Self Contained Navigation Tools

[Newhampster]

Just noodling about a tool you could wear that would help you find your way back to where you entered the water.

Someone made the mistake in an earlier thread of assuming that GPS would work. Well, the signal won't make it into the water so that's out.

But micro-machine type accelerometers are now getting reasonably cheap (or will be in a year or two). With three of them, it shouldn't be real hard to build a diver's inertial guidance device, i.e., a computer and accelerometer based unit that would keep track of where you were, give you a vector towards your start point and, perhaps, even show you how to go to return the way you came.

With a pressure sensor, there would be extra info to help calibrate the Z-axis calculations, helping improve the accuracy of the device.

What got me thinking of this was reading about some more transmitter-based "find the boat" devices. And reading about the general inaccuracy of the vector they give you.

I think the accelerometer chips are getting really cheap because the auto industry uses some of them (but probably not yet at the accuracy level needed for a good inertial guidance system).

Anyone have contacts at some of the dive computer firms? TI (for accelerometers)? Other ideas?

 

[TexasMike]

Very interesting idea.....and I think you might be on to something.

I think you need to find the right techie to help you develop a good design and head to the patent office with this one.

 

[Jonathan]

H'mmmm interesting idea. It's all a bit mumbo jumbo for me but I have a friend that makes gyros for the offshore industry. He claims things are quiet at the moment.....

If you're interested drop me an email and I'll put the two of you in touch.

Jonathan

 

[scuba_adventurer]

I have always wondered if somebody could make a GPS surface unit that you mount to your boat, flag, etc, with an underwater device similar to the Neverlost by Uwatec, and then you could plot some rough waypoint maps. Would be nice, but I am sure to combine those two systems would cost a fortune. If Scubapro ever does it, it will cost a ton. Why, other than the imprecision of sonic locaters, would that not work.

 

[syruss32]

As you posted there is no true GSP for underwater, but there are some alternatives. The first being UWATECs underwater digital compass. It saves up to 9 headings and times so you can get the recipricals to these and return to your starting point. That is probably not totally accurate as far as getting you back exactly like GPS but it sure would help. They go for about $250 I think and on ebay they come up occassionaly for $159.00 buy it now price, or if you prefer to bid it will go for $200.

The next choice is an underwater locator. I was reading about the device I think from divers direct. It basically detects a signal from another device and lets you know which way to go to go towards it. The main device will handle up to 8 receivers in the water so you could put this on a dive boat with 8 divers and all return right to the boat.

I will see if I can find the link for the locator. I think uwatec info is at http://www.uwatec.com

Hope this helps you out some.

 

[Ontario Diver]

There are "pocket GPS" concepts that have been around for years.... Air navigation tools like Loran and VORs are good examples. 20 or so years ago, artic surveyors would set up 5 radio beacons and use them like we now can use GPS sats. A modern GPS set up uses 5-12 sats to figure out where you are. You couldn't mount a single unit on a boat and use it to figure out where the heck you are....You would need at least 3 units and they have to be far enough apart to remove any angle of error. Not enough room on a dive boat (unless you are on Queen Mary Dive charters )

Automatic recipricals are nice but your course is still affected by currents which compasses don't understand.

Accelerometers are interesting but tend to be very sensitive to being held upright.(My bouyancy control is not that good.....) and since they only measure a change in vector, you'd still need a timer to correct the vector into distance. By using a larger gyroscope to keep it upright; well the size and power may make it unsuitable for diving (Maybe I could get rid of my weight belt..)

Hmmm, maybe its time to sign up for that UW Nav speciality.

 

[scuba_adventurer]

I realize how a GPS works. I was saying that the GPS unit would be used to pinpoint your starting position above water, basically putting you in the right area on the underwater map, then a sonic locator could measure your distance and direction from the GPS, plotting your close to exact position on a map.

It is kind of complex, but I think it would probably work. The other problem is underwater topographical maps in detail enough to be suitable for diving are rare, so you might not be seeing what your map says you should be seeing.

 

[Butch103]

hmmmmmmmm a compass I find works really well, in any weather, conditions and it is fool proof. .................. I am proof of that. ..........My wife keeps calling me an old fool.................hehehe

To high tek for me. I still follow the old KISS formula.......

ahh that means Keep It Simple Stupid for u young ones. hehehe

Butch eace:

 

[Se7en]

Originally posted by Newhampster
But micro-machine type accelerometers are now getting reasonably cheap (or will be in a year or two). With three of them, it shouldn't be real hard to build a diver's inertial guidance device, i.e., a computer and accelerometer based unit that would keep track of where you were, give you a vector towards your start point and, perhaps, even show you how to go to return the way you came.

We use a device just like this racing cars, and they are accurate enough to draw a map of the track (with various acceleration details for each point) and show you where you have gained or lost time at any point, or where you were getting more or less acceleration or deacceleration. Used like this they are accurate to a couple of metres.

However, by design, they are incredibly sensitive to any tilting away from their set orientation - this is how they measure movement. Swimming with one would be out of the question.


And then we have currents...

Mike