gives Lat and Long ... no moving map or color screen :)

[KWS]

I figure the Navy has to have developed somehing to assist with undewater navigation. I was thinking along the lines of of ULF wave triangulation. The problem with that is that those waves travel at different speeds through waters with differing salt content which would make the system fairly inaccurate without a very large number of reference points. Also ULF waves have been linked in a corrolary (not causal) fashion with disruption to marine life.

runvus4

you are right about the navy however the others are right also. LF coms is still radio and needs antenna on the surface or close to, as in the gps. to make a radio device work reliably is going to be expensive. your reasonable alternative is a sonar related device like suggested. if ou are any where adaquate at navagating (one minute = 1 mile n/s) you can use a sonic locator. the expensive one that gives direction and distance (not signal streignth) and plot from a known point. it has more than enough range to it as compared to air limitations and the distance you can go with that air. it would be far more accurate than the sonar ulf concept as the speed of sound variations will not give you the accuracy you would want let alone the loran similar issues that would have to be delt with by redundant signal sources that the environmentalists would not like.

regards

KWS retired submariner

[spiderman]

My Garmin Rino 120 is waterproof for 30 minutes in up to 1 meter of water. You can't take it underwater, but you can keep it on a float above water. It can keep a record of where you have gone.

[archman]

My Garmin Rino 120 is waterproof for 30 minutes in up to 1 meter of water. You can't take it underwater, but you can keep it on a float above water. It can keep a record of where you have gone.

Most Garmin GPS units have this weatherproofing standard. I would be extremely wary of floating one on the surface however. Besides, I think the submerged waterproofing measure assumes that external power/data ports are not in use and plugged up. You'd need these open in order to say, run some sort of data screen on a submerged tether.

[BlueDevil]

The latest issue of of Scuba Diver (Australasia) has the following short piece:

"Chinese scientists have developed the first high precision underwater global positioning system (GPS). Tests have shown the new system can detect horizontal position within 5cm and depth precision within 30cm."

That is the only information given so I can't elaborate further.

[BlueDevil]

Further to my last post have a look at: http://news3.xinhuanet.com/english/2004-01/11/content_1269648.htm

Doesn't sound like something a diver could use.

[archman]

"Chinese scientists have developed the first high precision underwater global positioning system (GPS). Tests have shown the new system can detect horizontal position within 5cm and depth precision within 30cm."


This is a joke, right? Last I heard there was no chinese GPS constellation in orbit. And the reported accuracy here is simply ludicrous. Even using WAAS, you're not likely to get better than 9 foot accuracy... that would be something like three HUNDRED centimeters.

This supposed chinese system requires four floating GPS receivers/transitters I suppose for triangulation, and the sonar system would be used to get precise depth values. I'm assuming the four floating buoys are fixed sites hooked hooked into something like a WAAS network in order to achieve this absurd 30cm accuracy.

[spiderman]

You're right that the Garmin waterproofing is very limited and all the data ports must be closed. I was not suggesting anything but tracing the location of the float on the surface. Of course this could only be done in a calm lake environment and I would still want added protection like a ziplock bag or something. My biggest fear would be the guy on the Jet Ski that decided he wanted my GPS and borrowed it on the no return plan. It's great to use on a boat when you want to return to a specific location. We also use them to ice fish when we find a good location. I have seen excellent fishing locations vary by only a few yards. Just as a side note, I have had an estimated accuracy as low as 6 feet under the right conditions. We have 2 Rino 120's and use them constantly. The Rino will transmit your position to the other unit and my son and I play Hide-n-seek up in the mountains.

[IceFrog]

This is a joke, right? Last I heard there was no chinese GPS constellation in orbit. And the reported accuracy here is simply ludicrous. Even using WAAS, you're not likely to get better than 9 foot accuracy... that would be something like three HUNDRED centimeters.

This supposed chinese system requires four floating GPS receivers/transitters I suppose for triangulation, and the sonar system would be used to get precise depth values. I'm assuming the four floating buoys are fixed sites hooked hooked into something like a WAAS network in order to achieve this absurd 30cm accuracy.

Here's a link (http://www.underwater-gps.com/) to a similar system that claims similar results but goes into a bit more detail on how the system operates. It describes the system using DGPS from a shore station with an accuracy of +/- 10 metres to +/- 1 metre depending on the shore station used. The underwater portion of this is described as follows: "The timing resolution of the time of arrival of an acoustic signal is of 0.5 10-5 second, the accuracy is close to 10-4 second when working at 30 Khz, that means +/- 15 centimeters. Same accuracy is achieved using spread spectrum signals."

The chinese system must be identical or very similar.

Regards

[darkmoon3d]

I found this site a while back. A bit pricy but and not sure if it uses gps or not; but it allows for underwater measurements and modeling very precisly.

Can't wait until this product becomes cheaper for consumer rather than profesional use...

Here's a link (http://www.underwater-gps.com/) to a similar system that claims similar results but goes into a bit more detail on how the system operates. It describes the system using DGPS from a shore station with an accuracy of +/- 10 metres to +/- 1 metre depending on the shore station used. The underwater portion of this is described as follows: "The timing resolution of the time of arrival of an acoustic signal is of 0.5 10-5 second, the accuracy is close to 10-4 second when working at 30 Khz, that means +/- 15 centimeters. Same accuracy is achieved using spread spectrum signals."

The chinese system must be identical or very similar.

Regards

[archman]

Here's a link (http://www.underwater-gps.com/) to a similar system that claims similar results but goes into a bit more detail on how the system operates.

That's a neat website. It gets over my head in some places. As for affordability, well besides the handheld unit there's the infrastructure cost of the shore and and buoy transmitters to factor in. I don't see this becoming an option really anywhere within the next ten years, 'specially with the reductions being planned in NOAA's budget (to help pay for NASA of course).

[IceFrog]

Unfortunately for most divers the only affordable option for probably quite a while would be carrying a handheld GPS with them in a waterproof box and either send it to the surface on a towline, or carry it on their dive flag to mark where they travelled underwater.

You can also try this link for an underwater unit (http://www.battelle.org/navy/special-ops/mugr.stm). (www.geodiving.com) for the military. I have yet to see a civilian version of this unit though. I can say though that the unit is just waterproof and probably does not work underwater (as in aquire GPS Signals).

Regards

[pearcey]

i have a compass, call me old fashioned but i have never been lost.
if you really want to mark a wreck for example why not use a rope and bouy, and then calculate your gps whilst sipping cup a soup on the boat

[IceFrog]

i have a compass, call me old fashioned but i have never been lost.
if you really want to mark a wreck for example why not use a rope and bouy, and then calculate your gps whilst sipping cup a soup on the boat

There's no reason you couldn't do this. The GPS just allows you to record a large number of locations within it's memory. (Mine has the ability to store 1000 points - although I haven't even come close).

