[Jason DeRusha’s Note: I’m excited to welcome Kate Raddatz as the Good Question intern for this summer. Kate is an accomplished student journalist from the University of Minnesota, and a west-metro native. She’ll be answering viewer questions here at the blog once a week. This is her first effort! Feel free to comment at the end!]

Question

Remember when we had to ask other people for driving directions? Before the age of Garmins, Tom-Toms, and other GPS devices in our cars and apps on our phones, we had to do it the old fashioned way.

But Judy Lyons of Owatonna wants to know how exactly GPS devices collect their data?

Background

The U.S. Department of Defense first used GPS in the 1960s as a way to navigate during military operations. But after the Korean Airline Flight 007 tragedy, President Ronald Reagan let the public have access to GPS in 1983.

“GPS might have averted that kind of disaster,” University of Minnesota Aerospace Engineering and Mechanics professor Demoz Gebre said. “It was made available to the public but it wasn’t until the late 90s and early 2000s are when things really took off.”

The Global Positioning System (GPS) is really an arrangement of 27 satellites orbiting the earth. Only 24 are operational — there are three extra in case any of the satellites fail.

Each solar-powered satellite orbits the earth twice a day and is arranged so that there are at least four satellites visible in the sky from any location.

These satellites are responsible for transmitting geographic data to receivers in our GPS devices. But how is that data collected?

The Process

The GPS we use today collects geographic data from satellite and aerial images, and from data collectors who drive around the globe.

GPS receivers use triangulation, a mathematical method of determining position, to find a user’s precise location on earth and create a digital map of the surrounding area.

Triangulation determines the amount of time it takes for a signal to be transmitted from the satellite to the receiver as well as the distance between the receiver and the visible satellites in the sky.

Unlike direction services like Mapquest, GPS is in real time so it should avoid sending you down a road under construction or one with heavy traffic.

A GPS receiver needs signals from at least three satellites to determine a 2-D position and at least four for a 3-D, more accurate, position.

Best Buy technology specialist Levi Taylor says the big name GPS devices we use today all give relatively accurate information.

“Price doesn’t have a huge impact on how your device will work because they all use three satellites in relation to where you are,” Taylor said. “But you could pay more if you want a better receiver which could ensure more accurate maps on your device.”

Problems

What happens when there’s an error on the map? Your directions lead you to a dead end or a road that’s recently been renamed.

“There are lots of things that can go wrong with the satellite signals coming in, but in the future our receivers will recognize these errors and know how to correct them,” said Gebre.

Today digital mapping companies like Tele Atlas and Navteq monitor customer feedback of GPS users in order to fix inaccurate data.

Taylor says it could also be a problem with the GPS device.

“If the internal hardware gets overheated it might display wrong information — it takes a lot of energy to power that info,” he said.

Taylor advised not letting your GPS device get too hot or cold and preserving its battery life to help minimize problems with the receiver and any errors in the map.

1. Doris Schutz says:

Are you telling me to contact Tele Atlas and Navteq and they will fix the inaccurate data, because that is what I wanted to know. Thanks