Dive planning software compared

[Mark Chase]

Originally Posted by ianfirmin

Dear All, most of my diving has been no-stop (ish) to a max of 40m. I don't plan dives in the classical sense but use my Suunto Vytec to guide me and I make sure I keep deco obligations below about 10 minutes. Being on the cusp of staged decompression I thought I had better get into the habit of planning a dive before I did it.

I have access to four bits of dive planning software and have compared the four with a test profile. To keep it simple I've used a 20m/min descent rate and 5m/min ascent rate. 28% nitrox. I descend to 35m and start my ascent to 25m at 7 minutes runtime. I spend 30 minutes at 25m and calculate an ascent from 25m at 39 minutes runtime.

HL Planner (0 conservatism) gives me a total runtime of 45 minutes as does V-Planner (nominal VPM-B) which gives me the same.

Suunto Dive Manager gives me a runtime of 51 minutes and DecoChek gives me a runtime of 58 minutes.

Increasing the conservatism factor in V-Planner from 0 to 2 gives me 50 minutes and increasing it to 4 gives 57 minutes.

I've always been happy using the Suunto in water with a nice slow ascent rate of 5m/min but the DM software is so user unfriendly I don't feel confident to use it to plan a dive.

I need a benchmark so that I can plan a dive and use it to remain within the parameters of the Suunto when wet.

I would really appreciate some comments on this.

Tia
Ian

Sorry I am late I was at work


As said V - Planner on level 2 is a common serting for every day diving. When I do 120min+ 60m+ dives i run it on VPMBE Level 2 and monster (for me) dives I run it on VPMBE level 3.

I have gone back to diving Gradient Factors (GFs) The reasion for this was i couldent make head nor tail of the bailout plans using VPMB. If i missed a load of deep stops to conserve gas i wasent realy sure how this worked with the profiles.

So for thicko's like me GFs are easy peasy. The diferance between a soft 20/80 and a more agresive 50/100 profile is simple and obvious.


I have found by trial and error that to match the total run time of a VR3 or a Suunto Vytec I need to run 20/80gf's using deco planner on standard settings.

Your decent rate is high (20m/min is damed fast) but thats OK because it makes the tables safer. Your ascent rate of 5m/min is again making the deco longer on the deeper dives. If you set it to 10m/min you will notice a drastic diference on bigger dives.

10m/min is damed fast. I reckon I do arround 8m/min to the first stop depth and that feels very fast.

As a result i prefer to leave it set to 8m. This extends my deco but I know i am more comfortable with it than I am with 10. The Suunto dosent have variable ascent rates in the profile. As a result it asumes you will do its preset ascent rate. That can be quite fast. If you dont do it the Suunto will ADD deco. So you leave the bottom with it showing 30mins deco and you end up doing 40mins before the computer clears. That was one of the big things that I hated about it.


As for the software packages themselves. V planners latest guise is good but i struggle understanding the modle. As a result you need to cut lots of tables just in case. Nautalus is nice to use and can be set up easily but my personal favorite for OC diving is GUEs Decoplanner.


The lay out is good, its very simple to make alterations and see the impact and the new one does VPM and GF so you get the best of both worlds.

See a GF profile below.



ATB

Mark

[tom]

Originally Posted by mjgreen

It uses suunto's version of RGBM, so dive planner might be most appropriate (I'm assuming that suunto's own software uses its own model), however the VPM site seems to suggest that RGBM is not buhlmann based, but VPM based:

VPM Algorithim

Similarly, it suggests that RGBM will generate similar results to VPM, so compare & see what you get.

apparently suunto 'rgbm' is just a Buhlmann algorithm with some tweaks to do with penalising repetetive dives. it's not a proper rgbm implementation, just marketing blurb. allegedly.

[David Pye]

I found the best thing I could do with my Vytec DS was to stop trying to predict what it might say at a given moment, because I find it so unpredictable.

So I cut tables, and slam it into gauge mode.

That way it never gets upset and beeps at you either

[ianfirmin]

Originally Posted by Mark Chase

Your decent rate is high (20m/min is damed fast) but thats OK because it makes the tables safer. Your ascent rate of 5m/min is again making the deco longer on the deeper dives. If you set it to 10m/min you will notice a drastic diference on bigger dives.

10m/min is damed fast. I reckon I do arround 8m/min to the first stop depth and that feels very fast.

As a result i prefer to leave it set to 8m. This extends my deco but I know i am more comfortable with it than I am with 10. The Suunto dosent have variable ascent rates in the profile. As a result it asumes you will do its preset ascent rate. That can be quite fast. If you dont do it the Suunto will ADD deco. So you leave the bottom with it showing 30mins deco and you end up doing 40mins before the computer clears. That was one of the big things that I hated about it.

Thanks for that Mark. The highish descent rate is a reflection on my normal descent rate and the fact that planning for a higher than actual ascent rate can add a safety factor.

The slow, 5m/min ascent rate is usually only over the last 20m, mainly because it feels nicer. I'm aware that this may pad out deco but it adds some "bubble model" in my head. At any point in the dive I always have the option of speeding up to the Suunto rate.

I think I'll start with V-Planner plus 2 and see how it pans out. Seems a reasonable place to start.

Thanks for all the comments guys,

ATB
Ian