GPS study guide

GPS study guide

GPS

Once upon a time, your ancestors used to look at the night sky to determine their location. Then we used a Thomas Guide, remember those? Today, it only takes one magical technology to get driving directions, send your picnic spot to a lost friend, or track how far you’ve gone during a workout. That technology is called GPS, and you’re about to find out the secret behind it.

Birthday of Navstar now known as GPS

Navstar, and the first satellite was launched in 1973. But not all the Navstar satellites made it to orbit, so it was still a work in progress. 

Multiple Choice

When was GPS made public in the USA

• 1973

• 1990

• 1994

• 1993

Poll

When was it available for use in cars?

• 1996

• 1994

Is cell service needed and when is the signal sent?

GPS doesn’t need an Internet connection or a phone signal to function properly; but with them, it becomes more effective. GPS is literally everywhere, and you can now even purchase GPS insoles to keep track of your kids or relatives with Alzheimer’s disease. The GPS signal is transmitted 24 hours a day. THE GPS SIGNAL NEVER STOPS!!

How does it work?

Grounds stations use radars to find out if the satellites really are where they’re supposed to be. A receiver in your phone or in your car is following signals from the satellites to determine how far it is from them. When it finds out how far you are from four or more GPS satellites, it can tell exactly where you are, with an accuracy within 20 feet

Multiple Choice

How many active satellites are orbiting earth in the GPS system?

• 24

• 22

• 36

• 32

Multiple Choice

How many of the satellites are the Core satellites used in the GPS system?

• 32

• 24

Can the GPS signal work in every location on earth?

GPS works in any weather, rain or shine; but there is one important condition. A receiver on Earth has to see at least 4 satellites to calculate an accurate location because the GPS uses a trilateration mechanism. 

2-D and 3-D trilateration

2-D trilateration is about calculating its latitude and longitude position on a map.

3-D trilateration

3-D trilateration, it’s basically the same, but there’ll be spheres instead of circles on your drawing. 3-D position includes your latitude, longitude, and altitude. If the radii from the previous example went in all directions, you’d get a series of 3-D spheres.

Doing the calculations

GPS satellites send information about their position and current time to a GPS receiver at certain intervals. The receiver gets the information in the form of a signal. The GPS receiver analyzes radio signals from the GPS satellites to figure out two important things: the location of at least three satellites in space above you, and the distance between you and those satellites. Radio waves travel at the speed of light. The receiver takes the time it took for the signal to travel from space to the Earth to calculate how far t’s traveled. And it’s not so simple.

How does a GPS satellite work?

GPS satellites have atomic clocks that keep the most precise time, but it would be impossible to install these clocks in every receiver. They cost somewhere between $50,000 and $100,000, so it would make your phone really, really expensive. So, receivers have regular quartz clocks in them that keep updating themselves to get the most precise time, thanks to the information they receive from satellites.

Multiple Choice

How many satellites will provide the most accurate location?

• 4

• 2

• 1

• 3

How high are GPS satellites above earth's sea level?

20,000 meters

Open Ended

Which device can receive GPS signals?

Do the satellites talk to each other?

Where is the timestamp generated for the satellite signal?

How does the phone and satellite find your location?

What other speed is needed to calculate your location?

What shape helps satellites find your location on earth?

What subjects are useful to know about when using a GPS?

What does a cartographer do?

What is a GPS used for?

Navigation using GPS

Knowing your location, speed and altitude — and knowing someone else's — is an immensely powerful tool, with implications far beyond military use. Perhaps its most pedestrian use, at this point, is helping people navigate journeys, whether it's by foot, by car or by boat. But GPS is also incredibly important for aircraft pilots, who use it to avoid mid-flight collisions and to land.

GPS navigation is now offered in a bevy of apps, and city governments are using technology and sharing data in an effort to ameliorate traffic problems in urban environs.

Open Ended

Have you ever used GPS?