Imperial versus metric

[StrandedonEarth]

19 minutes ago, 18Watt said:

Fuel is ordered in gallons, mass is in pounds in the US and Mexico.  Not sure about the rest of the world, but in Canada fuel is normally weighed in pounds, but ordered in liters.  So that can be odd.  

Yeah, fuel data conversion was a contributing factor in the Gimli Glider incident, although ultimately the aircraft should never have been in the air with faulty fuel-level gauges....

Quote

After taking a dripstick measurement, Pearson converted the reading from centimetres to litres to kilograms. However, he did his calculation with the density figure for jet fuel in pounds/litre from the Air Canada refueler's slip, used for all other aircraft in the fleet, instead of kilograms/litre for the all-metric 767 aircraft, which was new to the fleet.

 

2 minutes ago, Kerbart said:

The issue with the US sticking to imperial measurements is not that (as much as it does) imperial has shortcomings; it's that the rest of the world doesn't use it. That's where conversion errors come from. ATC doesn't have that problem; everyone; everyone, worldwide, uses nautical miles for distance and feet for altitude. As long as you're all using the same units, there's not an issue. Switching to metric wouldn't really have benefits, be a gigantic operation and arguably be unsafe.

International trade is a good example. Everyone agrees on the length of a standard container; it's 40 foot*. Nobody calls that a 12.19m container and no one is insane enough to demand that the standard size should be 12m; Everyone agrees on the same unit, 40', and little need to switch (Ironically, temperature for reefer containers is set in Celsius, not Fahrenheit. Once in a while you'll have an American shipper learn that lesson with a container full of rotten meat).

* Yes, there are 20' containers, and 45' containers and occasionally a few 53' containers will make their way across the Pacific, but by far the most prolific size is 40'

....Which is why i figured a full metric conversion would be a PITA and more in ATC.

Yeah, standard pallets and containers are Imperial-sized. Tires are fun; tread base width in mm, rim diameter in inches. And there are all the old tools and machinery built to Imperial measure to make phasing out even more difficult. Should I go with a 16-inch (40.64cm) rim or theses new-fangled (and currently non-existent AFAIK) 40-cm rims?

[Kerbart]

5 minutes ago, StrandedonEarth said:

Yeah, standard pallets and containers are Imperial-sized. Tires are fun; tread base width in mm, rim diameter in inches. And there are all the old tools and machinery built to Imperial measure to make phasing out even more difficult. Should I go with a 16-inch (40.64cm) rim or theses new-fangled (and currently non-existent AFAIK) 40-cm rims?

Standard bicycle wheel size in the Netherlands (a very metric country) is 26" and 28". Here in the US it's 700mm. Go figure,

[StrandedonEarth]

Just now, Kerbart said:

Standard bicycle wheel size in the Netherlands (a very metric country) is 26" and 28". Here in the US it's 700mm. Go figure,

Plenty of bicycle rims in inches here in Canada, which went metric in the 70s…

[Pthigrivi]

1 hour ago, 18Watt said:

Yes.  Speed in knots or Mach, altitude in feet.  Flight Levels are hundreds of feet.  US and Canada report altimeter settings in inches of mercury, although the setting is available in most of the rest of the world in hPa, kPa, or millibars.

Fuel is ordered in gallons, mass is in pounds in the US and Mexico.  Not sure about the rest of the world, but in Canada fuel is normally weighed in pounds, but ordered in liters.  So that can be odd.  

Like my whole professional life is about clear transmission of very specific technical information without errors or misunderstandings and Im internally screaming. 
 

And don’t get me wrong base 10 sucks. Is not the right primes. Watt and Lavoisier and Lagrange should have gone all the way with base 30 symbology. But we are where we are. At least its a consistent and understandable system in which ordinary humans can make fast calculations in their heads. If I want a tile cutter to make 2.5mm grout lines so the shower head lands exactly centered on the drain that shouldn’t be impossible to communicate. 

