Enriched Air RDP Formulae?

[jvilalta]

Jeff,

You shouldn't apply any sort of formula to the tables. They're all computed using a base algorithm that isn't linear, and in some cases have been tweaked by using doppler analysis. Simply extrapolating values based on the tables could produce a profile that is not safe. If you want to create your own custom table you should consider using one of the several custom table generators out there. Or build your own if you are so inclined. I've collected a bunch of deco related links that might be helpful if you are going the DIY route: jvilalta's deco Bookmarks on Delicious

 

[DiveNav]

"............but what I am really attempting to do is to eliminate the rounding error when using the EAD with the Air table. .......

Do you want to eliminate the table's rounding error? Use a dive computer
Or, since you want to write some code, implement your own dive computer

Alberto

 

[Skippums]

You shouldn't apply any sort of formula to the tables. They're all computed using a base algorithm that isn't linear, and in some cases have been tweaked by using doppler analysis. Simply extrapolating values based on the tables could produce a profile that is not safe.

Yeah, I must have not been clear with what I was looking for. Interpolating the tables is exactly what I am trying to avoid. I never intended on using a formula to interpolate table values; instead, I was planning on generating new tables from a formula, to avoid all cumulative rounding errors. I plan to use the links sent to me in the initial response, but will look at the link you included as well to ensure I am getting the full story. Thanks,

-Jeff

 

[Skippums]

Do you want to eliminate the table's rounding error? Use a dive computer
Or, since you want to write some code, implement your own dive computer

Alberto

I do use a computer... I want the tables as a backup just in case my computer fails for some reason. As far as implementing my own, I would love for vendors to create a dive computer that I could write applications for. It would be great if I could customize the UI through some C-style API calls for the device, as the current capabilities are severely limited, and it is clear from the response time that some of the algorithms could use some work. Oh well, a man can dream.

 

[reefduffer]

If you want to avoid interpolating the decompression tables, the rule, as others have mentioned, is to round up to the next highest depth. However, note that you probably (assuming PADI) have access to three tables, for air, EANx32, and EANx36. The latter two are still discrete intervals (some of them only 5 feet), but these are actually different EADs than the air RDP.

I think you could compute an EAD for each discrete depth on the EANx32 and EANX36 RDP, and then to generate your EANx28 RDP, use the rule that you round up to the next highest EAD on any of the three RDPs (air, EANx32, EANx36) and use that bottom time and pressure group value. You aren't doing any interpolation, you're still following the round-up rule. Just taking advantage of the greater visibility into the actual multi-compartment deco model used to generate the RDPs. While it won't eliminate it, it ought to significantly reduce the "round-up" error by effectively providing ~ three times as many depth values to round up to.

I'd start by generating one consolidated air RDP, and in fact can't see any reason other than it's a bigger, clumsier table not to use it for air diving as well as the basis for generating an RDP for any other O₂ percent. Ii seems to me that this conforms to all the rules you'd be expected to follow if using the RDPs to calculate NDLs for a hypothetical sequence of multiple dives using variously air, EANx32, and EANx36.

To generate a real EANx28 RDP you'd need the deco model expressed algorithmically.

 

[vjanelle]

I would love for vendors to create a dive computer that I could write applications for.

There's an open source dive computer (HW) and the liquidvision X1 has multiple third party software packages so you can upload things like v-planner, etc.

 

[DiveNav]

Skippums;4670352...... Oh well, a man can dream....

As programmers and divers ... we are living our dream having designed our own scuba diving simulator

And now we got the additional benefit of having to add any sort of real dive computer to it .... I have ~30 DC right now on my desk ....

Alberto