A number of people like to know where they are while underwater. Although none of the GPS units work underwater, there are a few methods.

Regards

[got4boyz]

http://www.longbeachdive.com/scubanav-detail.htm

Has anyone heard of or used this Scuba-Nav? I came across the website doing a search for dive flag floats. Sounds interesting and I'd like to try it, but kind of pricey without knowing how well it really works and how easy/difficult it is to use.

Any thoughts would be appreciated.

Thanks

[got4boyz]

Even if you have never used or heard of the Scuba-Nav before I'd be interested in hearing your opinion of it.

Basically, this is how it works.

The Scuba-Nav has a remote GPS antenna which is mounted to a dive flag float. The antenna has a 55 ft cable which is an attached to a GPS unit in a waterproof housing. The GPS satellite signals are sent through the antenna to the GPS reciever that the diver carries underwater. This allows the diver to know where he is underwater.

I haven't done a lot of shore diving but want to do more and thought this would be a great way to get back to where I started from! Or to navigate out to someplace I wanted to go, like a wreck or something. Many have already been given GPS coordinates that you can program into your GPS and then use it to get there with.

Anyway, I'm interested in what others think of this.

[ArcticDiver]

Even if you have never used or heard of the Scuba-Nav before I'd be interested in hearing your opinion of it.

Basically, this is how it works.

The Scuba-Nav has a remote GPS antenna which is mounted to a dive flag float. The antenna has a 55 ft cable which is an attached to a GPS unit in a waterproof housing. The GPS satellite signals are sent through the antenna to the GPS reciever that the diver carries underwater. This allows the diver to know where he is underwater.

I haven't done a lot of shore diving but want to do more and thought this would be a great way to get back to where I started from! Or to navigate out to someplace I wanted to go, like a wreck or something. Many have already been given GPS coordinates that you can program into your GPS and then use it to get there with.

Anyway, I'm interested in what others think of this.

A 55 ft cable? The GPS unit will tell you where the Antenna is not where You are. Depending on how deep you are diving You could be anywhere from directly under the antenna to 55' away. Is a location with that big a diameter accurate enough for what you do?

If so why not just get one of the waterproof Garmin units and mount it to the float?

[got4boyz]

A 55 ft cable? The GPS unit will tell you where the Antenna is not where You are. Depending on how deep you are diving You could be anywhere from directly under the antenna to 55' away. Is a location with that big a diameter accurate enough for what you do?


The cable is used like your line on a dive float. If you are only 30 feet deep you wrap it around a reel so only 30 feet of the cable is out (I believe the cable is marked every 10 feet), so essentially it would be almost above you. Of course it would be slightly behind you since you are pulling the float with the cable, but that only means you reach where you are headed a few feet before the GPS unit shows you are there.

[coliseum]

Its a good idea but it would be a bit of an annoyance having it connected to you the whole time!

[Don Burke]

It looks to be one step short of being done right.

55 feet of antenna cable (abused cable at that) is going to be pretty lossy at 1200 MHz.

I'd put the GPS receiver in the buoy and run the data down a fiber optic link to the diver.

Have you thought about one of those SONAR systems that tells you how to get back to a transmitter set? No wires is always a good thing.

[got4boyz]

Its a good idea but it would be a bit of an annoyance having it connected to you the whole time!

Many people dive with dive flags attached to them all the time don't they?


Have you thought about one of those SONAR systems that tells you how to get back to a transmitter set? No wires is always a good thing.

Never heard of a SONAR system. How does that work?

[Gary D.]

It looks to be one step short of being done right.

55 feet of antenna cable (abused cable at that) is going to be pretty lossy at 1200 MHz.

I'd put the GPS receiver in the buoy and run the data down a fiber optic link to the diver.

Have you thought about one of those SONAR systems that tells you how to get back to a transmitter set? No wires is always a good thing.

Those little units are perty cool. I've been able to play with them a couple of times.

One just has to remember to still keep up the navigation skills and not rely on the little electronic tubes. You never know when one of the two little units is going to display the middle finger and take a siesta.

There is a real nice wireless GPS unit out there. Just a big pain to use for sport diving. Besides it works on a frequency that appears to attract sharks for a less than frendly encounter. They like to bite the unit the diver carries.

Gary D.

[DoUDive2]

I'm a big GPS fan, but dragging a bouy around behind me all day long is not something that I do for fun. This system is not any good for deep diving since the bouy umbilical is only 55' long. Also remember that if the wind changes the location of the boat can change during the dive. Trying to preload the the location of the anchor point on the seafloor is a non-trivial mathematical exercise. Any diver that can use this this device to reliably find the boat anchor is probably already very good at underwater navigation.

Other than that, it sounds like a great gadget!

Chris

http://www.longbeachdive.com/scubanav-detail.htm

Has anyone heard of or used this Scuba-Nav? I came across the website doing a search for dive flag floats. Sounds interesting and I'd like to try it, but kind of pricey without knowing how well it really works and how easy/difficult it is to use.

Any thoughts would be appreciated.

Thanks

[archman]

at this recent locale.
http://www.scubaboard.com/t27622.html

The last postings were a week or so ago. Unfortunately it's hard to run a search for "GPS" as it's only three letters long (and thus excluded from search criteria). I'm sure tech admin will eventually get enough complaints to rectify this.

[DivemasterSteve]

at this recent locale.
http://www.scubaboard.com/t27622.html

Unfortunately it's hard to run a search for "GPS" as it's only three letters long (and thus excluded from search criteria). I'm sure tech admin will eventually get enough complaints to rectify this.


all you need to do is put * in it when you search and it will give you what your looking for. *GPS will work fine.

steve

[Don Burke]

Many people dive with dive flags attached to them all the time don't they??I'm not one of them. The float would have to be big enough to keep the antenna clear of the water and small enough to not be a big source of drag. That's a tough balance to strike.Never heard of a SONAR system. How does that work?Here's a discussion about the SONAR gadgets.
http://www.scubaboard.com/t26321.html

Many rave about them. I've never tried one.

[got4boyz]

Thanks archman for that thread. I did do a search on GPS and like you said, it didn't work of course. I also tried different searches without finding any info.

Thanks Steve for the * tip. I'll use it to turn all my 3 letter words into 4 letter words! LOL

Thanks for the SONAR thread link Don. That's cool, but I want more. I want to navigate to places not just back to where I started!

