It seems that almost everyone has heard of GPS (Global Positioning System) in one form or another. The most well known GPS device is the car navigation system that shows and tells the driver through voice commands how to get to their desired pre-programmed destination. But if you’re wondering how these little technological wonders work then you’ve come to the right place.
A GPS receiver is an electronic device that uses the Global Positioning System to determine its exact location on earth with pin-point accuracy. This system is made up of the three parts; 27 satellites that send out continuous positioning signals, ground stations around the world that help synchronize the satellites, and various types of GPS receivers.
In this article we’re going to concentrate on how a GPS receiver works within this system since it’s the piece of the GPS puzzle that keeps you from getting lost. Its main function is to calculate its position on the earth using the signals that it receives from the satellite system.
To do this the receiver needs to lock onto the signals of at least 3 satellites. Once 3 or more satellites have been detected it then needs to determine the distance between the satellites and the distance between itself and each satellite. It then uses the basic math principles of triangulation or trilateration to compute its location on the earth’s surface.
The signals a GPS receiver uses to figure its location are radio signals transmitted by the satellites. These radio signals have three bits of information embedded in them; ephemeris data, almanac data, and a pseudorandom code. Using this information the GPS unit is able to triangulate its position and report that back to its user.
Accuracy is another question many first time users wonder about. The good news is GPS receivers are very accurate with the ability to pin-point your location to within a radius of 20 meters. There are ways to increase accuracy through the use of DGPS (Differential GPS) and WAAS (Wide Are Augmentation System) which can get within 3 meters of accuracy. Units with these two features normally cost more but the increase in accuracy can be well worth the cost.
There are many factors that can and do affect how accurately a GPS unit reports its position. These include:
1. The number of visible satellites
2. Signal delays caused as they pass through the earths atmosphere
3. Signals bouncing off of objects
4. Inaccurate clock in the GPS unit
5. Ephemeris errors
6. Satellites in poor positions
7. Satellite signals that are blocked because of terrain or manmade features
GPS is a great technology that has found its way into many everyday applications. Depending on your needs for keeping track of where you are there is sure to be a GPS receiver that fits the bill.
By: Andrew Bicknell
Posts Tagged ‘Satellites’
What Is GPS and How Can It Be Used?
February 8th, 2010
GPS stands for Global Positioning System and was initially designed to be used by the U.S. military and is operated by the U.S. Defense Department. This system consists of 24 satellites, these satellites are 12,000 miles above us, are constantly moving in a precise orbit, have an atomic clock, and are solar powered. They do have a battery backup so they will continue to run in the event of a solar eclipse, and each satellites has a small rocket booster to maintain their orbit. The first satellite was launched in 1978 and it wasn’t until 1994 when there were a total of 24 satellites. Each satellite has a life expectancy of about 10 years, so new satellites are constantly being built and launched. Each satellite weighs about 2,000 pounds and is approximately 17 feet in width when the solar panels are extended. In the 1980s the GPS became available to the public, and although it is still maintain by the U.S. Defense Department there is no charge for its usage by the public.
These 24 satellites orbit the earth twice a day and continuously sends the location of the satellite. A GPS system can tell how far a satellite is away by comparing the time difference between the time a signal was transmitted and the time it was received, the longer it takes the signal to be received by a receiver, the farther away the satellite is. If a GPS is receiving signals from three satellites it can calculate latitude and longitude. Altitude can be determined if the GPS is receiving signals from four satellites.
GPS can be used for navigating your car through traffic day-to-day or tracking a fleet of vehicles. Not only can a driver use a GPS for directions the main office knows where that vehicle is and the speed of the vehicle. GPS can be used while on vacation for activities such as hiking, camping, or hunting. Is your passion fishing but get frustrated trying to find the fish? With a fish finder which uses both GPS technology and sonar you’ll know exactly where to go to find those fish. GPS technology is also being used as a way to track your pet if he wanders off or to safeguard a pet from being stolen.
Another use for GPS is as a child finder with a receiver in a child’s cell phone or wristwatch to ensure a child’s safety. It can be used in a teenager’s car in order to both know where they and how fast they are driving. This could also be used to keep track of someone who tends to ‘roam’ but is not capable enough to find there way back; i.e. someone with Alzheimer’s disease.
As GPS technology improves, it uses will increase. Who knows where it will take us next?
Copyright 2006 Angela Carter
By: Angie Carter
