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Scuba Forum / UK Scuba / December 2004Deco Planning Software
Just completed the TDI Deco-Procedures course (very humbling, and eventually enjoyable). Our instructor recommended VPlanner (but demonstrated several others including Vplanner, Proplanner GAP and mentioned ddplan). Since I currently know no better, I am intending to follow my instructor's lead and purchase a copy of VPlanner (£40) but would be interested to hear if anyone has strong opinions about any of the other pieces of software out there. TIA David > Just completed the TDI Deco-Procedures course (very humbling, and > eventually enjoyable). > > Our instructor recommended VPlanner (but demonstrated several others > including Vplanner, Proplanner GAP and mentioned ddplan). I have dived Vplanner, Proplanner, the free version of GAP and have ddPlan tables stuffed in my pocket. They all work. I also tend to cut the plan on zero conservativeness and then dive the computer/tables with extra time dependant on how cold or bored I am and what my buddy is signalling. Tables are a good drill for courses but in the real world they are backup. I can always add time/stops on the dive but if things are going technical on me I want advice on shortest time to surface and I'll breath down my oxygen tank back on the boat. nigelH > Tables are a good drill for courses but in the real world they are backup. > I can always add time/stops on the dive but if things are going technical on me I want advice on shortest time to surface and > I'll breath down my oxygen tank back on the boat. > > nigelH Nigel, Sorry mate but I'm going to disagree with you. It may be OK to use a dive computer to run a dive (note I did not say plan), but IMHO they are pretty crap if you want to do deep stops to minimise the risk of a DCI from microbubbles. Instead of rewarding the use of deep stop(s) they penalise the diver and increase the deco time at the shallow stops. The only dive computer I completely trust is between my ears. On dives using accelerated deco gases I use tables and switch my computer into Gauge mode. This has many advantages. Firstly, if the DC fails and I become reliant on my backup dive timer then this does not become a great issue, secondly, and much more importantly, it makes me plan and think about the dive, to the point that after planning and executing several dives of similar depths & time, using standard gas mixes, I can remember my run-times & deco schedule without even referring to my pre-cut tables. Once I had standardised my deco gases (EAN 50 & EAN 100) I have prepared tables for: Dives to specific depths (45, 50, 55m etc) Bottom times of: 20 minutes (bored & cold) 25 minutes (wife bored & cold) 30 minutes (normal) 35 minutes (delayed leaving bottom due to issue, which may be a buddy issue or getting that last stubborn lobster out) 40 minutes (delayed leaving bottom due to significant issue) These are laminated and kept in my leg pocket for reference) This also covers eventualities such as he skipper getting the depth wrong and the wreck being either 5m shallower or deeper than planned for, it simply means that I switch over to one of the other pre-cut tables. If after a few seasons of regularly diving with deco gases you then want to use a computer to (potentially) reduce your deco schedule, you will have the ability and practices to get out of a DC failure by experience and using the pre-cut tables, which should still be taken on each dive. TonyH. >nigelH wrote >> Tables are a good drill for courses but in the real world they are backup. [quoted text clipped - 3 lines] > > Sorry mate but I'm going to disagree with you. That's quite OK. It's a free country and you are allowed to be wrong. <grin> > It may be OK to use a dive computer to run a dive (note I did not say plan), > but IMHO they are pretty crap if you want to do deep stops to minimise the > risk of a DCI from microbubbles. Instead of rewarding the use of deep > stop(s) they penalise the diver and increase the deco time at the shallow > stops. Pyle stops. Easy although I'm stuck with the VR3's version these days or it gets all sulky. Plus it doesn't mind how long I over-run its idea of a shallow stop because I fancy some extra margin today. > The only dive computer I completely trust is between my ears. If there is one thing I do not trust at depth it is my brain. I have made more mistakes than I have had gear failures and I suspect I am not alone in that. I like procedures, cross checks and rules. The last thing I want to do is have to think except as a last resort. eg: Sunday. 