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mikealder
Pocket GPS Moderator
Joined: Jan 14, 2005
Posts: 19638
Location: Blackpool , Lancs
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 Posted: Sun Mar 18, 2007 1:41 pm Post subject: |
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p800 that is similar to the methods a few of us have mentioned, however I am a little concerned as to the explaination of why GPS won't work underwater!
| Quote: | | GPS doesn't work underwater, as the signal cannot reach the satellite from a submersible |
The GPS is the receiver not the satellite, but I guess the rest of it is accurate - Mike |
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40apple40
Occasional Visitor
Joined: Aug 06, 2005
Posts: 11
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| Posted: Fri Mar 23, 2007 6:54 am Post subject: we use pingers |
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hi,
here's some info that may be of interest.
i'm a subsea engineer / R.O.V pilot. R.O.V stands for remotely controlled vehicle. the vehicles are fitted with cameras, sonar & beacons (pingers).
the vehicles are used to go down to as much as 3000m water depth, to lay, bury & repair telecoms cables, power lines & pipelines.
positioning of the cables & pipelines is critical, as is the location of the vehicle. this is ascertained by a similar method to the quote above - the R.O.V is launched from a surface vessel equiped with Differential GPS (a more accurate form of GPS accurate to a metre or so) & an accoustic receiver/transmitter.
during a dive, the ship will transmit an accoustic ping on a channel specific to the pinger (also called beacon or transponder) on the R.O.V at a settable rate of maybe once a second.
this causes the R.O.V pinger to be interagated & it will respond by emitting a reply signal. this reply signal is decoded by the receiver on the ship (using the time delay & known speed of accoustics) to give an accurate position relative to the ship & depth (to just a few metres but i'm not sure of exact figures - normally, cotracturally this needs to be within 10m though).
obviously, the ships positon is known. during diveing ops a navigation screen is used that displays graphically the location of ship, R.O.V & work site so while flying the R.O.V it can be a bit like playing a computer game (a crappy one that is).
if there were enough surface gps receivers then under water positioning would be generally possible if the person under water had a receiver to decode the surface ping signal. |
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40apple40
Occasional Visitor
Joined: Aug 06, 2005
Posts: 11
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| Posted: Fri Mar 23, 2007 7:04 am Post subject: we use pingers |
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forgot to mention that the receivers used on ships are directional, so is knows the bearing of any transmitted signal.
i'm not sure about all the technicalities but because only 1 receiver & one beacon is required with these systems to get an accurate 3D position of range, bearing & depth.
hope i didn't waffle on too much. |
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40apple40
Occasional Visitor
Joined: Aug 06, 2005
Posts: 11
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| Posted: Fri Mar 23, 2007 7:14 am Post subject: we us pingers |
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| hello again - here's a link that explains things better than i can: |
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gascap
Occasional Visitor
Joined: Sep 21, 2008
Posts: 1
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| Posted: Sun Sep 21, 2008 2:39 am Post subject: underwater gps |
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Underwater GPS
I have an idea that I have been working on for underwater gps its alittle crude but I think for all practical purposes it should do the trick. It will work on 2 parts one from a dive boat transmitting a ping for sonar and update the next is a cute little dive computer that will send out periodic pings to find the boat or bouy transponder and update a position with depth and profile even update current position and adjust for current and depth a downloadable scan of the ocean bottom from a larger piece of boat mounted equipment and you can have a visual map on your dive giving you original position and boat position against the backdrop of a topographical map. anyway its a work in progress. Still waiting on some financial backing to move things alittle faster. |
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