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Author Topic: How do you convert non-metric distance units?  (Read 6086 times)
BartvanderWolf
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« on: August 09, 2013, 04:38:03 AM »
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Hi folks,

Here's one for the weekend.

Units of length
"The system for measuring length in the United States customary system is based on the inch, foot, yard, and mile, which are the only four customary length measurements in everyday use", according to Wikipedia. And I do know that the UK and the US have some sort of an agreement on these units (with exceptions).

I have a question, which may seem odd at first glance, but there is a reason for asking. I'm writing, amongst others, a software routine that converts between units of length. I also know there is probably not a definitive answer, so I'm looking for feedback based on everyday normal use. This is not a trick question, so all answers will be considered in my final evaluation, and encoding.

Now, with that out of the way, here is the question.

When do you, in everyday use, switch from inches to feet, and when from feet to yards, and when from yards to miles?

I know that 12 inches equals 1 foot, and 3 feet equals 1 yard, but do you usually say e.g. something is 36 inches or 3 feet, or one yard, long or distant? Or are inches used to avoid fractional feet ('x' feet and 'y' inches)? Or is it context dependent, e.g. when talking about precise measurements you use the smaller unit of length? Or are you not an engineer and convert everything to the largest practical unit, 'x' feet and a bit (but then when does the bit become large enough to give it more meaning, like 'give or take an inch')?

The same for yards and miles, but maybe the same principles apply?.

Thanks in advance for some soul-searching (or maybe there is an official recommendation?) and any resulting useful feedback you may have to offer.

Cheers,
Bart
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LoisWakeman
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« Reply #1 on: August 09, 2013, 06:24:56 AM »
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I don't think that's possible to answer definitively - different people use different measures, and a woodworker will give you different answers from a housewife in all probability! And of course here in the UK most younger people use metric (except for miles - don't ask!), but older folk still remember the days of imperial measures.

(I did my O level science exams in imperial, but my A levels in SI - so  think in both!)

I'd say that it's the context rather than the distance that gives the answer. I'll try to illustrate by example (for UK- USA may be different!).

How long do I need to cut this timber? 72 inches.
How far is it to the next turning? About 250 yards.
How far to the shop? About 3 miles.
How tall are you? 5 feet 4 inches
How big is that table? I'd guess about 4 feet by 6 feet.
What's the right setting for the points in my vintage car? 20 thou (sandths of an inch)

Generally, as you say, the precision will dictate the best answer.
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Gary Brown
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« Reply #2 on: August 09, 2013, 08:18:42 AM »
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Another example regarding the point that it depends on what you're measuring:

In American football, you'd generally never hear that “they're 12 feet from the goal line”; it's always “four yards.”

But few would say “the bedroom is four yards wide”; it's always “12 feet.”

And while driving in the U.S., people typically use only miles: It's 1/4 mile away, not 440 yards, unless referring to very short distances, like “it's illegal to park within 10 feet of a fire hydrant or 20 feet of a crosswalk” (with yards typically never used in that context).
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k bennett
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« Reply #3 on: August 09, 2013, 09:24:45 AM »
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Agreed, yards are used only in very specific circumstances, usually sports-related. The hundred yard dash. The twenty yard line.

I tend to use inches when things need to be accurate for short distances, as in measuring objects like furniture, or for cutting wood. My dresser is 72 inches tall, it might be 6 feet, it is most certainly not 2 yards tall (even though it is, technically.) Fractions of an inch are common, for woodworking they tend to be eighths (so, 15 5/8 inches long), for precise engineering they might be in thousandths.

Feet are for less accurate measurement of short to medium distances. I'm six feet tall, more or less, my driveway is 40 feet long, it's 1500 feet to the exit ramp (that actually appears on signs here in NC.) If I need an accurate measurement, I use feet and inches -- my living room is 12 feet 8 inches long, or whatever. I've never heard anyone use fractions of a foot, except for very rough estimates like "5 and a half feet."

Anything longer than that is expressed in miles or fractions thereof. These are inherently less accurate most of the time, but that's expected. It's 30 miles to Greensboro. It's 250 miles to the beach. The Appalachian Trail is 2200 miles long. It's a quarter mile to the lake.

I expect the same questions can be asked about the metric system, and answered in a similar way. I'm not ever .00185km tall, for example, even though that's an accurate measurement.
« Last Edit: August 09, 2013, 09:28:24 AM by k bennett » Logged

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Peter McLennan
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« Reply #4 on: August 09, 2013, 10:11:42 AM »
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It gets worse.  North Americans typically measure longer distances by time.

"How far is it to the next town?"
"Oh, about half an hour"
« Last Edit: August 09, 2013, 05:43:36 PM by Peter McLennan » Logged
hjulenissen
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« Reply #5 on: August 09, 2013, 11:56:34 AM »
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It gets worse.  North Americans typically measure longer distances by time.

