TeChNoLoGy

Global Positioning System also known as GPS device was developed by the US Department of Defense to provide all-weather, round-the-clock navigation capabilities for military ground, sea, and air forces. GPS navigation is also an integral part of many civilian applications.Though global positioning system was started to enhance the effectiveness of the U.S. military forces, GPS is widely now being acclaimed as an integral component of the emerging global information infrastructure. The global positioning system has applications ranging from surveying and mapping to global change research and international air traffic management. The increased demand from civil, commercial and scientific users has encouraged the GPS equipment and service industry.

The primary application of the global positioning system is to enable forces to target locations for missile troops. The application of global positioning system includes its' usage as a navigation aid in ships, aero planes and cars.

The global positioning system, which is a satellite based navigation system, is made up of a network of 24 satellites placed into orbit by the U.S department of defense. Global positioning system is defined as the constellation of satellites, navigation payloads that produce the GPS signals, data links, ground stations, associated command and control facilities that are maintained by the department of defense.

Be it summer, winter or fall, the global positioning system works in all conditions. Be it day or night, GPS works for 24 hours. You do not even have to pay subscription fees or set up charges to use the global positioning system. GPS satellites transmit signal information to the earth after circling the earth twice a day. GPS receivers make use of triangulation to calculate the user's exact location. The global positioning system receivers compare the time a signal was transmitted by a satellite to the time it was received. The time difference enables the GPS receiver to calculate how far away the satellite is. The receiver could also determine the user's position and display it on the unit's electronic map. The application of GPS includes its' usage by computer-controlled harvesters, mine trucks and other vehicles.

The three segments of GPS are user, space and control.

Note that all global positioning system satellites transmit accurate positions and time signals. Simultaneous measurements from the four satellites are processed to solve for the three dimensions of velocity, time and position.

GPS has a wide range of applications. All of them fall under five basic categories:

Differential GPS enables to make corrections on various inaccuracies in the GPS system. Differential global positioning system could provide accurate measurements that help GPS in becoming a universal measurement system that is capable of positioning things on a precise scale. Differential GPS functions with the cooperation of two receivers: stationary receiver, roving receiver that is making position amendments. The stationary receiver ties all the satellite measurements into a solid local reference. Note that all the differential global positioning systems are not equal. Some do not require radio link, as they do not have an immediate need for precise positioning.

GPS Device

A GPS device or a GPS unit is an electronic device using which one can determine his approximate location. A GPS receiver uses triangulation of the GPS satellites' navigational signals to determine their current location. The coordinates for the GPS devices are normally given in terms of the latitude and longitude. The satellites provide two different signals, the position and the time signal, that provide different accuracies. Coarse acquisition (C/A) code is for civilian use and is deliberately degraded. The positional accuracy would be about 100 meters. The military uses Precision (P) code and is not corrupted. The positional accuracy would be approximately within 20 meters. The GPS device can be used to navigate from the current location to another location. The unit may have other add-ons, depending on its complexity. These include maps, built-in electronic compasses, voice navigation units, etc.

GPS receivers can be classified on the basis of:

· Architecture
     - Sequential receivers
     - Continuous receivers
     - Multiplex receivers

· Method of operation
     - Code correlation
     - Carrier phase

· Application
     - General purpose handheld
     - Attitude determination
     - Aviation
     - Automobile navigation, IVHS and Fleet location
     - Mapping and data collection
     - Marine
     - Original Equipment Manufacturer
     - Space
     - Surveying
     - Timing

GPS Navigation

GPS navigation is one of the everyday applications of Global Positioning System. One of the original design goals of GPS navigation was to provide navigation information for planes and ships. GPS is only an aid to navigation and navigators must also know and use the traditional piloting and navigational techniques. GPS provides precise navigation tools and accurate landing systems, thus making flying safer and more efficient. The precise point-to-point navigation of a GPS system helps save fuel and extends the aircraft's range by ensuring pilots stay on the most direct routes to the destination. In space navigation, a GPS receiver is used to determine the position and velocity of a satellite, to accurately determine the time of observations from other tracking or scientific instruments and many more.

The future of global positioning system is bright as predictions range from its' increased usage to expansion into new areas of application. It is estimated that there will be 50 million users of the global positioning system by 2010 that perform applications in the following fields:

Positional accuracy and reliable calculations are also predicted in the GPS technology. It is hoped that additional civil frequencies and civil codes will be developed to meet the requirements of civilian users. GPS users have also considered the benefits of interoperating the GALILEO and NAVSTAR systems. The advantages of interoperability include improved signal redundancy and more available signals that enable users to access satellites from remote areas.