A friend within a kilometre, and what the name is said to mean

The notes open with something the writer had actually tried. A Facebook update, for people who had agreed to share location, showed which added friends were nearby — within a kilometre, or in which busy street. The accuracy felt impressive, and also a little frightening: how did the service know so well, and was the information only for convenience? That hook is left as the writer told it, not as a later official description of the app.

GPS is unpacked as Global Positioning System, and as a worldwide positioning scheme: geographic information is gathered for the whole earth, and a particular place can be fixed from it. Before the technology was widely sold, the notes say, Korean renderings such as a global positioning system were tried; the words felt unfamiliar and no more convenient than the letters themselves, so GPS, or the Korean pronunciation, became usual. The National Institute of Korean Language is quoted as a system that uses satellites to find one’s position exactly, from a person to the navigation of planes, ships and cars, and to surveying and map-making. Hoffman, in 2009, is called the most sensible technical account: an all-weather system of a satellite group, ground control stations and users, receiving satellite signals anywhere on earth without a time limit, to place a still or moving object. That account stays in 2009.

Transit, Timation, and the satellites that made the name usable

The notes say the work began in the United States defense system. The name GPS is dated from 1973, but the groundwork is placed in the late 1950s. From the late 1950s into the early 1960s the U.S. Navy began satellite surveying and navigation; two systems are named, Transit and Timation. Transit, the earlier one, ran from 1964 and was shown to the public in 1969. Timation, almost ten years later in this telling, still looked like a basic outline until it was joined to an Air Force plan called 621B and could run as DNSS, the Defense Navigation Satellite System, then as what the notes call Navistar GPS — unpacked there as Navigation System with Timing And Ranging Global Positioning System.

The 1970s are treated as a period of tests. A satellite that could actually do the work, NTS-2, is placed in mid-1977 and is said to have run only about half a year, long enough, the notes say, to show that satellite navigation was possible. The first Block I satellite follows in early 1978; after a broader check, nine more were launched over six years. Block II, a second generation, is dated to the end of 1985, when a third stage of development began. The notes also mention about 15 billion dollars spent over some twenty years on the military project. Those dates stay where they are written.

KAL-007, a 1984 permission, and figures left in 1993

The notes tie the opening of the military system to civilians to a Korean story. In September 1983, they say, the Soviet Union shot down Korean Air KAL-007, a civilian aircraft, and everyone on board died. It was the Cold War; the Soviet side said the plane had been taken for a hostile aircraft, though the notes add that it already seemed to have been known as a civilian flight. After the worldwide shock, President Reagan in 1984 allowed free civilian use of the technology.

Regular civilian service, in this account, began only at the end of 1993, once a group of 24 GPS satellites was complete. Accuracy for civilians then is given as 30 to 100 metres, because the United States was deliberately sending noise so that precise positions would not be openly available; military service is given as 5 to 15 metres. Those figures stay in 1993, and are not recast as later official totals. The notes list other kinds — a local correction system (LADGPS), a wide-area correction system (WADGPS), and a carrier-phase correction system (CDGPS) — but the extracted core does not explain how they work, so those workings are not added here. The same Korean report, at fuller length, is on CampusDown.

Sources

1. Notes titled Stand-alone GPS, opening with a Facebook nearby-friends hook and a definition after the National Institute of Korean Language and Hoffman (2009).
2. History as the notes give it: Transit from 1964 and public in 1969; Timation joined to Air Force 621B as DNSS and then as what the notes call Navistar GPS; NTS-2 in mid-1977; Block I in early 1978; Block II at the end of 1985.
3. Civilian opening after the September 1983 shootdown of KAL-007, Reagan’s 1984 permission, and regular civilian service at late 1993 with the 24-satellite group and the 30–100 m and 5–15 m figures left in that year.

Last updated: 14 November 2026