Dive Planning Mode — eRDPml Study Notes

eRDPml — Topics

Dive Planning Mode Surface Interval Mode Multilevel Dives Practice Questions
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The Standard Two-Dive Diagram

Before touching the eRDPml, draw the standard two-dive diagram. It represents the dive profile as two peaks — dive 1, a period on the surface, then dive 2 — with labeled slots for the information you know and the information you need to find. Fill in the depth and time for each dive from the question. The three pressure group boxes (end of dive 1, end of surface interval, end of dive 2) start blank — the eRDPml fills them in as you work through the question. The diagram keeps you oriented at every step, which matters most when the device asks you a yes/no question mid-sequence.

Dive Planning Mode

Use Dive Planning Mode when a question gives you the depths and times of both dives and asks for the ending pressure group — or when it gives you a starting pressure group and asks for the adjusted no-decompression limit (ANDL) or ending pressure group of the next dive. It is the most commonly tested mode in Divemaster and Instructor exams.

Dive Planning Mode eRDPml tutorial — Will Welbourn, Go Pro Caribbean

Step by Step — First Dive of the Day

Dive Planning Mode — First Dive Sequence 1. Select Dive Planning Mode → Enter
2. Multi-level? → No (for a standard two-dive question) → Enter
3. First dive? → Yes → Enter
4. Enter depth of dive 1 → device shows NDL for that depth (the maximum time available — useful reference, but press Enter to continue if the question already gives you the planned time)
5. Enter planned time of dive 1 → if a safety stop is required, the device flashes a warning; press Enter to continue
6. Device shows pressure group at end of dive 1 → write it on your diagram
7. Enter surface interval
8. Device shows pressure group at start of dive 2 → write it on your diagram
9. Enter depth of dive 2 → device shows ANDL for that depth given your current pressure group
10. Enter planned time of dive 2 → safety stop warning if required → Enter
11. Device shows ending pressure group
Worked Example — Dive Planning Mode, First Dive Two dives: 100 ft for 20 min, then 50 min surface interval, then 50 ft for 45 min. What is the ending pressure group?
  1. Enter depth of dive 1: 100 ft. Device shows NDL = 20 min (the NDL for 100 ft is exactly 20 min — a safety stop will be required).
  2. Enter planned time: 20 min. Safety stop warning appears → press Enter. Device shows PG O after dive 1.
  3. Enter surface interval: 50 min. Device shows PG F at start of dive 2.
  4. Enter depth of dive 2: 50 ft. Device shows ANDL = 56 min.
  5. Enter planned time: 45 min. Safety stop warning → Enter.
Ending pressure group: V.

Starting From a Known Pressure Group

Some questions do not describe the first dive at all. Instead, they give you a pressure group and ask what you can do next. The device handles this through the same Dive Planning Mode, but the yes/no sequence changes. Drawing your diagram and filling in what you know before you pick up the device is what makes the yes/no answers obvious.

Dive Planning Mode repetitive dive with known pressure group — eRDPml tutorial, Will Welbourn
The Key Yes/No Question — Pressure Group After Surface Interval When the first dive answer is No, the device asks: "Pressure group after surface interval — yes or no?"

Look at your diagram. There are two pressure group boxes before the second dive begins: one after dive 1 and one after the surface interval.

If the question gives you the PG at the start of the repetitive dive (i.e. the post-SI pressure group) → answer Yes. Enter that PG. The device then asks for depth and gives the ANDL.

If the question gives you the PG at the end of dive 1 and a surface interval duration → answer No. Enter the end-of-dive-1 PG, then the SI duration. The device calculates the post-SI PG for you, then continues to depth and ANDL.
The most common mistake with the diagram Students sometimes read "you are in pressure group G at the start of a repetitive dive" and place the G in the end-of-dive-1 box instead of the post-SI box. The phrase "at the start of a repetitive dive" means at the beginning of the second dive — which is the post-SI slot. Placing it correctly means you can confidently answer Yes to "pressure group after surface interval?"
Worked Example — Starting From a Known Pressure Group At the start of a repetitive dive you are in pressure group G. What is the ANDL for a dive to 60 ft, and what pressure group do you end in if you dive for the maximum time?
  1. Draw the two-dive diagram. Place G in the post-SI box (start of repetitive dive).
  2. Dive Planning Mode → Multi-level? No → First dive? No.
  3. "Pressure group after surface interval?" → Yes. Enter G.
  4. Enter depth: 60 ft. Device shows ANDL = 34 min.
  5. Enter planned time: 34 min (the maximum). Safety stop warning → Enter.
ANDL = 34 min. Ending pressure group: W.

Maximum Depth Mode

Maximum Depth Mode answers a different question: not "what pressure group do I end in?" but "how deep can I go?" You give the device a planned dive time and it tells you the deepest you can go within the no-decompression limits. The units button at the top of the device switches between metric and imperial — select your units before entering any values.

Maximum Depth Mode eRDPml tutorial — Will Welbourn, Go Pro Caribbean

First Dive

For a first dive, Maximum Depth Mode is straightforward. The device asks how long you want to dive and returns the maximum allowable depth for that time.

Worked Example — Maximum Depth Mode, First Dive You want to do a dive of 50 minutes. What is the maximum depth?
  1. Maximum Depth Mode → Enter.
  2. First dive? → Yes.
  3. Enter planned time: 50 min. Safety stop warning (any dive to maximum possible depth will require one) → Enter.
Maximum depth = 60 ft. The NDL for anything deeper than 60 ft is less than 50 minutes.

Repetitive Dive

For a repetitive dive, Maximum Depth Mode needs the pressure group after the surface interval — not the ending PG from the previous dive. This is where the confusion usually starts. Look at your two-dive diagram before entering anything.

Maximum Depth Mode — Repetitive Dive Sequence 1. Maximum Depth Mode → Enter
2. First dive? → No
3. "Pressure group after surface interval?" → Yes if you know it; No if you only have the end-of-dive-1 PG and SI duration
4. Enter the post-SI pressure group
5. Enter planned dive time → safety stop warning if required → Enter
6. Device shows maximum depth
If you do not have the post-SI pressure group If the question gives you the ending PG from dive 1 and a surface interval, you do not have the post-SI PG yet. Go into Dive Planning Mode first — enter the end-of-dive-1 PG, then the SI duration. The device calculates and displays the post-SI PG. Note it on your diagram. Then switch to Maximum Depth Mode and continue.
Worked Example — Maximum Depth Mode, Repetitive Dive You are in pressure group F at the end of your surface interval. You want to do a 40-minute dive. What is your maximum depth?
  1. Maximum Depth Mode → First dive? No.
  2. "Pressure group after SI?" → Yes. Enter F.
  3. Enter planned time: 40 min. Safety stop warning → Enter.
Maximum depth = 55 ft.