UWIS - Underwater GPS?

[SeaWarden]

Has any one heard about this or used it?

It popped up on my ads: https://uwis.fi/en

Seems like it would make sense, using 3 points to find a diver's location on the surface. And using Ultrasonic to communicate.

 

[CuriousRambler]

The diver unit is attached on the air tank and it communicates with the display wirelessly via Bluetooth, Wi-Fi or inductive data transfer.

So...the display doesn't work underwater then? Bluetooth is 2.4GHz. Wifi has some 900MHz channels, but is mostly 2.4-5GHz. 2.4GHz radio loses >60% of its power in 1-2cm of water. If the transmitter was 5watts (pretty much guarantee it's not nearly that powerful) you'd effectively have less than 2mW in a foot of separation through water.

Lower frequencies will penetrate water better, which is why they're using ultrasonic for surface communication - ~20,000Hz vs 2,400,000,000Hz of bluetooth, or even twice that for wifi.

By comparison, GPS satellites operate on 1200-1500MHz, or 1,200,000,000Hz. - 50% lower frequency than wifi/bluetooth, and we know that doesn't penetrate water, or there'd be no need for this concept at all.

I'm not sure what they mean by inductive data transfer, but magnetic energy essentially drops off with the inverse cube of the distance (in air. I'm not a magnetics/electronics guy, so I don't know if water has a dramatic impact), so if you double the distance, you get 1/8th the power. Three times the distance, you're at 1/27th the power. Again, I don't see "inductive data transfer" having a useful range to communicate between a tank-mounted antenna, and a display in the diver's hands (on the other side of a metal tank, backplate, and human body, no less).

If surface support crews can use it to monitor divers and guide them via comms, I imagine that could be useful. The underwater display looks like a gimmick at first glance.

 

[michael-fisch]

Sounds like it would be as useful as a Ford Nucleon and as likely to be built or bought.
Not for me!

Michael

 

[SeaWarden]

So...the display doesn't work underwater then? Bluetooth is 2.4GHz. Wifi has some 900MHz channels, but is mostly 2.4-5GHz. 2.4GHz radio loses >60% of its power in 1-2cm of water. If the transmitter was 5watts (pretty much guarantee it's not nearly that powerful) you'd effectively have less than 2mW in a foot of separation through water.

Lower frequencies will penetrate water better, which is why they're using ultrasonic for surface communication - ~20,000Hz vs 2,400,000,000Hz of bluetooth, or even twice that for wifi.

By comparison, GPS satellites operate on 1200-1500MHz, or 1,200,000,000Hz. - 50% lower frequency than wifi/bluetooth, and we know that doesn't penetrate water, or there'd be no need for this concept at all.

I'm not sure what they mean by inductive data transfer, but magnetic energy essentially drops off with the inverse cube of the distance (in air. I'm not a magnetics/electronics guy, so I don't know if water has a dramatic impact), so if you double the distance, you get 1/8th the power. Three times the distance, you're at 1/27th the power. Again, I don't see "inductive data transfer" having a useful range to communicate between a tank-mounted antenna, and a display in the diver's hands (on the other side of a metal tank, backplate, and human body, no less).

If surface support crews can use it to monitor divers and guide them via comms, I imagine that could be useful. The underwater display looks like a gimmick at first glance.

Thanks for analyzing. My full face mask uses ultrasound to transmit, and it goes about 1km. I would imagine they are using the same thing? But doesn't seem like it. Going to save the money and stick to surface comm unit.

 

[CuriousRambler]

Thanks for analyzing. My full face mask uses ultrasound to transmit, and it goes about 1km. I would imagine they are using the same thing? But doesn't seem like it. Going to save the money and stick to surface comm unit.

I just glanced briefly, but it looks like the location buoys use ultrasonic, just like your FFM, so the theory could be solid, at least for the location function. The section I quoted seems to be communication from the receiver/antenna the diver wears and the diver's display. Their swag photos look like they've got an underwater iPad the diver can use in real time. That's BS based on the technology they claim to be using to communicate between the receiver and the tablet display...but again, I'm not an expert in this stuff, just a little passing experience.

The other thing is that GPS essentially relies on hyper accurate atomic clocks to determine your location from a satellite. My receiver knows what time it is now, when it received the satellite's transmission - which is simply a very accurate time readout. A little math to figure out the difference between the time stamp the satellite transmitted and the time stamp when my receiver picks that up - you can calculate your distance from that satellite. Do this with at least three satellites and you can resolve a position. More satellites equals greater resolution. One major hiccup in this system is atmospheric interference. Anything that slows a signal, even slightly, impacts your accuracy. Clouds, pollution, tree cover, even air temperature impact this to some extent.

