GLOBAL POSITIONING SYSTEM (GPS) GLOBAL POSITIONING SYSTEM (GPS) 3802 O/C AMTR DASSANAYAKE MTS INTAKE 28 3802 O/C AMTR DASSANAYAKE MTS INTAKE 28 HISTORY OF GPS SEGMENTS OF GPS APPLICATIONS OF GPS GEOSTATICS ASSIGNMENT 01 HISTORY OF GPS SEGMENTS OF GPS APPLICATIONS OF GPS GEOSTATICS ASSIGNMENT 01 ASSIGNMENT I Prepare a detail report regarding GPS including following features…… 1. Historical development. 2. Segment of GPS. 3. Wide variety of applications of GPS. INTRODUCTION * GPS is a satellite-based navigation system originally developed for military purposes and is maintained and controlled by the United States Department of Defense. GPS permits land, sea, and airborne users to determine their three-dimensional position, velocity, and time. * It can be used by anyone with a receiver anywhere on the planet, at any time of day or night, in any type of weather. * There are two GPS systems: NAVSTAR - United States system, and GLONASS - the Russian version. * The NAVSTAR system is often referred to as the GPS (at least in the U. S. ) since it was generally available first. * Many GPS receivers can use data from both NAVSTAR and GLONASS; this report focuses on the NAVSTAR system. 1. Historical development GPS is primarily a navigational system, so a background on navigation will give insight as to how extraordinary the Global Positioning System is. * People first navigated only by means of landmarks - mountains, trees, or leaving trails of stones. * This would only work within a local area and the environment was subject to change due to environmental factors such as natural disasters. * For traveling across the ocean a process called dead reckoning, which used a magnetic compass and required the calculation of how fast the ship was going, was applied. The measurement tools were crude and inaccurate. It was also a very complicated process. * When traveling over the ocean, people began using the stars as guidelines. * The stars appear different from different locations on Earth so analyzing the stars gave sailors the basic direction to follow. * Celestial navigation was our primary means of navigation for hundreds of years. It was a time-consuming and complicated task of measuring the angles between stars - a process of triangulation. * The degree of precision was limited. The sextant was developed during this time but since it only measured latitude, a timepiece was also invented so that the longitude could also be calculated. * This type of navigation only worked at night and in clear weather which was a great disadvantage. * It was not until the 20th century that ground-based radio navigation systems were introduced. Some are still in use today. * GPS is a satellite radio navigation system, but the first systems were ground-based. * They work in the same way as does GPS: users (receivers) calculate how far away they are from a transmitting tower whose location is known. When several towers are used, the location can be pinpointed. * This method of navigation was a great improvement, yet it had its own difficulties. An example of such a system is LORAN. * Each tower had a range of about 500 miles and had accuracy good to about 250 meters. * LORAN was not a global system and could not be used over the ocean. Because ground based systems send signals over the surface of the earth, only two-dimensional location can be determined. * The altitude cannot be calculated so this system could not be applied to aviation. The accuracy of such systems could be affected by geography as well. The frequency of the signal affected accuracy; a higher frequency would allow for greater accuracy, but the user would need to remain within the line of sight. * The first global navigation system was called OMEGA. It was a ground-based system but has been terminated as of 1997. * Timeline of GPS Development * Late 1960s, concept development. * Early 1970s, program funding and establishment of a Joint Program Office within the Department of Defense. * December 1973, proposal for GPS approved by the Defense System Acquisition and Review Council (DSARC). * Mid-1970s, ground testing of the GPS concept. February 22, 1978, launch of the first GPS satellite. * 1989, Magellan Corporation introduces the first hand-held GPS receiver. * 1991, detection and fix of a major a glitch that slowed progress. * January 1991, military use of GPS in Operation Desert Storm in Iraq. * December 1993, declaration of Initial Operational Capability (IOC) by the U. S. Secretary of Defense. * May 2, 2000, SA is turned off by presidential directive; inexpensive civilian GPS receivers increase their horizontal accuracy from "no worse than" 100 meters to 15-25 meters. * Oct 1, 2005 First Modernized GPS Satellite with improved accuracy. . SEGMENTS OF GPS GPS uses radio transmissions. The satellites transmit timing information and satellite location information. The system can be separated into three parts: i. Space segment ii. Control segment iii. User segment Connection of three segments, i. Space Segment * The space segment consists of the satellites themselves. * According to the United States Naval Observatory, there are currently 27 operational GPS satellites about 11,000 miles up in space. * This constellation (see Figure 2 below) provides between five and eight GPS satellites visible from any point on the earth.