The other underwater GPS thread is discussing the possibility of doing what the Scuba-Nav already does. I'm wanting to know what others think of this device not a discussion of whether it will work or not. It's out there to buy, so it must work. They also have a pro model that has a 100 ft cable.

Now many of you say you don't want to pull a float around but I know many of you do. I'd like to hear from you about what you think about this.

Here's a scenario:

You are shore diving and want to go to a couple nearby sites, let's say a boat wreck and a plane wreck. You have the GPS coordinates for those sites so you make a waypoint for them before the dive into your GPS unit. You then just follow the path to the boat wreck first and to the plane wreck next.

On the way to the plane wreck you see a cool fish and want to follow it for awhile, so you do. By looking at your GPS unit you can now continue on to the plane wreck from where you quit chasing the fish. On the way back to shore a current has drifted you off course many feet. With a compass you'd have to guess how far of mark you had drifted and try and get back to your starting place using your guesstimation of the direction you needed to go on your compass. But if you had a GPS unit with you it wouldn't be a problem. You can see exactly what direction you need to go to get back to your shore entry. Wouldn't this make for a more enjoyable dive?

[Don Burke]

Now many of you say you don't want to pull a float around but I know many of you do. I'd like to hear from you about what you think about this.

Here's a scenario:

You are shore diving and want to go to a couple nearby sites, let's say a boat wreck and a plane wreck. You have the GPS coordinates for those sites so you make a waypoint for them before the dive into your GPS unit. You then just follow the path to the boat wreck first and to the plane wreck next.

On the way to the plane wreck you see a cool fish and want to follow it for awhile, so you do. By looking at your GPS unit you can now continue on to the plane wreck from where you quit chasing the fish. On the way back to shore a current has drifted you off course many feet. With a compass you'd have to guess how far of mark you had drifted and try and get back to your starting place using your guesstimation of the direction you needed to go on your compass. But if you had a GPS unit with you it wouldn't be a problem. You can see exactly what direction you need to go to get back to your shore entry. Wouldn't this make for a more enjoyable dive?You can do this with a SONAR system as well. Prior to the dive, figure out range and bearing from each of your points of interest to the point where the transmitter unit is to be placed. It's a technique similar to pilots using VOR/DME or TACAN to go from point to point by doing the trig in their heads. In your case, you can have your computer or GPS unit do the trig ahead of time and you'll have a list of ranges and bearings on a wetnote..

I've tried chasing fish while pulling a float. It was a lot of work and my gas consumption went to hell.

My GPS often is thirty-five or so feet off. That's not a big deal when I'm trying to find a wreck with a few hundred horsepower pushing me. It would suck big time with fin power in low viz.

[ArcticDiver]

Sounds like you have already made up your mind about this toy.

Now that more folks have posted I think it wouldn't be accurate enough for my use. Plus, dragging 50' or 100' of cable around would be a royal pain. Plus, it would only be good for shallow diving.

But, putting an eTrex on the float; taking the float to the precise coordinates; mooring the float; and descending from there would be cool. Plus, it would be cheaper; always a good thing for me.

If you get a few hours of experience with it be sure to post your impression then. I can always be persuaded to change my mind.

[archman]

this version of "false GPS" would have utility in underwater archaeology and shallow surveys... I wouldn't be suprised if jury-rigged setups weren't already in use by these folks.

Divers that...
A) stay shallow
B) don't move much

...would be fine for this technology, provided they don't get annoyed with a strung surface cable. The application would be best used to mark points of interest, to better position a boat on subsequent dives. It would not be effective as a navigational tool due to it's...
A) annoying and potentially dangerous tether
B) high power drain (GPS units suck batteries pretty hard)
C) awkwardness underwater (most portable GPS units have small screens and are not diver-ergonomic)

B & C could be rectified with improved GPS models. You're still stuck with the dang tether, that would require near-constant attention. Personally I'd "put up with" false GPS on dedicated survey trips, and then use the data to create line-of-bearing maps for later dives using the good 'ol compass and slate. I don't see a realistic market for recreational diving, though. Maybe as a rental...

**
This thread should be bumped to the general equipment forum, and maybe folded into the existing thread(s) on this topic.

[got4boyz]

Sounds like you have already made up your mind about this toy.

Not really. I love my GPS and what it can do, so I'm very intrigued by this idea, but I have my reservations. That's why I'm asking questions. I don't want my excitement about something that seems cool to cause me to waste lots of money if it's not really worth it.

I've done very little shore diving and have never pulled a float, so I don't know what that is like, but I know people who dive all of the time pulling floats. I was hoping to hear more from them too. Those of you who don't like pulling floats are not going to be as receptive to the idea as to someone who is used to pulling a float around behind them. And since I've never done it, I don't have any idea what it's like.

Guess I need to go buy me a float and try that out first.

And you're right archman, this probably should have been in the general equipment forum. Didn't think about that!

Thanks y'all for your comments!

[divebunnie]

OOh this sounds interesting.

I have just got back from working on a project where at one point we were creating a GPS map of a particular reef, noting the depth and life forms at certain points whilst someone on the surface registered the actual way points. This system would have been great, as we could have guaranteed far more accuracy, wouldn't have needed to synchronise with the surface (not always so easy at 18M). We had to tow a float along with us anyway so that the person at the surface could see where we were, so that would not have been a problem either.
Any ideas of cost? I am guessing it will be out of the current budget of a conservation team, but who knows??
By the way, yes… towing a float is a bit of a pain, for those of you who haven't done it before, but I guess sometimes it is necessary. We were quite isolated, so it was just one more safety method. :)

[Falcon99]

I'm a big GPS fan, but dragging a bouy around behind me all day long is not something that I do for fun. This system is not any good for deep diving since the bouy umbilical is only 55' long. Also remember that if the wind changes the location of the boat can change during the dive. Trying to preload the the location of the anchor point on the seafloor is a non-trivial mathematical exercise. Any diver that can use this this device to reliably find the boat anchor is probably already very good at underwater navigation.

Other than that, it sounds like a great gadget!

Chris

Chris, the big problem here is obviously getting around the water's inability to pass L-band RF - not to mention the host of decoding issues that would come with the water-air boundry :)

I've seen another system that converts this over to what looks like a ~50 Khz sonic data medium that allows the information to be displayed on an independant diver unit. This still has some problems mandated by the laws of Physics. You still have to calculate a 3-D position from the boat to the diver. This cannot be accomplished with a single-point device such as a unit on the boat talking to the remote. Even if a two-way communication protocol is implimented, you could only get the distance from the unit to the boat. I can't do much with that. Water is a hard nut to crack when it comes to this.

just my $.02 worth

James

[got4boyz]

divebunnie, The ScubaNav is $400 and comes with only 55' cable. The professional model is more heavy duty and comes with 100' cable. It is very pricey at $1200! Then you still have to provide a GPS unit. The site if you are interested is www.longbeachdive.com.

