Need help with dive tables, braking them down.

[WillAbbott]

What I need ( I just taught myself by reading the booklet how to use my PADI recreational chart today) is a brake down of calculating NDL's etc without a dive chart. Or similar. What I want to do so you can understand is to create a software app/add-in for my Dive log program I'm working on to allow for dive planning. I can't see an easy way to store ALL the information off the dive planner, and I figure there must be some sort of equations, where I can say, have users give me the depth, then it figure out the max NDL, and then they can set there dive time to whatever (not exceeding NDL) then it could tell them what pressure group they would be in after the amount of hours/mins they specify etc.... There must be some equations for this, where I can figure out the NDL limit for a depth, then figure out what PG someone would be in after x mins at depth, and x mins of SI.

I appreciate any and all help, I'm working on trying to do this without the equations if I have to, mindstorming ideas of coding it.

Thx,

Also, if you don't know the equations/math maybe you know of a freeware application that does this, I can usually figure out the math in reverse having something that works already

 

[budgy]

Hi Will,
Are you planning on doing deco diving, like deep saturation or are you planning on doing recreational non deco diving? All that work with computers sounds time consuming, though I know there are a great many diver programmers who just like to write code. For the single tank 100' diver using the right system its quite easy to do all the dive planning calculations in your head.

 

[WillAbbott]

budgy once bubbled...
Hi Will, are you planning on doing deco diving or are you planning on doing recreational non deco dives?

I'm not going to do any deco dives, the software I'm writting is for non-deco as I know nothing about deco, nor have charts etc. I figured I have the PADI rec chart for non-deco (has the Non Deccompression Limits as max time) and thats the diving I'm going to do, at least for a while (though I at this point doubt I'll ever do deco or technical at all)

 

[budgy]

Look at your tables carefully, you don't have to dive to the limits see if by increasing the safety margin and reducing certain figures if you can make the depth and non stop time linear. I have got my own system but its in metres.

 

[GearHead]

These are all for Palm OS, but I think this is at least close to what you're looking for:

ASDP Dive Calculator

DiveCalc - Calculator/Log
This one lets you use NAUI, PADI, or SSI tables

I hope some of that's useful.

Rick

WillAbbott once bubbled...
Also, if you don't know the equations/math maybe you know of a freeware application that does this, I can usually figure out the math in reverse having something that works already

 

[nickjb]

I had a look at doing this for a couple of applications I have written. The tables don't follow smooth curves so I don't think there is a simple formula. In the end I used look up tables (Although I wasn't trying to get as much data as you)

Also, a look up table will probably be quicker that a lot of math.

 

[Walter]

Carry your tables, I'd suggest a more conservative table than the RDP, or buy a computer.

 

[dc4bs]

I put together an Excel spredsheet last year that does what it sounds like you're looking for. Partly, I just did it to teach myself excel and partly it's a way to quickly show the differences in how the various tables work...

It requires Excel (office 97 or better) to load it.

It has spaces to enter the following:
1: nitrox % - default is 21 for air
2: current pressure group (leave empty if first dive of day)
3: planned depth of dive
4: planned bottom time of dive
5: post dive surface interval
6: Surface Air Consumption rate (SAC)

It uses the PADI air table numbers for all calculations.

For nitrox diving, the Equivalent Air Depth (EAD) is calculated from entries 1 and 3 above.

Once an EAD is calculated, the max NDL is shown (if there is a pressure group entry, the max NDL is modified accordingly).

If any dive planned will cause a required deco stop, the planner will display a warning message as PADI does not allow for deco in rec. diving.

If any nitrox/depth causes a ppO2 of 1.4-1.59999 an alert message is displayed. For ppO2 of 1.6 or greater a stronger warning message comes up.

The spreadsheet takes all the stuff above and calculates an ending group letter. Given a post dive surface time it will then show a final group letter for repetitive dive planning.

Given a SAC rate, it will also calculate gas requirements (the rule of thirds is assumed) and it includes the gas required for the safety stop.

Finaly, it will calculate and display the O2 dose for the dive.

Private Message me if you want more info on how I converted the tables to a format that Excel could understand. It's a time consuming pain in the behind but you REALLY know how the tables work by the time you're done.

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I also made sheets using the US Navy dive tables and the Canadian DCIEM tables. These allow for deco dive planning although DCIEM does not allow repetitive deco dives.

These also calculate gas requirements, etc. for all deco stops. While they do allow for seperate deco gasses, they do not calculate any accelerated deco times for them as I don't yet know enough about it to safely add that functionality to the sheets.

 

[WillAbbott]

Thanks everyone for the replies on this subject. I finnaly figured out a way to do it thats not too much of a pain, but works.

I'm basically recreating table 1 completely. Then it allows a user to click on the time on table one (following your depth column to the time row you want, for example diving 40feet for 25mins) it then knows which pressure group you will be in (D for the example) and brings up only the possible surface intervals you can have (4 possible for D) you then would chose in a drop down box which depth your next dive will be to, and it will bring up all the RNT and Adjusted NDL for the PG's available, so basically the user only needs to click on the dive time/depth, then select the next dives depth, and there all set, its pretty much a shortened version of the RDP where the only table you see completely at all times is table 1, the others are only one row at a time.

 

[weight_for_me]

Any chance of you guys putting up your work as an attachment? I'd like to do this too (probably in Excel) but why re-create the wheel. Thanks
Randy...