Edited January 5, 2023 by Pthigrivi

[18Watt]

18 minutes ago, Pthigrivi said:

Like my whole professional life is about clear transmission of very specific technical information without errors or misunderstandings and Im internally screaming. 

As long as units are specified, it's no big deal.  Even if the entire world bowed to the wishes of the metric crowd and went metric, you would still have errors if the units were not specified.  I see this frequently.  I need 500.  500 what?  Liters, farads, metric tons?  As you can imagine, that is a source of frustration for me.

Another example of something which would be odd for me to use metric for:  beer volume.  A pint is about 470 mL (taking a guess).  Yeah, if they rounded it up to 500 mL it would amount to the same thing.  But I think a large portion of the world would prefer to order a 'pint' of beer, not a half-liter.

Interestingly, other alcoholic beverage sizes have gone metric, even here in the US.  A 'fifth' (of a gallon) is now sold as 750 ml, a half gallon has become 1.75L.

A quart of oil is almost exactly 1 L, but here in the US it's still sold by the quart or gallon.  I've even seen motor oil sold by the quart in Canada, which does strike me as odd since they supposedly went metric decades ago, and the difference between a quart and a Liter is very small, almost negligible.

I do find it amusing how worked up people get over units.  They're just numbers.  

[Pthigrivi]

26 minutes ago, 18Watt said:

As long as units are specified, it's no big deal.  Even if the entire world bowed to the wishes of the metric crowd and went metric, you would still have errors if the units were not specified.  I see this frequently.  I need 500.  500 what?  Liters, farads, metric tons?  As you can imagine, that is a source of frustration for me.

Another example of something which would be odd for me to use metric for:  beer volume.  A pint is about 470 mL (taking a guess).  Yeah, if they rounded it up to 500 mL it would amount to the same thing.  But I think a large portion of the world would prefer to order a 'pint' of beer, not a half-liter.

Interestingly, other alcoholic beverage sizes have gone metric, even here in the US.  A 'fifth' (of a gallon) is now sold as 750 ml, a half gallon has become 1.75L.

A quart of oil is almost exactly 1 L, but here in the US it's still sold by the quart or gallon.  I've even seen motor oil sold by the quart in Canada, which does strike me as odd since they supposedly went metric decades ago, and the difference between a quart and a Liter is very small, almost negligible.

I do find it amusing how worked up people get over units.  They're just numbers.  

Mainly my issue is in architecture I live in a broad set of scales both in distance and in mass and load equations between pounds, feet, miles, inches, and the binary fraction madness all the way down after that. I have multiple subcontractors that are operating on civil engineering and landscape sales and precision machined components that need to be accurate and coordinated down to 1/64th of an inch, and all of that needs to be captured in digital files and converted to physical, scaled drawings which themselves are legal contracts that we can be sued over if mistakes are made anywhere along the chain. A very small scale error made when converting a paper site plan from 20 years ago into a digital format can result in a setback dispute costing hundreds of thousands of dollars. Same with quantifying material orders or precisely lining up steel fabrication with footing formwork and town site drainage standards. The units themselves are incomprehensible garbage and it has very real and obnoxious costs for working people. 

Edited January 5, 2023 by Pthigrivi

[Gargamel]

11 minutes ago, Pthigrivi said:

precision machined components that need to be accurate and coordinated down to 1/64th of an inch,

I would very much hesitate to use the terms ‘precision machined’ and ‘1/64’ in the same sentence.    Anything over .01” tolerance could be called ‘A good starting point’.  I’m often dealing in tolerances +/-.0004” and often switch between metric and imperial with no issues.   

[SingABrightSong]

4 minutes ago, Gargamel said:

I would very much hesitate to use the terms ‘precision machined’ and ‘1/64’ in the same sentence.    Anything over .01” tolerance could be called ‘A good starting point’.  I’m often dealing in tolerances +/-.0004” and often switch between metric and imperial with no issues.   