"How far is it to the next town"
"Oh, about half an hour"
Over here, it is measured in binary: "oh, it is a coffe trip". This means that travelling this distance you will pass 10 houses or so. In rural districts that can be anywhere from 5 minutes to a couple of hours.

-h
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Eric Myrvaagnes
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« Reply #6 on: August 09, 2013, 04:10:55 PM »
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Peter and H's replies remind me of the old tale about the man left on the dock after the ship has left. His friend, on board the ship, yells: "Jump! Jump! You can make it in two jumps!"   Grin

Actually, most of the replies cover the ground pretty well, I think. Having lived in the U.S.A. for 74 years, I agree that "yards" are used pretty much only in athletic contexts (plus: measurement of cloth: "This pattern requires 3 yards of green velvet.").

So, unless your software routine is likely to be used in either an athletic or dress-making situation, I would not bother to include "yards." As for the other measurements, here are two possible approaches:

A.   Pick a useful range for each kind of result, perhaps something like this:
          If total distance > say 500M, give result in miles and decimal fractions (3.25 miles);
          If distance is between, say, 1M and 500M, give it in feet and inches, with decimal fractions of inches (17 feet, 3.25 inches); and
          For shorter distances, just give it in inches (27.596 inches).

B.   Or, let the user select the range from a menu, including some or all of the following possibilities:
          Miles, Miles and feet, Feet, Feet and inches, or Inches.

I don't think anyone ever accused Americans of being consistent!
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Schewe
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« Reply #7 on: August 09, 2013, 04:57:11 PM »
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When do you, in everyday use, switch from inches to feet, and when from feet to yards, and when from yards to miles?

Generally, it boils down to the level and degree of precision you need...2.5 feet is an explicit length which would be as precise as saying 30 inches, but if the measurement was actually 30.5 inches then it would be cumbersome to say 2.5 feet plus 1/2 inch instead of 30.5 inches. So, what unit you use depends on the precision of the measurement you need.

Having said that, I also agree that certain uses have customary traditions of measurement expressions. A home run distance in baseball is always x number of feet. In American football, everything is discussed in yards. In recent years, American track and fields has pretty much transitioned to metric measurements...

So, I would ask why are you asking? What specific dimensions are you using in what context?
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David Sutton
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« Reply #8 on: August 09, 2013, 06:42:10 PM »
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Hello Bart. Having been raised with Imperial but am living in a country that has converted to metric, I use both systems.
I use inches for distances that I can measure without moving (in other words the span between my hands), and feet when I have to use a tape measure and physically move from one end of the measured distance to the other. Not so different from centimetres and metres. When do I switch from inches to feet and inches? Somewhere between two and four feet.
I don't use yards for measuring dimensions but to indicate distances that I will have to physically walk or run. So, how long is my block of land? One hundred feet, four and three quarter inches. If I'm standing at the back fence, how far is it to the front gate? A bit over thirty yards.
Inches are used to avoid fractional feet. But fractional inches are fine. Inches are handy because thirds and quarters of feet come out as whole numbers of inches.
For dividing miles, it's probably easier to use decimal points (6.25 miles) rather than miles, yards, feet and inches.
FYI, I usually use this program to do conversions: http://msosno01.tripod.com/programs.htm
Cheers, David
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Peter McLennan
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« Reply #9 on: August 09, 2013, 07:26:14 PM »
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When I was building my house, I ran the chop saw for the carpenter.  His system for measurement was something like  " make me one fifty seven and five eighths plus"  Meaning one little black line on the tape more than the five eighths.

It must have worked.  The house is still standing. : )
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langier
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« Reply #10 on: August 09, 2013, 07:43:07 PM »
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Take the length you are given (inches, feet, feet and inches, yards, miles [hands, paces, rods, chains and furlongs]), put into a web converter of some kind and make the conversion.

For me, I simply convert feet or yards into meters and miles into kilometers roughly in my head and visually process the info. If I need something more accurate, I get out my calculator and do simple math to go from avoirdupois into metrics when I need to. When I'm in Europe, I simply change my mindset and think in metric.

Luckily for me, when we were thinking of changing to the metric system in the 1970s, I was taking many science and lab classes in high school and college and got the gist. Today, it's fairly easy to do the rough conversions in my head.
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k bennett
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« Reply #11 on: August 09, 2013, 08:41:54 PM »
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Luckily for me, when we were thinking of changing to the metric system in the 1970s, I was taking many science and lab classes in high school and college and got the gist. Today, it's fairly easy to do the rough conversions in my head.

