Tec Dive computers and dive plans

[KenGordon]

Also, read this Evolution of Dive Planning - Shearwater Research

 

[dmaziuk]

... That software then say simply spits out a set of basic tables ... [that] ... can then be downloaded to the actual dive computer (and CRC'd and parity checked as normal)

You're assuming everyone's a good player and is uploading those tables from that software, and for this dive. That simply is not what happens in real life.

 

[boulderjohn]

It could also display an "off target" indicator, tell you how to get closer to your plan.

This goes back to what I wrote earlier and what is covered nicely in the Shearwater article mentioned in post #20.

When you make that initial plan, it is essentially a worst case scenario that ensures you have enough gas. As Ken and I said in previous posts, you do the dive that presents itself to you, which you cannot predict well enough to create a perfectly accurate plan. You just need to be able to stay within that worst case scenario. There is no reason to get closer to your plan, so there is no need to have a computer function telling you how to do it.

Quite a few years ago, in one of the previous eras I described earlier, a well-known wreck diver had a raging ScubaBoard debate on this very topic. He and his fellow wreck divers, often doing exploration dives, used two computers, way back then, and the "plan your dive and dive your plan" extremists were arguing that you had to plan your dive ahead of time to the minutest detail and then follow it perfectly to the surface. The wreck diver said it was impossible for him to do that, and he said that if you know the dive you will have that completely before you do it, then you are doing very, very boring dives.

 

[MaxTorque]

You're assuming everyone's a good player and is uploading those tables from that software, and for this dive. That simply is not what happens in real life.

True, and false lol!

Yes, the user will have to correctly load the right plan into their computer, but then they also have to correctly take all the right kit with them too! It's gonna be bad if the stage cyl your really need for THIS dive is still sitting nice and safely in the rack on the boat 100m above your head! (And here, the preloaded diver computer could also be used to help the user check they have the right setup for the dive they are about to do!)

There is no reason the computer can't hold multiple plans, with a text and number, and even a date / time check if necessary

It's no different to remembering to write your plan on your slate, or label your cyls with MOD etc Fallable is Fallable.....

The target plan is only a useful and reliable reference to what you planned, your deco obligation for the actual dive profile followed is still being calculated and displaid as normal

 

[happy-diver]

In a dive today, we would have made the same basic plan and planned on the same gas amounts, but we would have gotten out of the water a lot sooner but with a lot more gas left over.

This sentence is driving me nuts boulderjohn

 

[Centrals]

True, and false lol!

Yes, the user will have to correctly load the right plan into their computer, but then they also have to correctly take all the right kit with them too! It's gonna be bad if the stage cyl your really need for THIS dive is still sitting nice and safely in the rack on the boat 100m above your head! (And here, the preloaded diver computer could also be used to help the user check they have the right setup for the dive they are about to do!)

There is no reason the computer can't hold multiple plans, with a text and number, and even a date / time check if necessary

It's no different to remembering to write your plan on your slate, or label your cyls with MOD etc Fallable is Fallable.....

The target plan is only a useful and reliable reference to what you planned, your deco obligation for the actual dive profile followed is still being calculated and displaid as normal

I am not aware any dc will let you input any plan at all.

 

[dmaziuk]

It's no different to remembering to write your plan on your slate, or label your cyls with MOD etc

Yes it is: not writing your plan down on your slate is your fault, a computer not matching your uploaded plan is a class-action suit in the making.

 

[MaxTorque]

Yes it is: not writing your plan down on your slate is your fault, a computer not matching your uploaded plan is a class-action suit in the making.

er, i think you might be missing something rather important:


The computer making a mistake could lead to a liability, the user misusing the computer and making a mistake, less so (as longs as the instructions and warnings for use are clearly laid out in the instruction / user manual)

So, if the user downloads the wrong plan, that is no different to me going to my current computer and setting a Nitrox air percentage of say 40%, but still using atmospheric air at 21% and as a result, getting bent because the computer steering me onto a deco massively undercalculating my nitrogen loading and hence my deco obligation.

The computer hasn't made an error, i have!

And please remember, i am talking about a dive plan that simply allows the computer to provide a "target depth at this time as planned". It won't change the deco calc, because that is still being done on MEASURED values (ie pressure) and user set inputs (gas concentrations etc)

Checking the plan has been transfered correctly to the dive computer is simple, and plenty of suitable checksum and error detection/correction algorythms exist already to just that. If those doesn't match, the dive computer simple rejects the downloaded plan and says "try again"

 

[MaxTorque]

BTW, in my head, the most userful bit of a target depth is to help the diver stay on target rates rather than at setpoints.

Ie if you plan an ascent of 9m/min, your target depth will start scrolling up and away from you, so all you have to do to ascent at 9m/min is to keep up with it. Rather than doing mental maths in your head during an ascent that seems like a useful prompt i think?

 

[broncobowsher]

No matter how much you wing it once you get to a dive site and let the computer take care of things...
You still have to plan ahead of time your gas needs. And follow the limitations.

There are days where I am not sure where I will be diving at. What is the crowd like? What is the water like? Weather? Who happens to be there that I didn't know was going to show up. etc. A fair bit of winging it. But it isn't really winging it. There is just a lot more planning done ahead of time. The winging it part is which plan to use. Which comes down to overplanning. And not using most of the options.

I'll make a list of options with the gasses I brought. Essentially a half dozen different dive plans. Get to go deep, ok with the gasses I have, this is my window. Shallower, I get more time with this other plan. Made up the night before while checking the mixes. It's what you do when you have soft plans. It's one thing to have a dive site that is fixed, you will be going here, diving this, no other options. Or when you have a lot of variables right up until you are in the water (and sometimes while in the water).

Have no shame in coming back with more gas than planned, better than not having enough.