Terms

[Mndiv]

Hello

Quick question, what is the difference between 'Actual Bottom Time (ABT)' and Bottom time?

I was reading a book on how to use rec dive tables and they defined the terms using practically the same words..

Thanks!

 

[devildoc5]

As far as I recall the Actual Bottom Time is the time spent under water from your descent until your direct ascent to the surface. Bottom Time is a combination of ABT and your Residual Time (if any) to help you determine your post dive nitrogen loading group for repetitive dives.

Hope that clears things up!

 

[DevonDiver]

ABT = Actual Bottom Time. This is the actual time spent on the dive, where you are on-gassing/absorbing nitrogen. This is defined as being: 'from the start of the descent until the start of the direct ascent to the surface', although many divers add conservatism and also include the ascent (i.e. surface-to-surface).

RNT = Residual Nitrogen Time. This is the 'theoretical' time, that is added to subsequent repetitive dives to account for pre-existing nitrogen saturation within our bodies from previous dives.

TBT = Total Bottom Time. This is the 'theoretical' time, used for diving planning, that includes both the ABT for the planned dive and the RNT calculated from previous dives.

ABT + RNT = TBT

 

[Bubbletrubble]

A similar topic has been discussed before on ScubaBoard.
Here's a link to a relevant 2007 SB thread entitled: "what is bottom time?"

FWIW, most dive computers treat all profiles as multi-level dives and, as such, depending on the PC download software, might loosely refer to total run time (amount of time in-between leaving the surface and returning back to the surface) as "bottom time." I can see how this could be really confusing to a diver who has always used tables.

 

[Mndiv]

Thank you, I guess it was just the wording
That cleared things up!

 

[DivemasterDennis]

eggsactly