The Decompression section sets which model computes the ascent and how much of its permitted supersaturation you use. Choosing between the models is Decompression models.
Choosing the algorithm
The Algorithm card opens with a single selector; the rest of the card changes with it.
Algorithm
Both options obey the same gradient-factor ceiling. Committed fixes the first stop depth as the ascent leaves the bottom; continuous re-checks the ceiling at every stop and follows it upward, starting decompression shallower and repaying the time at the shallow stops.
| Option | What it runs |
|---|---|
| Bühlmann ZHL-16C | Bühlmann with gradient factors. The default. |
| Thalmann E-L | The Thalmann exponential-linear model, on the selected parameter set. |
| VPM-B | Not implemented yet. See the caution below. |
| Hybrid OC | Both models in parallel; the deeper ceiling governs every stop. |
| DiveLogic Frontier | Both models across a range of conservatism settings, returning the balanced schedule. |
| Thalmann GF Calibration | Fits a gradient-factor pair to a Thalmann schedule. |
Gradient factors
The GF pair is offered for Bühlmann ZHL-16C and both hybrids, entered as
two whole percentages and written as a pair: 40/70.
- Presets: three chips above the fields, Conservative (GF 30/70), Standard (GF 40/85) and Aggressive (GF 50/95). A chip highlights when the current pair matches it exactly.
- GF Low: governs the deepest stop. Lower it and the first stop moves deeper.
- GF High: governs the surfacing gradient. Lower it and the shallow stops grow, considerably faster than GF Low grows the deep ones.
A new plan starts at GF 40/70, matching none of the presets. Under Thalmann E-L the fields have no effect: that model’s conservatism is carried by its parameter set. Gradient factors covers the trade.
What the other selections add
- Parameter Set, for Thalmann E-L, both hybrids and GF Calibration: VVal-79 (Air/N₂-O₂) for air and nitrox, which a new plan uses, and a group of XVal-He sets for helium diving, each labelled with the DCS incidence it was fitted to. Those carry the caution above.
- Bühlmann Weight, for both hybrids: 10 to 90 %, shown as a split, 70 % Bühl / 30 % Thal. It sets how the two risk scores combine, not either model’s ceiling.
- Fitted GF Low and Fitted GF High, read-only, under GF Calibration: the gradient factors that reproduce the Thalmann schedule most closely. See The GF solver.
Next
Air breaks is the next page. Stop Settings, this section’s other card, is on Environment and stops.