Me too, and it helps that my lovely wife was trained as a biologist. Also, we measured lots of distances in kilometers ("klicks") in the military, as we had to get along with the rest of the world, so that sort of stuck, too.
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Eric Myrvaagnes
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« Reply #12 on: August 09, 2013, 11:26:22 PM »
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For a while before I had my BMW motorcycle, I had a one-cylinder (500cc) Norton. As an American I had to have three sets of socket wrenches to work on nuts and bolts: American (inches, etc.), Metric, and ... Whitworth! How many of you are old enough to remember Whitworth sizes?   Cheesy
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« Reply #13 on: August 10, 2013, 12:26:44 AM »
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Whitworth! How many of you are old enough to remember Whitworth sizes?   Cheesy

What the hell model of bike used Whitworth? I've heard of it, never actually used it...
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David Sutton
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« Reply #14 on: August 10, 2013, 12:51:09 AM »
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Off topic. Sorry Bart.
Whitworth!!! What a curse that was. My first car was a 1950s Wolseley and I'd think I'd have the right bolt in spares until half way through a difficult repair I'd find I need to travel across town to a shop that sold Withworth, but have no car to use because it was in pieces. I still have the spanners. English ones. Made by village blacksmiths (like their cars).
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Rhossydd
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« Reply #15 on: August 10, 2013, 03:08:37 AM »
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How many of you are old enough to remember Whitworth sizes?   Cheesy
Given there's a whitworth thread on the bottom of almost every camera....... (although that's now been bastardised to 1/4" UNC, which is only subtly different)

Pedant's note; If you really did any serious work on a Norton you'd actually use three different thread standrads; Imperial, whitworth and cycle thread which was used on cylinder head bolts.
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Jim Pascoe
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« Reply #16 on: August 10, 2013, 03:55:03 AM »
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Huh - you think that's complicated Bart?  I was born in 1961 and so my education here in the UK straddled the conversion to decimalisation of our currency - so a GB Pound had 100 pence in it rather than the old Pound that had 240 pence.  Similarly, we were taught metric measurements at school, metres and kilogrammes etc.  The trouble is, apart from the money which everyone had to adopt immediately, everything else has seen a slow transition that is still going on after 40 years.  Most of our products and goods are now sold in metric units, even though they are often conversions from the imperial.  Orange juice is sold in one litre cartons, but milk in two-pint cartons (1.13 litres).  Petrol in Litres, beer in pints.  Only fairly recently where shops forced to stop selling loose groceries in Pounds.

Regarding distances, all our road signs are in Miles and Yards, but most lengths are in metres or millimetres.  So for building work and dimensions most things are expressed in millimetres (mm).  A table would be say 2050 x 750mm.  Annoyingly, a picture frame that is listed as 16x20 inches may in fact be that size, or in small print underneath may be 400x500mm ( a bit smaller).  Bigger picture sizes are often A4 or A3, but smaller sizes in inches - 7x5 etc.

A persons height is almost universally expressed in feet and inches, and their weight in stones and pounds, but children's clothes are listed by the child's height in Centimetres.

All of this leads to a lot of complications.  Personally, I interchange units quite freely and regularly mix imperial and metric measurements.  For very small items I think using millimetres is much the best bet - avoiding all those fractions.  But then I learned the metric system, so just missed out measuring stuff in fractions of an inch.  But the feet, yards, miles thing just lingers on.  It means that although all young people now are bought up in the metric system, they still have to have a good working knowledge of the Imperial system too.  Crazy really.  I'm sure if the US went metric (like the rest of the civilised world) the UK would quickly follow.

Jim
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Rhossydd
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« Reply #17 on: August 10, 2013, 04:26:59 AM »
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Huh - you think that's complicated Bart?  I was born in 1961 and so my education here in the UK straddled the conversion to decimalisation of our currency .....  Similarly, we were taught metric measurements at school
And if you were born five years earlier, you started at school with imperial, then changed to metric mid way through your education.

Actually I'm pretty happy with that. I'm comfortable with both systems and use whatever suit the task at hand best. Sometimes I've even used different units in different directions because they suit better.

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IanB
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« Reply #18 on: August 10, 2013, 06:44:51 AM »
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The building industry in the UK converted from Imperial (as we call it!) to metric, starting in 1973. The process has led to some interesting results. Basically, materials and component sizes generally came to be quoted in mm, but production tended to carry on using the same equipment. One inch is 25.4mm, and one foot is 304.8mm (305 is close enough for most users). That means that the UK building industry has come to work in metric in multiples of 25 or 300mm. It's not quite feet and inches, but close-ish, and it's not the same as Europe where they use centimetres (in multiples of 10) instead of mm. We don't use cm as the powers that be in the early 70s decreed that there was too much potential for confusion with inches.

Context - I'm a historic buildings architect with a career behind me of working in metric on buildings built in feet and inches. You do get the hang of it, but if you want to do anything accurately you should never be without a calculator. Very rough estimates of size are still often quoted in feet and inches, but if you ask for 4 feet of timber you will probably actually get 1200mm.

I love metric - it's so simple...

Am I helping here?

I also like old motorcycles - fortunately, a 13mm open spanner (as we call them!) almost exactly fits half-inch Whitworth.  Grin
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Eric Myrvaagnes
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« Reply #19 on: August 10, 2013, 08:13:48 AM »
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I also like old motorcycles - fortunately, a 13mm open spanner (as we call them!) almost exactly fits half-inch Whitworth.  Grin
Once I made that discovery, it saved me much time sorting out my spanners.
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