Inside GPS

Inside GPS — page 1 — CHAPTER ONE

Inside GPS — page 2 — WORLDWIDE NAVIGATION Anthony is lost He has been driving for hours but can’t find his friend’s new house He drives into a gas station and puts the car in park He then turns on a car app that uses the Global Positioning System GPS Anthony enters the street address A map appears onscreen The GPS receiver locates his car on the map Then the map shows the house Anthony is looking for As he drives the car’s location changes on the map The GPS shows his car on the map Soon Anthony arrives at the house thanks to GPS satellites thousands of miles overhead The GPS unit and map in a car can help someone find his or her way around

Inside GPS — page 3 — ACCESS FOR ALL At first the GPS signals that civilians could use were not very good The US government made the civilian satellite signals less accurate than the military ones This is called selective availability The readings could be wrong by as much as a football field The government did this on purpose It wanted the military to have an advantage The government worried that enemies could use GPS technology against the United States Eventually the US government realized the importance of accurate GPS for everyone It stopped the selective availability in 2000 Public GPS became up to ten times better Today anyone with a receiver has access to free and accurate signals GPS is a worldwide navigation system that uses satellites The satellites send signals to receivers A receiver uses these signals to determine its exact location This ability to track location has many helpful uses GPS FOR EVERYONE GPS was invented by the US military The first satellite was launched in 1978 GPS was designed for both civilians and the military to use At first GPS was only used

Inside GPS — page 4 — GPS satellites are built on the ground before being launched into space by the military It guided rockets and missiles to their targets It helped ships navigate and tracked troops on the ground Soldiers used GPS to find their way around new places GPS was made available for public use in 1983 The military still uses it But now more than 3 billion people around the world use GPS

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