Adherence is the difference between two depth-time curves: the one the planner produced and the one your dive computer recorded. It is a set of named measurements and a score out of 100, not a risk number, and it says nothing about decompression sickness. The plan is the reference curve.
The metrics, and what each costs
The score starts at 100 and each deviation deducts from it, capped per category and floored at zero.
| Measurement | What it is | Deduction |
|---|---|---|
| Mean depth deviation | Average distance from the planned depth, in metres. Never negative. | 4 per m, up to 30 |
| Descent delay | Minutes later than planned that you reached working depth, 90 % of the planned maximum. | 3 per min, up to 20 |
| Max depth delta | Recorded maximum depth minus planned, in metres. | 4 per m past the plan, up to 20 |
| Peak ascent rate | Fastest ascent between two consecutive readings, in m/min. | 2 per m/min over the threshold, up to 20 |
| Short stops | Each planned stop against the time spent within 1.5 m of it. | 3 per missing min, up to 15 per stop |
| On plan | Share of the dive spent within 3 m of the planned depth. | Nothing |
| Runtime delta | Recorded runtime minus planned, in minutes. Negative means you surfaced early. | Nothing |
Descending early, diving shallower than planned and staying longer all cost nothing. A stop asking 1 minute or more counts as short when the recording holds a minute less.
The differences
The measurements are narrated as a list, warnings first:
- Reached depth later than planned: delay of 1.5 min or more.
- Descended faster than planned: working depth 1.5 min or more early.
- Went deeper than planned: 2 m or more past the plan.
- Ascent was fast in places: peak above 10 m/min.
- Time spent off the planned depth: under 80 % within 3 m.
- Surfaced earlier than the plan: runtime 2 min or more short.
- depth m stop was short: cut by more than a minute.
When none trips, the analysis says the dive tracked the plan closely.
What the score is not
- Not a risk number. Not a probability of decompression sickness, and not calibrated against outcome data.
- Not comparable between dives. The same 8 points can come from an ascent rate, a short stop, or an optimistic descent.
- Not a judgement of the plan. A perfectly flown dive on an aggressive plan scores 100; gradient factors and the planner’s warnings examine the plan.
- Not a reading of how the dive felt. Thermal state, exertion and hydration are invisible to a depth-time curve; the questionnaire covers them.
- Not a clearance. A score of 100 does not make decompression sickness impossible, and no number here can rule it in or out. If you have symptoms, treat them as symptoms.
How often your computer recorded is a floor under all of it: one logging every ten seconds cannot resolve a short fast ascent.
Next
- Starting a review: pairing a dive with a plan.
- Reviewing a plan: the schedule this measures against.