DDPLAN

The Drogon Dive Planner

Copyright © 1999 - 2001 Gordon Henderson

Deep Stops

The Big Thing that seems to have happened to decompression diving in the mid 1990's seems to be Deep Stops. The general consensus seems to be that deep stops are a good thing. Richard Pyle could probably be regarded as the one who first publicly made a big deal of it all. His method of calculating deep stops is simple and easy to do in your head while diving with a wrist mounted dive computer, or from conventional tables. You can read Richards full article about deep stops here. If this link doesn't work, then you can read a local copy here.

Erik Baker came up with a simple modification to the standard Buhlmann algorithm to implement a slightly different kind of deep stop strategy. Opponents of the Pyle method say that the first Pyle stop is too deep and that there is still to big a jump from the first stop to the next. The Baker method seems to address this. However, it can't be calculated in your head as you do the dive, it has to be computed in advance. Erik Baker published his articles in Immersed magazine and they can be found here in Adobe PDF file format. On the positive side, Pyle stops can be calculated in your head if you are basing your dive plans on a wrist-mounted dive computer. Eg. Dive computer says your first stop is at 9m and you are currently at 50m then your first Pyle stop is (50 + 9) / 2 = 30m. Your next stop is (30 + 9) / 2 = 20m. Keep doing this until the depth between your next calculated Pyle stop and the mandatory stop as indicated by the computer is less than 10m. Using desk-top software and diving to run-times, it's still easy to calculate and add in Pyle stops as waypoints on the ascent.

Erik Bakers ``Gradient Factors'' method uses 2 parameters to control the stops. The low factor and the high factor. The factors control how far away from the ideal Buhlmann line the stops are. Erik Baker used a low factor of 30% and a high factor of 75% in his test example, however I have heard that a certain cave-diving team use 20% as the low factor and 100% as the high factor. Since there have been little scientific studies with published results on this method of decompression there there's not a lot to go by yet and you will have to use your own judgement on choosing these factors - So you will have to use DDPLAN in conjunction with other dive modelling software to compare results and make up your own mind.

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Gordon Henderson