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Fly the Linux Skies

Apr 04, 2008, 22:30 (9 Talkback[s])
(Other stories by Brian Proffitt)

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By Brian Proffitt
Managing Editor

Altimeters... lie.

For those of you who are a bit uneasy about flying, this bit of news may not make you feel any better. Nor will this piece of information: most analog instruments on airplanes are prone to quite a bit of error. Yet for over a hundred years, these instruments were more than enough to get most aircraft safely from place to place.

The reason for all of this non-accuracy is because the things these instruments actually measure change as a plane moves from place to place. Compasses are not 100 percent accurate, for instance, because the magnetic north pole is not located at the true north pole, so as a plane moves over long, cross-country jaunts, pilots have to factor in degree variations to figure out where north is.

Altimeters are even more finicky. Altitude is calculated on the air pressure outside the plane. When you fly from one pressure center into another, that change affects the measurement of the instrument. That's why most air traffic controllers regularly update pilot in the sky with "altimeter readings," which is really just the air pressure at the airport measured in inches of mercury. So, when I am flying into Indianapolis, and the flight controller informs me the altimeter is "two-niner-niner-five," I can dial my altimeter to 29.95 inHg, and my altimeter will reflect a more accurate altitude.

What makes this work is the constant flow of other information that correct for all of the inherent errors in the instrumentation. The radio lets me figure out what the pressure reading. My transponder lets the air traffic controllers know where I am. My map and the navigation radio can help me pinpoint my position and my comm radio can let me ask the controllers (rather sheepishly) where I am if I get completely lost. (Not yet, knock on wood.)

Now, in today's more modern planes with glass cockpits of all-digital instruments, such errors are non existent, or too small to care about. I can turn on a GPS unit and see where I am instantly, even in altitude. With newer navigation systems at airports, such as the wide area augmentation system, GPS accuracy is boosted to such a degree that with a WAAS-approved instrument panel at an airport with a WAAS approach, I could (were I so rated) a plane with very little visibility.

But in the event of an electrical failure, I would still have standard-six cluster of analog instruments, just in case.

This sudden fixation on flying technicalities was actually prompted by the story yesterday about's revelation that the Linux desktop has broken the two-percent mark in total deployment.

It seems such a small number, except when you take into account that Macs, according to the same data, only comprise 5 percent of the desktop market. Then things are put into a different perspective.

But still, this survey, and all the others like it, are really analogous to flying a plane with analog instruments. They each individually may be very wrong, but when data is collaborated from the other instruments, then a clearer picture can be formed.

I submit that these numbers do not give a true picture of the state of the Linux desktop by themselves. But when put together with all of the other clues, you can get a better sense of where things are going: Windows is coming down; Mac and Linux are going up. How fast and how much? Well, that's still Magic 8 Ball territory. Ask again later. It would be nice if there were something analogous to GPS/WAAS for determining real desktop numbers. Maybe something will be created soon to handle that. In the meantime, we can take comfort in the fact that Linux is slowly gaining altitude.

And as any pilot will tell you, the more space there is between you and the ground, the better.