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This almanac is transmitted repeatedly over 12.5 minutes. Almanac data can be received from any of the GPS satellites and is considered valid for up to 180 days. Warm or normal The receiver has estimates of the current time within 20 seconds, the current position within 100 kilometers, its velocity within 25 m/s, and it has valid almanac data.
The navigation messages include ephemeris data which are used both in trilateration to calculate the position of each satellite in orbit and also to provide information about the time and status of the entire satellite constellation, called the almanac. There are four GPS signal specifications designed for civilian use.
The GPS almanac, as part of the data transmitted by each GPS satellite, contains coarse orbit and status information for all satellites in the constellation, an ionospheric model, and information to relate GPS derived time to Coordinated Universal Time (UTC). Hence the GPS almanac provides a similar goal as the ancient Babylonian almanac, to ...
When applied to GPS, it is known as assisted GPS or augmented GPS (abbreviated generally as A-GPS and less commonly as aGPS). Other local names include A-GANSS for Galileo and A-Beidou for BeiDou. A-GPS is extensively used with GPS-capable cellular phones , as its development was accelerated by the U.S. FCC 's 911 requirement to make cell phone ...
Assisted GPS (A-GPS) uses a combination of satellite data and cell tower data to shorten the time to first fix, reduce the need to download a satellite almanac periodically and to help resolve a location when satellite signals are disturbed by the proximity of large buildings. When out of range of a cell tower the location performance of a ...
A Notice Advisory to Navstar Users (NANU) is a message issued jointly by the United States Coast Guard and the GPS Operations Center at Schriever Space Force Base in Colorado. [1] Such notices (NANUs) provide updates on the general health of individual satellites in the GPS constellation. NANUs are typically issued approximately three days ...
The GPS week number rollover is a phenomenon that happens every 1,024 weeks, which is about 19.6 years. The Global Positioning System (GPS) broadcasts a date, including a week number counter that is stored in only ten binary digits , whose range is therefore 0–1,023.
The RINEX format is designed to evolve over time, adapting to new types of measurements and new satellite navigation systems. The first RINEX version was developed by W. Gurtner in 1989 [1] and published by W. Gurtner and G. Mader in the CSTG GPS Bulletin of September/October 1990. Since 1993 the RINEX 2 is available, which has been revised and ...