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Author Topic: Could we develop an underwater GPS?  (Read 6876 times)

Emilio Romero

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Could we develop an underwater GPS?
« on: 11/05/2010 14:30:02 »
Emilio Romero asked the Naked Scientists:
   
Hi. You're great guys, thanks for a fantastic show.

My question is: Would there soon be a GPS that works underwater as well as those on the surface?

What do you think?
« Last Edit: 11/05/2010 14:30:02 by _system »


 

Offline graham.d

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Could we develop an underwater GPS?
« Reply #1 on: 11/05/2010 15:36:23 »
No. The GPS system is based on radio signals transmitted by a number of satellites. These signals will not penetrate water to any significant extent.
 

Offline imatfaal

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Could we develop an underwater GPS?
« Reply #2 on: 11/05/2010 17:11:06 »
AS an alternative you could use sound waves - obviously not from a satellite - which could create a triangulation system.  We read that whale song can travel hundreds of miles - presumable an artifical analogue could be created.  Not sure why one would want to though - and it might further confuse the whales and dolphins who already have to put up with terrible sound pollution.
Matthew
 

Offline engrByDayPianstByNight

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Could we develop an underwater GPS?
« Reply #3 on: 10/06/2010 03:08:23 »
Providing underwater satellite-guided navigation will assume that the GPS system (the constellation of satellites) maps oceanic terrain as it does the land mass on earth. I'm not sure if that's been done. If this were true, then theoretically, one approach I could think of is to deploy a large number of buoys out in the ocean that translate the electric signals to sonic signals and emit them underwater.

Obviously there will be environmental and ecological concerns with this approach. Also, you'll want to ask what the application is that can use such a service. For scuba divers, you probably don't go far underwater to need a GPS system to navigate for you. Most submarines these days have their dedicated satellite uplinks (and the submarines themselves are equipped with powerful antennas) to guide their navigation.

Also, let's face it, there're far more people living on land than underwater. So it probably doesn't make commercial sense to bring the GPS service 50 feet below sea level, even if it's technologically possible.
 

Offline Bored chemist

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Could we develop an underwater GPS?
« Reply #4 on: 10/06/2010 07:01:11 »
"Providing underwater satellite-guided navigation will assume that the GPS system (the constellation of satellites) maps oceanic terrain as it does the land mass on earth."
No it doesn't.
If you took away all the water from the oceans the GPS system would work fine on what is now the sea bed.
Relaying the signal by sonar from the surface wouldn't work properly because of the effects of currents and the variation of the speed of sound in water with temperature and salinity.
 

Offline LeeE

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Could we develop an underwater GPS?
« Reply #5 on: 10/06/2010 07:42:03 »
I was under the impression that short range sonar beacons were used by deep sea submersibles for location finding when working on long term fixed location projects.
 

Offline engrByDayPianstByNight

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Could we develop an underwater GPS?
« Reply #6 on: 10/06/2010 17:54:37 »
"If you took away all the water from the oceans the GPS system would work fine on what is now the sea bed."

Mmm… If you’re talking about pinpointing the location of someone standing somewhere at the bottom of the ocean (with all the water removed), the current GPS system could do that. However, for navigational purposes (from Point A to Point B), I think you’d still need to have a map of the whole terrain (as is done on land) for that, which requires mapping of the terrain. 

Since underwater GPS navigation’s never been done before, there’d be a number of new factors to take into consideration if we ever wanted to do that (signal propagation, environmental, ecological, etc.). Sonic waves may or may not be the best way, and some modulation/encoding would certainly have to be applied in order to protect/sustain signal propagation in the water.
 

Offline Bored chemist

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Could we develop an underwater GPS?
« Reply #7 on: 10/06/2010 18:52:20 »
The GPS system gives you latitude, longitude and altitude; nothing else.
If you have some gadget that uses that data to show where you are on a map that's very nice for you, but it's not the GPS system.
Sat nav is not the same as GPS.
 

Offline engrByDayPianstByNight

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Could we develop an underwater GPS?
« Reply #8 on: 10/06/2010 19:52:22 »
Yes, you’re right. I stand corrected. I should have separated GPS-based applications from GPS itself.
 

Offline engrByDayPianstByNight

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Could we develop an underwater GPS?
« Reply #9 on: 10/06/2010 19:58:40 »
Although I'm not sure: with all the water removed from the oceans, how altitude would be determined by the GPS. Currently, is altitude measured with respect to the sea level?
 

Offline Pumblechook

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Could we develop an underwater GPS?
« Reply #10 on: 11/06/2010 04:42:02 »
No. The GPS system is based on radio signals transmitted by a number of satellites. These signals will not penetrate water to any significant extent.

Probably a matter of millimetres at GPS frequencies.  Communications with submarines is via ELF ..extremely low frequencies which can only carry very very slow information. 
 

Offline Bored chemist

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Could we develop an underwater GPS?
« Reply #11 on: 11/06/2010 07:14:39 »
Although I'm not sure: with all the water removed from the oceans, how altitude would be determined by the GPS. Currently, is altitude measured with respect to the sea level?
It's measured with respect to the satellite (and, therefore, the centre of gravity of the Earth).
It's reported as height above sea level.
 

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Could we develop an underwater GPS?
« Reply #11 on: 11/06/2010 07:14:39 »

 

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