[archman]

I sincerely hope that these long cables have some sort of angle leveler built into the base. Otherwise you're going to have to guesstimate the horizontal difference between the float and the GPS. At 100 feet what appears to be a vertical line could be off by a significant margin.
If you:
A. maintain a constant depth
B. know how much float line you've released
C. know the oblique angle between true vertical and the float line

... then it's possible to determine the "drift error" from the float line. Sounds like a lot of work, right? Now factor in:
A. not maintaining a constant depth
B. changes in the oblique angle due to shifting current flows
C. variations in current regimes along compass bearings (i.e. which way do I compensate for drift now?)

Now this technology becomes a friggin' nightmare regarding both accuracy AND precision. I would not have any faith on it deeper than 50 feet, even with a full dive team doing the mapping. I can predict massive variation from repetitive or even concurrent surveys. The scientist and reef ecologist in me is screaming out "bad data!"

Now at clear shallow depths lacking current, you could probably do much better with the thing. You could eyeball the float and visually mark it directly overhead... this solves all of your error problems (except natural GPS error) right off the bat. You would still have to follow a very strict protocol for marking points. Both you and your dive buddy would be doing nothing else on the dive, needless to say. The California website advertising these units is being extremely conservative in their error reporting, and bordering on absurd for California waters. You'll note in the FAQ that they "cop out" of a full explanation.


7. How accurate is the Global Positioning System ?
The short answer is: depending on the type of civilian GPS receiver used, down to 3 meters of accuracy. The long answer is: understanding and determining the accuracy of civilian GPS depends on many variables, and factors, and is too long a discussion for a FAQ page.

[DoUDive2]

Chris, the big problem here is obviously getting around the water's inability to pass L-band RF - not to mention the host of decoding issues that would come with the water-air boundry

I've seen another system that converts this over to what looks like a ~50 Khz sonic data medium that allows the information to be displayed on an independant diver unit. This still has some problems mandated by the laws of Physics. You still have to calculate a 3-D position from the boat to the diver. This cannot be accomplished with a single-point device such as a unit on the boat talking to the remote. Even if a two-way communication protocol is implimented, you could only get the distance from the unit to the boat. I can't do much with that. Water is a hard nut to crack when it comes to this.

just my $.02 worth

James

Wow! I've spent the last 30 minutes trying to figure out how to move this thread to the General Equipment forum. I never did figure it out, but somehow it seems to have magically moved by itself. It must be an act of :god: !

Back on topic:
I agree that GPS signals cannot penetrate water to any significant depth. That is why the receiving antenna must be on the surface float and the signals are passed to the diver's receiver via the 55' umbilical line. I have heard that military diver's have a similar system in which the antenna is deployed to the surface only when a fix is needed. The system gives the surface location of the antenna float, not the actual location and depth of the diver. WAAS is not available in all dive locations. So the accuracy of the system is probably about 50 ft 95% of the time.

I'm waiting for the differential version in which the boat acts as a GPS base station. The float is not attached but uses its own propulsion system and keeps itself stationed above the diver using a sonar transponder based guidance system. The location of the diver is displayed on the diver's gage console and is decoded from the sonar signals sent from the float. How's that for dreaming!

3-Dimentional positioning of the diver underwater using sonar trilateration seems like a great idea, but it is way too expensive for me. However, I am interested in sonar devices such as Neverlost, Eye Sea, and XIOS which provide bearings back to the boat. They are still expensive, but I have read some interesting threads that describe their operation. see: http://www.scubaboard.com/t26321.html If you keep the batteries charged and dry, they beat dead reckoning.

Chris

[Falcon99]

3-Dimentional positioning of the diver underwater using sonar trilateration seems like a great idea, but it is way too expensive for me. However, I am interested in sonar devices such as Neverlost, Eye Sea, and XIOS which provide bearings back to the boat. They are still expensive, but I have read some interesting threads that describe their operation. see: http://www.scubaboard.com/t26321.html If you keep the batteries charged and dry, they beat dead reckoning.
Chris

Ahh! Now you have something! You have solved the last variable. IF you can obtain a bearing (in either a boresight LOS, or Magnetic) from the "box" to the boat AND receive the boat's GPS position, AND obtain the point-point diver-boat distance (sonic transponder), you have everything you need. You can now provide the exact 3D position of the diver with surprizing accuracy. The unit has all the variables it needs to calculate the exact coordinates. It can now do anything a normal GPS can do as well - log position, times, depth, ect....

No need for differential here. Differential would be hard to do with the boat anyway. You don't know its exact position with better accuracy than GPS, so there will be no benefit. You could use a very similar method, but for the point-point calculations - as I said above, get an angle and the distance, everything else is elementary.

Most differential GPS systems are post-processed now anyway :)

You da man!

(It doesn't take much to get an Engineer like me excited - I work with Inertial and GPS stuff at my "normal" job :)

James

[Don Burke]

(It doesn't take much to get an Engineer like me excited - I work with Inertial and GPS stuff at my "normal" job :)Here's a system that has some possibilities:

http://www.underwater-gps.com/3uwgps/ugps1.html

A master buoy and two slave buoys would seem to be all you'd need to form the net.

[Falcon99]

Here's a system that has some possibilities:

http://www.underwater-gps.com/3uwgps/ugps1.html

A master buoy and two slave buoys would seem to be all you'd need to form the net.

Yep. It looks like they use two bouys for a spherical solution to calculate the diver's range. I still think it can be done without a tether, though.

[darkmoon3d]

Whoops... Forgot to post the link!

Here it is -- http://www.plsm-instrumentation.com/

I found this site a while back. A bit pricy but and not sure if it uses gps or not; but it allows for underwater measurements and modeling very precisly.

Can't wait until this product becomes cheaper for consumer rather than profesional use...

[Helmet]

I get questions about underwater GPS all the time in classes. What anyone who uses GPS knows is that they aren't always accurate down to the foot. In fact, the satallites can be "detuned" during times of international conflict. Mariners often travel many miles and use GPS to get within 50 to a few hundred feet of a destination. Divers usually travel a few hundred feet max underwater. What good would a system be that was only accurate to a few hundred feet at any given time? A good ol' compass and proper navigation training and practice make totally adequate tools for getting to where you want to underwater. Having underwater GPS would be overkill. It would be like having GPS to go down to the basement of your house or to navigate around your backyard.

