Manual calculation for accelerated deco

[lowviz]

...//... At 2,000 meters (ignoring the salt water/fresh water difference for this illustration), the diver is at 3 ATA for the water and 0.8 for the atmosphere, for a total of 3.8 ATA. ...

Your altitude calculation is back-referenced to sea level atmospheric pressure.

Diving at altitude is nothing more than changing the value that one atmosphere represents. Indeed, water does not change. So at a reduced atmosphere, it takes less depth to equal that 'atmosphere' that is sitting on top of the water. M values have to do with differences in pressure, not absolute pressures.

 

[Dan_P]

Alright, I feel I've accounted for this already, but let's get this cleared up:

As far as sticking a hand up goes, in fairness, I did cause some confusion when I brought a previous discussion on altitude and bouyancy, into this one.
I acknowledge that was an unnessesary transcendance.

I've said that I think altitude practically insignificant in terms of bouyancy - I stand by that - but I'm not saying altitude doesn't matter in terms of decompression.
I apologize for any confusion that may have caused.

As for the "right" emphasis on deep stops, I acknowledge that this is an open question: my point is simply that I look at the graph posted above and see an increased need to manage both bubbles and dissolved gas, given an increased relative pressure differential.
Hence my view that an increased baseline emphasis on deep stops coupled with arbitrary extension of shallow stops, seems sensible, given an increased relative pressure differential. To my mind, there is a vast difference between that statement, and saying the total ascend process should be shifted deeper.

Am I okay with the extension of shallow stops being arbitrary?
Yes.
Remember, Ratio Deco is not an algorithm. It's a tool that is based on algorithms and helps make calculations based on relationships between depth, gas and time, while maintaining an average ppO2 of approximately 1,2.

There are more accurate approaches, but I prefer Ratio Deco because I find it much more practical.

On a sidenote, paradoxally, the only ones telling me what to think, seem to be Scubaboard patrons telling me to think that altitude doesn't matter

I hope this clarifies my position as whether I'm right or wrong, I'll want to be so on my own accord.

Happy holidays

 

[victorzamora]

I'm going to say this one more time:

We don't disagree that altitude has an impact on the physiological process of decompression.
It is my belief that it does, and I adjust my altitude dives accordingly.

Do try to disregard John's heuristics-soaked narrative about my position on the matter.

Okay, Dan. I'll ignore John (though I think his points are valid and on-topic, especially since his training was directly from the horse's mouth) for now.

However, you haven't explained any reasoning for your belief that you should add emphasis to deep stops when diving at altitude. You haven't acknowledged my graph or explanation of the counterpoint to your belief. You didn't answer the relatively simple question of a 30m dive from sea level to a 24m dive from 2000m altitude. I'm trying to understand your side, but I'm simply not seeing a reason for it.

 

[tursiops]

I read several of the preceding posts and am either impressed at the sarcasm or stunned at the confusion.

1 ATM is a unit of measure, and has exact equivalences in other systems of units.
It does NOT change with altitude, or sea level pressure.
If the surface pressure is 0.8 ATM, that does NOT mean that you get 1 ATM of water pressure above you at 8m; that amount of water only weighs enough to cause 0.8 ATM. You've got to go to 10m to get 1 ATM of water above you. and at that depth your total pressure is 1+0.8=1.8 ATM.

 

[Dan_P]

Okay, Dan. I'll ignore John (though I think his points are valid and on-topic, especially since his training was directly from the horse's mouth) for now.

However, you haven't explained any reasoning for your belief that you should add emphasis to deep stops when diving at altitude. You haven't acknowledged my graph or explanation of the counterpoint to your belief. You didn't answer the relatively simple question of a 30m dive from sea level to a 24m dive from 2000m altitude. I'm trying to understand your side, but I'm simply not seeing a reason for it.

I hope the below (well, and above) answers your question to your satisfaction.
I acknowledge the graph you posted (well, at least in principle, as I didn't exactly double-check the numbers, but that's not relevant - to answer your question, yes, I acknowledge that relative pressure differential exponentiates with approximation to the surface, to an increasing degree on an altitude dive, compared to sea level).

This is why I add shallow stops.
I also deduct an increased need for deep stops, to manage impending micronuclei propagation by way of gas mechanics. To be clear, I don't mean that the entire ascend process should be shifted further down, but that I am satisfied with the deep stops in Ratio Deco, coupled with extended shallow stops. I hope this clears up any confusion as to my position on the matter:

Alright, I feel I've accounted for this already, but let's get this cleared up:

As far as sticking a hand up goes, in fairness, I did cause some confusion when I brought a previous discussion on altitude and bouyancy, into this one.
I acknowledge that was an unnessesary transcendance.

I've said that I think altitude practically insignificant in terms of bouyancy - I stand by that - but I'm not saying altitude doesn't matter in terms of decompression.
I apologize for any confusion that may have caused.

As for the "right" emphasis on deep stops, I acknowledge that this is an open question: my point is simply that I look at the graph posted above and see an increased need to manage both bubbles and dissolved gas, given an increased relative pressure differential.
Hence my view that an increased baseline emphasis on deep stops coupled with arbitrary extension of shallow stops, seems sensible, given an increased relative pressure differential. To my mind, there is a vast difference between that statement, and saying the total ascend process should be shifted deeper.

Am I okay with the extension of shallow stops being arbitrary?
Yes.
Remember, Ratio Deco is not an algorithm. It's a tool that is based on algorithms and helps make calculations based on relationships between depth, gas and time, while maintaining an average ppO2 of approximately 1,2.

There are more accurate approaches, but I prefer Ratio Deco because I find it much more practical.