"And a thousandth of an inch to give us play"

[kerbiloid]

1 hour ago, Kerbart said:

Standard bicycle wheel size in the Netherlands (a very metric country) is 26" and 28". Here in the US it's 700mm. Go figure,

1 hour ago, StrandedonEarth said:

Plenty of bicycle rims in inches here in Canada, which went metric in the 70s…

Biker mafia. They are like alcomafia with gallons, pints, and quarts but with wheels and inches.

No need to say that the bikers are fond of pints and quarts, too. Aggressively toxic masculine conservatism.

52 minutes ago, 18Watt said:

But I think a large portion of the world would prefer to order a 'pint' of beer, not a half-liter.

No problem. Just pour 470 ml in a 500 ml bottle and take money for 500.

52 minutes ago, 18Watt said:

Interestingly, other alcoholic beverage sizes have gone metric, even here in the US.  A 'fifth' (of a gallon) is now sold as 750 ml, a half gallon has become 1.75L.

It's a time to replace those ugly .45 and .38 with clear and accurate 11.5 and 9 mm.

Starting from cowboy movies. "Get my eleven-and-half,  you unpleasant person! Bartender! 470 ml of whiskey!"

Edited January 5, 2023 by kerbiloid

[FleshJeb]

11 minutes ago, Gargamel said:

Anything over .01” tolerance could be called ‘A good starting point’.  I’m often dealing in tolerances +/-.0004” and often switch between metric and imperial with no issues.   

My tolerance is 1/8" but I can give it to you 500 feet away and over rough terrain.

31 minutes ago, Pthigrivi said:

civil engineering

This is your friendly reminder not to rotate and translate the site plan, and use DVIEW TWIST and a viewport in Paperspace instead.

(In my area, architects are notorious for having exceptionally bad CAD workflow.)

37 minutes ago, Pthigrivi said:

converting a paper site plan from 20 years ago into a digital format can result in a setback dispute

Honestly, put the liability for that on your civil/survey sub.

Picking on the architect aside, I agree that converting too many types of units is fraught with danger. The one where I have to interface with your discipline is feet and fractional inches to decimal feet. Especially if I'm staking a foundation plan and I need to do it in the field, in my head.

Feel free to PM me if you want to complain about stupid surveyors.

[steve9728]

In a country like China where metric units are used exclusively, the only non-metric system is the size of the cake. Every time when I need to buy one, I always need to find out how big exactly the damn cake is: what you meaning about 6-inch, 8-inch, and 10-inch?

And one day I went to Portsmouth and this thing hit me: isn't that the size of the naval gun?!

"152mm cake please!"

Edited January 5, 2023 by steve9728

[Codraroll]

4 hours ago, 18Watt said:

Another example of something which would be odd for me to use metric for:  beer volume.  A pint is about 470 mL (taking a guess).  Yeah, if they rounded it up to 500 mL it would amount to the same thing.  But I think a large portion of the world would prefer to order a 'pint' of beer, not a half-liter.

That's just language. The half-liter is as ingrained in the language over here as the pint is in the UK. And I doubt it would cause that much critical confusion if the word "pint" became established short-hand for half a liter. Few people would complain about getting 3 cl more beer than they asked for.

[Gargamel]

40 minutes ago, steve9728 said:

In a country like China where metric units are used exclusively, the only non-metric system is the size of the cake. Every time when I need to buy one, I always need to find out how big exactly the damn cake is: what you meaning about 6-inch, 8-inch, and 10-inch?

And one day I went to Portsmouth and this thing hit me: isn't that the size of the naval gun?!

"152mm cake please!"

I don’t often laugh at this thread…..

[Pthigrivi]

6 hours ago, Gargamel said:

I would very much hesitate to use the terms ‘precision machined’ and ‘1/64’ in the same sentence.    Anything over .01” tolerance could be called ‘A good starting point’.  I’m often dealing in tolerances +/-.0004” and often switch between metric and imperial with no issues.   

Haha yes, true, “precision” relative to the scale of a city block, not relative to any actual machine. 