Sound through water is exactly the same. If you know what speed sound will propagate, you can easily solve for distance based on a time difference. You don't usually find major thermoclines in air, but they're abundant in water. Varying salinity has an impact (probably not so much in a given operating location, but a "general" calibration won't be accurate in every location on earth), etc will all impact the accuracy. I'm no expert here either, but some different passing experiences in life; we would use submerged hydrophones to determine a location of a noise source. To do this with any accuracy required knowing our surface location exceptionally well, tracking water temperate at several depths, tracking currents, and knowing a fair amount of other fixed information. With all that information in hand, we could have a few PhD types back out a location within a couple of days.

Is it possible? Absolutely. 100%. But there's no shortage of technical hurdles to making a functional system, and I frankly don't think anybody could build such a system cheaply enough to interest anyone outside of BIG money industries/governments. I certainly won't rush to invest in the venture. It would be cool to be proven wrong though.

 

[seeker242]

So...the display doesn't work underwater then? Bluetooth is 2.4GHz. Wifi has some 900MHz channels, but is mostly 2.4-5GHz. 2.4GHz radio loses >60% of its power in 1-2cm of water. If the transmitter was 5watts (pretty much guarantee it's not nearly that powerful) you'd effectively have less than 2mW in a foot of separation through water.

It could just be that you need to place the display next to the tank mount in order to transfer data.That wouldn't be BS. Close meaning 1cm or something like that.

 

[CuriousRambler]

It could just be that you need to place the display next to the tank mount in order to transfer data.That wouldn't be BS. Close meaning 1cm or something like that.

That's a good point. I was thinking of a realtime readout, which wouldn't work. If it's something you could sync as needed, that could work. Seems silly bordering on pointless to me though. I get a readout that is several seconds old at best, with essentially zero refresh rate. All while spending extra money to incorporate wireless technology that has no place under water, instead of just making the display wired to the receiver. Or, assume they're using an actual iPad and don't want to hack wire it, your idea would work great with a wrist mounted hardwired transmitter to communicate between the display and the tank unit.

It's just the wrong technology for the application. You could make it work with some serious limitations, or you could select a more appropriate technology for the environment. I suspect it has more to do with "brand recognition" and low integration costs than any sound engineering. Everybody loves Bluetooth in their car. We can sell that underwater!

 

[tursiops]

That's a good point. I was thinking of a realtime readout, which wouldn't work. If it's something you could sync as needed, that could work. Seems silly bordering on pointless to me though. I get a readout that is several seconds old at best, with essentially zero refresh rate. All while spending extra money to incorporate wireless technology that has no place under water, instead of just making the display wired to the receiver. Or, assume they're using an actual iPad and don't want to hack wire it, your idea would work great with a wrist mounted hardwired transmitter to communicate between the display and the tank unit.

It's just the wrong technology for the application. You could make it work with some serious limitations, or you could select a more appropriate technology for the environment. I suspect it has more to do with "brand recognition" and low integration costs than any sound engineering. Everybody loves Bluetooth in their car. We can sell that underwater!

Most of your objections are quite sensible. Except...it IS a working system and has been for a while.

 

[CuriousRambler]

Most of your objections are quite sensible. Except...it IS a working system and has been for a while.

You've used it? I definitely have no experience with it, and don't intend to sound like I do. I do have experience with ultrawideband RF and the impact various media have on signal strength over distances. Based on my experience, I'm 100% comfortable saying they are not using standard Bluetooth and successfully carrying a signal underwater from a diver's tank to a device held in front of them in a position to be viewed. It's just not going to happen. They may be using the framework of Bluetooth or wifi, or some other technology altogether. If they ARE using out of the box Bluetooth in this application successfully, I would VERY much like to speak with their engineers. I know of several organizations who would be extremely interested in how they overcame fundamental physics.

Edit: if you're referring to the location aspect of it working, then that's awesome. Like I said, it's absolutely doable. I'd be curious about accuracy and the dynamic stability of their accuracy with a three buoy system, as well as rough pricing. If they're selling it for a price palatable to "normal people," I definitely give them props.

 

[Storker]

The other thing is that GPS essentially relies on hyper accurate atomic clocks to determine your location from a satellite. My receiver knows what time it is now, when it received the satellite's transmission - which is simply a very accurate time readout. A little math to figure out the difference between the time stamp the satellite transmitted and the time stamp when my receiver picks that up - you can calculate your distance from that satellite. Do this with at least three satellites and you can resolve a position. More satellites equals greater resolution

Just a slight nitpick: Your GPSr doesn't have a hyper accurate atomc clock. Which is why it needs a signal from minimum four satellites, not three, to resolve your position in three dimensions.