-Helmet

[archman]

In fact, the satallites can be "detuned" during times of international conflict.


I have been informed that such "detuning" is only implemented within GPS constellations over areas of conflict. Divers shouldn't be in such areas, needless to say.

As for accuracy, well if you have enough satellites in a non-obstructed sky, you should have errors limited to less than 20 feet. With WAAS implemented (and many nearshore dive areas in the U.S. are in range of this), you can pin that down to less than ten feet. I've used it quite a bit in the lower Keys to locate small reef features less than 15 feet across, and it's never let me down. I use a Garmin MkV.

[Don Burke]

I get questions about underwater GPS all the time in classes. What anyone who uses GPS knows is that they aren't always accurate down to the foot. In fact, the satallites can be "detuned" during times of international conflict. Mariners often travel many miles and use GPS to get within 50 to a few hundred feet of a destination. Divers usually travel a few hundred feet max underwater. What good would a system be that was only accurate to a few hundred feet at any given time? A good ol' compass and proper navigation training and practice make totally adequate tools for getting to where you want to underwater. Having underwater GPS would be overkill. It would be like having GPS to go down to the basement of your house or to navigate around your backyard.

-HelmetIf you take a GPS receiver around your back yard and record the raw positions and times, you can get precision corrections for those positions and know where every shrub in your yard is within a couple of feet.

Such a capability would be pretty handy for a reef survey, although I do see your point relating to wreck dives. The original question was related to shore dives in fairly shallow water and geo position would be a handy thing to know there since a diver can go quite a distance under those conditions.

[got4boyz]

WAAS is not available in all dive locations. So the accuracy of the system is probably about 50 ft 95% of the time.

In North America WAAS will be available at most dive sites. Afterall, when you are diving you are usually out in a big lake or the ocean so you have no obstructions to block the sattelites. With my external antenna I get WAAS inside my house and I'm not near any windows!!!

Helmet - You are a bit behind on the capabilities of GPS. Newer GPS units are WAAS capable now, which means they are typically accurate to 9 feet, 95% of the time. And in time it will only get better. Check out this link if you are interested in learning more about WAAS.

http://www.garmin.com/aboutGPS/waas.html

[Cabo31]

Submarines use Inertial navigation to navigate underwater. Thus at a certain point in time they know where they are, ie just before they submerge, then the Inertial navigation system is used until they surface again.

[Don Burke]

Submarines use Inertial navigation to navigate underwater. Thus at a certain point in time they know where they are, ie just before they submerge, then the Inertial navigation system is used until they surface again.I've run those systems. They aren't the magic solution many would lead you to believe, especially in shallow water.

[ba_hiker]

Navy uses inertial navigation for subs. Dos not even require working surface stations. Expensive, but getting cheaper and smaller...

[archman]

Inertial navigation accuracy degrades with length of use. Submarines prefer to surface when they can to get satellite fixes to "re-calibrate" their INS, especially when operating in confined waters.

At least that's what I learned from Tom Clancy...

[Don Burke]

Inertial navigation accuracy degrades with length of use. Submarines prefer to surface when they can to get satellite fixes to "re-calibrate" their INS, especially when operating in confined waters.

At least that's what I learned from Tom Clancy...I've worked with various systems on various submarines.

We would take external fixes to compute reset parameters and actually perform resets as needed to meet whatever mission goals we were after.

The systems are subject to disturbance from variious sources including gravitational anomalies, power, temperature, bum inputs, and physical shock to the system. The newer ones are better, not perfect.

A submarine doesn't need to surface to get a satellite fix. As long as an antenna can be raised above the surface, the boat can stay at periscope depth. The exposure to RADAR involved is not a minor consideration.

I made Polaris patrols in the days before GPS and we would track LORAN for months at a time with checks against other systems from time to time. LORAN is pretty good within it's limitations. TRANSIT was fun to operate, but I don't miss it at all since it exposed the boat too much. The early days of precision bathymetric navigation were pretty neat too.

When I got on a boat with GPS, I thought I'd died and gone to heaven. Not only is there position available virtually constantly, but satellite reference velocities are available for damping for the whole time the receiver is locked on.

[BigJetDriver]

All,

The problem is simple. All we need is a Ring Laser Gyro for IRS (Inertial Reference System) input, and a GPS (Global Positioning System) to update it when we do surface. The B-777 has three of these systems linked in a "voting logic" set-up. This is why we can be over a thousand miles out in the South Pacific and look down to see an aircraft directly below us, and another one directly above us. (Doesn't happen that way often, but it does happen!)

Now, what we need is some genius to shrink one of these systems, reduce the power requirements to battery power, AND make it affordable to divers! (It would take a genius!!) Any takers???

Cheers!! BJD :anakinpod

[archman]

Now, what we need is some genius to shrink one of these systems, reduce the power requirements to battery power, AND make it affordable to divers!


I'm free on Sunday. :eyebrow:

[DoUDive2]

I'm free on Sunday. :eyebrow:
That made me chuckle. So I posted my response in the "Scuba Humor" subforum, which is under the forum on "Non-Diving Related Stuff."

[red dwarf]

Does anybody know why they dont make an underwater GPS, I figured this would be something really kool, you would never have to worry about not finding a wreck, or the dive boat again.

Anyway just a thought.

Thanks
lots of probs in this regard due to the nature of the GPS that the USA let us use
the power of the signal is one prob, the signal is very low power at a high freq. this is not what you need underwater ULF is better not 1200 odd Mhz

[archman]

You're gonna get an awful low transfer rate using ULF. You'd probably have to sit tight for an hour or so in order to tag your position. It was my understanding that the Navy only sent ULF messages saying "come to the surface so we can use higher frequencies". Or maybe that's ELF, or HOBBIT maybe.

[Don Burke]

You're gonna get an awful low transfer rate using ULF. You'd probably have to sit tight for an hour or so in order to tag your position. It was my understanding that the Navy only sent ULF messages saying "come to the surface so we can use higher frequencies". Or maybe that's ELF, or HOBBIT maybe.ELF is a very low data rate business. I seem to recall only a few characters per minute and the transmitter power being obscene. The plan was for war orders and such to be sent when nothing else worked.

For a SCUBA nav system, I like the one where buoys with GPS receivers compute the diver's position from some sort of transponder system and send it to the diver's set on an acoustic link. You can make something like that work with two buoys, although I'd prefer three stations to eliminate ambiguity.

