Leaving the bottom, your ceiling is a real depth: the shallowest the model will let you go. Ascend towards it and it moves. The leading compartment is still exchanging gas the whole way up, so the ceiling that sent you towards 21 m is not the ceiling you meet when you arrive. First Stop, in the planner’s Decompression section, decides which of those two readings fixes the stop.
The two settings
Committed reads the ceiling once, as you leave the bottom, and fixes the stop there. You ascend to that depth and hold, whatever the ceiling has done in the meantime. This is how MultiDeco and V-Planner cut a schedule, and how Erik Baker described gradient factors originally. It is the default, and it is the only setting under which GF Low governs the depth it chose.
Continuous re-reads the ceiling at every stop depth and lets you keep ascending while it allows. Because the ceiling falls as inert gas comes out, you pass the depth the bottom reading implied and begin decompressing shallower. This is how a dive computer behaves in the water: it shows a live ceiling, and you follow it up.
What the choice does to a dive
Both sides plan the same dive, 45 m for 25 minutes on 21/35 with 50 % for decompression, at the same gradient factors. Only the First Stop setting differs.
Committed
Gradient factors 40/70
First stop Committed
- Runtime
- 72min
- Time to surface
- 45min
- First stop
- 21m
Continuous
Gradient factors 40/70
First stop Continuous
- Runtime
- 72min
- Time to surface
- 45min
- First stop
- 15m
The same length of dive.
The runtime is the same. Committed begins decompressing 6 m deeper and spends the difference at the deep stops; Continuous carries that time to the shallow ones. Here the setting changes the shape of the ascent, not its length.
The gap widens with the length of the free ascent. On a deep dive with a long swim up — most of all on an open-circuit bailout, where you leave the bottom on a helium-rich mix and the ceiling climbs before it falls — Continuous can pass four stop depths that Committed holds.
What it does not change
Neither setting moves the ceiling itself, and neither lets you surface before the model allows. A dive that owes no decompression gets no stop under either. From the first stop onwards the two are the same ascent: hold until the ceiling rises past the next stop depth, then go up one stop.
Next
- Gradient factors sets the ceiling this page decides when to read.
- Ascent rates sets how long the swim from the bottom takes, which is how far the ceiling moves before you arrive.