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The Space Segment * It takes each satellite about twelve hours to orbit the earth. There are six orbital planes with at least four satellites in each plane. * The orbits are tilted to the equator of the earth by 55° so that there is coverage of the Polar Regions. * The satellites continuously orient themselves to ensure that their solar panels stay pointed towards the sun, and their antennas point toward the earth. * Also each satellite carries 4 atomic clocks. ii. Control Segment * The control segment is a group of ground stations that monitor and operate the GPS satellites. There are monitoring stations spaced around the globe and one Master Control Station located in Colorado Springs, Colorado (see Figure 3 below). * Each station sends information to the Control Station which then updates and corrects the navigational message of the satellites. * There are actually five major monitoring systems, the figure below does not include the Hawaiian station. * The stations constantly monitor the orbits of the satellites and use very precise radar to check altitude, position and speed. * Transmitted to the satellites are ephemeris constants and clock adjustments. The satellites in turn, use these updates in the signals that they send to GPS receivers. The Control Segment iii. User Segment * This part consists of user receivers which are hand-held or, can be placed in a vehicle. * All GPS receivers have an almanac programmed into their computer, which tells them where each satellite is at any given moment. * The GPS receivers detect, decode and process the signals received from the satellites. * The receiver is usually used in conjunction with computer software to output the information to the user in the form of a map. As the user does not have to communicate with the satellite there can be unlimited users at one time. * The user requires a GPS receiver in order to receive the transmissions from the satellites. * The GPS receiver calculates the location based on signals from the satellites. * The user does not transmit anything to the satellites and therefore the satellites don't know the user is there. * The only data the satellites receive is from the Master Control Station in Colorado. * The users consist of both the military and civilians. 3. Applications of GPS Today, GPS has a wide variety of applications and GPS is finding its way into cars, boats, planes, construction equipment, movie making gear, farm machinery and even laptop computers. * The most obvious application for GPS is satellite navigation in vehicles, aircraft and ships. * It allows anyone with a GPS receiver to pinpoint their speed and position on land, air or sea, with incredible accuracy. * Drivers can use in-vehicle portable navigation devices to follow a route, find detours around traffic problems and with additional software receive traffic alerts and warnings on safety camera locations. GPS is used for tracking devices; people can pinpoint any object on the earth. For example, GPS vehicle tracking systems or GPS fleet tracking systems can point out where their stolen vehicle is or where their ship sails at present. * Main uses of GPS technology are as follows: a) Location ”The first and foremost palpable application of GPS system is the simple determination of a position? or location; Navigation ” b) The primary design of GPS tracking system was to provide navigation information or ships and planes; c) Tracking “With the accurate data provided by the system, monitoring mobile objects or people is not difficult task anymore; d) Mapping “GPS can help in creating maps and models of everything in the planet. Mapping the earth had never been an easier task; e) Timing” GPS satellites carry highly accurate atomic clocks, and GPS tracking devices here on the ground when synchronized with those in the satellites are themselves atomic accuracy clocks providing accurate time. * There are many applications for military in GPS, * The military utilizes GPS in land, marine, and airborne navigation. In addition, GPS satellites are equipped with sensors to monitor and detect the donations of nuclear weapons. * Navigation is the main function of GPS with uses in all branches of the military. * Some examples are; photo reconnaissance, low-level navigation, target acquisition, command and control, en route navigation, and missile guidance. * Although GPS was designed for military use, civilian use of the navigation technology has dramatically increased with the advent of affordable, portable GPS receivers and the ability to increase the accuracy of civilian GPS readings. A major use of GPS is for surveying and mapping, including land, marine, and air borne surveying, local and global deformation monitoring, and geodetic control. * Applications in transportation and communication and include automotive navigation aids, with an