2 mistakes (minor but still mistakes) and one wing inflator problem. Is somebody going to come back and tell me they have had more gear failures this year than errors made? > On dives using accelerated deco gases I use tables and switch my computer > into Gauge mode. This has many advantages. Firstly, if the DC fails and I > become reliant on my backup dive timer then this does not become a great > issue, If? If? Why are you switching off one of the devices that can contribute to the dive and hence depriving yourself of, at worst, a backup to the tables? > secondly, and much more importantly, it makes me plan and think about > the dive, to the point that after planning and executing several dives of > similar depths & time, using standard gas mixes, I can remember my run-times > & deco schedule without even referring to my pre-cut tables. I don't want to trust my memory with something important like my health. I plan a lot of dives, normally I'm more worried about the gas consumption if it all goes to pot and I have to bail out. The object is to end up back in the boat looking at a bill to mend something rather than in a helicopter wondering how significant X minutes of missed stops will turn out to be. > Once I had standardised my deco gases (EAN 50 & EAN 100) I have prepared > tables for: <snip> > These are laminated and kept in my leg pocket for reference) I have some ddPlan tables with depths to 60m and total run times out to three hours. OK they go in quite big steps but rounding up doesn't hurt unless I have multiple gas failures to go with the computer failure. > This also covers eventualities such as the skipper getting the depth wrong > and the wreck being either 5m shallower or deeper than planned for, it > simply means that I switch over to one of the other pre-cut tables. But this is what a computer does best of all. > If after a few seasons of regularly diving with deco gases you then want to > use a computer to (potentially) reduce your deco schedule, you will have the > ability and practices to get out of a DC failure by experience and using the > pre-cut tables, which should still be taken on each dive. I'm not sure I use a computer to *reduce* the times unless we hit the shot and it is in the midst of acres of featureless sand. There seems to be an elitist idea amongst some deco divers that "Computers are bad". Yes I agree that like all your dive equipment you need to have a backup plan to manage a failure and complete the dive safely but that does not mean that you have to do things that way every time. This is the skills v technology argument that has been fought over and over again on ABLJs, BCDs, manifolds, etc. We always end up with the same answer: Have the skills, use the technolgy. I reiterate: I use the computer to quote "minimum time to surface" for me. This is the bailout option and the ladder from which I start to add conservatism. I, and many of the people I dive with, like deep stops and slow ascents so sometimes I wash out the VR3's stops and put in my own (2 mins based on some DAN stuff I read). Then shallow I overrun the time a bit if possible especially at 6m. I don't try and do 3m as the surge is usually too much for me (blurp) unless we're somewhere very calm like Chepstow. I like computers. I think computers are a good idea. I use computers on deep(ish), accelerated decompression diving and what's more I think that other people should do so too, subject to the caveats about having a fallback stance. nigelH >> Tables are a good drill for courses but in the real world they are backup. >> I can always add time/stops on the dive but if things are going technical [quoted text clipped - 12 lines] >stop(s) they penalise the diver and increase the deco time at the shallow >stops. OK, I'll bite: Which algorithms credit you for deep stops? Buhlmann with either Pyle or GFs, even when computed on tables do not credit you for doing deep stops - it will keep you in the water for longer that pure Buhlmann alone. VPM(B) and RGBM may give you credit for the deep stops, but are enough divers actively using them and getting out of the water quicker than a Buhlmann (+ deep stops) profile to have any statistical use yet? Gordon > >> Tables are a good drill for courses but in the real world they are backup. > >> I can always add time/stops on the dive but if things are going technical [quoted text clipped - 23 lines] > > Gordon Well, I have been using VPM-B almost exlusively for about a year now (~50dives) and generally for my kind of diving at 40-50m with runtimes in the 60-70 minute range (it's cold up here!) VPM-B and Buhlmann GF produce almost identical bottomtime/runtime combinations. It's just the shape of deco that is different. There is also a fairly extensive comparison at the VPM site (ftp://decompression.org/pub/Maiken) of VPM-B vs. RGBM vs. GF and indeed, for a typical set of patameters the total RTs are quite equal, save for GF with high conservatism that produces very long RTs compared to the other two. Whether any of these profiles is safe, well... timo > OK, I'll bite: Which algorithms credit you for deep stops? Buhlmann with > either Pyle or GFs, even when computed on tables do not credit you for [quoted text clipped - 4 lines] > divers actively using them and getting out of the water quicker than > a Buhlmann (+ deep stops) profile to have any statistical use yet? I'd vote for VPM (B) in a second. Not only beause we will have the tables printed here in February, but becuase the results seem to be consistant with my experiences. Not that I used it, but the way I tweaked and felt like in my VR3 profiles while having an Aladin at its side told me it might not be a bad thing. Whereas I suspect a little bit the relevance of all the RBGM's fudge factors, because I cannot merge in the data they are said to be derived from. IMHO, at least some of this RGBM data base does not reflect the same statistical data base from which I would like to derive my own. Matthias >> OK, I'll bite: Which algorithms credit you for deep stops? Buhlmann with >> either Pyle or GFs, even when computed on tables do not credit you for [quoted text clipped - 10 lines] >I used it, but the way I tweaked and felt like in my VR3 profiles while >having an Aladin at its side told me it might not be a bad thing. So let me get this straight - You like VPM-B, but you have tweaked it so that the profiles look the same as your aladin and VR3 - both of which use Buhlmann... Riiiiight .... There are some 9 factors you can fiddle with while generating a VPM profile, and while it's true that you'll not ever fiddle with many of them, it's still a lot of things you potentially cause a fork-up ... I'm going to put VPM back into the next version of DDPLAN though, there does seem to be enough people wanting to use it.... Now all I need is time & motivation to do it... Gordon > So let me get this straight - You like VPM-B, but you have tweaked it so > that the profiles look the same as your aladin and VR3 - both of which > use Buhlmann... > > Riiiiight .... Errr, no. While ascending with the VR3 I noticed some feature I did not like, and while looking at the logged graph, I thought about what I would do different, and did. Later I compared that to VPM schedules, and found it not that much different. Still, I'd prefer Bühlmann + GF over RGBM. You can adjust the Bühlmann model in ways it will produce most every result you desire with a minimum of math. Matthias > You can adjust the B?hlmann model in ways it will produce most every > result you desire with a minimum of math. Are you sure? I have the fixed set of constants that Buhlmann produced but no variables. I like GFs as they control how close to the model I go with out frigging the underlying maths. Other people's 'pretend we're deeper' or 'pretend the mix isn't as rich' conservatism has no justification and are just an arbitary way to make it generate longer times. nigelH >>You can adjust the Bühlmann model in ways it will produce most every >>result you desire with a minimum of math. > > Are you sure? > I have the fixed set of constants that Buhlmann produced but no variables. I should have specified "every result you desire" into "almost every curve you want it to look alike. That's what Suunto did. Making exponential graphs look like RGBM ( which was calculated before on a big computer) by adding a "black math box" whchs coeeficients produce the desired results ( that is, their desired results) Matthias >> So let me get this straight - You like VPM-B, but you have tweaked it so >> that the profiles look the same as your aladin and VR3 - both of which [quoted text clipped - 11 lines] >You can adjust the B?hlmann model in ways it will produce most every >result you desire with a minimum of math. I don't think you can.... You can make up your own A/B values and plumb it into a "Neo-Haldane" model, but Buhlmann published his 3 sets of air tables (and one Helium). The only other modification that he subsequently made was to increase conservatism by multiplying the depth by 1.03 and adding 1 (metre) to it after he found it to be producing more bends than he expected. Other people have produced different A/B values (Abyss with their 31 (?) compartment model) but then it's not Buhlmann... GFs and Pyle stops with with the existing algorithm and don't change it. (Although you can argue that GFs are changing the slope of the M-Value line, but the calculations are still the same) Gordon > I don't think you can.... You can make up your own A/B values and plumb > it into a "Neo-Haldane" model, but Buhlmann published his 3 sets of air [quoted text clipped - 5 lines] > Other people have produced different A/B values (Abyss with their 31 > (?) compartment model) but then it's not Buhlmann... Pint taken, but isn't it far from reality to put all the exponential diffusion based models into one box? This includes e.g J. Bohnert model, who introduces a 17th, fast compartment low tolerance for supersaturation. Matthias >Just completed the TDI