switching to metric-unit diving

[techintime]

I'm moving overseas to an area that does its diving in metric units. In the interest of team diving continuity with the locals, it makes sense to me that I make the transition (a new SPG, new charts, and put my computer in metric units). I'm interested in hearing from anyone else who has grew up diving English units and then had to switch. It doesn't sound like too big of a deal, but i'd rather hear about the gotchas (if there are any) before I experience them on my own. Thanks.

 

[Karl_H]

I grew up in the UK with English units and then moved overseas I got used to metric, luckily they are the same Can of worms opened!fftopic:

In terms of learning imperial I find been able to use both sets of units a good set of skills to have, 90% of dive mechanical is far easier in metric, although some still works better in imperial – visualizing ascent rates for the example – the standard recreational 60ft/min - -i.e. 1ft per second is a bit easier to visualize than 18m per minute!

I actually prefer PSI to bar, it’s generally easier to use with the rule of thirds and is normally easier to track gas consumption as the magnitude of numbers are easier to work with – based on this I wouldn’t worry about changing SPG, the other equipment may be worth converting to metric though, especially if it’s a question of changing setting over new equipment.

Depth wise just work on 100ft being 30m then every 10ft being 3m (add or subtract) to get the rough depth. I still think in metric but often need to work in feet for classes so that the rue I use to switch between rough depths, I guess doing this in reverse may be the best options for you until you get familiar with both. If you have them it may even be worth diving with two computers, one in metric and one in imperial to give you a quick reference at depth?

For technical diving, or even recreational nitrox, make sure you mark all MODs with “ft” or “m”, this could be a killer.

 

[PfcAJ]

A little over a year ago, I did some technical diving in Italy that was all in metric. I transitioned fairly easily, but I wore an imperial depth gauge that I would revert too from time to time. I grew out of it pretty quickly and was full-on metric by the end of the week. I still stumble a bit with metric stuff, but I think it all comes down to practice.

I would certainly switch over to metric everything if your team is metric. Mental-math mid-dive is never a good option (no one gets smarted underwater), and botching communication could lead to a bad time. Double check your MODs.

 

[ajduplessis]

^^^ Good advise by PfcAJ. I dive metric and have had exposure to imperial. I much rather dive metric but this is a biased opinion. I would not go out and by a metric gauge(s) but would rather rent them. I would however take a imperial gauge with on the trip, always nice to see something familiar.

Diving metric is very easy, so are on the fly calcs. I guess anything familiar is easy.

 

[DevonDiver]

Metric is very intuitive for 'on-the-fly' calculations.

Take extra precautions to avoid errors through habitual/instinctive automation. Mark 'M' on MODs and transribe a quick 'crib sheet' of depth/pressure conversions into your wetnotes etc. You won't need them after a short while though.

You can also get SPGs dual-marked; in both BAR and PSI. They can be useful. I make use of these as I regularly dive with sensible people who use metric and the odd USA-preferred anomaly.

 

[Diver0001]

I'm moving overseas to an area that does its diving in metric units. In the interest of team diving continuity with the locals, it makes sense to me that I make the transition (a new SPG, new charts, and put my computer in metric units). I'm interested in hearing from anyone else who has grew up diving English units and then had to switch.

I did. I learned how to dive in Canada using PSI and feet for the first ....mmmm 600-odd dives I made.

In my case the biggest translation I had to make was to get a feeling for how deep I really am. I had a good feeling by what 100ft was but 30 metres didn't seem as deep. For deco stops, the stop depths seemed funny. 18, 15, 12, 9, 6 and 4.5 metres just felt like smaller steps than 60, 50, 40, 30, 20 and 15 feet. At 3 metres I didn't feel like there was hardly any water above my head even though it's 10 feet.

It definitely took a while to get a "gut feeling" for metric depth.

The up side of it is that metric is a LOT easier to work with for calculations of things like gas planning etc because 1ata is 10 metres. It's all round numbers and even during the dive the calculations you need to make in your head (if any) are easier because it's all round numbers.

For the gas it wasn't as much of a problem. 200 bar is a full tank, 100 bar is 1/2 a tank. It doesn't matter if that's 3000psi or 1500psi because I already thought about it in terms of "full" "half" and "quarter". The associated number was mostly irrelevant information. There were a couple of new signs to learn in order to communicate your pressure but that part of the transition was easy in my case.

R..