How Does a Map-Based GPS Car Navigation System Work?

GPS System

A GPS receiver works through the use of GPS satellites. There are 24 satellites which orbit the earth, circling twice a day and transmitting signals. At least 4 satellites are visible at any one time. When a person uses their map-based car navigation system, the GPS receiver picks up the satellite signal and uses it to triangulate its location through trilateration. Each satellite will tell the receiver how far away the receiver is from the satellite. By picking up at least 3 satellites, the GPS receiver is able to pinpoint its exact location.

GPS Map and Software

A GPS Car navigation device, in addition to being a GPS receiver, is loaded with maps. Using the longitude and latitude coordinates that the receiver was able to get from the satellite signals, the map-based navigation system is now able to exactly place its location on a map. Now if the user wants to know how to get to a particular location, they just input the address into the navigation system and the system will come up with a route for the user and tell the user how long it will take to get to the destination. Specifics on how a GPS car navigational system calculates the time to destination varies and is proprietary, however most systems will take into account both posted speed limits and the actual speed the driver is traveling at. The GPS continues to receive signals from the satellite until the destination, giving turn-by-turn navigational cues and if a user accidentally misses a turn, it can re-calculate and give new directions to get to the location. Because maps change all the time, the best way for a user to get the most accurate information from their GPS is to update the maps at the maker's website.

Traffic Information

As we all know, traffic can make what should be a twenty minute trip turn into an hour long ordeal. One of the most impressive features of map-based GPS navigation systems is the ability to detect traffic congestion and offer alternate routes. The GPS receives updated traffic information through one of three sources (depending on the brand), Bluetooth, FM Radio Data Systems or XM NavTraffic. The GPS receives information identifying what the problem is and where it's located; the seriousness of the problem; the direction of affected traffic and how far it goes back; how long the problem is likely to continue and advice on alternate routes which it then uses to update maps and advise the driver.