How GPS Works Today

Summary

This script unravels the mystery behind GPS, a military-born technology now integral to our daily lives. It explains how GPS works through a network of satellites, ground stations, and receivers, enabling precise location tracking. The script also touches on the system's history, its free civilian access post-2000, and its applications beyond navigation, such as in timekeeping for banking and power grids. It humorously highlights GPS's occasional mishaps, like leading vehicles astray, emphasizing the technology's importance and occasional quirks.

Takeaways

• 🌌 GPS was originally a military invention, first named Navstar, with the first satellite launched in 1978.
• 🚗 GPS became fully operational in the US by 1995 and was first used in cars in 1996.
• 📡 The highest quality GPS signals were initially reserved for military use until May 2000, when they became freely available to civilians.
• 🛰️ GPS is managed by the US Air Force and uses a network of 32 active satellites, including 24 core satellites and 8 emergency replacements.
• 📍 GPS receivers calculate location by trilateration, which requires signals from at least four satellites for accuracy.
• 🕰️ GPS receivers use the time it takes for a signal to travel to calculate distance, aided by the precise time kept by atomic clocks in satellites.
• ⏲️ Receivers have less accurate quartz clocks but continuously update themselves using signals from satellites to maintain precision.
• 🌐 GPS satellites' atomic clocks must account for time dilation due to Einstein's general theory of relativity, which affects the clocks by 38 microseconds per day.
• 🌍 GPS is not only for navigation but also provides time signals accurate to within 10 billionths of a second, crucial for banking systems, power grids, and cellular networks.
• 🚧 Despite its accuracy, GPS can sometimes lead to unexpected or incorrect locations, as illustrated by anecdotes of people being directed off-road or into bodies of water.
• 👋 GPS is widely used but knowing its limitations and potential for error is important for safe and effective use.

Q & A

What was the original purpose of GPS?

GPS was originally a military invention, first named Navstar, and was launched in 1978.

When did GPS become fully functional and available for civilian use?

GPS became fully functional in the US by 1995 and was first used in cars in 1996. The highest quality signals were available to all civilians for free starting from May 2000.

How many active GPS satellites are there, and what is their purpose?

There are 32 active GPS satellites orbiting the Earth, with 24 being core satellites and the rest serving as emergency replacements.

What is the role of ground stations in the GPS system?

Ground stations use radars to ensure that the satellites are in their correct positions.

How does a GPS receiver determine its location?

A GPS receiver determines its location by calculating the distance from four or more GPS satellites and using trilateration.

What is trilateration and how does it work in GPS?

Trilateration is a method of determining location by measuring distances from known points. In GPS, it is used to calculate latitude, longitude, and altitude by measuring the distance from satellites.

Why do GPS receivers need to see at least four satellites to calculate an accurate location?

GPS receivers need to see at least four satellites to calculate an accurate location because it allows for the correction of time errors and provides a more precise location using trilateration.

How do GPS satellites communicate their position and time to receivers?

GPS satellites send information about their position and current time to GPS receivers at certain intervals in the form of signals.

What is the significance of atomic clocks in GPS satellites?

Atomic clocks in GPS satellites keep the most precise time, which is crucial for calculating the distance traveled by the signal from the satellite to the receiver.

Why are four satellites used instead of three in GPS calculations?

Using four satellites instead of three helps to solve the problem of time errors and to determine the precise locations of objects more accurately.

How does GPS affect other systems like banking, power grids, and cellular networks?

GPS provides time signals that are accurate within 10 billionths of a second, which is crucial for synchronized operations in banking systems, power grids, and cellular networks.

What are some common issues that can occur when relying on GPS for navigation?

GPS can sometimes lead people to unexpected places, especially in rural areas, due to difficulty distinguishing between actual roads and other paths.