[archman]

For a SCUBA nav system, I like the one where buoys with GPS receivers compute the diver's position from some sort of transponder system and send it to the diver's set on an acoustic link. You can make something like that work with two buoys, although I'd prefer three stations to eliminate ambiguity.

That's what I like too. In the slightly fanciful future I can maybe predict smaller sanctuaries ponying up for moored buoys, and local dive shops selling/renting the acoustic handheld unit. With miniaturiation of GPS ongoing, it may even be affordable to purchase small tethered buoys yourself... it's the acoustic hardware that'll likely be the pricey part.

[DoUDive2]

This thread seems to have migrated into the subject of sonar. So, I did a bit of research and obtained the following information about costs and environmental impact:

Neverlost ($790)
http://www.st-josephscuba.com/gauges.htm

XIOS Eyesea ($900)
http://divestore.scubacenters.com/Merchant2/merchant.mvc?Screen=CTGY&Store_Code=SD&Category_Code=Computers
http://www.aquaticadistributors.com/Products/products.html

Desert Star Sport ($550) and Scout ($300)
http://www.scuba.to/cgi-bin/link.cgi?url=http://www.desertstar.com/sport.htm

Environmental Impact Article
http://seattlepi.nwsource.com/local/143166_whales09.html

Happy Easter!
Chris

[Don Burke]

None of these gadgets would be of any help on a survey.

The "environmental impact article" isn't the worst piece of trash I've ever seen, but it's pretty close. I suspect the reporter and the "scientists" could use a few weeks in a clue acquisition course.This thread seems to have migrated into the subject of sonar. So, I did a bit of research and obtained the following information about costs and environmental impact:

Neverlost ($790)
http://www.st-josephscuba.com/gauges.htm

XIOS Eyesea ($900)
http://divestore.scubacenters.com/Merchant2/merchant.mvc?Screen=CTGY&Store_Code=SD&Category_Code=Computers
http://www.aquaticadistributors.com/Products/products.html

Desert Star Sport ($550) and Scout ($300)
http://www.scuba.to/cgi-bin/link.cgi?url=http://www.desertstar.com/sport.htm

Environmental Impact Article
http://seattlepi.nwsource.com/local/143166_whales09.html

Happy Easter!
Chris

[DoUDive2]

None of these gadgets would be of any help on a survey.


Agreed. Underwater surveying requires something along these lines:

Aquamap(TM) ($13000)
http://www.desertstar.com/newsite/price/pd012-c.pdf

Now I really like this!

GPS Intelligent Buoy Subsea Tracking System
(if you have to ask you can't afford it)
http://www.mkservices.co.uk/mks/files/GIB%20brocure.pdf

Chris

[ScubaDuba1]

Agreed. Underwater surveying requires something along these lines:

Aquamap(TM) ($13000)
http://www.desertstar.com/newsite/price/pd012-c.pdf

Now I really like this!

GPS Intelligent Buoy Subsea Tracking System
(if you have to ask you can't afford it)
http://www.mkservices.co.uk/mks/files/GIB%20brocure.pdf

Chris

Don't know if anyone has mentioned this device yet. Looks interesting, uses doppler velocity log and fluxgate compass. You enter your geodetic loaction (lat/long) as you enter the water and it keeps track of exactly where you go. Even records it for mapping.

http://www.rjeint.com/pdf/cobra_tac.pdf

Dont know how well it works, but it looked neat.

[Don Burke]

Don't know if anyone has mentioned this device yet. Looks interesting, uses doppler velocity log and fluxgate compass. You enter your geodetic loaction (lat/long) as you enter the water and it keeps track of exactly where you go. Even records it for mapping.

http://www.rjeint.com/pdf/cobra_tac.pdf

Dont know how well it works, but it looked neat.I worked with a Doppler Sonar navigator made by Ametek-Straza. It was a pretty good machine. A couple of microprocessors would have done it a world of good.

On the linked page, they are saying that it acts like "a GPS receiver", which is downright wrong. It's a dead-reconing device. Such a claim makes me wonder about the company.

[hometone]

Does anybody know why they dont make an underwater GPS, I figured this would be something really kool, you would never have to worry about not finding a wreck, or the dive boat again.

Anyway just a thought.

Thanks
undefined

go to www.longbeachdive.com

[HammerNoMore]

On the linked page, they are saying that it acts like "a GPS receiver", which is downright wrong. It's a dead-reconing device. Such a claim makes me wonder about the company.
Another example of how imprecise the English language is. I read the same thing but assumed they ment it emulated a GPS receiver. I.E. the UI is like that of a GPS.

James

[tfohl]

Does anybody know why they dont make an underwater GPS, I figured this would be something really kool, you would never have to worry about not finding a wreck, or the dive boat again.

Anyway just a thought.

Thanks

You can't even get a good GPS signal in a damp forest so I doubt that a simple unit would work well under water.

Tim Fohl

[rcain1]

Just dive with your wife. They know EVERYTHING! How could you get lost.

[The Kraken]

I think that calling the company a liar is a bit harsh.

What the company is offering is a powered antenna that will couple with a submerged GPS unit and transmit the signals from the geostationary satellites to the hand-held unit.

I have a Garmin 12XL with an external antenna. The current antenna cable length is about 8-9' long. I daresay that the resistance of an antenna cable 55' long would preclude the transmission of the data to the hand-held unit by existing antennae.

In order for the antenna to overcome the inherent resistance of the coaxial cable, it would have to generate an amplified signal.

So, that's what ya have. An amplified surface located antenna sending the acquired signals to the encapsulated, submerged GPS unit.

[rcain1]

Of my 11years in the Army as a 31U I worked with PLGR AN/PSN-11 It is a GPS, the first GPS and we regularly used 100foot ant cables.


I have a Garmin 12XL with an external antenna. The current antenna cable length is about 8-9' long. I daresay that the resistance of an antenna cable 55' long would preclude the transmission of the data to the hand-held unit by existing antennae.

In order for the antenna to overcome the inherent resistance of the coaxial cable, it would have to generate an amplified signal.

So, that's what ya have. An amplified surface located antenna sending the acquired signals to the encapsulated, submerged GPS unit.[/QUOTE]

[armyscuba]

GPS does work underwater..but that's classifed..SORRY..That's how I find things underwater with accuracy...

[armyscuba]

GARMIN does mfg the GPS for the U.S. Navy that is UNCLASSIFIED...

[zboss]

Most Garmin GPS units have this weatherproofing standard. I would be extremely wary of floating one on the surface however. Besides, I think the submerged waterproofing measure assumes that external power/data ports are not in use and plugged up. You'd need these open in order to say, run some sort of data screen on a submerged tether.

lasted about 2 seconds once it hit the water and it was the "water/weather proof" model.