[Codraroll]

59 minutes ago, Pthigrivi said:

Haha yes, true, “precision” relative to the scale of a city block, not relative to any actual machine. 

Back in my university days, there was a "greatest nerd contest" featuring participants from the various study programs. One of the questions was who had memorized the most digits of pi. The contestants from physics and mathematics rattled off dozens of digits, while the one from civil engineering stopped after six. When asked about what he thought about falling so far behind the others, he answered: "If you ever need to build a circular structure to a greater precision than one millimeter per kilometer, you are allowed to look it up".  That answer awarded him full marks on the question.

[Gargamel]

11 minutes ago, Codraroll said:

Back in my university days, there was a "greatest nerd contest" featuring participants from the various study programs. One of the questions was who had memorized the most digits of pi. The contestants from physics and mathematics rattled off dozens of digits, while the one from civil engineering stopped after six. When asked about what he thought about falling so far behind the others, he answered: "If you ever need to build a circular structure to a greater precision than one millimeter per kilometer, you are allowed to look it up".  That answer awarded him full marks on the question.

I forget the actual number, but ~12 digits of pi give you an accuracy suitable for a circle the size of the visible universe.  

[RCgothic]

42 digits calculates the circumference of the observable universe from it's diameter to a calculation precision of about a proton's width.

This is especially hilarious because the *first* digit of the diameter of the observable universe isn't precisely known, so there's no conceivable reason to calculate the circumference to  its 42nd digit. Garbage in, garbage out.

NASA/JPL use 15 digits for their most precise navigational calcs.

Edited January 5, 2023 by RCgothic

[kerbiloid]

It's enough to know that pi ~= 22/7

Precision = 0.04%

Try to find such ruler.

[RCgothic]

5 hours ago, Codraroll said:

That's just language. The half-liter is as ingrained in the language over here as the pint is in the UK. And I doubt it would cause that much critical confusion if the word "pint" became established short-hand for half a liter. Few people would complain about getting 3 cl more beer than they asked for.

A pint is strictly 568ml, but even in the UK you get a large number of bottles/pint glasses sold as "ISO Standard Pints" (AKA 500ml), and pretty much nobody complains about the missing 68ml.

[kerbiloid]

1 minute ago, RCgothic said:

A pint is strictly 568ml, but even in the UK you get a large number of bottles/pint glasses sold as "ISO Standard Pints" (AKA 500ml), and pretty much nobody complains about the missing 68ml.

500 / 568 = 0.88

Same as 9 eggs in a pack of 10.

Known as "a nine of eggs", when inattentive customer thinks it's "a ten".

[Deddly]

Ah yes, the beauty of the imperial system, where the US pint does not match the UK pint (just one example). 

[FleshJeb]

4 hours ago, kerbiloid said:

Precision = 0.04%

Try to find such ruler.

GLONASS/GPS

[kerbiloid]

27 minutes ago, FleshJeb said:

GLONASS/GPS

When you have GPS, you have a calculator, no need to calculate in head and spend your brain resources on remembering the useless pi numbers.

22/7 (i.e. also 11 * 2 / 7) works perfectly for me and the Phoenicians for thousands of years.

It's always good to remember that:

• ab * 11 = a[a+b]b, i.e. 25 * 11 = 275
• 0.11 ~= 1/9
• 0.14 ~= 1 / 7

Together, these simple formulas do wonders.

Also, sqrt(1.5)  ~= 5/4, sqrt(5) ~=9/4, 2^1/3 ~= 5/4, 

[Pthigrivi]

7 hours ago, RCgothic said:

 pretty much nobody complains about the missing 68ml.

I like how "pretty much" implies the existence of that guy.

[kerbiloid]

A pint of beer may differ from a pint of whiskey, because any bartender knows that moar foam makes it look nicer, while weighting less.

Also slapping the mug bottom sometimes helps to save the resource.

Edited January 6, 2023 by kerbiloid