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 ‘Triangulation’
How GPS Receivers Work
March 21st, 2010Posted in Article
Tags: Almanac Data Basic Math Car Navigation System Differential Differential Gps Electronic Device Exact Location Global Positioning System Gps Receiver Gps Receivers Gps Unit Math Principles Pin Point Accuracy Radio Signals Satellite System Satellites Technological Wonders Time Users Triangulation Trilateration
How GPS Works
October 4th, 2009
Global Positioning System (GPS) is a navigational aid originally developed for the military. The system simply receives signals. It is the applied technology that gives the GPS its versatility.
If you have ever used map and compass, you will understand a little about how the GPS works. In order to find your position on a map, you need to have three points of reference. The intersecting line from the reference points is where you are. Map and compass work uses triangulation (bearings), GPS uses trilateration (distances) to calculate location. Satellites orbiting the earth emit unique signals that can be received by a GPS. The GPS software interprets the signal, identifying the satellite that it came from, where it was located, and the time that it took for the signal to reach the system. Once the receiver has both time and distance it begins to determine position.
Three satellites provide the intersection point and the fourth is used to check that the positioning is accurate. Accuracy depends upon the synchronization of atomic clocks in the satellites with the clock in the GPS system. Although the clock in the GPS is not
atomic, utilizing the fourth satellite gives it that functionality as the internal clock adjusts itself to correct any discrepancy discovered.
GPS has gone far beyond its initial military application. Drivers can find their way through city streets, long distance trekkers use the technology to cross unfamiliar terrain, mariners and pilots use GPS enhanced data to cross the seas and skies.
In–vehicle GPS can be integrated into the car entertainment system or can be installed as a removable device. These systems need to tell the driver where he/she is and how to reach their destination. The information includes road directions plus relevant features along the way such as rest stops, gas stations, points of interest, etc. Auto GPS uses voice commands so that the driver can concentrate on the road.
Hikers and trekkers use similar technology, but normally without the inclusion of road systems on their devices. Mapping software defines the territory that the hiker will encounter. The user can enter waypoints (points of reference) so they can return using the same route. They can add points of interest such as water sources, possible campsites, and other items of interest on their trail. However, the portability demanded by hikers will also limit the functionality of the system as small screens mean that some detail will be lost.
It is GPS technology that is used to track individuals on home arrest, to trace missing pets, stolen vehicles, and missing people. Small systems can be incorporated into pet collars and wristwatches. As long as the receiver is active, it can be found.
Marine and aviation GPS units are sophisticated and specialized. The principles involved are the same as any standard system; the software is much more highly developed.
Any fisherman, who is using a fish finder on his boat, is using a GPS that is enhanced by sonar and tracking devices. Units have been developed for use on float tubes also -– as GPS technology advances, the systems become more and more compact and their uses
more and more extensive.
If you are considering purchasing a GPS, make sure that it can be updated easily. This is especially true if you buy a multi–function GPS or one that is used where conditions change regularly. An in–vehicle GPS soon loses its usefulness if it is not updated as road systems change.
Updates vary according to the device being used. They can come in CD/DVD packages or as computer downloads. The user can purchase maps specific to the area in which the GPS will be used or a range of maps and routes. These are available from GPS software
companies who will charge proportionally to the sophistication of the software.
GPS units vary in price according to their usefulness. It is possible to buy units for less than one hundred dollars to units costing more than one thousand dollars. What your needs are
will be a factor in the cost of your unit. If you are a backpacker then portability is a major consideration. If you are a trucker, you need to be able to find a delivery point as quickly and conveniently as possible. Whatever device you go for, cost is generally related to quality. Buy the best you can afford.
By: Anne King
Posted in Article
Tags: Atomic Clocks Car Entertainment System City Streets Compass Work Global Positioning System Global Positioning System Gps Gps Software Gps System Internal Clock Intersection Point Military Application Navigational Aid Reference Points Relevant Features Rest Stops Road Directions Time And Distance Triangulation Unfamiliar Terrain Voice Commands
