The Global Positioning System is a global navigation satellite system that helps precisely determine geographic locations PDF

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The Global Positioning System is a global navigation satellite system that helps precisely determine geographic locations...

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RUNNING HEAD: Term Report

The Global Positioning System is a global navigation satellite system that helps precisely determine geographic locations. It was initially developed by the U.S. Department of Defense for both military and civil users (What is GPS, 2020). The GPS concept was created by scientists at The Massachusetts Institute of Technology in 1957. The scientists examined the way the Russian satellite called “Sputnik” worked: the frequency of Sputnik went up as it approached and dropped as it moved away. That gave the MIT scientists an idea of the GPS concept, which, in a nutshell, sounds like this: “Satellites could be tracked from the ground by measuring the frequency of the radio signals they emitted, and conversely, the locations of receivers on the ground could be tracked by their distance from the satellites” (Sullivan, 2020). In 1973 the U.S. Department of Defence started the GPS project. 1974 is an important year in the history of GPS. It is the year when the U.S. launched the first NAVSTAR test satellite. Later on, they launched eleven more test satellites under their “Block I” GPS program (Ravikumar, 2020). The first GPS unit was certified for use in IFR operations by the Federal Aviation Administration in 1994. The certified GPS receiver was called “the Garmin GPS 155” (Connor, 2014). GPS is a part of the Global Navigation Satellite System (GNSS), along with other satellite-based navigational systems, such as GLONASS, developed in Russia, Galileo, created in Europe, and China’s BeiDou Navigation Satellite System (BDS) (What is GNSS, 2018). GPS comprises three segments: space, control, and user. The space segment is responsible for thirty operational satellites placed inside of orbital planes, which surround our planet. In 2011, the U.S. Air Force repositioned six of the satellites and added three new ones to the twenty-four

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RUNNING HEAD: Term Report that were in operation back then. At the moment there are 8 working legacy satellites and twentytwo modernized satellites in the GPS constellation (GPS.gov: Space Segment, 2020). The control segment is a whole network of Monitor Stations, Master Control Stations, Remote Tracking Stations, and Ground Antennas placed all over the world. The Monitor Stations serve the purpose of tracking the satellites as they fly over the stations, the Master Control Station is in charge of satellite maintenance. It also determines the exact locations of the satellites and ensures that this data is accurate. The Ground Antennas send commands and navigation data to the satellites and collect telemetry. To keep the control system secure and to ensure it performs well, the U.S. Air Force has developed the GPS Modernization Program, which helps upgrade the control system and enhance cybersecurity (GPS.gov: Space Segment, 2020). The user segment of GPS is in charge of receiving GPS signals and providing the users with coordinates, speed, and time required to reach a certain location. Each aircraft has thousands of receivers on-board. The signals are transmitted between those receivers and satellites (Global Positioning System (GPS) in Aviation, 2020). The way a GPS receiver works is it calculates the coordinates of an aircraft using two variables: the distance between the aircraft and the three transmitting satellites and the speed at which the radio waves travel (186,000 miles per hour). The altitude of the aircraft above the earth is calculated with the help of another variable – distance to a fourth satellite. Furthermore, GPS helps determine “speed, direction, bearing to a waypoint, distance traveled, time of arrival, terrain features, airport data, VOR/RNAV and approach information, communication frequencies, etc.” (Global Positioning System (GPS) in Aviation, 2020). The Global Positioning System is considered to be the fastest-growing type of navigation in aviation. Aircraft location is determined using a signal connecting a GPS receiver inside the

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RUNNING HEAD: Term Report aircraft with NAVSTAR satellites. The satellites transmit the signal in the form of a digital code, through designated frequencies. A frequency of 1575.42 MHz is the L1 transmission channel used in civil aviation, whereas the L2 channel with a frequency of 1227.60 MHz is used by the military (Global Positioning System (GPS) in Aviation, 2020). As for the benefits of the GPS unit, there are many. For example, the GPS service rarely ever gets disrupted by the weather. Even if that happens, pilots can use other systems installed in an aircraft to navigate (Global Positioning System (GPS) in Aviation, 2020). Also, GPS is a high-precision navigational system. “The accuracy of current GPS is within twenty meters horizontally and a bit more vertically” (Global Positioning System (GPS) in Aviation, 2020). The accuracy of GPS can be enhanced even further by integrating the WAAS (Wide Area Augmentation System), which narrows down the error to one-three meters and helps an aircraft perform precision approaches with no use of the ground-based approach equipment whatsoever. WAAS comprises over twenty-five ground stations that receive signals from the satellites and communicate them to the aircraft. Of course, there is still room for improvement of this system, which could be done in the future by adding at least two more transmissions from each satellite. Accurate and continuous navigational information provided by the Global Positioning System reduces congestion at the airports and helps the airlines save time, which is extremely important because time has a direct influence on the airlines’ income (Global Positioning System (GPS) in Aviation, 2020). GPS makes it really easy for pilots and air traffic controllers to share and receive positioning data, performance data, and other critical flight data through the use of the Automatic Dependent Surveillance-Broadcast (ADS-B) system. This system uses transponders to transfer signals between ground stations and aircraft. Nowadays ADS-B data can be easily accessed not only by

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RUNNING HEAD: Term Report aviation workers but also by other people. Anyone can find out the location of almost any aircraft through designated websites and applications (Global Positioning System (GPS) in Aviation, 2020). Due to the benefits stated above, GPS allows for “enhanced safety of flight, seamless navigation, and more efficient and flexible route structures” (Satellite Navigation - GPS, 2019). Another advantage of the Global Positioning System pertaining to aviation is the overall cost of GPS, which is relatively low due to its small infrastructure. Additionally, shortened flight times and reduced fuel consumption derived from the implementation of GPS help the airlines save money (Satellite Navigation - GPS, 2019). Other navigational systems that were in use in the 1950s like “VOR stations, glideslope shacks, localizer antennas, and radar arrays” are way more expensive to construct and less accurate (Connor, 2014). This is why GPS is the preferred method of en-route navigation in aviation. Overall, the introduction of the Global Positioning System was a huge step in the development of the aviation industry. It stands out of the other navigational systems, because it provides the most accurate coordinates along with the increased safety of flight, helps the airlines save time and money, and helps pilots and ATC to receive and relay positioning data.

Reference page

Eso.org. 2020. What Is GPS?. [online] Available at:

[Accessed 6 December 2020].

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RUNNING HEAD: Term Report Sullivan, M., 2020. A Brief History Of GPS. [online] PCWorld. Available at: [Accessed 6 December 2020]. Ravikumar, A., 2020. History Of GPS Satellites And Commercial GPS Tracking | Geotab. [online] Geotab. Available at: [Accessed 6 December 2020]. Connor, R., 2014. Twenty Years Of GPS And Instrument Flight. [online] National Air and Space Museum. Available at: [Accessed 6 December 2020]. Gsa.europa.eu. 2018. What Is GNSS?. [online] Available at: [Accessed 6 December 2020]. Gps.gov. 2020. GPS.Gov: Space Segment. [online] Available at: [Accessed 6 December 2020]. Aircraftsystemstech.com. 2020. Global Positioning System (GPS) In Aviation. [online] Available at: [Accessed 6 December 2020]. 2019. Satellite Navigation - GPS. [online] Available at: [Accessed 6 December 2020].

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