Why isn't DIR universally metric?

[Guy Alcala]

Going to take Fundies in a couple of months, but I've been wondering about this for a while. Given the amount of information that's involved in learning gas planning et al, ISTM that anyone who has the interest to devote so much time to learning this would have little or no difficulty dealing with the metric system, and the latter is far easier for making on the fly gas calcs in your head.

So why isn't DIR all-metric? The cost of buying an SPG marked in BAR can hardly be a major issue, given how much people typically spend to get themselves DIR equipment-compliant, and most dive computers with gauge modes are happy with imperial or metric displays. Those people who insist on Uwatec bottom timers now have an excuse to go out and buy the 330m model I can see how tech divers with lots of tanks could run into more significant expense replacing all their SPGs, but assuming that a changeover happened over the course of a couple of years ("after such and such a date, only metric gauges and measurements will be allowed"), this seems a no-brainer for an agency stressing uniformity of equipment, methods and training.

Guy

 

[JeffG]

because it evolved in the states and metric isn't very big there.

 

[Guy Alcala]

because it evolved in the states and metric isn't very big there.

Sure, but that's no reason to continue a practice that makes no sense from the standpoint of either uniformity or simplicity. I've lived all my life in the US, was raised on Imperial (actually US) units and usually think in them. But I'm able to convert to metric when needed and have no trouble using metric units when it makes more sense, as is the case with gas planning.

When I'm underwater, do I really care if my depth gauge reads 18.2m or 60'? As long as I know which one it is, no.

Guy

 

[liuk3]

Calculations are actually easier in metric. But, U.S. no likey metric.

 

[AndyNZ]

So why isn't DIR all-metric?

Just emigrate, it sounds like the right option for you.

 

[MXGratefulDiver]

because it evolved in the states and metric isn't very big there.

More's the pity ... there was a half-hearted attempt to convert to metric back when I was in grade school ... about 50 years ago.

I sometimes think Americans have a deep need to be different just ... because ...

... Bob (Grateful Diver)

 

[Kevrumbo]

For My Nominal Cold Water Surface Consumption Rate (SCR): 22 litres/min*ATA
Using Twin 11 litre tanks (double AL80's): 22 litres/bar total tank rating.

Now divide SCR by total tank rating (22 divided by 22). You get: 1 bar/min*ATA
[or same as 14.5psi/min*ATA in imperial. IMHO, it's much easier and better to work with unity integer reference values like "1bar" versus numbers like "14.5psi"]

So an intuitive table of depth in meters translating to pressure consumed in bar/min, by virtue of that 1 bar/min*ATA value above, looks like this:

18m depth, same as 2.8 ATA -->translates directly to 2.8 bar/min
21m depth, same as 3.1 ATA -->translates directly to 3.1 bar/min
24m depth, same as 3.4 ATA -->translates directly to 3.4 bar/min
27m depth, same as 3.7 ATA -->translates directly to 3.7 bar/min
30m depth, same as 4.0 ATA -->translates directly to 4.0 bar/min

Therefore, for an arbitrary & convenient time period of say, for example 10 minutes, at a particular depth in the above table, I would expect to consume:

2.8 bar/min(10min) = 28 bar
3.1 bar/min(10min) = 31 bar
3.4 bar/min(10min) = 34 bar
3.7 bar/min(10min) = 37 bar
4.0 bar/min(10min) = 40 bar

Essentially then, if you have the same SCR and are using Double AL80's (Twin 11 L Tanks), all you need to know is your depth in ATA and your time at that depth, and you'll know instantly how much gas you've consumed --even before looking at your SPG!

 

[Sas]

I sometimes think Americans have a deep need to be different just ... because ...

... Bob (Grateful Diver)

That doesn't really make sense in light of the fact that DIR originated in the US... (btw, not a criticism of DIR before anyone takes it that way )

 

[rjack321]

Why does it need to be? Gas calcs are not precise anyway. Tank factors are totally good enough.

 

[PfcAJ]

While I think metric is superior to imperial, I (unfortunately) grew up on imperial, and its just easier for me to work with.

Working in metric for diving stuff is like writing with my left hand. Ya, I can do it, but Its just not as good/fast for me as my right hand.

I rarely dive with people who are metric, and when I do, the only thing that each person needs to heed is bottle markings. Everything else (underwater) isn't dependant on both people knowing a measurement.