Dive tracker/Underwater navigation

[dmaziuk]

Tagged, I for one, like the idea of using accelerometers to monitor / calculate position.

It doesn't really work because of current drift. Or, rather, it does, but the gyros required need a submarine to house 'em. Or an ICBM.

What you could do is log the IMU readings along the way, and GPS coordinates of your start and end positions, and then try to back-fit the calculated trajectory after the fact. At that point you're back on the boat already, so here's little practical use, but until someone starts doing this, we won't know how (in-)accurate the cellphone/dive computer IMUs really are.

 

[lostsheep]

I want to see a quantified estimate of the error accumulation rate.

 

[BoundForElsewhere]

hmmph. best thing is still cave line. whether they find you or not just depends on how big of a spool you have.

 

[CT-Rich]

I agree, competence with a compass would be the first line of defense. That takes time to develop. Underwater strobes are also an option. A blinking light will carry pretty far. A light hanging from an anchor line will increase the chances of you finding your way back to it.

If you are going to leave something like a deco bottle on the anchor, you need to make damn sure you will find it. A wreck reel would be useful and a beacon would work.

 

[moose_grunt]

It doesn't really work because of current drift. Or, rather, it does, but the gyros required need a submarine to house 'em. Or an ICBM.

What you could do is log the IMU readings along the way, and GPS coordinates of your start and end positions, and then try to back-fit the calculated trajectory after the fact. At that point you're back on the boat already, so here's little practical use, but until someone starts doing this, we won't know how (in-)accurate the cellphone/dive computer IMUs really are.

Also, acceleration is change in velocity over time. To oversimplify things a lot, once you reach a constant velocity, acceleration is zero. That’s a LOT different than calculating speed and direction. IMUs try, but most seem to rely on GPS positioning to verify starting and ending points (your car GPS nav unit when going through a tunnel, for example).

That’s why units like the Seacraft nav computer uses an external log, to actually get that velocity information rather than relying on acceleration.

I really wish it were simple to build a small, cheap, accelerometer-based nav unit that works underwater without GPS or other external signal processing. It seems like we’re not there yet.

Jim

 

[emoreira]

While I am at heart a complete nerd for new and interesting technology and gizmos, getting good with a compass is your best defense for getting back to your anchor. I (personally) view this as technology to fix a problem that is really fixable by developing a skill set. Certainly there would be uses but for the everyday run of the mill recreational diver learning to use a compass is the easiest and best bet.

All of my above mini rant aside though, both of those items look interesting.

This seems to be the standard answer whenever this question arise.
I can compare this to a GPS for a car. There are maps and signs in the roads, however every one uses a GPS.
If there is a device that can guide you to the entry point or to a specific point in your dive, why should you struggle with the heading of a compass ?
We as divers dive to see the bottom and the beauties of the environment, not to follow the heading of a compass to return to the entry point.
Such a device would be great to have.

 

[Magnus Lundstedt]

How advanced would it be to make a device that give me direction and distance to an boi or a beakon attatched to the anchor line?

 

[CT-Rich]

How advanced would it be to make a device that give me direction and distance to an boi or a beakon attatched to the anchor line?

A light beacon will be visible pretty far, depending in the clarity of the water. The problem with any beacon is it needs to transmit reliably through water. Sound transmits really well, but four times fast than air and can reflect off pretty efficiently. A blinking strobe And careful use of a compass is probably The best skills solution.

A gadget shouldn’t replace a skill.

 

[CoDiver303]

Tedious, but effective....

Nav-Finder

• CoDiver303
• Jun 15, 2020

 

[Scuba Lawyer]

I have had a Dive Tracker Sport for what seems like 20 years now. They were a lot cheaper back then. I love mine. I can jump off the boat hunting Halibut and travel any direction I want without worrying about where I am in relation to the boat. I can follow sand channels, cross over to reef lines, head off across featureless sand bottoms, etc... When I'm ready to head back to the boat I just swing my receiver unit around in a circle until I pick up the transceiver signal and it takes me back to the boat every time. No more surfacing to get bearings. No more compass work. It's fantastic (IMHO). Of course I have a pretty good idea of the general direction of the boat at all times anyway just from experience but a few times I've been surprised when it takes me in an odd direction, but straight back to the boat nonetheless. Awesome product. My 2psi.

DiveTracker-Sport | Desert Star Systems