An Almanac contains ephemeris data on all the satellites, and a complete almanac is valid for thirty days, at which time a new almanac must be downloaded from the satellites for the upcoming month. The GPS receiver automatically updates its internal almanac upon locking onto a GPS satellite. [Section 4.2.3

a library of coarse satellite orbital data used to calculate satellite position, rise time, elevation and azimuth

A data file that contains the approximate orbit information of all satellites. This set of parameters is transmitted regularly by all GPS satellites, and allows for a receiver to predict the approximate location of a satellite rapidly. Most receivers provide a facility for battery backup or non-volatile storage of the almanac to make power-on acquisition faster. The almanac is less accurate then ephemeris data, but remains valid for a longer period.

A set of parameters used by a GPS receiver to calculate the approximate location of a GPS satellite and the expected satellite clock offset. Each GPS satellite contains and transmits the almanac data for the GPS constellation. GLONASS satellites also provide almanacs for their constellation. (See Ephemeris.)

Information transmitted by each satellite on the orbits and state (health) of every satellite in the GPS constellation. Almanac data allows the GPS receiver to rapidly acquire satellites shortly after it is turned on.

A data file that contains orbit information on all satellites, clock corrections, and atmospheric delay parameters. It is transmitted by each GPS satellite in order to facilitate rapid satellite vehicle acquisition by GPS receivers.

Almanacs are approximate orbital parameters for all the SVs. The ten-parameter almanacs describe SV orbits over extended periods of time (valid for months in some cases). The full set of almanacs for all the SVs is sent by each SV over a period of 12.5 minutes (at least). Signal acquisition time on receiver start-up can be significantly aided by the availability of current almanacs. The approximate orbital data is used to preset the receiver with the approximate position and Doppler shift of each SV in the constellation.

A set of parameters included in the GPS satellite navigation message that a receiver uses to predict the approximate location of a satellite. The almanac contains information about all of the satellites in the constellation.

A data file that contains orbit information on all satellites, clock corrections, and atmospheric delay parameters. It is transmitted by a GPS satellite to a GPS receiver, where it facilitates rapid satellite vehicle acquisition within GPS recievers.