Deco-Procedures course (very humbling, and >eventually enjoyable). [quoted text clipped - 6 lines] >interested to hear if anyone has strong opinions about any of the >other pieces of software out there. Odd, I was under the impression that VPlanner was free, but I now see that it's not - it claims it's shareware, with a 30-day free trial, so I think you can pay as little or a much as you want... http://www.hhssoftware.com/v-planner/ http://www.ddplan.com/ is free, but not as screen pretty as the others though, and you'll need to use the keyboard to drive it rather than the mouse. Gordon DDPLAN Author >Odd, I was under the impression that VPlanner was free, but I now see >that it's not - it claims it's shareware, with a 30-day free trial, so [quoted text clipped - 8 lines] >Gordon >DDPLAN Author Gordon, I had downloaded ddplan a while ago and got confused by it. However, I suspect that was probably as at the time I knew absolutely nothing about decompression theory! I am now qualified to substitute "almost" for "absolutely" in the previous sentence, so perhaps I should have another look. My initial interest in Vplanner was based on my instructors personal preference. From your reply to Tony it I gleam you have some reservations about the VPM-B model? David > My initial interest in Vplanner was based on my instructors personal > preference. From your reply to Tony it I gleam you have some > reservations about the VPM-B model? Nothing more than the usual reservations about any models produced by amateurs with computers (OK some very smart amateurs with very big computers in certain cases) against Professor B?hlmann's work done over decades with divers in compression chambers at a major University. They might be wonderfully right but I want more than 'might' before I start shaving deco time down. Getting back in the boat five minutes earlier isn't so important now I bring my own Jaffa cakes. nigelH >>Odd, I was under the impression that VPlanner was free, but I now see >>that it's not - it claims it's shareware, with a 30-day free trial, so [quoted text clipped - 20 lines] >preference. From your reply to Tony it I gleam you have some >reservations about the VPM-B model? Not really - I just don't use it myself. (I did get a mild skin bend on the original VPM stuff though when I was testing it in DDPLAN, but thats now generally accepted to be "normal" with the orignial VPM) And just about everyone I've seen seems to crank the conservatism on VPM-B (or RGBM) so it keeps you in the water for about the same time as one of my oen Buhlmann+GF style profiles, so I'm not convinced that for the majority of sports/tech and even some deeper/longer dives theres any benefit in it. Sure the "shape" is different, but I'm not personally convinced that for these dives it makes much difference. However, "what works, works" as they say... And DDPLAN isn't the easiest of bits of software to get on with - but it's usable in the wheelhouse of a rocking boat if you want to do that sort of thing without a mouse, or much more preferably, cut and laminate tables - my current set are in their 3rd year... Gordon > you have some reservations about the VPM-B model? I'm not Gordon, but I also have reservations about the VPM/VPM-B model. The model cannot be used in real time because it will make assumtions about what you are going to do in the future to determine what you should do now. This means that in lost gas scenarios you may find that you "should" have done deeper stops for longer once you get to the gas switch and discover your deco gas is lost. In practice this is not such a big deal and it is dealt with by using a fudge - see VPM FAQ dealing with lost gasses. However, this does not give me much faith in the model itself and also means that a VPM based dive computer is impossible (without a collosal fudge, not that that bothers me much due to my religious beliefs - as percieved by other divers - dive computers are clearly the work of satan). Our physiology may actually work like VPM, but the large seperation of the ascent from the rest of the dive does not make sense to me (plus the fact that a few people have been bent diving VPM profiles). However, I am only a computer geek and diver, not a scientist, so take everything I say as being speculative bollocks. IME, Gordon's DDPlan seems to be an accurate an implementation of Buhlmann + GFs as any other of the multitude of deco programs out there and it is free. Sure the interface is a pain if you are used to girly guis, but it is VERY fast once you are used to it. The money you save by not buying software that does the same thing is probably better spent on something else... I dunno, beer or something... particularily if you are new to tech diving and have yet to come to grips with having a signifiantly smaller bank balance ;o) |
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