[HN Gopher] Ending the Era of the U.S. Survey Foot
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Ending the Era of the U.S. Survey Foot
Author : amjaeger
Score : 56 points
Date : 2020-01-31 18:13 UTC (4 hours ago)
(HTM) web link (www.nist.gov)
(TXT) w3m dump (www.nist.gov)
| opwieurposiu wrote:
| As an example of a problem that can occur: Client wants to survey
| the elevations of a parcel of land for building a house. The
| surveyor goes out and collects data with gps survey equipment,
| which produces a .csv file of northing,easting,and elevation
| values relative to some National Geodetic Survey benchmark. The
| engineer imports this .csv into his cad software, produces a
| grading plan .csv file. The earthmoving contractor imports the
| grading plan into his software and grades the site.
|
| Client gets house built, moves in and discovers that the front
| yard turns into a swamp after every rain.
|
| Somewhere in the chain of importing and exporting .csv files,
| software A was using survey feet and software B was using
| international feet.
|
| This can also cause problems like structures built in the wrong
| spot, fences built on neighbors land, etc.
| abofh wrote:
| The difference is .0002%. your examples would barely add up to
| an inch over a mile.
| opwieurposiu wrote:
| Sometimes the benchmark for northing/easting/elev is many
| miles away from the actual site. This is especially true with
| gps surveys.
|
| It only takes a few inches to wind up with a substantial
| drainage problem.
| clucas wrote:
| I worked as a CAD operator, surveyor, and occasional field crew
| worker at a civil engineering firm for a few years. We never
| ran into issues like this - by far the more common issue was
| the difference between NAVD and NGVD. At the time I was
| surveying, the FEMA flood insurance maps in our area were only
| partially updated, so the base flood elevation could be in
| either datum, and you had to really watch it so you didn't end
| up about 0.7' off vertically.
| dmtroyer wrote:
| seems like an issue that surveyors and engineers should be well
| acquainted with.
| alamortsubite wrote:
| If someone had told me this statement was part of a Monty Python
| script, I'd likely have believed them.
| DeepYogurt wrote:
| Imagine it being 2020 and not using the metric system.
| adamtj wrote:
| That's not hard to imagine. Quick, what's 1/3 of a meter? The
| sometimes problem with metric is it's base-10. The prime
| factors of 10 are 2 and 5. Feet are in base-12, which has the
| prime factors 2 and 3. Three is much more useful than five.
| There are marks on your measuring tape at exactly 1/3 of a yard
| or 1/3 of a foot.
|
| Metric is often easier and more convenient, but not always. So,
| in the US, we tend to use metric or customary units depending
| on which is more convenient for the task at hand. Actually,
| it's a lot like the UK and other countries where older systems
| still exist alongside metric. The difference with the US is
| that we don't have as many unnecessary laws mandating metric.
| You're an adult. You're working with other adults. You're
| perfectly capable of figuring out what to do without the input
| of lifelong politicians who've never measured a thing in their
| lives. Except for the amount of your money that they're going
| to spend. They like measuring that.
| clucas wrote:
| I do agree with you that base-12 is easier to work with, but
| I think it's worth pointing out, appropos of the article,
| that U.S. surveyors actually talk about feet in "tenths" and
| "hundredths" - so, quick, what's one third of a foot? About
| 33 hundredths of a foot. ;)
| jdkee wrote:
| "Quick, what's 1/3 of a meter?"
|
| About a foot.
| mrb wrote:
| 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.
|
| Convert a package's weight from oz to lb/oz? Ask mrb.
|
| Need to know how cold it needs to be outside in farenheit for
| water to freeze? Ask mrb.
|
| I lost count of the number of times they accidentally mix up
| for example 1.3 feet with 1 ft 3 in. Sometimes it's due to
| miscommunication, eg. I have seen "six pound five"
| interpreted as 6 lb 5 oz by one when the speaker meant 6.5
| lb. Or vice versa.
|
| It's just comical to see someone trying to argue that the
| imperial system is "sometimes easier."
| asdfasgasdgasdg wrote:
| > Quick, what's 1/3 of a meter?
|
| 33.3 cm?
