A decompression model is a set of rules for predicting how much inert gas your tissues hold at any moment, and how shallow you may be before that loading passes a limit the model treats as tolerable. Every schedule DiveLogic produces is one model’s answer, and different models answer differently for the same dive.
The Algorithm field on the planner’s Plan step offers six entries. Two are complete models, two combine them, one translates one into the other, and one is not implemented.
What each entry is
| Entry | What it decides | When a diver would pick it |
|---|---|---|
| Bühlmann ZHL-16C | Your ceiling from tissue loading, with gradient factors setting the margin | The default, and what nearly every dive computer runs. |
| Thalmann E-L | Your ceiling from a fixed off-gassing assumption, with no conservatism control | Comparison and research. Its parameter sets are unverified; see the banner above. |
| VPM-B | Nothing. It runs Bühlmann instead | Not implemented. See below. |
| Hybrid OC | Runs both models and holds you at whichever ceiling is deeper | When you want the more conservative of two disagreeing models at every stop. |
| DiveLogic Frontier | Runs both models and produces a family of schedules from fastest to longest | When you want the trade between runtime and conservatism laid out rather than resolved. |
| Thalmann GF Calibration | Runs Thalmann as a reference, then reports the gradient-factor pair that comes closest to it | When you want a Thalmann result expressed in the vocabulary your dive computer uses. |
Selecting Thalmann, either hybrid, or GF Calibration also reveals a Parameter set field. Read the Thalmann page before relying on any of those sets.
VPM-B is not implemented
The list offers VPM-B and the planner does not have it. Selecting it runs Bühlmann ZHL-16C and puts a warning at the top of the plan’s warning list saying so. The schedule you get is a Bühlmann schedule, and it will not show the deep-stop profile VPM-B is known for. The Conservatism field that appears alongside it, offering 0 to +5, has no effect on the schedule.
What choosing a model does not do
Changing the algorithm changes the schedule, not the dive. Gas density, oxygen exposure, narcosis, thermal stress and exertion are the same whichever model produced the stops, and none of them is modelled by any of the six. A model that returns a shorter runtime has made a different assumption, not a safer dive.
Nor is a model a probability. None of these entries returns a chance of decompression sickness. Frontier reports a number it calls risk, which orders schedules against each other and nothing more.
Next
- Bühlmann ZHL-16C, the default model.
- Decompression settings, where the algorithm is set.