How Does GPS (Global Positioning System) Work?

GPS (Global positioning system) GPS (Global positioning system) is a satellite sourced navigation system developed by the Unites States Department of Defense and is administered by United States Air Force 50th Space Wing. With technological advances in leaps and bounds, a system was developed specifically for army utilization which is now widely used as GPS for precise tracking and mapping purposes, it was made available to civilians in 1980's.

Worldwide positioning on your handheld does not put in the picture of how complex the GPS technology is. U.S. defense department spent $12 billion on developing this system which made Navigation and positioning a child's play.

It uses a constellation linking 24 to 32 satellites orbiting earth that transmit well defined radio wave signals, which allow GPS receivers to establish their existing location, the timings, and their speed.

GPS satellites GP system makes use of the information provided by the GPS satellites orbiting around earth twice in every 24 hours at around 7000 miles per hour.All GPS satellites are equipped with solar panels and thus make use of solar energy to power the resources. They have backup batteries installed onboard to keep active whenever a solar eclipse or any such event takes place. These satellites are provided with small rocket boosters which can be deployed when they deviate from their original path.

Satellite signals Each of these satellites recurrently sends signals to the receivers on the earth which work out all the information. Based on these calculations the exact position can be known. These signals give out the location, speed and time with use of accurate orbital information and relative orbit distances of GPS satellites. The signal comprises of three basic parts - a pseudorandom code, ephemeris data and almanac data .Satellites transmit 2 low powered radio signals L1 and L2, civilian GPS makes use of L1 signal which has a frequency of 1575.42 MHz in UHF band. These signals are thus unable to pass through solid buildings, mountains etc. The pseudorandom code gives the information about the satellite which is identified by a unique code. Ephemeris data gives an account of the satellite position and other related orbital information. Almanac data is provided at regular intervals and it contains the valuable information about the current date and time which is very important to determine the position of the receiver.

Trilateration The GPS concept is based on "Trilateration" or in simple words "triangulation". Trilateration is a method which uses the geometry of triangles to determine the relative positions. Computing the distances of different satellites we can determine the location of the receiver. Magellan and Garmin offer superior GPS receivers which are exceedingly accurate due to their parallel channel design. These receivers lock into satellites and maintain their link even in dense forest areas or regions which are highly populated and have large number of buildings. Certain atmospheric factors also affect the accuracy of these receivers. A GPS receiver locked in to 4 different satellites can accurately determine the three dimensions that is, the latitude, the longitude and the altitude. With a device locked into 2 satellites can conclude only 2d view that is, the longitude and the latitude. The GPS needs an highly accurate clock. The most perfect clock made upto date is the atomic clock. GPS makes use of this same clock in its satellites. But for the receiver end, installing clocks in the devices would have made it unaffordable so the developers came up with the idea of using a 4th dimension in determining the position. So a normal position can be easily established using signals from not three but four satellites.

MAGELLAN AND GARMIN Leading brands with GPS solutions, Garmin and Magellan have a variety of products on offer.

For portable and on board navigators such a nuvi and zumo series from Garmin and Magellan maestro and triton series offer exceptional on-road and off road coverage for all types of vehicles. These navigational handhelds and fixed navigators are best for hiking, biking and camping purposes around the world whether you are in a vehicle or trekking by foot.
Both Garmin and Magellan have equally competitive products for land, airborne and sea navigation, mining and agriculture machine products, vehicle navigation, and Aerospace solutions. They provide professional GPS solutions for avionics and safety, radars and autopilots, marine networking, sensors and boards for surveys and recreational application.
Blackberry and PDA's for Mobile and laptop integration with the GPS receivers is another range of products. Now you can have the GPS on the go with these revolutionary products on offer.
Customized software solutions from Magellan and Garmin GPS' handheld for topographic, marine and street navigation. Fully detailed maps with extensive coverage points including lakes, mountains, streets, monuments, parks and comprehensive range of addresses make these a world class navigational equipments.

Newer and more accurate technology is flooding the market such as the upgradation to differential global positioning system (DGPS) offered by Garmin is cuurently deployed by the U.S. coastal guard which gives an accurate account of position with a range of three to five meters. Recent Garmin GPS receivers are equipped with WAAS (Wide Area Augmentation System) which corrects to the average of 3 meters by improving and transmitting GPS signals through beacon transmitters.

Limitations and error introduction in the GPS receivers

Delays in the atmosphere while passing through Ionosphere and troposphere introduces delay time errors in the signals.
Improper synchronization and correction of atomic clock time in satellite and receiver.
Ephemeris errors- errors due to incorrect location co ordinates of the satellite.
GPS does not work under water, under ground or inside the buildings.
Needs clear Line of sight from the satellite to the receiver. Any obstructions due to buildings and dense flora introduce erroneous results.

GPS has a widespread use and thus has innumerous applications. They can be broadly categorized to military and civilian industry. Whether it is land, sea or air GPS has become seamlessly important. Surveyors, mariners and aviation industry have become highly dependent on these technological wonders. Others active customers include the automobile clients and recreational sports activity patrons. GPS has undoubtedly transformed the way of living and taken it to new heights.

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Why Use a Portable GPS (Global Positioning System) Device?

A handheld GPS unit not only saves you a lot of time but also makes your commuting process easier and simpler than usual. These devices guide your way to unfamiliar destinations without much hassles.

I have been using a portable GPS device for a couple of years now and believe you me, traveling has been way more pleasurable than what it used to be. No one likes to be lost and asking directions can be quite annoying at times. And printing pages after pages of maps can be an arduous task. A GPS navigation unit is probably the best answer to all such problems.