automated display of the vehicle position on an electronic map. This is particularly useful for emergency vehicles and search and rescue missions. * Monitoring the location and movement of vehicles such as taxis, trucks, and boxcars can also be achieved using GPS. Recreational activities have also become a large market for low-cost, portable receivers. Boating, backpacking, biking, and horseback riding are a few of the activities whose participants use fairly inexpensive, relatively low accuracy GPS receivers. * GPS is also available for other uses: hikers and ramblers can use GPS receivers to ensure they are following their chosen route and to mark rendezvous points along the way. * While gamers can take part in geocaching, a kind of treasure hunt for the digital age, which uses precise GPS signals to help the players track down a hidden stash. The emergency services, for instance, can use GPS not only to find their way to an incident quicker than ever before but also to pinpoint the location of accidents and allow follow-up staff to find the scene quickly. * This is particularly useful for search and rescue teams at sea and in extreme weather conditions on land where time can be a matter of life or death. * Scientists and engineers also have applications for GPS receivers, in scientific experiments, and in monitoring geological activity such as earth tremors, earthquakes and volcanic rumblings. They can use strategically positioned GPS devices to assist them in tracking climate change and other phenomena. Fundamentally, GPS can now be used to produce very accurate maps. * GPS is a term that most commonly conjures up images of vehicle navigation systems, space-age satellite technology, and interactive maps for outdoors-types and sportsmen as well as below usages, * Know where children are using services from companies like uLocate Communications. * Keep track of elderly members of your family, so that they don’t wander off alone. * Plan a road trip around interesting points of interests, landmarks, campsites, diners, etc. Get emergency road side assistance at a touch of a button from the vehicle, so you can get help exactly where and when people need it. * Keep a visual journal and bookmark collection of your favorite hot spots, sceneries, and points of interests that may not be listed in any travel guide. * Find lost pets easily using collars with built-in GPS. * Feel safer with cellular phone emergency calls, so emergency person can pinpoint your location once you make an emergency call. * Track your luggage, laptops, and anything of importance while traveling. Track and find family, friends in a crowded concert, graduation, or any social gathering. * When going on a vacation, feel free to separate from group for a while to venture on your own based on your own interests and find them later on with your GPS enabled device- even in an unfamiliar place. * Creative and educational uses of GPS; * Stay physically active and fit by playing Ray Gun! A locational based cell phone game based on GPS technology. * Become more cultured, make global friends, and learn about the world playing Geocache, a global GPS based treasure hunt. GPS boosts productivity across a wide swath of the economy, to include farming, construction, mining, surveying, package delivery, and logistical supply chain management. * Major communications networks, banking systems, financial markets, and power grids depend heavily on GPS for precise time synchronization. Some wireless services cannot operate without it. * GPS saves lives by preventing transportation accidents, aiding search and rescue efforts, and speeding the delivery of emergency services and disaster relief. GPS is vital to the Next Generation Air Transportation System (NextGen) that will enhance flight safety while increasing airspace capacity. * GPS also advances scientific aims such as weather forecasting, earthquake monitoring, and environmental protection. * GPS use to determine a position from measurements of distances is known as triangulation (not triangulation, which involves the measurement of angles). * GPS receivers receive satellite signals; they do not transmit or bounce signals off the satellites. GPS Systems are a passive, receive-only system, GPS Systems can support an unlimited number of users, both military and ivilian. * GPS system provides a 24 hour per day global coverage. GPS systems are an all-weather system which is not affected by rain, snow, fog, or sand storms. * GPS use to measure distances to four or more satellites simultaneously and knowing the exact locations of the satellites (included in the signals transmitted by the satellites), the receiver can determine its latitude, longitude, and height while at the same time synchronizing its clock with the GPS time standard which also makes the receiver a precise time piece.
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