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It must acquire each satellite signal and obtain that satellite's detailed orbital information, called ephemeris data. Each satellite broadcasts its ephemeris data every 30 seconds with validity of up to 4 hours. Hot or standby The receiver has valid time, position, almanac, and ephemeris data, enabling a rapid acquisition of satellite signals.
In astronomy and celestial navigation, an ephemeris (/ ɪ ˈ f ɛ m ər ɪ s /; pl. ephemerides / ˌ ɛ f ə ˈ m ɛr ɪ ˌ d iː z /; from Latin ephemeris 'diary', from Ancient Greek ἐφημερίς (ephēmerís) 'diary, journal') [1] [2] [3] is a book with tables that gives the trajectory of naturally occurring astronomical objects and artificial satellites in the sky, i.e., the position ...
The time needed to acquire the ephemeris is becoming a significant element of the delay to first position fix, because as the receiver hardware becomes more capable, the time to lock onto the satellite signals shrinks; however, the ephemeris data requires 18 to 36 seconds before it is received, due to the low data transmission rate.
If a fast time to first fix (TTFF) is needed, it is possible to upload a valid ephemeris to a receiver, and in addition to setting the time, a position fix can be obtained in under ten seconds. It is feasible to put such ephemeris data on the web so it can be loaded into mobile GPS devices. [6] See also Assisted GPS.
An ephemeris is a table of the calculated positions of astronomical objects and various other data, usually for a specific time of the day, either noon or midnight. A uniform time measurement is needed to establish accuracy, and ephemerides will use variously Greenwich Mean Time, Universal Time or Ephemeris Time.
The {{Graphical timeline}} template allows representations of extensive timelines. The template offers complex formatting and labeling options to control the output. Typically, each use is made into its own template, and the template is then transcluded into the article. See an example here, and an example of it being used in an article here.
The Astronomical Almanac [1] is an almanac published by the United Kingdom Hydrographic Office; it also includes data supplied by many scientists from around the world.On page vii, the listed major contributors to its various Sections are: H.M Nautical Almanac Office, United Kingdom Hydrographic Office; the Nautical Almanac Office, United States Naval Observatory; the Jet Propulsion Laboratory ...
What remains is the set of data needed to update the original G-card data as additional measurements are made. The data is fit into 69 columns and does not include a trailing character. TLEs are simply the transmission format data rendered as ASCII text. An example TLE for the International Space Station: