Are you still imperial?

[Jamdiver]

This topic often comes back and I thought I would post a poll to add to the "debate". I was "metric born" but as I'm living in the States, I dive imperial (and hate it) in the US and dive metric in the rest of the world.

A lot of my American friends seem to have a problem understanding that the rest of the world has adopted the metric system. The reason: it's simpler and more precise. There are 1,000 grams in a kilogram, 1,000 meters in a kilometers. Who knows how many feet in a yard? How many yards in a mile? Most don't. Most need a conversation tool to switch from one imperial measure to another. Not with the metric system. On top of it, metric makes it easier to transposing weights and volumes: 100 liters of water is 100 kilos or 0.1 cubic meter. Can you do that with ounces and cubit feet without a piece of paper? Finally, do you know that 1 UK ounce is 0.96076 US ounce? Well, grams are the same all over the world...

According to the US census bureau (blue.census.gov), the world population is 6,257,911,365 while the US population is 284,796,887. That's about only 4.55% of the world population that's still sticking to imperial. Oh, yes, there are two other countries still using the Imperial system: Liberia and Burma, two countries with a stellar record regarding human rights, but that's a whole different debate...

So, are you still Imperial?

Don't forget the difference between a UK gallon (4.546092 litres) and a US gallon which is about 3.5 litres I believe.

I'm comfortable using both metric and imperial especially when it comes to diving.

 

[Blox]

It is latitude anywhere. There is a reason they are called "parallels".

At the equator, one minute of longitude is equal to one nautical mile. I can dig the Bowditch reference out for you if need be.

I think we probably mean the same thing (probably I misunderstood/expressed myself not clearly enough - sometimes being not a native English speaker has its downsides). My apologies.

I was trying to say that a nautical mile is the distance of one minute of arc, measured on the equator - this is what you express as "one minute of longitude".

 

[Rick Murchison]

You have to admit though, using 10 as the base simplifies things a lot!

Well, no, actually using base 10 only seems to work well because our most common numeric system uses base 10. But base 10 is forever a PITA for a computer, where rounding errors can create the strangest results. For example, if you just do simple decimal subtraction to two decimal places, you should always get answers to two decimal places, right? But nay... because a computer is base 2, the best it can do is approximate .67, for example, and unless the programmer goes to the trouble to write a routine to "correct" the computed answer, you're liable to get something with a dozen decimal places. But a computer can represent halves, fourths, sixteenths, etc exactly, for they are base 2, and the computer understands that. So do the laws of quantum physics.
Base 10 is for counting on your fingers. All real math ends up being base 2.
Ain't this fun... ?
Rick

 

[Charlie99]

I was trying to say that a nautical mile is the distance of one minute of arc, measured on the equator - this is what you express as "one minute of longitude".

Before you and Don go around one more time, take a look at a globe. 1 minute of latitude (North/South) is the same size everywhere, approximately 1nm.

OTOH, 1 minute of longitude (East/West) is 1nm only at the equator, and gets smaller the closer one is to the poles.

 

[Kim]

It's pretty hard to express an exact third using base 2. I agree though that binary is actually a simple system - except that the length of the numbers it uses don't lend themselves to human mental calculation very easily. As far as halves, thirds, quarters etc are concerned - it's funny how they don't include them on your computer keyboard - it's a pain having to access them through symbols lists - or remembering the ALT codes.
This is getting a little far from the point though. I am not saying at all that general maths is always better in decimal. I am saying that the bar/liter diving measurement enable quick mental computations of things like how much gas you actually have left. That's hard to do in Imperial. In the end though both systems work and both systems have advantages in diving that the other doesn't. Trying to prove that one is always better than the other is futile.

 

[SeanQ]

If we really wanted to simplify things we could measure all pressure in mmH20! Anyone need to brush up on scientific notation first?

 

[Blox]

Before you and Don go around one more time, take a look at a globe. 1 minute of latitude (North/South) is the same size everywhere, approximately 1nm.

OTOH, 1 minute of longitude (East/West) is 1nm only at the equator, and gets smaller the closer one is to the poles.

I did not have the intention to keep going with this - I thought it had been cleared up. You and me are saying the same thing - just two different ways.

 

[fmw625]

Rick,

Halves, fourths, eights, sixteenths, thirtyseconds, sixtyfourths, hummm sounds sorta like imperial measurement fractions. Could our (US) inch fractions be base 2?

 

[KrisB]

Well, no, actually using base 10 only seems to work well because our most common numeric system uses base 10. But base 10 is forever a PITA for a computer, where rounding errors can create the strangest results. For example, if you just do simple decimal subtraction to two decimal places, you should always get answers to two decimal places, right? But nay... because a computer is base 2, the best it can do is approximate .67, for example, and unless the programmer goes to the trouble to write a routine to "correct" the computed answer, you're liable to get something with a dozen decimal places. But a computer can represent halves, fourths, sixteenths, etc exactly, for they are base 2, and the computer understands that. So do the laws of quantum physics.
Base 10 is for counting on your fingers. All real math ends up being base 2.
Ain't this fun... ?
Rick

Actually, Rick, that's not quite why the computer has trouble doing a decimal subtraction. The issue is with the implementation of "floating point" numbers. A computer will *always* get integers correct, but floating point math often introduces a margin of error of ~0.000001%.

The programmer's trick here is to deal with integers only... sometimes obscenely huge ones, but integers nonetheless, when precision matters. For instance, in accounting calculations, the dollar amounts are usually stored in "number of cents" -- i.e. $130.24 is stored as 13024 -- that way all calculations can be made accurate to the penny, after which rounding errors are not only acceptable, but expected.

Here is a good [technical] explanation of why floating point is inaccurate:
http://docs.sun.com/source/806-3568/ncg_goldberg.html#680

 

[KrisB]

Rick,

Halves, fourths, eights, sixteenths, thirtyseconds, sixtyfourths, hummm sounds sorta like imperial measurement fractions. Could our (US) inch fractions be base 2?

I think that would best be described as inverted base-2...