Can We Agree On How To Measure The Similarity Of Dive Profiles?

[agilis]

Pressure, strictly speaking: depth as shorthand for pressure.

One could calculate gas loading at, say, 2-minute resolution for the entire dive, treat this as a sequence of values, then run a sequence similarity search on two of those. Commonly used sequence similarity algorithms include phoneme matching in natural language processing (speech recognition) and residue matching in DNA/RNA/protein sequences in bioinformatics.

No, pressure as an indicator of depth, not shorthand for depth, just as pressure is an indicator of gas reserve in a container of known dimension. Otherwise, pressure is simply an abstraction.

Your reply does not address my point, which is infinite human variability and the pointlessness of metrics which have no operational utility.The sequence similarity would be nothing more than records of a specific past events.

Speech recognition? DNA/RNA? Try throwing in some Thomistic metaphysics if you really want to impress the gullible. Counting the potential number of angels on the head of a pin is about as utilitarian..

 

[kr2y5]

No, pressure as an indicator of depth, not shorthand for depth, just as pressure is an indicator of gas reserve in a container of known dimension. Otherwise, pressure is simply an abstraction.

Your reply does not address my point, which is infinite human variability and the pointlessness of metrics which have no operational utility.The sequence similarity would be nothing more than records of a specific past events.

Speech recognition? DNA/RNA? Try throwing in some Thomistic metaphysics if you really want to impress the gullible. Counting the potential number of angels on the head of a pin is about as utilitarian..

I think you're going too far, that's like saying that the metric of distance has no operational utility, because when you're actually trying to get somewhere, distance alone isn't enough to know how long it's going to take: you also need to know the speed at which the person or vehicle can move. Of course, at some level, you're right: distance alone isn't enough to answer many practical questions, but that doesn't make it useless as a metric. Imagine that we had no ability to quantify distance, and the only thing at our disposal was a subjective case-by-case assessment of "far" and "near" (which you could only do in very specific context, and in a full consideration of all circumstances). We wouldn't have advanced much past the stone age.

 

[agilis]

I think you're going too far, that's like saying that the metric of distance has no operational utility, because when you're actually trying to get somewhere, distance alone isn't enough to know how long it's going to take: you also need to know the speed at which the person or vehicle can move. Of course, at some level, you're right: distance alone isn't enough to answer many practical questions, but that doesn't make it useless as a metric. Imagine that we had no ability to quantify distance, and the only thing at our disposal was a subjective case-by-case assessment of "far" and "near" (which you could only do in very specific context, and in a full consideration of all circumstances). We wouldn't have advanced much past the stone age.

I think my only contention was that almost infinite human variability, especially in the context of situational variability, makes pragmatic comparable measurements of diving profiles and related strategies extremely difficult to structure.

I certainly don't think that the measurement of human reactions to diving situations is in any way even remotely comparable to the metric of speed/distance. To maintain that distance measurement has no operational validity because there are other obvious variables like speed is absurd and irrational. Speed, like distance, is easily measured objectively and is not a subjective human (or otherwise organic) phenomenon, at least not in a real world pragmatic non-Einsteinian context.

It is only the human reaction to nitrogen loading that gives decompression computers any utility. Measurement for the sake of measurement may be fascinating, but of limited use, especially in areas which attempt to generalize results for operational purposes.

 

[kr2y5]

You seem to be implying that anything that relates to human body is "incomparable", but without qualifying in what sense it is incomparable, how or why, it is just an assertion. Human body is not the only complex system, in the context of which people define metrics for operational purposes (so it's not clear why the same techniques that are used in other domains can't be applied successfully in this context to produce useful results). But, correct me if I'm wrong, it is my understanding that even in the context of human body, we take measurements and make predictions. Perhaps someone with background in medicine or physiology can say a few words about how that works, what is possible or not, and why.

 

[DiveNav]

First order approximation:
if 2 dives have the same maximum depth, dive time and average depth then are similar

 

[lv2dive]

The dive is similar until one stars applying different decompression models to it. If one decompression model calls for 30 minutes more deco than another - IMHO those decompression models are NOT similar.

