DIR and Computers

Please register or login

Welcome to ScubaBoard, the world's largest scuba diving community. Registration is not required to read the forums, but we encourage you to join. Joining has its benefits and enables you to participate in the discussions.

Benefits of registering include

  • Ability to post and comment on topics and discussions.
  • A Free photo gallery to share your dive photos with the world.
  • You can make this box go away

Joining is quick and easy. Log in or Register now!

wetlettuce

Contributor
Messages
88
Reaction score
0
Location
East Yorkshire, UK
Hi

I've just finished JJ's book on DIR. It's not bad but I have a question regarding computers.

In his book he states three methods of dive planning.

Tables, Computers and Personal Decompression Software. He then states 13 disadvantages of computers without stating any positives about the other two methods although I assume he supports his deco software. He does say that tables are the foundation and should be learnt and understood by divers.

One of his disadvantages of computers is the algorithm they use and how they extend deco time. When I looked at the GUE decoplanner software they use Buhlmanns algorithm which is the foundation for virtually all computers on the market today.

I can understand the GUE software giving me the best mix to use, and then if I was inclined I could upload this to a technical dive computer like the VR3. However this would still not be DIR, (unless of course they team up with or create their own brand of Dive computer). However I am a nitrox diver and so dive shallow and have no need for advanced mixes as yet. Many people are now doing so and I have heard whispers in BSAC that they are considering teaching nitrox as part of their main syllabus rather than a technical skill.

JJ states that Oxygen toxicity is now the biggest danger for nitox divers and yet he criticises dive computers for showing that critical information.

When we are using computers we are told that if the battery fails (which has been checked during the dive) or the computer fails during the dive then immediately abort the dive and stay at six meters for as long as possible then do not dive for 24 hours. Seems logical to me.

I like computers, they are more accurate than me, they track depth, time and temperature and speed of ascent and descent better than me and then can calculate Buhlmanns algorithms better than me. If I use tables then many dives that I do would not be possible due to the conservatism of them. I do back up with tables if I need to although this is irrelevant when you consider what to do if your computer fails.

The same things could be said of a bottom timer. If they fail you have no record of your maximum depth and so how can you use tables to carry on ? Also my computer will calculate decompression and bubble creation live and so is using more accurate data. Deco software can be nothing other than a forecast of what you should do if all of the parameters are correct and if you do something different during the dive then all subsequent info is invalid.

With all the benefits of DIR it seems a shame that they are so resistant to what could be the real breakthrough in diving. Technology will only get better. Better algorithms better deco planning and more reliable.

I'd like to be a DIR diver however until their attitude changes and they embrace such a useful piece of kit I shall be forever discounted as a 'stroke'.

Comments welcome

Kindest Regards

Andy
 
this subject has the potential of turning into a flame if not replied to delicately . the points I am making are my opinions . that said here goes.most computers enter in some safety margin in the programming . I would rather run my own tables and enter my own safety margin that I am comfortable with than have some computer guy that is not even a diver do it for me.you mentioned about the tracking of O2 by computers . most computers only track part of the O2 picture and not all. you can get into trouble with nitrox computer and not ever know it.we always have 2 bottom timers so even if one quits you can still follow your dive plan .we always draw up emergency dive plans so if something goes wrong and we have to go deeper /stay longer we have a plan for it .I used do dive computers exclusively but after going to tables I feel much more comfortable .as I am more aware of my profile ,instead of letting a bar graph do my dive planning for me.
Of course using tables requires an element of pre-dive planning some divers arent willing to commit to.
joens
 
Hi

When I did a little research into Dive Computers I found that the companies enlist the help of Buhlmann et al to create the algorithms (at least uwatec and suunto as well as the VR3). The Deco planning software uses the same type of algorithm in its calculations and these algorithms are created by scientists, not software programmers.

My comment isn't really about tables being bad, I think they're great. Easy to use, understand and err on the side of caution. However, tables were created a long time ago, different agencies use different tables and this is still before the advances recently made in the application of deeper stops to prevent mico bubble formation.

However, my question is why should deco planning software be superior and why should computers be criticised by JJ et al? I know that enhanced mixes etc will need more specific solutions but I am talking about rec diving and nitrox. Surely computers are a benefit and make diving easier.

It sounds like you're more technical diver 'running your own tables' etc. but an inexperienced or recreational diver may find referring to tables underwater more task loading than being guided by a computer.

Kindest Regards

Andy

PS Whats a 'flame'?
 
