So often rather than experiment a bunch of models: the navy hypothesized a probable competitor to existing formulas and did in depth analysis. It's not relative to anything but their specific work and task. That's how I interpret the datum. Is that more correct?
Yes! You are exactly correct. As others have pointed out the Navy is testing profiles that no sane sport diver (includes both rec and tec) would do let alone even plan. Let's look at the profiles from the NEDU study which includes two dives to 170 ft for 30 minutes on air. Both profile's were adjusted to have the same decompression time but the second profile inserted deep stops.
Shallow deco stops (depth/time): 40/9, 30/20, 20/52, 10/93. DT = 174.
Deep deco stops (depth/time): 70/12, 60/17, 50/15, 40/18, 30/23, 20/17, 10/72. DT = 174.
DT is total decompression time neglecting the ascent time. DT is calculated by adding the times for all the stops. The significant thing about these profiles is the DT - it is the same. The Navy had to shorten the DT for the deep stop profile to make it a constant between the profiles. But in doing so they added a variability to the test in the off-gassing rate.
Running the same dive plan on my Perdix with VPM-B +2 gave this profile:
Deep deco stops (depth/time): 100/1, 90/2, 80/3, 70/4, 60/5, 50/5, 40/7, 30/14, 20/20, 10/34. DT = 95.
Looking at the difference between both deep stop profiles DT time for the first four stops yields 12,17,15,18 and 1,2,3,4. The NEDU's definition of deep stops is very different from what sport divers use. The stops are shallower and longer. Rossh has repeatedly pointed this out in previous posts. In order for the NEDU study to compare their so-called deep stop profile with VPM-B they had to create a non-existent conservative setting of +7 to achieve the same DT!
What did I learn from the study? I learned that increasing the length of deep stops and for the same dive shortening the shallow stops (against what DC's will tell you) will get you bent. Gee, no surprise there!
So, here is a question I posted in Decompression Controversies:
Why would you be so quick to agree that bubble models in general and VPM in particular are inferior to dissolved gas models in general and Buhlmann GF's in particular, when the NEDU study is testing something quite different from what [non-Navy] bubble models are doing?
Note: [non-Navy] was not part of the original post. It was added here for clarity.