| thomk wrote:
| Oh, you rounded. Got it. ;)
| SketchySeaBeast wrote:
| Let's not pretend that any real world application of a
| third of a foot has infinite precision.
| thomk wrote:
| Agreed. If you have ever done any type of construction you
| are very thankful that you can divide a foot evenly by 2, 3,
| 4 and 6.
| irrational wrote:
| Yeah, woodworking is so much easier when using feet and
| inches. It's so incredibly useful to be able to divide a
| foot into half, thirds, quarters, sixths, and twelfths.
| runxel wrote:
| Well, architectural construction is based on the
| "octameter", so 12.5 cm.
|
| That adds pretty well ;)
| [deleted]
| war1025 wrote:
| The metric system doesn't really have anything intrinsically
| better about it.
|
| Sure the power of ten thing is convenient, but really that is
| just sticking to one unit and adding a prefix. You could call
| "thousandths of an inch" a "milli-inch" and it'd be about the
| same.
|
| Fahrenheit is absolutely a more useful human-scale measurement
| than Celcius. The boiling point of water is mostly irrelevant
| to everyday life. At that point you might as well just do
| things in Kelvin.
|
| Perhaps the usefulness of Fahrenheit is only a thing when you
| live in a continental climate though.
|
| 100F is about as hot as it's going to get here in Iowa.
|
| Similarly, 0F means that it's the depths of winter. Anything
| above 0F is pretty manageable. When you start going below 0F
| you're getting into "real cold" territory.
|
| Point being, Fahrenheit is a scale that matches well to the
| climate extremes (at least around here), which I think is a
| significant advantage for it.
|
| As to the rest of it, a meter is basically a yard. A liter is
| basically a quart. A kilogram is just two pounds. Not really
| that difficult.
| dang wrote:
| " _Eschew flamebait. Don 't introduce flamewar topics unless
| you have something genuinely new to say. Avoid unrelated
| controversies and generic tangents._"
|
| https://news.ycombinator.com/newsguidelines.html
| 3fe9a03ccd14ca5 wrote:
| I don't really mind that we're not on the metric system. I just
| wish our measurements were consistent as they increase. E.g.
| foot, kilofoot, etc. instead of foot, yards, miles.
| alkonaut wrote:
| What you want is metric, so 10 inches to a foot and so on.
| Switching makes of units isn't so bad so long as the
| multipliers are 10,100,1000
|
| Next you want your units to make sense across dimensions. You
| want your volume units to ALL be based on your length units.
| A cubic foot is ok. It then contains 1000 cubic inches. There
| are no quarts, gallons, pints (unless they are names for
| decimal quantities of cubic units).
| thechao wrote:
| And base-2, rather than the computer-unfriendly base-10.
| Aaaaactually ... with a bit of squinting the U. S. customary
| volume system(s) define a complete set of base-2 nouns (which
| could be used as prefixes): tbspn
| oz jill gill cup pint
| quart half gallon peck
| kenning bushel rundlet barrel
| hogshead butt tun
|
| Where each item below the next item is exactly 2x the
| previous one. It turns out there's also some base-3 stuff
| (for measuring simplicity), like the teaspoon, etc.
|
| I've always imagined we could redefine a few things to make a
| "completely rational" U.S. customary measure. That'd be:
| 1 in == 2.5 centimeters (as Thomas Jefferson wanted)
| 256 in^3 == 1 gallon (water at 32deg F)
|
| 1 in is a bit awkwardly small. A cup-inch is ~1.3ft. A pint-
| inch is _exactly_ .8125m. Luckily, a 'tun-tun-inch'
| (65536in) is 1.0343 miles, so we could define a a 'tun-tun-
| inch' to _be_ a mile, etc., etc.
| madcaptenor wrote:
| That gives you a gallon of exactly 4 liters (256 * 2.5^3 =
| 4000 mL). Alternatively, a quart is now just another name
| for a liter.
| Yhippa wrote:
| IDK, if you're going to be non-standard might as well go all
| the way.
| Animats wrote:
| Fortunately, the inch is defined as 0.0254 meter exactly. So we
| have consistency for the really important units.
| AnimalMuppet wrote:
| Then which "foot" is exactly 12.000000 inches?
