Editing Loran-C (section)

===LORAN method===
[[File:loran pulse.svg|thumb|left|LORAN pulse]]
In the case of LORAN, one station remains constant in each application of the principle, the ''primary'', being paired up separately with two other ''secondary'' stations. Given two secondary stations, the time difference (TD) between the primary and first secondary identifies one curve, and the time difference between the primary and second secondary identifies another curve, the intersections of which will determine a [[Geography|geographic]] point in relation to the position of the three stations. These curves are referred to as ''TD lines''.<ref>{{Cite web|url=http://www.nga.mil/portal/site/maritime/?epi_menuItemID=c56aa099e2bff9525b2a7fbd3227a759&epi_menuID=35ad5b8aabcefa1a0fc133443927a759&epi_baseMenuID=e106a3b5e50edce1fec24fd73927a759|archive-url=https://web.archive.org/web/20091201173931/http://www.nga.mil/portal/site/maritime/?epi_menuItemID=c56aa099e2bff9525b2a7fbd3227a759&epi_menuID=35ad5b8aabcefa1a0fc133443927a759&epi_baseMenuID=e106a3b5e50edce1fec24fd73927a759|url-status=dead|title=The American Practical Navigator, An Epitome of Navigation, page 173|archive-date=1 December 2009}}</ref>

In practice, LORAN is implemented in integrated regional [[phased array|arrays]], or ''chains'', consisting of one ''primary'' station and at least two (but often more) ''secondary'' stations, with a uniform ''group repetition interval'' (GRI) defined in [[microsecond]]s. The amount of time before transmitting the next set of pulses is defined by the distance between the start of transmission of primary to the next start of transmission of primary signal.

The secondary stations receive this pulse signal from the primary, then wait a preset number of [[millisecond]]s, known as the ''secondary coding [[Propagation delay|delay]]'', to transmit a response signal. In a given chain, each secondary's coding delay is different, allowing for separate identification of each secondary's signal. (In practice, however, modern LORAN receivers do not rely on this for secondary identification.){{Citation needed|date=May 2009}}