In 1973, the circumference of the Earth was chosen as a neutral standard. The only obvious example is the measurement of altitude in international aviation. men's hight is usually expressed in feet combined with inches).įeet are not widely used outside of the English-speaking world. Canadians and the British use a mix of both systems - metric and imperial (e.g. The other two countries using the imperial system are Liberia in Africa and Myanmar (also known as Burma) in Southeast Asia. The US is the only industrialized country in the world that hasn't officially adopted the International System of Units, also called the metric system. It's defined as exactly 0.3047996 m:įeet - and the whole imperial system - are used widely in the US. There's one other foot measurement - the Indian survey foot. Furthermore, the legislation on the survey foot varies between the 50 states:Ģ4 states have legislated that surveying measures should be based on the US survey footĨ states have decided that it should be made on the basis of the international footġ8 states haven't specified the conversion factor from metric unitsīut don't worry too much - if you need the conversion for your everyday land surveying or real estate transactions, the difference is really negligible for short distances (< 1 mile), so it doesn't matter which definition you settle on. It's important because the difference is negligible if we measure relatively small objects, but it grows significantly if we begin measuring hundreds of thousands of feet, as in mapping or using state plane coordinate system (SPCS). mĪs you can see, it looks like a really tiny difference - something changes at the seventh decimal place! Which is a difference of ≈0,609 μm ≈ 609 nm, comparing the one type of a foot to another. The US survey foot is almost identical in measure to the international foot. The international foot measure corresponds to a human foot with a shoe size of 13 (UK) or 14 (US male). Used widely in many applications, it's equal to 0.3048 m:ġ international foot ≡ 0.3048 m, where we used the ≡ sign to emphasize it's equal to exactly this value In the US, two types of feet are used on a daily basis: the international foot and the survey foot:Īlso named the standard foot it's the one standardized in the 1950s. As yard was defined, the foot could be calculated as well. Since then, yard in the United States and countries in the British Commonwealth is equal to exactly 0.9144 meters. The final agreement on the foot length came much later, in 1959, when the international yard and pound agreement was accepted. Then Edward II of England introduced some kind of standardization by introducing the statute foot which was 10⁄11 of the old foot. The feet definition varied from region to region, city to city, later even the kings changed the measure according to their desire - e.g., Henry I was said to have ordered a new standard based upon his arm. In England, the foot measure also changed through the ages - it started from Roman standards, then Belgic Celts foot of 13.2 inches or Welsh foot came and went. acoustics - microphones' and loudspeakers' diameters some sport equipment uses the values in inches e.g.screen resolution in pixels per inch (for more information, head to our ppi calculator).
0 Comments
Leave a Reply. |