Random Thought / Question....start / end guidance

[KerrenL]

Was thinking earlier, my Suunto Ocean maps out my dive route, which I assume it does by logging where you enter using GPS, then perhaps using compass and depth to plot the route (although I have no idea how it maps distance, maybe an assumption on time?). I might be wrong but I didn't think computers could stay connected to GPS when on a dive?

So it got me thinking, if it can figure out my route, why can't I set a start point then press a button to navigate back to start point? I know most computers (inc my shearwater) have a bearing marker so you can follow a bearing then a reciprocal bearing, but for dives that are round reefs it would be really useful if you could just mark an entry point then have your computer guide you back to it when you want to turn the dive.

I know it's lazy, blah blah blah, but just wondering why it's not been done, if it can be done? Surely would also help with safety if a diver ever lost the group and needed to find way back to boat (even at the surface)

 

[MB NZ]

That would be a great feature to have on a dive computer, but I don't think it exists yet. Happy to be corrected. The Suunto Ocean doesn't appear to give real time information on your location, yet it can map your dive. Not sure how that works!

 

[Johnoly]

(although I have no idea how it maps distance,

That's the UW mapping accuracy problem with so many factors affecting it's measurement.

 

[inquis]

It estimates during the dive based on the compass/accelerometers but then corrects everything after surfacing, based on the final GPS fix.

 

[Mobulai]

It estimates during the dive based on the compass/accelerometers but then corrects everything after surfacing, based on the GPS fix.

Exactly!
1st gps fix pins the start; acc/compass/imu does some estimation, after surfacing the 2nd gps pins the endpoint and the computer scales and re-stitches the trajectory estimate in between, correcting the dead-reckoning error
Kinda like a panorama image

Without the 2nd gps fix there’s no way to remove the error and you’d continue drifting away

E2A: While we are at it, I kinda suspect/hope that Garmin would be the ones to bring „live“ underwater navigation
Their transmitters already ping distances and can relay/bridge information, and there’s a surface submerged beacon as part of the ecosystem (the buoy)

So they have the best chance to kind of use the buoy as a fix beacon for gps, and various transmitters + the imu mapping to continuously correct the trajectory

But that means at least a few (maybe a min of 3/4) are needed to be able to get a barely decent triangulation— so the feature would be highly unstable (or you’d need three bouys around the site) and expensive

Who knows, someday

 

[Belzelbub]

So it got me thinking, if it can figure out my route, why can't I set a start point then press a button to navigate back to start point? I know most computers (inc my shearwater) have a bearing marker so you can follow a bearing then a reciprocal bearing, but for dives that are round reefs it would be really useful if you could just mark an entry point then have your computer guide you back to it when you want to turn the dive.

Yeah, that's not how it works. During the dive, it really has no idea where you are. It knows your depth, and direction you are heading, but it doesn't really know how far you traveled. It uses that information to make a guess at your actual route. But, it needs to know where you ended to put together the map.