Metric versus Imperial System for Diving?

[redacted]

I cant really say that as a European the choice to use imperial units in the USA provoke me very much or bother me either.
I DON'T however get why people think that imperial is "easier" or that they "cant relate to a meter" as I have no problem knowing what a foot (or three) is, but its quite a way from there to be offended by your choice of units

Some of it is just what we are used to. Range in meters - OK. Depth in meters - OK. Height (person) in meters - problem. It does not compute.

I heard NY state is going to redo their road signs: mile and meters; English and French..... NOT

I do have one metric computer (not switchable) and a couple metric SPGs. I don't believe I have ever seen another dive so equipped.

 

[DaleC]

I DON'T however get why people think that imperial is "easier" or that they "cant relate to a meter" as I have no problem knowing what a foot (or three) is, but its quite a way from there to be offended by your choice of units

I don't think it's a matter of easier; I think it's a matter of primary language.

I went to school right when Canada switched from imperial to metric. My brain sees some measures in one, and some in the other. Distance in metric, weight in metric. Height/weight (for people) in imperial. I see temperature in F. To use C I have to do a conversion in my head first (and have a few memorized set points).

I see scuba in imperial. I can visualize my calculations in my head and see how they play out IRL. To use Bar/L I first have to think what that represents in PSI/CuFt. It requires an extra step and is not intuitive.

So the question would be: why should people switch from an intuitive language (set of measures) to one where they have to think more and incur a greater risk of danger due to conversion errors when they already can dive safely? What's the pay off? To say "so you will be like the rest of us" is really not a selling point for people who probably won't dive with the rest of us and, if they did so, could adjust enough to also be safe.

There's just no real upside for the transitioning generation.

 

[Tigerman]

I don't think it's a matter of easier; I think it's a matter of primary language.

I went to school right when Canada switched from imperial to metric. My brain sees some measures in one, and some in the other. Distance in metric, weight in metric. Height/weight (for people) in imperial. I see temperature in F. To use C I have to do a conversion in my head first (and have a few memorized set points).

I see scuba in imperial. I can visualize my calculations in my head and see how they play out IRL. To use Bar/L I first have to think what that represents in PSI/CuFt. It requires an extra step and is not intuitive.

So the question would be: why should people switch from an intuitive language (set of measures) to one where they have to think more and incur a greater risk of danger due to conversion errors. What's the pay off? To say "so you will be like the rest of us" is really not a selling point for people who probably dive with the rest of us and, if they did so, could adjust enough to also be safe.

There's no upside for the transitioning generation.

Why would you need to convert anything for scuba other than a one-time conversion of your cuft/min sac?
200 bar is full, that means 100 bar is half and 50 is quarter. If you want to plan how much gas you need, wheres the room for error in conversions? 15l x 200 bar = 3000l - If my sac is 15l/min (which is .53 cuft/min) 200 minutes at the surface or 50 minutes at 4 ata, aka 30 meters..

 

[dfx]

So the question would be: why should people switch from an intuitive language (set of measures) to one where they have to think more and incur a greater risk of danger due to conversion errors when they already can dive safely? What's the pay off? To say "so you will be like the rest of us" is really not a selling point for people who probably won't dive with the rest of us and, if they did so, could adjust enough to also be safe.

There's just no real upside for the transitioning generation.

You only perceive imperial to be more intuitive because you're used to it. Old habits and all that, yeah we all get it. But objectively speaking, metric is more intuitive and more useful, and yes, it does take an effort to make the transition. The upside becomes obvious when and if you ever want to do anything useful with the values you're working with, such as doing basic calculations or communicating them with other people. Of course you're right that if you never do any of that and you're certain that you never will (not sure how you could be certain of that, but OK), then by all means, dive in whatever units you fancy, even the old Burmese units if you like (ngase tha per square let thit, how's that for pressure?)

 

[Bob DBF]

Why would you need to convert anything for scuba other than a one-time conversion of your cuft/min sac?
200 bar is full, that means 100 bar is half and 50 is quarter. If you want to plan how much gas you need, wheres the room for error in conversions? 15l x 200 bar = 3000l - If my sac is 15l/min (which is .53 cuft/min) 200 minutes at the surface or 50 minutes at 4 ata, aka 30 meters..

The numbers are easy, however I think in Imperial so while I'm say calculating rock bottom in metric I don't have the same "feel" that I'm right and therefore no ability to catch an error in my mental calculations. For a simple dive I wouldn't have a problem with metric, but I would be a lot more careful on a more complex dive.

As an example, I was in England recently and it took me a while to be able to make correct change and I was slow even then. Here in the US I can make correct change out of my pocket without looking at the coins. Point is that I am good at what I'm used to, and it takes time to be good at a new system, no fault of either system.



Bob
-----------------------------------------
There are more ways than one to skin a cat, however the cat never likes it.

 

[nimoh]

You only perceive imperial to be more intuitive because you're used to it. Old habits and all that, yeah we all get it. But objectively speaking, metric is more intuitive and more useful, and yes, it does take an effort to make the transition. The upside becomes obvious when and if you ever want to do anything useful with the values you're working with, such as doing basic calculations or communicating them with other people. Of course you're right that if you never do any of that and you're certain that you never will (not sure how you could be certain of that, but OK), then by all means, dive in whatever units you fancy, even the old Burmese units if you like (ngase tha per square let thit, how's that for pressure?)

more useful?

This seems to suggest that there are things that can be calculated in metric that can't be done in imperial. The examples given (doing basic calculations and communicating them with other people) can be done in imperial.

 

[dfx]

more useful?

This seems to suggest that there are things that can be calculated in metric that can't be done in imperial. The examples given (doing basic calculations and communicating them with other people) can be done in imperial.

Entirely depends on what you want to do, the circumstances and how much effort you want to put into it. Generally speaking, a simpler/easier system is more useful than a more difficult one.

 

[mrdre]

more useful?

This seems to suggest that there are things that can be calculated in metric that can't be done in imperial. The examples given (doing basic calculations and communicating them with other people) can be done in imperial.

Let's see. Suppose we have a LP 95 tank filled with ~2800 PSI ~190 bar. The volume of Faber LP 95 is 14.8 liters. LP 95 means it will have 95 cubic feet at 2640 PSI. So.. you want to know how much gas you have.

In metric it's: 190 * 14.8 - you can calculate it in your head. you can round up 14.8 to 15 or 14. if you round up to 15 you get 190 * 10 + 190 * 5 = 1900 + 190/2 * 10 = 1900 + 950 = 2850 cubic liters. 2800 is a good estimate (assuming we chose 15 instead of 14.8).

In imperial it's: 95 / 2640 * 2800 - now tell me how you are going to calculate that in your head? I can't. I can only say that "2800 is bigger than 2640 so it must be more than 95 cubic feet" - that's it. Moreover in imperial you had to remember 2 numbers about your tank: 95 and 2640, while in metric just 14.8, just one number which can be actually measured. it's a real measurement. not some volume IF it was filled at that pressure, the question still remains "at what temperature?". but the physical volume - is a physical volume.


Of course you can do all calculations in both systems, but what's the difference between the two? Using one calculations can be done in your head, using another - cannot. That's why in real life metric people do a lot of calculations just on the fly, imperial people are lost without electronic calculators and google to refresh all these "magic numbers".

That's why in military the US use only metric. You are on the battlefield and your enemy changed the position, you need to make quick adjustments for your artillery. In metric you do it quick, in your head. In imperial you'd have to use calculators and the chances of making an error are much greater. If you use imperial then you will be at great disadvantage over your enemy.

In science - in imperial the calculations would be much more complex and more error prone. If you are dealing with a lot of divisions then you are left with 2 options: use long long numbers or round them up. In first case you are more likely to do a mistake in second you accumulate error.

So theoretically you can do all the calculations in both systems, but in reality calculating in imperial becomes so problematic, that at one point you will have to make a choice: switch to metric or give up.

 

[nimoh]

In imperial it's: 95 / 2640 * 2800 - now tell me how you are going to calculate that in your head? I can't.

why not just remember that a LP95 has a tank factor of 3.5?

 

[mrdre]

why not just remember that a LP95 has a tank factor of 2.8? ...and actually, 3 is close enough.

Another "magic number" to remember. Actually 95 / 2640 ~ 0.034. So the tank factor is 3.4, not 2.8. See? Already a mistake, 2.8 is for high pressure. So in imperial you have to remember high or low pressure, 95, 2640, tank factor.

In metric you have to remember just ONE!!! number - it's the volume in liters, it's a physical measure, can be measured directly, can be guesstimated by just looking at the tank.

See the difference? You just demonstrated the problems of imperial system, how easily errors can happen. And errors like that do happen and they cost.