These gadgets are incredible devices that offer you a wide array of ways in order to get the best of them. Below we will discuss how best you can use these devices.

Driving: A GPS unit can be used in cars for an enhanced driving experience. The mapping software incorporated in the device helps you steer your way to a desired destination and back and that too by leading you through the fastest routes. These devices contribute towards efficient travelling by choosing the shortest routes and notify you of the current traffic conditions of roads you are driving on. Another interesting feature of these GPS units is that they come with a number of 'points of interest'. These gadgets are designed to inform you about gas stations, restrooms and the like while you are approaching them. Now that sounds good, doesn't it?

Boating: other than cars, a portable GPS device can also be used while boating. These devices help to point different stops like, fishing spots, great scenic view, and favorite landing points etc. and later in case you want to get back to these points, your GPS navigator will guide your way back to your desired spot.

In airplanes: GPS gadgets are also used while flying commercial airplanes. In this case, a GPS device helps you determine the distance from your destination, your current location, how high you are flying and at what speed.

Tourism and vacations: in case you are going to a new unfamiliar place for your vacation, your GPS device can prove to be a great help as it can locate places of special interest, to mark places that you may like to return to and also to find local restaurants.

Biking: regardless of the fact whether you are a casual or a serious biker, a portable GPS unit can be a great way to track your progress. It can record the distance you have travelled, your halt time, average speed, current speed etc.

There are several ways to use a GPS navigation device, abovementioned are just a few. There are various kinds of GPS devices with varied features that are found on the market. It is advisable that you do your necessary research and then purchase a device that will suit your needs the best.

So, to conclude, now that you have a fair idea about what GPS devices are and how to use them, feel free to go ahead and get your brand new portable GPS unit today and enjoy all that it has to offer.

SNS Designs, INC. owns a number of websites. They carry wide selection of Garmin GPS, Magellan GPS systems, Handheld GPS Units and Tom Tom GPS they offer the most popular gps navigation equipment for cars and mobile devices as well as computers for everyone.

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Global Positioning System (GPS)

Originally designated the NAVSTAR (Navigation System with Timing And Ranging) Global Positioning System, GPS system was developed by the US Department of Defense to provide all-weather round-the-clock navigation capabilities for military ground, sea, and air forces. Since its implementation, GPS system has also become an integral asset in numerous civilian applications and industries around the globe, including recreational uses (e.g. boating, aircraft, hiking), corporate vehicle fleet tracking, and surveying.

The GPS system employs 24 spacecraft in 20,200 km circular orbits inclined at 55 degrees. These spacecraft are placed in 6 orbit planes with four operational satellites in each plane. All launches have been successful except for one launch failure in 1981. The full 24-satellite constellation was completed on March 9, 1994.

The first eleven spacecraft (GPS Block 1) were used to demonstrate the feasibility of the GPS system. The orbit inclination used for these satellites was 63 degrees, differing from the 55 degrees used for the operational system. The Block 2 spacecraft began the operational system. The Block 2A spacecraft (A = Advanced) were a slight improvement over the Block 2.

The Global Positioning System (GPS) was designed as a dual-use system with the primary purpose of enhancing the effectiveness of U.S. and allied military forces. GPS is rapidly becoming an integral component of the emerging Global Information Infrastructure, with applications ranging from mapping and surveying to international air traffic management and global change research. The growing demand from military, civil, commercial, and scientific users has generated a U.S. commercial GPS navigation systems equipment and service industry that leads the world. Augmentations to enhance basic GPS services could further expand these civil and commercial markets.

GPS systems receivers use triangulation of the GPS satellites' navigational signals to determine their location. The satellites provide two different signals that provide different accuracies. Coarse-acquisition (C/A) code is intended for civilian use, and is deliberately degraded. The accuracy using a typical civilian GPS receiver with C/A code is typically about 100 meters. The military's Precision (P) code is not corrupted, and provides positional accuracy to within approximately 20 meters. Numerous on-line tutorials on how GPS works and its applications are available, including those at the University of Texas and Rentec International. GPS systems satellites are controlled at the GPS Master Control Station (MCS) located at Falcon Air Force Base outside Colorado Springs, Colorado. The ground segment also includes four active-tracking ground antennas and five passive-tracking monitor stations.

GPS receiver technology has developed by leaps and bounds over the last few years. GPS receivers were initially the size of a suitcase with the antenna the size of a kid’s blow up swimming pool. Over time, the system has been developed into a civilian friendly program, and GPS receiver technology has miniaturized as well. Automobile GPS receivers are the size of a deck of cards. The gps receiver used in hand held devices is not much larger than a small cell phone. Many newer cell telephones have a GPS receiver integral in their hand set. As manufacturers develop the GPS receiver, they will have to work through display, power use and dexterity limitations. An individual will need a screen with a size that can be viewed from any angle and at a reasonable distance. The GPS receiver is generally always on while in use, so managing power will continue to be an on going problem. The ability to push the small buttons will limit just how small a GPS receiver can be. As touch screens develop and other input systems are introduced, we will see the GPS receiver continue to change in appearance and use.

Author: John B. Whitsell

Making Tracks GPS

www.makingtracksgps.com [http://www.makingtracksgps.com]

Information referenced from NASA and USCG data

John Whitsell is a retired Navy Surface Warfare Officer with 24 years navigation experience both at sea and with land based units. He currently owns Making Tracks GPS.

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