Global Positioning System

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 s.

History
The concept behind the GPS system was conceived by scientists of the (APL) at  and takes advantage of the  to determine distances from satellites and  one's position on the ground. The first global positioning system,, consisted of 36 satellites launched between 1960 and 1968. The system was developed by the (ARPA) with APL and managed by the  for military and some commercial use. Accuracy was within tens of meters.

In November 1972, Colonel  began work to supervise development of an improved system called NAVSTAR that would use 24 satellites with s instead of s for greatly improved accuracy. aided in the development of the satellites which used atomic clocks from the (NRL). The first four satellites were launched in 1978.

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. The first publicly-available handheld GPS device, the, offered a few hours of battery life in a 1.5 pound receiver that cost 3,000 in 1989. 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.

In 2005, the United States began launching newer GPS satellites capable of transmitting "L2C" signals for improved accuracy by accounting for. Though the U.S. Air Force began transmitting navigational signals in 2014, L2C has not yet been declared operational for civilian use. 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.

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 ) and the GPS Map app developed and released by Gerd Staudenmaier in 1994. Third party developers also created licensed Newton clones with built-in GPS capabilities. The MessagePad 2000, released in 1997, supported the grayscale display of aviation maps.

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 chip to also receive data from Russian satellites to improve GPS accuracy. In September 2017, the iPhone 8 and 8 Plus were released with support for navigation signals from satellites operated by the. All cellular-capable iPads also have a GPS receiver. Apple Watches, iPod touches and iPads without cellular capability instead use the to determine their location, though with less accuracy and subject to Wi-Fi signal availability.

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.