kd5izq
Guest
Very true, and I'm afraid that be the future impedement on underwater GPS, but who knows what the future may hold. I'm probably wrong, but doesn't it take a very low range frequency to make its way through a material as dense as water?
Underwater Cellular
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weight_for_me
Contributor
kjunheart...good point..I can see a definate use for something like that for SAR work.
Randy...
Randy...
tinman
Contributor
uptight stock broker closing deals at 100' wreck dives, bored teenages suffering from Gameboy withdrawl getting their fixes on OW cert dives, yah can't wait....This is the only place my cellphone & the WORLD can't reach me...
Always the optimist, I suppose this could be a potential emergency communication tool - perhaps better than shooting a bag and hoping someone sees - NEED AIR, TRAPPED...SEND PIZZA & GAS quick...
Always the optimist, I suppose this could be a potential emergency communication tool - perhaps better than shooting a bag and hoping someone sees - NEED AIR, TRAPPED...SEND PIZZA & GAS quick...
Grajan
Contributor
Well - You can have it - at a price.
A basic installation cost about $1,000,000 p/a to install - probably more but its kind of academic with that many noughts.
Go to the following link and hit the NASNet button on the left:
http://www.nautronix.com/otg/main_products.html
We are doing some fun stuff out in the 'deep'.
A basic installation cost about $1,000,000 p/a to install - probably more but its kind of academic with that many noughts.
Go to the following link and hit the NASNet button on the left:
http://www.nautronix.com/otg/main_products.html
We are doing some fun stuff out in the 'deep'.
kd5izq
Guest
Had to pick myself back up off the floor after reading that price 
. From the sounds of things they have basically submerged GPS antanaes, but it will only work in an area they have submerged the GPS Receiving / NASNet Sending units. Did I understand that right?
. From the sounds of things they have basically submerged GPS antanaes, but it will only work in an area they have submerged the GPS Receiving / NASNet Sending units. Did I understand that right?
Grajan
Contributor
Like all (most) underwater positioning systems it uses the speed of sound as a distance reference.
To date this has always been done by sending a signal from one beacon to another, getting a reply back and measuring the distance by travel time.
The NASNet system works by having an array of beacons continuously transmitting synchronised signals (like GPS satellites).
The reciever measures the relative timing of those signals and thus positions itself in the array, hence the analogy with GPS.
This is new stuff and only likely to be used to provide positioning in large subsea fields.
I hope that makes sense. I do ot know why their URL to the PDF description does not work.
To date this has always been done by sending a signal from one beacon to another, getting a reply back and measuring the distance by travel time.
The NASNet system works by having an array of beacons continuously transmitting synchronised signals (like GPS satellites).
The reciever measures the relative timing of those signals and thus positions itself in the array, hence the analogy with GPS.
This is new stuff and only likely to be used to provide positioning in large subsea fields.
I hope that makes sense. I do ot know why their URL to the PDF description does not work.
kd5izq
Guest
Makes sense to me. It was basically what I thought, just minus the actuall interface with GPS signals. Oh well.
Grajan
Contributor
You do not need a direct interface to surface GPS. Each of the NASNet beacons is boxed in to precise (as possible) surface coordinates using a DGPS equiped surface vessel. Unlike satellites they stay still.
Once we have the coordinates of the beacons accurately placed in our surface coordinate system all underwater measurements of position are in that same coordinate system. The GPS becomes un-nessecary for subsea positioning at that point although we would still use it for positioning surface equipment due to speed of sound variations in the subsea positioning system.
Once we have the coordinates of the beacons accurately placed in our surface coordinate system all underwater measurements of position are in that same coordinate system. The GPS becomes un-nessecary for subsea positioning at that point although we would still use it for positioning surface equipment due to speed of sound variations in the subsea positioning system.
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