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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

#111

Post by jonas21 »

mark-r wrote: post #61
oneplane wrote: post #13

Earlier quoted context omitted.

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).

I once tried to imagine a metric time system, with a deciday of 14.4 minutes. I realized that it would never catch on, because a half-hour TV show would have to be cut to 28.8 minutes losing at least 2 commercials.

They actually tried this, during the French Revolution:

https://en.wikipedia.org/wiki/French_Republican_calendar

It didn't catch on then either.

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

#112

Post by mark-r »

jessaustin wrote: post #106
mark-r wrote: post #65

Earlier quoted context omitted.

I once worked with a guy who had just bought a surplus cylindrical water tank, and wanted to get an idea of what it would weigh when filled. I asked him for the dimensions and multiplied each by 2.5 to convert to approximately centimeters. Then I multiplied the diameter by 3, approximating pi. I converted each to the nearest power of 2 so I could multiply by adding the exponents. Assuming 1 cubic cm of water is 1 gra…

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

In metric, the weight of water in grams is equal to the volume in cubic centimeters, by definition. The volume of a cylinder is the area of the circle times the length. The area of a circle is pi * r^2. So my description above skipped a step or two.

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

#113

Post by abduhl »

jessaustin wrote: post #106
mark-r wrote: post #65

Earlier quoted context omitted.

I once worked with a guy who had just bought a surplus cylindrical water tank, and wanted to get an idea of what it would weigh when filled. I asked him for the dimensions and multiplied each by 2.5 to convert to approximately centimeters. Then I multiplied the diameter by 3, approximating pi. I converted each to the nearest power of 2 so I could multiply by adding the exponents. Assuming 1 cubic cm of water is 1 gra…

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.

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

#114

Post by Taniwha »

irrational wrote: post #98
Taniwha wrote: post #82

Earlier quoted context omitted.

nah, a mm is an incredibly useful unit for woodworking, it's a little less than the width of a saw cut, it's just about the right precision for most woodworking

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.

I remember when we built our holiday home - yelling out the lengths of dwangs in millimeters - they were perfect for the job, we never needed to divide them in 3

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

#115

Post by 1-6 »

beerandt wrote: post #97
opwieurposiu wrote: post #92

Earlier quoted context omitted.

It has been 20 years since I worked in this area so likely I have some details wrong. If elevation is distance to the center of the earth 1/8" per mile is 40 feet! From the link below you can see the noaa benchmark is using both elevation in feet above sea level and in meters from the center of the earth. https://www.ngs.noaa.gov/cgi-bin/ds_mark.prl?PidBox=aa3449

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.

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

#116

Post by 1-6 »

function_seven wrote: post #54
opwieurposiu wrote: post #10

Earlier quoted context omitted.

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.

Wouldn't the elevation difference between benchmark and site be the important bit here? If so, then the difference would rarely be more than a mile, and the resulting error would be at most an 1/8"

We're not even getting to the topic of elevation (yet). The US Survey Foot is 1200/3937 which is a not a clean value that terminates after a few decimal places. With high grid coordinates (X,Y), your origin is based at 0,0 as origin. When you scale between metric and US Imperial, if you're not using enough significant digits it impacts how the model scales. This can cause a difference of 1 foot or more from my experience. Floating point operators also become an issue especially in CAD. Standardizing to one number is a great start.

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

#117

Post by 1-6 »

drdeadringer wrote: post #62
dmtroyer wrote: post #26

Earlier quoted context omitted.

seems like an issue that surveyors and engineers should be well acquainted with.

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~!'

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

#119

Post by 1-6 »

asdfasgasdgasdg wrote: post #34
adamtj wrote: post #29

Earlier quoted context omitted.

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…

> Quick, what's 1/3 of a meter? 33.3 cm?

That's why you pick highly composite numbers to create your object. 'Quick, what's 1/3 of 12 meters?' Why do they make raised floors 600mm tiles?

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

#120

Post by mrb »

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…

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 to do actual work with temperatures, this doesn't work so well. Case in point: many Americans don't know the freezing and boiling point in ⁰F. So, no, it's not "objectively better."

> That's like saying "100 centi 57 meters"

No European ever says this. In contrast, many American routinely say "six pound five".

> How long did they live in the US and how long have they lived where they are now?

Their whole life. Born and raised in America.

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