A dive computer is a tool that provides information based on algorithms and input of realtime data.
Dive planning software is a tool that provides information based on algorithms and input of planned data.
Current dive planning software allows consideration of more variables than current dive computers.
Dive computers can compensate for more plan deviations as they occur than pre-planned tables cut with topside software.
I use both. I cut tables to back up the computer, and I back up the tables with the computer. But I know which one is more flexible in the water, too.
Make your own decisions. But don't believe any computer (or software, for that matter) than gives you an unreasonable answer. How do you know what's unreasonable? That's where study and experience come in. Go diving.
Rick :)
PS This answer is my opinion and has not been cleared by any DIR czar.
 
one aspect of computers that can and does get people in trouble on multiday repetitive dives [ and tables also depending on the tables ] is that every tissue in your body ongasses and offgasses at a different rate some tissues become completely saturated in a manner of minutes and some take days not only to become saturated but to eliminate the nitrogen as well, most computers and tables take several of the main tissues and calculate based on them but on a multiday repetitive dive you can gradually build up levels of nitrogen that can cause troubles .for instance most computers completeley zero out after 24 hours same with some tables some do it sooner . in reality after 12 or 24 hours you still have residual nitrogen in parts of your body even though your computer says you dont and if you keep diving day after day there is a possibility of those levels increasing to a level causing injury without you knowing .that is why many people reccomend taking a day off in a week of diving . but some" topside software "
calculate that for instance GUE's Deco planner takes up to 2.5 days to indicate completely offgassed .Granted a diver who dives on a 30' deep reef would likely not get in trouble even if they didnt even use a computer or anything . but the closer and more often you dive to the no deco limit and certainly if you do deco diving you need to have an increased awareness that most dive computers cannot keep track of for you.
Chris Joens
P.S. a flame is when we forget we are discussing opinions and then the discussion gets real lively.
 
Obviously computers vary, but the Suunto computers take days to zero out, certainly over 72 hours.

I'd also argue that most computers are so conservative that the chances of getting a DCS hit even on multiday dives is pretty much non existent as long as you dive within the computer limits.

Now on technical dives, I can see where most current computers fail to be really useful, the algorithms aren't designed for deco diving, and they will keep you in the water unnecesarilly long. Plus the rot the brain factor (see below) :wink:

I suspect a large part of the GUE rejection of computers comes from consistent equipment across a wide spectrum of diving mantra. If you one day want to do technical diving it just makes good sense not to become reliant on a piece of equipment that won't work for you when you do.

just my opinions.

Personally I dive with my vyper in computer mode, but use it largely as a depth guage and bottom timer.
 
Now on technical dives, I can see where most current computers fail to be really useful, the algorithms aren't designed for deco diving, and they will keep you in the water unnecesarilly long. Plus the rot the brain factor (see below)
Given what we currently know about decompression it doesn't make sense to use a computer for deco dives...at least not a Sunnto Vyper. I have one and use it in computer mode most of the time, but not on deco dives..I have played with it and it does not do what I consider to be safe and efficient deco, hence my reluctance to use it on those types of dives.

I don't think the issue is so much one of computers inherently being bad, but I think it boils down to a couple issues already mentioned by ERP:

1) The potential for a computer to be a crutch for someone who does not understand decompression or relies on the computer too heavily at the expense of his/her education in diving physics and could end up in trouble in the case of computer failure.

2) Most computers do not incorporate the cutting edge of decompression research and are lagging behind current knowledge in the field (i.e. RGBM, deep stops, etc.).

IMHO, when a computer comes out that makes sense (like the one possibly coming out next year with the full blown RGBM model) I wouldn't be surprised to see DIR proponents advocating its use (with proper education, training, and table backup). But...the problem becomes one of the algorithm developers keeping abreast with the rapidly evolving field of decompression research. We all know it takes time to develop computers, algorithms, and associated software and that by the time they hit the market there is a chance they are already obsolete. Guess we will have to wait and see what happens...

BTW, I wouldn't consider yourself a stroke just because you use a computer. A stroke, IMHO, isn't someone who disagrees with one aspect of DIR.
 
Hi

I read through the computer section again and apparently computers are OK if used for educational purposes only just as most of you have stated. Thats great. I'm not a stroke !

I didn't know about the extra deco facilities of the deco planning software. Does that mean that GUE have altered the Buhlmann algorithm as it seems strange that suunto or uwatec should use a cut down version ?

Kindest Regards

Andy

Merry Christmas!
 
wetlettuce once bubbled...
Hi

I read through the computer section again and apparently computers are OK if used for educational purposes only just as most of you have stated. Thats great. I'm not a stroke !

I didn't know about the extra deco facilities of the deco planning software. Does that mean that GUE have altered the Buhlmann algorithm as it seems strange that suunto or uwatec should use a cut down version ?

Kindest Regards

Andy

Merry Christmas!
GUE's decoplanner is based on Buhlmann, but with the addition of gradient factors we make it work for us. We adjust gradients and a couple other little things that we learned from George when he was up here...the Suunto is based on RGBM, but is not a full implementation of the model. IMHO, RGBM is where I would like to go in the future, and supposedly there will be full RGBM software next year and possibly a computer introduced...I know Abyss has RGBM too, but I don't care for the program personally...just my opinion.

As for why the algorithm isn't completely RGBM in the Suunto stuff, I have no idea...I should have asked BRW when he was up here, but I didn't think of it. It could range from sensible things like "the model wasn't completely done when the computer algorithm was developed" to beyond the pale things like "the major certification agencies pressured us not to release something that does deep stops when they aren't teaching them".

Your guess is as good as mine, but I bet somebody on here knows...
 
Suunto does not have true RBGM, Bruce is coming out with his own software program in the future, that I hear is a true RGBM. Should be interesting.

Eric
 

Back
Top Bottom