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Global Positioning System (GPS), formerly NAVSTAR, is a system for determining a position on the Earth's surface by comparing radio signals from man-made satellites.[1]

History[]

The concept behind the GPS system was conceived by scientists of the Applied Physics Laboratory (APL) at Johns Hopkins University and takes advantage of the Doppler effect to determine distances from satellites and triangulating one's position on the ground. The first global positioning system, Transit, consisted of 36 satellites launched between 1960 and 1968. The system was developed by the Advanced Research Projects Agency (ARPA) with APL and managed by the United States Navy for military and some commercial use. Accuracy was within tens of meters.[2]

In November 1972, U.S. Air Force Colonel Bradford Parkinson began work to supervise development of an improved system called NAVSTAR that would use 24 satellites with atomic clocks instead of crystal oscillators for greatly improved accuracy. The Aerospace Corporation aided in the development of the satellites which used atomic clocks from the U.S. Naval Research Laboratory (NRL). The first four satellites were launched in 1978.[2]

In 1983, U.S. President Ronald Reagan authorized the use of NAVSTAR, which became known as GPS, by civilian airlines for improved air travel safety. However, the GPS satellites provide reduced precision when accessed by anyone other than the U.S. military. The first publicly-available handheld GPS device, the Magellan NAV 1000, offered a few hours of battery life in a 1.5 pound receiver that cost US$3,000 in 1989.[2] Depending on geographic location, the GPS receiver would sample data from up to six satellites, and then calculate the time taken for each satellite signal to reach the receiver, and the difference in time of reception, to determine the receiver's location.[1]

In 2005, the United States began launching newer GPS satellites capable of transmitting "L2C" signals for improved accuracy by accounting for atmospheric ionization. Though the U.S. Air Force began transmitting navigational signals in 2014, L2C has not yet been declared operational for civilian use.[3] In May 2010, the first "L5" satellite was launched to work with older legacy signals, retroactively referred to as "L1", to improve signal strength through obstructions.[3]

Usage by Apple[]

The first handheld devices from Apple Computer that supported GPS Navigation were Newton MessagePads running Newton OS 1.3 or later, when used in conjunction with a GPS receiver (such as a Garmin GPS 90) and the GPS Map app developed and released by Gerd Staudenmaier in 1994.[4][5][6] Third party developers also created licensed Newton clones with built-in GPS capabilities.[7] The MessagePad 2000, released in 1997, supported the grayscale display of ICAO aviation maps.[8]

The first iPhone model to include a built-in "assisted" GPS receiver was the iPhone 3G, released in July 2008. In October 2011, the iPhone 4S was introduced with a GLONASS chip to also receive data from Russian satellites to improve GPS accuracy.[9] In September 2017, the iPhone 8 and 8 Plus were released with support for Galileo navigation signals from satellites operated by the European Union Agency for the Space Programme.[10] All cellular-capable iPads also have a GPS receiver. Apple Watches, iPod touches and iPads without cellular capability instead use the Wi-Fi positioning system to determine their location, though with less accuracy and subject to Wi-Fi signal availability.[11][12]

In September 2022, Apple introduced the iPhone 14 Pro and 14 Pro Max, which included dual-frequency GPS support to receive both modernized "L5" signals from newer GPS satellites, along with legacy "L1" signals, for improved coverage around buildings and trees.[13]

References[]

  1. 1.0 1.1 Global Positioning System at the Free On-Line Dictionary Of Computing. 1998-02-10.
  2. 2.0 2.1 2.2 A Brief History of GPS, Aerospace. 2021-02-02.
  3. 3.0 3.1 New Civil Signals, GPS: The Global Positioning System. Accessed 2022-10-03.
  4. Apple Newton does GPS Navigation, My Apple Newton. 2009-06-20.
  5. Introduction, GPS Map and GPS Map Lite. Archived 1996-11-14.
  6. Distribution of GPS Map, GPS Map and GPS Map Lite. Archived 1997-01-11.
  7. Part II: Hardware Newton FAQ. Accessed 2022-10-03.
  8. Introduction, GPS Map and GPS Map Lite. Archived 1997-10-17.
  9. Which Apple devices have GPS? by Rufus Muckala, CityMac. 2013-09-02.
  10. The latest iPhone 8, iPhone 8 Plus, and iPhone X are Galileo-enabled, European Union Agency for the Space Programme. 2017-09-18.
  11. Which iPad Models Have Built-In GPS? by Fred Zahradnik, Lifewire. 2022-01-16.
  12. Use Apple Watch without its paired iPhone, Apple Support. Accessed 2022-10-03.
  13. iPhone 14 Pro Models Feature Improved GPS Accuracy by Joe Rossignol, MacRumors. 2022-09-10.

External links[]

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Wi-Fi: 802.11a · b · g · n · ac (Wi-Fi 5) · ax (Wi-Fi 6)  |  AirPort: Base Station · cards · Express · Extreme
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FOLDOC logo This page uses GFDL licensed content from the Free On-line Dictionary of Computing.
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