Ending the Era of the U.S. Survey Foot • Hacker News Board

Re: Ending the Era of the U.S. Survey Foot

#141

Post by doctor_eval » Sat, Feb 01, 2020, 11:58 AM UTC

basicplus2 wrote: post #122

DeepYogurt wrote: post #21

Imagine it being 2020 and not using the metric system.

I get the impression that fractions are very much engrained in American psychi and cultural identity and thus is a strong influence for opposition to a metric system.

Yes, as an Australian I find the idea of using fractional measurements to be super weird.

People in these threads talk about 1/3rd of an inch as if that’s a real number :)

But seriously I think you are right. I never use fractional notation or thinking when I’m building something, while it seems very common when reading US sites. I have a socket set which US Customary sizes in fractional inches and mm; I cant tell which of the US sockets is bigger without comparing them, but 11mm is obviously larger than 10mm (to me).

I think your observation about cultural identity is spot on, but as always it goes both ways - I think the US system is nuts because of all these crazy fractions.

Until now I didn’t realise that this was my own cultural bias against fractions leaking in.

Re: Ending the Era of the U.S. Survey Foot

#142

Post by Symbiote » Sat, Feb 01, 2020, 12:12 PM UTC

abduhl wrote: post #113

jessaustin wrote: post #106

Earlier quoted context omitted.

How would one use the diameter to determine weight? Do we square it then divide by four?

I have no idea what the GP is doing but you would just do Pi * D^2 / 4 * H * 62.4 Where D is tank diameter in ft H is tank height in ft and 62.4 is the unit weight of water in lbs per cubic foot. Divide by 144 of D is in inches and 12 if H is in inches. Or if you want to be real lazy you can see Pi/4*62.4 is ~49 and round to 50.

Do most people know 62.4 lb/ft³?

The equivalent metric factor is 1 g/cm³ or 1 kg/L [1] so with D and H in centimeters the calculation is

  π D²/4 × H

kilograms of water.

[1] Assuming we're talking about a normal water tank, not a space rocket. Density varies with temperature, it's 0.9970474 g/cm³ at 25 °C.

Re: Ending the Era of the U.S. Survey Foot

#143

Post by Symbiote » Sat, Feb 01, 2020, 12:32 PM UTC

big_chungus wrote: post #72

mrb wrote: post #39

Earlier quoted context omitted.

My wife's family, who almost all have university degrees, who were all born and raised in the US, and who are very familiar with the imperial system NEVER seem to be able to do math with it. They ask me, a European raised with the metric system, for help. Find out how many fl oz of milk are in a measuring cup graduated in units of cups? Ask mrb. Convert my daughter's height from feet/inches to inches? Ask mrb. Conver…

This is also just an anecdote, but I'll second thomk's opinion on woodwork/manual measurement of most kinds. Twelve has one, two, three, four, six, and twelve for divisors, and that is incredibly handy when you're trying to do manual measurement. Even sixteen has one, two, four, eight, and sixteen, making for easier division of pounds to even numbers of ounces; compare this to ten, which has only one, two, five, and…

150mm has 2, 3, 5, 6, 10, 15, 25, 30, 50, 75 so that works very nicely if you want something that can be combined with many combinations. European kitchen cupboards and appliances are designed with a width of N×150mm.

Re: Ending the Era of the U.S. Survey Foot

#144

Post by Symbiote » Sat, Feb 01, 2020, 12:36 PM UTC

nwallin wrote: post #108

mrb wrote: post #39

Earlier quoted context omitted.

My wife's family, who almost all have university degrees, who were all born and raised in the US, and who are very familiar with the imperial system NEVER seem to be able to do math with it. They ask me, a European raised with the metric system, for help. Find out how many fl oz of milk are in a measuring cup graduated in units of cups? Ask mrb. Convert my daughter's height from feet/inches to inches? Ask mrb. Conver…

> Find out how many fl oz of milk are in a measuring cup graduated in units of cups? Ask mrb. 8. Volume is base 2. Two tablespoons in an ounce, 8 ounces in a cup, (there used to be other units in between, but nobody used them, like deci in si) two cups in a pint, two pints in a quart, four quarts in a gallon. If you were going to sell me on switching units, it would be based on hexadecimal instead of base 10. > Conve…

NB your fluid calculations are for US customary measures. The Imperial system has 20 fl oz in a pint, and people never use cups or quarts. Take care if you come across an old British recipe, or drink beer in pints in Britain.

0°F is colder than the coldest temperature I've ever experienced, your definition seems very arbitrary.

Re: Ending the Era of the U.S. Survey Foot

#145

Post by ajuc » Sat, Feb 01, 2020, 12:58 PM UTC

war1025 wrote: post #84

mark-r wrote: post #67

Earlier quoted context omitted.