On a sidenote, paradoxally, the only ones telling me what to think, seem to be Scubaboard patrons telling me to think that altitude doesn't matter

I hope this clarifies my position as whether I'm right or wrong, I'll want to be so on my own accord.

Happy holidays

 

[victorzamora]

I hope the below (well, and above) answers your question to your satisfaction.
I acknowledge the graph you posted (well, at least in principle, as I didn't exactly double-check the numbers, but that's not relevant - to answer your question, yes, I acknowledge that relative pressure differential exponentiates with approximation to the surface, to an increasing degree on an altitude dive, compared to sea level).

This is why I add shallow stops.
I also deduct an increased need for deep stops, to manage impending micronuclei propagation by way of gas mechanics. To be clear, I don't mean that the entire ascend process should be shifted further down, but that I am satisfied with the deep stops in Ratio Deco, coupled with extended shallow stops. I hope this clears up any confusion as to my position on the matter:

It really doesn't. From an earlier post, Dan:

Finally, you might care to know that I am confidently diving altitude dives believing that the increased emphasis on deep stops incorporated in RD, matches reasonably well my view of decompression during altitude diving.

You talk about RD requiring you to emphasize deep stops and about you agreeing with the logic behind it (which I still haven't seen). I'm also still perplexed by the below quote, where you are claiming that people are accusing UTD's Ratio Deco of underemphasizing deep stops. I have seen zero evidence of that. UTD's RD overemphasizes deep stops pretty dramatically, in my opinion. If you're saying (per the quote above) that UTD's RD increases its Deep Stops time when you're diving at altitude, then I think it's starting to move from "bad but probably harmless" to "quite dangerous." As I've shown above, I think there's plenty of basic concepts that would strongly suggest reducing deep stops...which is against the UTD RD recommendation.

​

There is of course also some who favor a Schrödinger paradigm in arguing that Ratio Deco at the same time overemphasises deep stops and underemphasises deep stops.

​

 

[lowviz]

...//... 1 ATM is a unit of measure, and has exact equivalences in other systems of units.
It does NOT change with altitude, or sea level pressure.

Please note that I said 'atmosphere', not ATM or ATA.

Thought experiment. Assume that we ascend to 380 mm Hg from the sea level 760. Half the atmospheric pressure at sea level. Dive to some great depth at that altitude and measure the pressure in pounds per sq inch. It will be very nearly the same as you would find at the same dive depth at sea level, just as John said.

Now we begin our ascent. The goal is to reach the air above the water with an appropriate gas saturation that will prevent bubbling. Even though there is the same psi at the bottom of either dive, the altitude dive is a much, much 'bigger' dive. I see this as very simply being under many more 'atmospheres' of pressure (at that dive depth when at elevation) as compared to fewer 'atmospheres' at that same dive depth when at sea level. It is nothing more than a change of reference point. You like everything referenced to sea level, it is more intuitive for me to reference to where I want to finally equilibrate. Works out the same either way.

 

[Dan_P]

You talk about RD requiring you to emphasize deep stops and about you agreeing with the logic behind it (which I still haven't seen). I'm also still perplexed by the below quote, where you are claiming that people are accusing UTD's Ratio Deco of underemphasizing deep stops. I have seen zero evidence of that. UTD's RD overemphasizes deep stops pretty dramatically, in my opinion. If you're saying (per the quote above) that UTD's RD increases its Deep Stops time when you're diving at altitude, then I think it's starting to move from "bad but probably harmless" to "quite dangerous." As I've shown above, I think there's plenty of basic concepts that would strongly suggest reducing deep stops...which is against the UTD RD recommendation.

Hold up, let me just stop you here for a second.

Roughly put, I'm saying that in my view, it makes sense to have more shallow stops and more deep stops.
As RD already has an emphasis on deep stops, by using RD, I believe it reasonable to add more shallow stops when at altitude. So I add more shallow stops.
I'm not saying I believe I need to take RD and then add more emphasis to deep stops when at altitude.

That's it.

I haven't said that UTDs RD increases it's deep stop emphasis when diving at altitude, at all. Nor does it.
I'm simply saying that I to an increasing degree appreciate that emphasis, when at altitude. Granted, I probably skipped quite a few steps too many in explanation with the Schrödinger-reference, but make no mistake:
The overall ascend is not shifted downwards when at altitude.
Rather, I arbitrarily shift it upwards, for precisely the reasons you mention and I agree on.

As for the general emphasis on deep stops (altitude aside), I will be pleased to see the results of future trials.

 

[boulderjohn]

When I was a UTD diver diving at altitude, we were told to use Ratio Deco exactly as designed because there was no need to adjust it for altitude. You seem to be saying it is fine to use Ratio Deco at altitude, as long as you make appropriate adjustments. Appropriate adjustments seem to be lengthening the final stops. How long to you lengthen those stops? Does it depend upon the altitude?

 

[victorzamora]

Things are certainly making more sense. We'll likely never agree, but I at least understand your point.

I'm simply saying that I to an increasing degree appreciate that emphasis, when at altitude.

The above has me concerned, because I think that altitude diving certainly doesn't benefit from deep stops any more than diving from Sea Level, and that you're actually increasing your risk by using the sea-level deep stops at altitude. Increasing your shallow stops makes sense, but it seems to me like the overall ascent profile is just extra flawed when diving from altitude. Again, though, we'll never agree but I believe I at least understand you now.

Granted, I probably skipped quite a few steps too many in explanation with the Schrödinger-reference, but make no mistake:
The overall ascend is not shifted downwards when at altitude.

My point with bringing up your Schrodinger quote was that you created a strawman arguing that UTD's RD underemphasizes deep stops. I have not seen a single reference to that.