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There is a whole lot of power and capability packed into a GPS receiver. They are linked to complex satellite systems in outer space, providing a reliable navigational system to users on earth. Many new cars have GPS receivers included as standard equipment. Hikers use them to find their destinations, and treasure hunters rely on them for Geocaching excursions.
Simply, a GPS is an electronic device that can determine one's precise location on earth. The entire system is anything but simple; and the GPS receiver is but a single and minute part of this immense network. GPS is the short form of Global Positioning System. This very large navigation system was developed and implemented by the United States' Department of Defense (DOD). The system is composed of a network of 27 satellites, various ground stations located at points throughout the world and individual GPS receivers. Most of the 27 satellites in the GPS are active, and continuously send radio signals. GPS receivers use these signals to determine their geographical location.
Function
The primary function of a GPS receiver is to pinpoint its actual location on earth using the signals it intercepts from GPS satellites. To do this, the GPS receiver must be able to locate and intercept signals from three or more GPS satellites. After intercepting the signals, GPS receivers use basic principles of mathematics called triangulation or trilateration to compute its actual position. Before any triangulation calculation can be implemented, however, the GPS receiver must verify two points:
1- The positions of at least 3 satellites
2- The distance between each satellite and the receiver.
GPS receivers decode the signals in order to determine the locations of at least three GPS satellites. The signals transmitted by GPS satellites are radio signals, and each contains three different bits of information: ephemeris data, almanac data and a pseudorandom code. The ephemeris data is the information that the GPS receiver needs to be able to determine the actual position of the satellite transmitting the signal.
The distance of a GPS receiver to a satellite is measured using the signal's speed, or the time delay from the initial transmission of the signal, to its reception by the GPS. From this speed or time difference, the GPS receiver calculates the satellite's distance.
With information about the location of at least three or four satellites, along with their individual distances, a GPS receiver utilizes the basic principle of triangulation to calculate its actual position in terms of altitude, latitude and longitude.
Accuracy
GPS receivers are incredibly accurate, usually to within twenty meters of radius. It is possible, however, to increase this accuracy level using supplemental technologies. Some GPS receivers using multiple parallel channels can achieve an accuracy level to within fifteen meters. More complex systems such as DGPS (Differential GPS) and WAAS (Wide Area Augmentation System) can reduce this range to an impressive three meters.
Despite the use of these supplemental technologies, there are still many factors that can cause even the best GPS receivers to broadcast inaccurate locations. Among these factors are:
* Number of visible satellites
* Radio signal delays caused by the passage through the ionosphere and troposphere
* Signal multipath (bouncing of the signal as it hits an object)
* Inaccuracy of GPS receiver clocks
* Ephemeris errors (inaccuracy of the satellites' reported locations)
* Poor positioning of satellites (i.e.: satellites in a linear position, or in a tight grouping)
Some, but not all, of the GPS errors caused by these factors can be remedied by the software that is packaged with personal GPS receivers. If you are having difficulty with the accuracy of your GPS receiver, check your user guide or refer to the software to see if the problem can be fixed.
Technology has given us wonderful gifts and powers beyond imagination. A GPS receiver is one technological wonder that is so accessible, many people use them on a daily basis. If you travel locally or across country, or enjoy exploring the great outdoors, pick up a GPS receiver and you'll always be able to find your way home.
The GPS receiver is a handheld, sometimes portable device that works with the Global Positioning System (GPS) network. The GPS network is comprised of 27 satellites that constantly orbit the earth. As the earth rotates, so do the satellites. Of these 27, 24 of the satellites actually work, while three are used as backups. As you can imagine, running the GPS is quite costly.
The GPS network was originally developed by the United States military. The military used it to increase navigational accuracy. However, it was not long before the GPS network was open for use by anyone.
How it works is simple. First, the satellites have multiple orbit routes around the earth. At any one moment in the day, at least four of the satellites are able to transmit information from the satellites to GPS receivers. Of course, it is imperative that the view between the satellite and the GPS unit is unobstructed. That is why GPS receivers sometimes do not work right in areas with high mountains, a lot of trees, or skyscrapers in the way.
GPS receivers work with the satellites. First, the GPS hunts down four of the satellites that can connect with and transmit information to the GPS unit. Once four satellites have been found, the distance to each of the satellites is recorded, and the GPS can pinpoint its location, by the distance it is from each satellite.
This mapping and estimating is based on a principle in mathematics, which is known as trilateration. How it works is by traveling through three-dimensional space. This is complex to understand, but the result is amazing, and it should be what you look for when purchasing a GPS unit of your own.
Trilaterion that works in 3-D is what is used to map your location. A series of spheres line the distance from one place to the next, based on the location of the satellites at the time of the transmission to the GPS receiver. The spheres intersect and meet and as the distances from different locations on different spheres are measured, your exact location is pinpointed. All of the four satellites' plots work together, to intersect in one place through the spheres.
GPS receivers generally try to use more than four satellites at one time. This provides a more accurate location and less room for error. The Earth is also used as a marker, which works with the GPS network to help pinpoint locations on the surface of the planet.
GPS receivers have to know how far a distance it is from the satellite to the unit. To do this, radio signals sent from the GPS satellites are analyzed. These signals are high in frequency though they are relatively low in power. The better your GPS unit is the better chance you have of using multiple satellites in order to pinpoint your exact location.
Since radio signals travel at the same speed light does, GPS receivers are able to determine how fast the waves travel and how far they have traveled. At random times, the satellites transmit pseudo-random code, which are digital patterns, to the GPS receivers. The GPS unit will then play the digital pattern, though there will be a lag. This lag is based on how fast the signal traveled, and is a major part of the GPS plotting process.
In order to track the signal's pattern, the satellite and the GPS receiver use clocks, which synchronize together. The Satellite uses an atomic clock, while the GPS receiver uses a regular clock. However, to accommodate synchronization, the clock in the GPS unit is able to constantly reset. This prevents any type of clock problems from occurring.
There are various types of GPS systems. These systems work to fix any inaccuracies and errors in the GPS receiver's location tracker. These systems include WAAS and DGPS.