The boiling point of water may not be useful on a day-to-day basis, but the freezing point certainly is. 0C is a lot less arbitrary than 32F. Other temperature mileposts are just a matter of getting used to them; 100F is pretty hot, as is 35C. I think you underestimate the usefulness of powers of 10.

> The boiling point of water may not be useful on a day-to-day basis, but the freezing point certainly is The freezing point of water is interesting, but in practice it is pretty variable depending on what adulterants are mixed with it. Realistically, any day that it gets up to the 20s F you will get some amount of snow melt. Any time it is above ~0F the roads will de-ice during the day from the salt they put down. I…

If they predict sub-zero temperatures in early spring you have to cover your plants in the garden or they are likely to die. If you leave your house for a week or longer and they predict consistent sub-zero temperatures you have to set heater to keep it above 0C or drain your pipes so they won't burst. That's pretty practical threshold if you ask me.

Nobody says in the weather prognosis "beware people it will get sub-negative 17 C at one point", they just say the lowest it will get. But they do warn if it will get sub-zero C at any point, there's a separate word for it.

> Any time it is above ~0F the roads will de-ice during the day from the salt they put down.

The ~0F for salt-water mix is a very fuzzy threshold, depending on the proportions it can be anything up to 0C in reality. In practice I just expect ice if it's sub-zero C, I don't really know if they will salt the roads before I'm there and how much of it will remain when I'm driving there.

I also don't understand why you need 100 degrees when you can't distinguish between for example 70 and 80 F. Could just as well be using dekoF without perceived loss of precision.

> Powers of ten are just scientific / engineering notation, they aren't really all that dependent on the underlying base units.

The problem is converting between feet, pounds, inches, miles, gallons, etc. It introduces ugly factors everywhere. Sure you can do it, but it turns something you can do instinctively on the fly with metric into something you have to solve on a paper or with a calculator.

Fun exercise to showcase this - how many 50x50 cm tiles to tile a 2m wide pavement 5 km long? Now do the same with 20x20 inches tiles for 5 feet wide pavement 3 miles long :)

See roman numerals vs positional system. Multiplication with roman numerals is a daunting task, while kids in primary school can multipy long numbers with positional system. Despite that there was over a century where both systems coexisted, and some people even complained that "positional system makes falsifying accounting books too easy".

Also 1 kg ~ 1 liter for most liquids is very useful for quick estimation of mass and volume, can't do that with pounds and gallons.

Re: Ending the Era of the U.S. Survey Foot

#146

Post by sfRattan » Sat, Feb 01, 2020, 1:59 PM UTC

mrb wrote: post #120

nwallin wrote: post #108

Earlier quoted context omitted.

> Find out how many fl oz of milk are in a measuring cup graduated in units of cups? Ask mrb. 8. Volume is base 2. Two tablespoons in an ounce, 8 ounces in a cup, (there used to be other units in between, but nobody used them, like deci in si) two cups in a pint, two pints in a quart, four quarts in a gallon. If you were going to sell me on switching units, it would be based on hexadecimal instead of base 10. > Conve…

The conversion techniques you explained, I use them myself (that's why they always ask for my help, I can do it in my head.) But the fact many Americans are unable to do that is, in itself, evidence the imperial system doesn't work that well for them. > This is definitely the worst example. 0°F is really cold. 100°F is really hot. This might be a sufficient explanation to give to a 5-year-old, but as soon as you need…

> But the fact many Americans are unable to do that is, in itself, evidence the imperial system doesn't work that well for them.

The set of anecdotes you have put forward about Americans you know could be evidence of any number of things. You hypothesis is that the US customary system doesn't work well for them. An equally valid hypothesis is that public education doesn't work for them.

You keep asserting that your anecdotes are broadly indicative, but multiple people are telling you the opposite (and presenting an equivalent level of anecdotal evidence with similar limits in broad applicability).

For my part, I've lived in several parts of America my entire life and never met another American:

* who says "six pound five" for weight.

* who doesn't know that water freezes at 32°F.

* who would express length/distance as tenths of feet (e.g. 1.3). [1]

But I wouldn't therefore conclude anything about Americans generally.

In fairness, you could probably take a camera and get an 'average man on the street is dumb' effect if you looked hard enough and cut a bunch of disparate interviews together. I suspect you are encountering selection bias. All the people who are bad at math (independent of measuring system or educational background) have found and glommed onto you for help. All the people who don't have trouble with unit conversion (who possibly outnumber the former group) don't trouble you with their unit conversions.

[1]: I have seen halves and quarters (X.25, X.5, X.75) of feet expressed in decimal.

Re: Ending the Era of the U.S. Survey Foot

#147

Post by sfRattan » Sat, Feb 01, 2020, 2:19 PM UTC

doctor_eval wrote: post #140

irrational wrote: post #98

Earlier quoted context omitted.