[The Kraken]

Hey, Armyscuba, what type of unit is it? Is it TO&E for the army or is it also available for the civilian market?

[tiswango]

Any ideas of cost? I am guessing it will be out of the current budget of a conservation team, but who knows??
By the way, yes… towing a float is a bit of a pain, for those of you who haven't done it before, but I guess sometimes it is necessary. We were quite isolated, so it was just one more safety method. :)

Someone already quotes Wades Page for taking underwater GPS. The whole set up will cost less than $300. Wade developed the system for lobster hunting North of West Palm Beach where you hit a small ledge for bugs or nothing for sand.

As discussed the problem is the difference between where the GPS is floating on the flag and where the diver actually is. The GPS numbers on the flag can be corrected to account for the divers using good ole fashioned math. For us techies, Wade made a spreadsheet to do it for you.

Below is a pic of a map of a shore dive off Fort Lauderdale Florida. The two vertical lines are the first and second reef lines. The other is a pic of the site.

Below is line to the PBCRRT maps page.

PBCRRT Maps Page (http://www.pbcrrt.org/PBCRRT_GPS.shtml)

The PBCRRT is a volunteer dive team and will teach any interested diver how to do this for free!

[rmediver2002]

GPS does work underwater..but that's classifed..SORRY..That's how I find things underwater with accuracy...


Your not really saying your on some secret SCUBA team that uses a classified underwater GPS are you?

[rmediver2002]

Hey, Armyscuba, what type of unit is it? Is it TO&E for the army or is it also available for the civilian market?


It is possible to establish a position through triangulation with a secondary receiver. You would have a series of GPS or known position buoys that could triangulate the divers position on the bottom.

There is a system known as the Cobra-Tac on the market now that is able to track divers location by entering the water at a known point (GPS coordinate). The unit tracks the divers depth and movements to calculate the current position, this technology is not classified but is pretty costly... (going from memory, between $15,000 and $20,000)

It is available from RJE technologies.
http://www.rjeint.com/default.htm



I am afraid statements like "it is classified" or on another thread "trained to kill" are pretty typical of posers and not at all typical of trained proffesionals especially on a public forum...

Don't try and pretend your something your not, be proud of the contributions you are making!

[The Kraken]

The positional error caused by the difference between the diver's location and the location of the GPS antenna, for the most part, is going to be so small that it will be positionally insignificant. This is assuming that the antenna is being towed on a float. All one has to do is to put enough tension on the up line to the float to pull it over one's location.
Current GPS's, even the little hand held units, are accurate to about 1 meter since the DOD removed the signal degradation from the transmitters.

[zboss]

All,

The problem is simple. All we need is a Ring Laser Gyro for IRS (Inertial Reference System) input, and a GPS (Global Positioning System) to update it when we do surface. The B-777 has three of these systems linked in a "voting logic" set-up. This is why we can be over a thousand miles out in the South Pacific and look down to see an aircraft directly below us, and another one directly above us. (Doesn't happen that way often, but it does happen!)

Now, what we need is some genius to shrink one of these systems, reduce the power requirements to battery power, AND make it affordable to divers! (It would take a genius!!) Any takers???

Cheers!! BJD :anakinpod

I think I saw that as a downloadable video from the Do-It-Yourself channel... right after the model airplane do-it-yourself video.

[DoUDive2]

World wide, the 95% accuracy of GPS is 8 to 15 meters (25 to 50 ft).

[DoUDive2]

There is a system known as the Cobra-Tac on the market now that is able to track divers location by entering the water at a known point (GPS coordinate). The unit tracks the divers depth and movements to calculate the current position, this technology is not classified but is pretty costly... (going from memory, between $15,000 and $20,000)


It is also primarily an inertiial system, meaning that its positioning accuracy degrades with time. The concept of using a pressure sensor to determine the altitude (depth) of the diver is an innovative idea that allows the unit to significantly reduce the rate at which the position accuracy degrades. However, even with the pressure sensor, the accuracy of the system is degrading at 0.5 cm/s*. That means that after an hour of being underwater the Cobra-Tac position error will typically be about:

0.005 m/s * 3600 s = 18 m (or 60 ft)
Chris

*reference: RJE Cobra-Tac Data Sheet

[alemaozinho]

what about a navigation specialty course mmmhh?

[tfohl]

Another approach is to use an acoustic positioning system. See, for example, http://www.plsm-instrumentation.com/site_an/. They require that you create a bench mark at a known position (with a surface GPS for example) and your underwater position is determined quite accurately by acoustic signals. The range depends on signal strength but the accuracy is always there--for a price.

Best,
Tim Fohl

[Joffren]

don't submarines use gps? of course their technology may not quite be in our price range.


Actually, submaries use a gyroscopic device that works essesntially like an "underwater GPS". Because the underwater environment is "3D", a gps which works by cross referencing or triangulating the position of the gps receiver this would not be practical underwater even if the signals would reach.

[Joffren]

Thank the government for the inaccuracy of GPS. The gov't uses Selective Availabilty, which is a program that makes
GPS innacurate by a varying degree, but no more than 350 feet. Nowadays, though, most GPS are WAAS enabled. WAAS is a feature that cross references radio signals from permanent land-based locations therefore making the reading accurate to .49" Yes, thats less than half an inch.

[rmediver2002]

President Clinton dropped selective availability in May of 1999.

If you are interested in thanking the government, you can thank them for GPS and the satellites that support it.

[O2BBubbleFree]

Thank the government for the inaccuracy of GPS. The gov't uses Selective Availabilty, which is a program that makes GPS innacurate by a varying degree, but no more than 350 feet. Nowadays, though, most GPS are WAAS enabled. WAAS is a feature that cross references radio signals from permanent land-based locations therefore making the reading accurate to .49" Yes, thats less than half an inch.

Really? Where did you find that information?

It seems to me that Garmin makes the most 'recreational' GPS units of anyone, and according to their site WAAS improves standard GPS to "better than three meters, 95% of the time."

http://www.garmin.com/aboutGPS/waas.html

I'm not an expert, but I've read about several schemes for improving position finding using GPS over the years. Generally called Differential GPS, some have used GPS + Loran, some US GPS + USSR GPS, some using RF + GPS. WAAS apparently uses the later. But I really doubt if anything gives sub-inch accuracy, especially in a unit I could afford. I know about three years ago surveyors units made by Tremble and costing thousands of $, were bragging about 1 meter accuracy.

President Clinton dropped selective availability in May of 1999.

If you are interested in thanking the government, you can thank them for GPS and the satellites that support it.

