Origin of the

**meter** :

Surprisingly enough for a lot of posters on this thread, it is equivalent to the nautical mile. The revolutioin scientists started with the

**grad**, 100 of which would give a right angle and 400 of which the full circle. This grad was divided into 100 *minutes*... It was then decided that one minute of the earth circumference would be equivalent to a kilometer after the meter, the first handy unit was set at 1/40.000.000 of that circumference.

Now, another forgotten aspect of measuring units is that there is

**only one** system - the International System, i.e

SI -, from which all other units in used will be derived. So the foot is a fraction of the meter.....etc...

Quoting YULWinterSkies (Reply 57):
*The HUGE advantage of metric system over imperial is the factor of 10 everywhere* |

Not only that, it has also to do with coherence and adherence to the dimensional equations of the measurements : For instance, a pressure is physically defined as the ratio of a force against surface, therefore, a unit of force would be F/S.

In this case, it comes down to a force of one Newton over a square meter (that's the definition of a Pascal). Then if the unit is not handy, change it into a more manageable sub-unit. In our example, a pascal is very low, so why not use 100 pascals as the measurement base . Et voilà, you get the

**hecto**pascal !

Another aspect is that writing down a unit is very clear : a speed is given in kilometers per hour, i.e km/h. The Yankee way of kph is another dumbing-down of a good practice (k is just a prefix meaning 1000 times of...)

What makes people laugh in Europe is when - apparently- the US still uses a measuring tape for pressures ( the in/Hg).

It is also to note that the first ICAO conference in

**1949** issued the so-called ICAO Tables, viewing the end of 1959 as the year of complete adherence to the final table.

In my opinion, it is very amazing to see the most advanced country in the world resisting most of the moves toward an internationally agreed common technical language. In the field of aviation, it is a bore and a chore to need a set of decoding booklets to be able to get something as *natural* as weather info.