It's not the precision. It's the divisibility. 10 can only be divided in half. It can't be divided into thirds, quarters, sixths or twelfths evenly and that ability is invaluable. This is the same reason why, in the old days of grid layouts, grids were 12 columns wide and not 10.

What’s so special about thirds, sixths or twelfths? 10cm = 100mm; 100mm can easily be divided by 2, 4, 5, 8 (=12.5), 10, 20, 25, ... That’s a nice thing about metric. If you don’t like the units you can multiply them

Specifically, twelve is a superior highly composite number.[1] In plain (and probably over simplified) English, it has more factors than other numbers in a similar range.

Historically, problems of division have been harder to solve than problems of multiplication. You can observe counting systems and their radices develop in multiple civilizations to make dividing easier by providing more factors. Twelve inches to the foot. The long hundred. 360 degrees in a circle. Ancient Mesopotamian sexagesimal arithmetic.[2] The fact that 'dozen' is a word.

In the modern industrial era, we have computers (mechanical then electronic) to help with problems of division, but for most of history we didn't have those tools.

What's so special about ten? Probably that we have as many fingers, so some counting systems developed as base-10 and spread across the world for reasons that have more to do with geopolitics than utility for mathematics. Of course, you can count to twelve on your knuckles.

[1]: https://en.wikipedia.org/wiki/Superior_highly_composite_numb...

[2]: https://en.wikipedia.org/wiki/Sexagesimal

Re: Ending the Era of the U.S. Survey Foot

#148

Post by samatman » Sat, Feb 01, 2020, 3:29 PM UTC

sdenton4 wrote: post #130

samatman wrote: post #94

Earlier quoted context omitted.

It frustrates my sense of aesthetics to no end that the inch isn't defined as 25.6 mm. That would make the imperial system a base-two variant of the SI system. This would have made the mile around 42 (current) feet longer, which is a non-starter; I just wish the foot had been a little longer, somehow.

If it helps, the miles-to-kilometers ratio is approximately the golden ratio... (1.609 vs 1.618.) So, as a level N nerd, you can convert miles to kilometers by rounding to a nearby fibonacci number, and then finding the NEXT fibonacci number (and maybe fudging a bit in the direction of rounding). Then, as a Level N+1 Nerd, you can realize that the Fibonacci Base exists, in which any integer can be represented as a co…

It doesn't help! If the inch were 25.6mm, the ratio would be 1.622!

That's a lot closer! argh!

Re: Ending the Era of the U.S. Survey Foot

#149

Post by war1025 » Sat, Feb 01, 2020, 3:40 PM UTC

ajuc wrote: post #145

war1025 wrote: post #84

Earlier quoted context omitted.

> The boiling point of water may not be useful on a day-to-day basis, but the freezing point certainly is The freezing point of water is interesting, but in practice it is pretty variable depending on what adulterants are mixed with it. Realistically, any day that it gets up to the 20s F you will get some amount of snow melt. Any time it is above ~0F the roads will de-ice during the day from the salt they put down. I…

If they predict sub-zero temperatures in early spring you have to cover your plants in the garden or they are likely to die. If you leave your house for a week or longer and they predict consistent sub-zero temperatures you have to set heater to keep it above 0C or drain your pipes so they won't burst. That's pretty practical threshold if you ask me. Nobody says in the weather prognosis "beware people it will get sub…

> If they predict sub-zero temperatures in early spring you have to cover your plants in the garden or they are likely to die

Around here they just call it a "frost warning"

> Nobody says in the weather prognosis "beware people it will get sub-negative 17 C at one point"

If it gets too cold out, they do advise people to take extra care being outside due to the danger.

> you can't distinguish between for example 70 and 80 F

You really can.

> can't do that with pounds and gallons.

A pint ~ 1 lb. So a gallon is ~8lb.

Re: Ending the Era of the U.S. Survey Foot

#150

Post by Enginerrrd » Sat, Feb 01, 2020, 4:28 PM UTC

1-6 wrote: post #117

drdeadringer wrote: post #62

Earlier quoted context omitted.

How often does a "should" translate into reality?

It's entirely possible that they might not be aware. Surveyors are concerned with measuring bearing and distance from an arbitrary location (5000,5000) in some cases. The distances they traverse are not enough to see differences between US Survey foot and Int'l Feet. Cartographers and GIS folks who tie into a photogrammetric basemap are probably more aware. Most Civil engineers are like 'NAD83? Ok, whatever you say~!…

This is true. I barely understand coordinate systems enough to get by and somehow I know them better than any other engineer I've talked to. Surveyors are 50/50 on whether they know all that stuff or not.

Really though, there's no excuse for errors caused by that stuff. Survey data should almost always only be used relative to itself.