Here here! I was in volunteer alpine SAR when they dropped SA. What an improvement! What an outstanding system that the DOD has made available to the common man! Not much else I'd thank Clinton for, but that get's political;)

[cancun mark]

Reuters headline:

"several divers were arrested and shot as spies in Saudi Arabia yesterday while the Underwater GPS unit they had been testing failed to return them to the Sinai side of the red sea.

The group had reportedly been communicating extensively before the event by internet and obviously planning for some time.

Recent connection with a similar group of underwater extreemists who trained by shooting scuba tanks in the Mojave desert is unsubstantiated, however the leader of the second group known as Kyle has dissapeared from sight."

.

[Fivetide]

Wonder if blue tooth would work under water? I have the tomtom software on a T740 handheld and a bluetooth connected gps.. must try that some time lol!!

[justleesa]

One of our instructors has a UW GPS and it works up to 50 fsw...don't know the brand and it looks military to me.

[Scubaddawg]

Taking GPS underwater is like taking a compass in to space.....

[cancun mark]

I actually have an underwater cellphone.

I bought it for two dollars at "toys R us" and keep it in my BCD pocket, whenever someones computer or watch starts beeping UW, I drag it out and pretend to talk, nod my head etc.

It fools about 50% of divers.

[justleesa]

I actually have an underwater cellphone.

I bought it for two dollars at "toys R us" and keep it in my BCD pocket, whenever someones computer or watch starts beeping UW, I drag it out and pretend to talk, nod my head etc.

It fools about 50% of divers.
:rofl: !!!

[GeekDiver]

Fivetide

Buetooth is limited to 5 ft or so range by design so wouldn't be of much help. There defined as a PAN (personal area network) device. If they had more than a 5 ft range it would end up disrupting communications for your co-workers who also may use bluetooth.

bet theres not many on the board who know where the name bluetooth comes from? (without looking it up on the internet first)

[DoUDive2]

One of our instructors has a UW GPS and it works up to 50 fsw...don't know the brand and it looks military to me.

Ask him what it is and where he got it. I like to keep up to date on things like this.

Chris

[Ragnar]

I figure the Navy has to have developed somehing to assist with undewater navigation. I was thinking along the lines of of ULF wave triangulation. The problem with that is that those waves travel at different speeds through waters with differing salt content which would make the system fairly inaccurate without a very large number of reference points. Also ULF waves have been linked in a corrolary (not causal) fashion with disruption to marine life.

Don't know a thing about U-boats, but I bet they use some type of inertial nav. Once it's initialized with GPS, or the coordinates are input manually on the surface and it knows it's present position, all future movement can be calculated from the forces felt on the laser gyros. In airplanes there are sometimes three of these which all cross check each other. Now the question is.........how in the hell did they do it back in the forties!!!....Hmmmm......

[justleesa]

Ask him what it is and where he got it. I like to keep up to date on things like this.

Chris
Sorry, I missed this one.

I know he got it from a military buddy....when I see him the next time I'll ask.

[The Kraken]

Don't know a thing about U-boats, but I bet they use some type of inertial nav. Once it's initialized with GPS, or the coordinates are input manually on the surface and it knows it's present position, all future movement can be calculated from the forces felt on the laser gyros. In airplanes there are sometimes three of these which all cross check each other. Now the question is.........how in the hell did they do it back in the forties!!!....Hmmmm......
Needle, ball, air speed, magnetic heading, and cellestial navigation.

[DoUDive2]

... all future movement can be calculated from the forces felt on the laser gyros. In airplanes there are sometimes three of these which all cross check each other. Now the question is.........how in the hell did they do it back in the forties!!!....Hmmmm......

The directional gyro was actually used on aircraft back in the 1930s. So, the concept of gyroscopic (inertial) air navigation is a very old technology. Of course, for me to compare today's ring laser gyro to a directional gyro is like comparing a modern home to a bear cave.

The forties, however, is when modern air navigation really took hold. From the 20s to the 40s air navigation transitioned from airway lights (originally bonfires stoked by Post Office stations across the country) to 4 course radio transmitters located strategically between towns. In the 40s, the airway lights were made electric and the 4 course radio transmitters were replaced by the very high frequency omnirange (VOR) transmitters. Airway lights were eventually phased out, but VORs are still used today to define most of the federal airways that cross the United States. The LOng RAnge Navigation (LORAN) system was also introduced in the 1940s. Long flights over water typically relied upon a whisky compass, an airspeed indicator, an altimeter, and a navigator familiar with celestial navigation techniques (sun or star fixes).

Inertial systems are useful for redundancy and ocean crossings, but even today, they rarely provide the primary means of air navigation. This is because they accumulate errors over time if they are not updated with "absolute" navigation reference. Radio-navigation systems (like VOR, LORAN, and GPS) provide "absolute" navigation references and can be used to periodically update inertial navigation systems. Submarines are able update their inertial navigation systems by measuring variations in local gravity along the sea floor. I'm fairly certain that this technology is not available to the sport diver yet. ;-)

Chris

[tfohl]

Novatel makes a combo GPS and inertial nav system. (www.novatel.com)

It possibly could be packaged for underwater use and looks like it would be useful in most dive scenarios.

Best,
Tim Fohl

[StingRob]

You may want to consider the marine units (even fish finder) which have both GPS (installed on the boat or wireless) and sonar. Bunch of products on the market, serarch the internet you'll find something.

Stingrob

Does anybody know why they dont make an underwater GPS, I figured this would be something really kool, you would never have to worry about not finding a wreck, or the dive boat again.

Anyway just a thought.

Thanks

[divebear49]

My research shows a GPS navigational system is available for divers. The recreational package price starts at $450. The system works off of an umbilical connection with the diver. Otherwise the GPS would not work. The umbilical standard length is 50 feet. See website http://www.longbeachdive.com/price-list.htm

Good luck.

DiveBear49



Does anybody know why they dont make an underwater GPS, I figured this would be something really kool, you would never have to worry about not finding a wreck, or the dive boat again.

Anyway just a thought.

Thanks

[Bill51]

With the price of solidstate laser ring gyros dropping the way they have been, it shouldn’t be too long before we get something that works well underwater, doesn’t require a link to the surface, isn’t depth limited by antenna feed, and will provide full 3 axis accuracy underwater. Furthermore a gyro based INS would provide instantaneous feedback of very small changes in position including depth, surge, and other factors that couldn’t be tracked by a GPS with the antenna on the surface.

[ScubaSteve_FS]

Here is a poorman's underwater GPS. You would want to use one of the small Garmin's these days as the Magellan