The GPS (Global Positioning System)

Many of us have already bought these electronic toys. 
In Houston, they are an absolute necessity. GPS devices, 
using satellite transmissions, can tell you where you are 
within a few yards. Even if you happen to be in rural Colorado.

I heard an interview last summer on NPR (National Public Radio) 
with the lady who is the nagging voice on my GPS. When asked 
about her crowning achievement, she gleefully said 
"To know that -- right now -- I am telling thousands of male drivers where to go."
 Sometimes it helps to turn her off and just have your 
passenger read the map directions.

A GPS catches signals from satellites, coordinates them, 
calculates where it is, matches that to a map and then 
decides the best route to your destination. 
All this in a fraction of a second! The screen shows you where you are, 
and where you are going. So does the lady, if you don't turn her off! 
Miss a turn and the lady says, with a sigh, "Recalculating." 
A few 20 seconds later she has a new route mapped out, usually suggesting a U-turn.

GPS devices are in widespread use. But they are a recent technology. 
In 1983, after Russia shot down the airliner KAL 007 that strayed into 
prohibited airspace because of navigational errors, Ronald Reagan announced that, 
when completed, the GPS would be made available for civilian use. It was to 
take awhile. GPS receivers for government use became operational on 
April 27, 1995. There have been 40 satellites launched to date, 
30 are still operational and more are planned.

In 1996, Bill Clinton issued a directive declaring GPS to be a 
dual-use system and established a board to manage it as a national asset. 
GPS devices became available to the public in 1997, but with intentional 
accuracy degradation. In 1998, Al Gore announced plans to upgrade GPS 
with two new civilian signals for enhanced user accuracy and reliability, 
and in 2000 the Congress authorized this. In May, 2000, intentional 
degradation was eliminated and GPS accuracy increased by a factor of five. 
In 2005, the first modernized GPS satellite was launched and began 
transmitting a second civilian signal for enhanced user performance. 
With this change, automobile use became possible. Today, a GPS can 
pinpoint itself to within thirty feet, sometimes better. 

Now -- shut up and listen to the lady. 
Just don't obey her command when she says "turn left" 
and there is a truck in your way.

Two reference web sites are:

http://en.wikipedia.org/wiki/Global_Positioning_System

http://www.maps-gps-info.com/gps-accuracy.html

John