GPS study guide

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.

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. 

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!!

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

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

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.

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.

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.

20,000 meters

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.