Originally posted by reddog
I am waiting for when they figure out how to transmit the GPS signals underwater. Will probably need a system of repeaters scattered about any dive area, but that would be the first significant improvement in underwater navigation in many years!
Don't hold your breath waiting for this.
Chip based 6 axis gyros are dropping in price. It would surprise me if someone didn't come out with a device like the following in the next 2 years:
Looks like a computer (indeed it is but it's only a navigational computer, at least at first). It gets "mounted" either to your vest or tank. Small display. Initial models will "turn on" when you hit the water (or go 3-5 feet down). They will record that as your "reference position".
The device will keep track of where you are and constantly display a vector (direction to go) pointing back at your "reference position". And indicate distance to the reference position (meters, feet...).
This is "rocket science", so to speak. But everything about it's known, it will work, etc. The chips (one with 3 rotational axis gyros and one with 3 directional gyros) are available today. The algorithms for computing location relative to your "reference" position have been around for many decades.
The key issues have been price and market size.
Price: As the cost of computers, displays and the gyro chips drops to about a hundred bucks, it becomes feasible to build this type of navigational device for scuba for "several hundred" dollars assuming product liability cost doesn't queer the deal and assuming a production run of maybe 5000 units.
Market: The other issue, of course, is market. How many people would really pay $795 for an underwater navigational computer? 5 to 10 thousand units may be the minimum volume at which most vendors will break even (after all startup costs, etc.) [This is a real SWAG.]
Accuracy is an issue that deserves some discussion. A black box like this will accumulate errors over time, i.e., the longer it runs, the greater the "slop" in the calculation. In theory, a device like this should, with very high accuracy gyros, be able to guide you back out of a complex cave and tell you every turn you should make, etc by memorizing exactly where you were every 10th of a second. I say in theory. In practice, particularly with the initial ones, you might be lucky to get 100 foot error (distance from reference point) on a one hour dive (again, this is a SWAG -- someone would have to do the engineering work to look at accumulated error).
Outside of accumulated error (which will vary depending on the price of the gyro chip and the length of the dive), the device concept is surprisingly robust. It doesn't count kicks or anything like that. It measures how far you've moved in 3 D by measuring total G forces (linear and rotational) that it's been exposed to.
Enough for now...
:doctor:
