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Ending the Era of the U.S. Survey Foot

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

#121

Post by 1-6 »

ranger207 wrote: post #70
thechao wrote: post #30

Earlier quoted context omitted.

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 (…

Fractional lengths in the US are commonly in base-2, ie, 1/2", 1/4", 1/8", 1/16", etc. Still annoying to remember that the next socket up from 1/2" is 9/16".

Just use Highly Composite Numbers... Babylon used base-60 and we still tell the time with it today. Base-12 is good too. It's divisible by 1,2,3,4,6,12. Base-10 is only 1,2,5,10 which is less usable for fractions.

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

#123

Post by Gormo »

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…

American here. I've never once in my 40 years on this earth heard someone say "six pound five". That parlance is often used for feet and inches (almost always in reference to human height), but I've never encountered anyone using it for pounds and ounces.

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

#124

Post by beerandt »

1-6 wrote: post #115
beerandt wrote: post #97

Earlier quoted context omitted.

If you're not converting H (gps orthometric height) to E (local elevation datum to "sea level") first, you're doing it wrong, for a number of practical reasons. Usually there's not even a reason to use H directly anymore, since elevations should reference a local benchmark. GPS has changed things, but surveyors are still obscenely practical when it comes to procedures for eliminating systematic error.

Using an RTK-GNSS requires a gravitational model of the earth to measure mean sea level (MSL). Using your position, you use the GEOID model to figure out the delta of the nav satellite's orbit to the MSL.

Yes, That's what I mean by going straight from H to e first. The geoid is that conversion.

Although for rtk, the delta isn't to any of the sats, it's to your base station. The deltas to the sats cancel out of the equations, which is where most of the gains in accuracy come from. But it still needs to be tied into a known elevation benchmark.

That said, most field crews will still be shooting a differential to a published benchmark, or plugging the geoid file into the data collector, or dialing into a vrs or cors that already is adjusting for the geoid. For them, H is just an extra data point asking to be plugged into the wrong data field.

Unless you're doing static observations or geodesy or manual network adjustments or direct gravity readings, the new way (22) isn't all that different from the old way (83). There's just different underlying theory of MSL and different math to adjust the network. And if you are doing any of those things, then you generally already know what you're doing.

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

#125

Post by beerandt »

p1mrx wrote: post #110
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.

At least you can't blame Johansson for that; 25.6mm would've been so far off (0.8% versus 0.0002%) that people wouldn't have bought his product. Now I'm wondering how the ratio landed so close to 25.4 in the first place; 25.4000508 and 25.399977 have too many 0s and 9s for random chance.

Johansson rounded the inches, but previous legal definition was in yards. The Mendenhall Order was the US agreeing to define it's units in terms of the metric pegs, instead of the UK's (which were unreliably changing). The US survey of the coast (today the national geodetic survey), defined conversion values for the yard and pound.

1 (survey) yard = 3600⁄3937 meters

Reduces to:

1 (survey) foot = 1200⁄3937 meters

1 (survey) inch = 1/39.37 meters ~ 25.4000508 mm

https://en.m.wikipedia.org/wiki/Mendenhall_Order

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

#126

Post by d-sc »

mark-r wrote: post #60
AnimalMuppet wrote: post #51

Earlier quoted context omitted.

Then which "foot" is exactly 12.000000 inches?

My calculation shows 12 * 0.0254 = 0.30479999999999996 meters. That may be off a little due to IEEE floating-point inaccuracy.

2 * 4 = 8 so the last significant digit should be an ‘8’

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

#127

Post by beerandt »

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…

Except 3 teaspoons to a tablespoon.

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

#128

Post by beerandt »

mark-r wrote: post #67
war1025 wrote: post #31

Earlier quoted context omitted.

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…

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.

0deg F was originally set as the freezing point of sea ice, which could be recreated in the lab using a mixture that's more thermally stable than the freezing point of fresh water.

Not as arbitrary as people think. Most units have a good reason for their definition, in the context for which they're used, and are divisible by numbers that are convenient.

Without needing decimals at all.

And in my experience, the people who benefit from base 10 metric are the same people who misplace decimal points.

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

#129

Post by beerandt »

zokier wrote: post #43
hadlock wrote: post #3

Mildly surprising that we are not just using meters at this point.

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

83 was also defined in metric, but most states chose to use feet for their actual grid.

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

#130

Post by sdenton4 »

samatman wrote: post #94
p1mrx wrote: post #55

> In 1959, the relationship of the foot to the meter was officially refined as 1 foot = 0.304 8 meter exactly. We can thank one man for this: Carl Edvard Johansson from Sweden. When making gauge blocks, he decided to round off the inch to exactly 25.4mm, and people around the world used his blocks to manufacture everything. The 1959 change just reflected what industry was already doing. - http://mitutoyo.com/wp-conte…

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 collection of distinct fibonacci numbers. (for example, 43 = 34 + 8 + 1, or, using a binary string to show which Fibs are involved, 42 = 10010001.) The conversion of miles to kilometers is then just a bit-shift operation.

Well, almost, anyway.

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