Will Air Integration in dive computers replace the SPG?

[lowviz]

Agree.

I believe that the concept now goes by "min gas".

Anyway, it is worthwhile to read the overview here: http://www.frogkickdiving.com/rock-bottom.html

 

[CuzzA]

@dumpsterDiver I agree the preciseness of what your SPG is displaying compared to a clock when you need to calculate time is not as important. My point was merely digital is easier to read. Doesn't necessarily mean better in all situations. I still wear an analog watch, but I sure as heck don't set my iPhone to the analog clock display and I've never seen a dive computer with an analog clock/stopwatch display, that would be silly for the reason I mentioned.

But you do bring up an excellent point to further the discussion. You're narced like a group of bachelorettes @ 5am in New Orleans and read your SPG and two seconds later you can't remember what it just said... If your tank pressure was on your wrist it would be much more convenient to just glance at your wrist again instead of going back to your waist for your SPG. As I'm sure most of you all know, I haven't knowingly experienced narcosis yet despite a few dives to 100 ft. so I'm not speaking from experience, but I imagine many have perished from being OOA because they were narced. Correct me if I'm wrong.

@Centrals I'll bet my bottom dollar if you were flashed cards displaying different times for 1 second you would either miss some of the analog ones or at a minimum be faster at reading the digital clock flash cards. No offense, but I'm confident in saying everyone.

 

[stuartv]

@dumpsterDiver I agree the preciseness of what your SPG is displaying compared to a clock when you need to calculate time is not as important. My point was merely digital is easier to read.

I think the point others are trying to make is, digital is easier to read - if you need a precise number. But, if you only need a rough idea, then analog is easier to read.

For example, if I just want to know whether I have half a tank (plus or minus 1/8, say), more or less, I can tell that via a glance at an analog gauge without having to mentally process exactly what number it is telling me. But, if it were a digital readout, I would more likely have to actually focus on it, read the number, and mentally process it. If I just want to know "am I getting low?" I can tell that more quickly by glancing at an analog gauge versus reading a digital gauge.

OTOH, there are ways to make a digital gauge comparably easier to read, I think. For example (just off the top of my head), a digital display of tank pressure could start out solid green and gradually change colors through yellow to red as you drop from full to, say 500 psi. It would only take a few different colors (shades of the 3 main ones) to use for the changes to let you read a "rough idea" from the digital gauge purely based on color and be just as accurate as a rough idea glance at an analog gauge. While still being as easy or easier to read an exact number, if you want to.

Or, heck, I think somebody already suggested, display the exact number with a bar graph next to/above/below it. Glance at the bar graph for a rough idea or read the number for precision. There's no doubt in my mind that you could make a display like is on a Petrel easier and quicker to read tank pressure under any/all conditions as compared to a mechanical analog gauge - with the right design effort.

 

[Kevrumbo]

I understand. I think it's an unwise use of a term that means something absolutely different in every other context.

I've never encountered it, but then how would I have? I don't do technical diving, generally dive solo, and have not been exposed to current trends in dive training, which is where I would guess the unfortunate misuse of the term originated. My approach is an antique one, I'll readily admit, but it has served me well for half a century. I basically follow the rule of thirds.

It's not an "unwise" term of usage --perhaps just an unfamiliar colloquialism to you. Otherwise --why would you honestly think that any sane non-suicidal Diver would plan "Rock Bottom" in a draconian semantic sense that you misunderstood it to be???

 

[agilis]

Agree.

I believe that the concept now goes by "min gas".

Anyway, it is worthwhile to read the overview here: http://www.frogkickdiving.com/rock-bottom.html

I think I understand the thinking that went into the redefinition of 'rock bottom ' from absolute depletion, the lowest possible level, to the minimum safe amount of reserve gas . Using the term 'rock bottom' is, I suspect, a method of creating an imaginary or artificial floor well above the actual zero point.

In effect, it becomes a virtual J valve.

 

[stuartv]

Better than nothing, but there are too many abstract numbers for sure. An analog dial would be extremely useful.

Which of the numbers on that display would you replace with an analog dial?

The only number I can think of in my diving that I think would be useful to display in an analog way is my tank pressure. It would be quicker/easier to process "am I down to 1/2 a tank yet" if I could glance at an analog display of tank pressure instead of reading a number.

But, depth, NDL, and dive time are all things I would rather have as numbers anyway.

 

[CuzzA]

@stuartv I understand and agree. Maybe I interpreted his post wrong, but it sounded like a blanket statement on analog displays vs digital.

As far as the computer goes, mine does exactly what you describe with a picture of a tank and color coded fill. I'll post the picture again for reference. Green equals above your preset mid tank point then it turns yellow and then red when you hit your preset reserve. These user entered tank pressure points are also good in my opinion for rec divers, especially new ones. It gets them thinking about gas planning. @lowviz's great links were ones I found a while back and I use those calculations to figure out what my rock bottom is and program it into my computer.

 

[lowviz]

I think I understand the thinking that went into the redefinition of 'rock bottom ' from absolute depletion, the lowest possible level, to the minimum safe amount of reserve gas .

Yes, you both surface with nothing left.

...//... Using the term 'rock bottom' is, I suspect, a method of creating an imaginary or artificial floor well above the actual zero point. ...

No, it is a PSI value that changes with where you are in your dive. It truly represents just how far as you can stretch your available gas. Nothing warm or fuzzy about it. Buddy divers calculate this number assuming a rescue. Two people breathing off one supply to the next gas switch or surface. So a buddy diver's rock bottom will seem generous to you, a solo diver.

Your personal, solo, rock bottom includes your plan for a direct return to the surface or a need to ascend the anchor line, safety stops and whatever else it takes to allow you to slide into home base while breathing hot and heavy and just running out of gas.

To make it manageable, you just calculate it for the very worst point in your dive. For example, at the furthest distance from the upline. This will limit how long you can stay there.

 

[Kevrumbo]

Again, If you know for example that you consume 6bar/minute at 18 meters, you would expect your analog SPG to read 60bar down delta consumption at the end of ten minutes elapsed time. And so on reductio ad finem to your Rock Bottom/Min Gas Reserve value.

And yet again -->Do you really need AI to perform this Subtraction Arithmetic for you?

 

[agilis]

It's not an "unwise" term of usage --perhaps just an unfamiliar colloquialism to you. Otherwise --why would you honestly think that any sane non-suicidal Diver would plan "Rock Bottom" in a draconian semantic sense that you misunderstood it it to be???

No, I do not. It's just a curious and misleading term. It's not a colloquialism,really, more an invented term to emphasize a point.