First order approximation:
if 2 dives have the same maximum depth, dive time and average depth then are similar

 

[rjack321]

Sure, there is a risk of misunderstanding when sharing thoughts on SB, in that those thoughts can enter minds of people with less experience and a different frame of reference, and invite unfair criticism, or what you refer to as deco BS. It seems to me that the people, who chose to participate in all those other threads, have already accepted that risk, and have not exactly been shy to share their opinions and face disagreements.

Presumably, the reason is because there is the upside: sometimes, useful ideas come from people with less experience, and a different frame of reference, and the number of dives is not a perfect predictor of someone's ability to understand or contribute. In my mind, the value of a place like SB is the ability to be exposed to different perspectives, that's what I come here for anyway. I think most of us realize that you need to approach things with a healthy dose of skepticism, and quite frankly, that also includes credentials. At least, ideas we can debate without hurting anyone in the process.

I think you need to get your deco training done and dive more. Data-less pontificating is just burying the truly salient data in a pile of hokum.

even in the context of human body, we take measurements and make predictions. Perhaps someone with background in medicine or physiology can say a few words about how that works, what is possible or not, and why.

And those model predictions are only deterministic until someone does the dive. The outcome is probabilistic. Humans are terrible at taking their handful of personal anecdotes (which still might be 100+ dives) and understanding how each one is to a large extent a success (or failure) based on the roll of some statistical dice.

 

[kr2y5]

I think you need to get your deco training done and dive more. Data-less pontificating is just burying the truly salient data in a pile of hokum.

Richard, this thread was meant as a friendly exchange with people, who might be interested in this type of discussion, and are willing to engage. If you don't really want to engage, because you feel the discussion has no merit or for whatever other reason, that's OK, we don't have to all like the same thing. No offense taken. If you do choose to share, your input will be greatly appreciated. I'm not sure what else there is to say. Peace.

And those model predictions are only deterministic until someone does the dive. The outcome is probabilistic. Humans are terrible at taking their handful of personal anecdotes (which still might be 100+ dives) and understanding how each one is to a large extent a success (or failure) based on the roll of some statistical dice.

Sure. I wouldn't expect the outcome to be anything other than probabilistic.

 

[agilis]

You seem to be implying that anything that relates to human body is "incomparable", but without qualifying in what sense it is incomparable, how or why, it is just an assertion. Human body is not the only complex system, in the context of which people define metrics for operational purposes (so it's not clear why the same techniques that are used in other domains can't be applied successfully in this context to produce useful results). But, correct me if I'm wrong, it is my understanding that even in the context of human body, we take measurements and make predictions. Perhaps someone with background in medicine or physiology can say a few words about how that works, what is possible or not, and why.

I'm not implying anything. I'm directly asserting that any measurements taken during work, stress, or similar circumstances from any animal, including humans, will be most applicable as a predictor to that specific being, with decreasing applicability as a predictive metric as the results are generalized beyond the specific creature that provided the test results.

When you add to this the difficulty of providing reasonably similar circumstances in a fluid and dynamic environment, the combination of ambient variability and organism variability limits most testing to very specific narrow areas, like the connection between nitrogen load and pressure.

 

[dmaziuk]

Your reply does not address my point, which is infinite human variability and the pointlessness of metrics which have no operational utility.The sequence similarity would be nothing more than records of a specific past events.

That's because I'm not disagreeing with it.

The issue is how you define "dive profile". In terms of calculated tissue loading, as in

Deco computers are actually making an estimate of one and only one phenomenon, the persistence of nitrogen gas in tissue, and are basing this estimate on time/depth permutations established primarily through experience and physiological analysis

-- then the profile can be represented as a sequence of gas loading values in time (normalized: recalculated to the same intervals using the same reference model and so on). Figuring out similarity between two sequences is, at this point, a fairly well understood area in Comp. Sci. and it's not going away just because you don't know about it.

Speech recognition? DNA/RNA? Try throwing in some Thomistic metaphysics if you really want to impress the gullible. Counting the potential number of angels on the head of a pin is about as utilitarian..

I think comparing two dive profiles would be about as utilitarian, had they actually tried counting the angels -- as far as anyone knows, that question was never posited seriously in any scholastic debate. And besides, it's 8.6766e49: Improbable Research