| DoofusOfDeath wrote:
| The article left me confused about what it means to have a
| legally binding redefinition of a term.
|
| Does this mean that all existing, legally binding contracts are
| to be reinterpreted using the new definition of "foot"?
|
| Does it mean that any _new_ legal document (contract,
| legislation, etc.) that uses the term "foot" without further
| clarification shall be assumed to mean this new definition of
| "foot"?
| oh_sigh wrote:
| As a general point, I don't think contracts can have their
| terms adjusted after the fact without both parties agreeing to
| it.
| ska wrote:
| I believe it is the latter.
| not2b wrote:
| In practice, since the difference is so small it does not
| matter in almost all cases, because no one was in a position
| to measure accurately enough. If you ask for 100 feet of
| rope, the difference between the two definitions of "foot" is
| much tinier than the smallest possible roundoff error you or
| the sales person will make.
| ska wrote:
| Ah, the joy of standards.
| [deleted]
| jackfoxy wrote:
| I knew about the survey foot because both the l00' tape measures
| I have are in survey feet. Messed me up on a home construction
| project about 13 years back. It was then I learned there are 2
| differing feet definitions.
| yathern wrote:
| If anyone else is curious - the "US Survey Foot" was 609nm larger
| than the US International Foot. Or, 0.0002% Larger.
| whatshisface wrote:
| It would take 41,708 feet for the error to add up to one inch.
| twic wrote:
| Which feet?
| oneplane wrote:
| The non-survey one
| hadlock wrote:
| Mildly surprising that we are not just using meters at this
| point.
| kbar13 wrote:
| think renaming a software library is hard? try changing units
| of measure!!!!!
| salgernon wrote:
| Saw this here somewhere previously: Sweden did something more
| insane: Hogertrafikomlaggningen. Do it once, get it over
| with?
|
| https://en.wikipedia.org/wiki/Dagen_H
| irrational wrote:
| What would the cost be to change everything for a country
| the size of the USA? I imagine it would be in the
| trillions.
| oneplane wrote:
| I think that's what they did in Canada and it worked out
| great as far as I can tell (except that they had a silly
| clock based on 10 hours instead of 12 IIRC which had little
| to do with metric units and nobody wanted it nor was it
| compatible with the rest of the world).
| kibwen wrote:
| I suppose it depends on what your goals are; despite being
| officially metric, my Canadian and British friends still
| seem to exhibit a melange of imperial and metric in
| everyday life.
| saghm wrote:
| I notice sometimes when watching British television that
| stones are commonly used as a unit of weight, which is
| interesting because it's imperial, not metric, but I've
| seen never it used in American contexts.
| sudasana wrote:
| https://en.wikipedia.org/wiki/Gimli_Glider
| zamalek wrote:
| The situation is far more bizarre than "use" or "not use." As I
| understand it, America uses something along the lines of
| "converted metric units" - i.e. the entire imperial system is
| defined according to metric/SI. Some subset of public records
| have been, supposedly, converted to metric. If you have a
| recent car, it should have km/h alongside mph (in a smaller
| font, or as a different digital readout). You'll find metric
| all over the place if you keep an eye out for it.
| sbierwagen wrote:
| US cars have had dual speedometers for decades. One example:
| https://www.ebay.com/itm/NOS-1980-1981-FORD-MUSTANG-85MPH-
| SP...
| zokier wrote:
| They are using metric:
|
| https://geodesy.noaa.gov/INFO/Policy/files/SPCS2022-Policy.p...
|
| > The meter is the unit of the defining linear parameters for
| SPCS2022
|
| > SPCS2022 coordinates are published in meters
| [deleted]
| alexpotato wrote:
| Back in the 90s, new construction for the US Govt was supposed
| to all be done using the metric standard even though all of the
| supplies were in US/Imperial units. Can't imagine the headaches
| that caused.
|
| Source: My uncle who is/was a contractor
| kevin_thibedeau wrote:
| The Comanche helicopter was subject to this dictum. The
| original drawings specified all metric fasteners. They found
| out nobody supplies aircraft grade metric bolts so everything
| had to be redesigned for the next size up in freedom-units
| with a corresponding weight penalty.
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(page generated 2020-01-31 23:00 UTC)