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Marcel, don't get me wrong I love the metric system and I use it all the 
time when it is convenient and useful to do so. However, in aviation, 
English units have proven to be useful and convenient to use so there is 
no pressure to change to metric units which offer no advantages. In 
addition there is a large infrastructure based on these units that would 
have to replaced at great cost and for no advantage. This is true in 
many things in our world, we have systems that reflect decisions made by 
prior generations that are locked in stone and are not going to be 
changed. An obvious example is the gauge of railroad tracks. The 
standard gauge used in the U.S., most of Europe and a large part of the 
rest of the world is four feet, eight and a half inches and resulted 
from that choice being made in 1826 in England by a railroad developer 
and was then written into English law in 1845. This spacing was chosen 
giving regard to the sizes of existing wagons which ultimately had had 
their widths determined by the width of a team of horses. Once such 
arbitrary choices are made and then implemented it becomes very 
expensive to change due to the great investment costs involved. About 
720,000 km of track world wide is of this gauge. Russia made a different 
arbitrary choice and standardized on a different gauge and their cars 
cannot run on their neighbor's European or Chinese standard gauge track 
and vice versa. There are about 220,000 km of the Russian gauge track 
and they are not going to incur the great expense of replacing all of 
their rolling stock and the cost to move all of their rails to a 
different spacing just to have interoperability with their neighbors 
(even though this would be advantageous) as their present system serves 
them well since most of there shipping is internal.

There are many other examples of our world being tied to ancient 
arbitrary choices. I have attached a photo showing a European electrical 
plug and a three way socket along side an American equivalent. The 
European connectors are much bulkier and the American system is more 
compact, which is an advantage. But the Europeans are stuck with the 
choice of electrical connector size because of of the extensive 
investment in the electrical grid and of all the electrical equipment 
that must plug into that grid.

Same thing in navigation where we continue to use nautical miles and 
degrees and minutes for measurement and for defining locations on earth. 
One could switch to the UTM grid which has coordinates in meters but 
then all the navigational charts would have to be redone and celestial 
computations would be more complicated. The location of the Blue Mosque 
is 41� 00.321' north, 28� 58.613' east. The latitude tells us how far it 
is north of the equator as measured in angular units. The UTM  
coordinates for the Blue Mosque are 35T 66245 4541233. The third group 
gives the location in meters north of the equator, 4,541,233 almost half 
way to the north pole. The meter is a "natural" unit, originally defined 
as one ten-millionth of the distance from the equator to the north pole. 
But then too the nautical mile is just as much a "natural" unit being 
defined as equal to one 5,400th the distance from the equator to the 
north pole so there is no reason to switch to the metric system if you 
just want "natural" units.

If you drive a French car you will see that the tachometer is marked in 
revolutions per minute (r.p.m.) and the speedometer is marked in 
kilometers per hour. However, neither of these are metric units. The 
metric unit for rotation is radians per second and the metric unit for 
speed is meters per second. But neither of these SI units are very 
useful to normal human beings doing everyday things so even the 
inventors of the metric system realize that there are occasions where 
you should forgo using metric units when other units serve better. For 
instance, if you are driving to grandmother's house and she lives 544 
kilometers away and your car is traveling at 25 meters per second will 
you need to stop for lunch and will you get to her house before dark? 
Not a very convenient unit for everyday things this the metric unit for 
speed.

So there are lots of compromises made in this world and there is no 
reason to switch from something that is working well  just for the sake 
of going metric.

BTW, we were in Istanbul in April 2009 and we were really impressed.


gl

Marcel Tschudin wrote:
> Yes, I'm more familiar with metric units but I'm aware that for
> certain applications, like aviation, the English units are kept being
> used. I don't know why in aviation they can't use 300m instead of
> 100ft. May be one fears that a change to metric would create a too
> high risk.
>
> So, if English units are the "decent" ones for you, why then you don't
> click on the link "Page Preferences" at the top of wunderground's page
> and adjust the units to be shown to those? Since the METAR are in
> English units you would see the original data without conversion.
>
> BTW, regarding English units: I noticed recently that the department
> stores here in Istanbul indicate the power of air conditioners in BTU.
> I guess that only a very, very small part of the population in this
> country knows what this stands for.
>
> Marcel
>
>
>
>
>   

   

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