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GPS Transmitter Frequencies

January 16, 2007 - By

Why are the two GPS Transmitter frequencies (1575.42 and 1227.6 MHz) coherently selected integer multiples of 10.23 MHz master clock? Question posted on CANSPACE on October 30, 2006, by Sivaraman Ranganathan. The document defining the GPS signal, IS-GPS-200, states that “The carrier frequencies for the L1 and L2 signals shall be coherently derived from a common frequency source within the... read more

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Why are GLONASS satellites launched on Christmas Day?

January 16, 2007 - By

Why are GLONASS satellites launched on Christmas Day? Question posted on CANSPACE on December 10, 2006, by Kerry Matthews The latest triple-satellite GLONASS launch occurred on December 25th at 23:18 Moscow Time. This launch is the sixth GLONASS December launch in a row. In fact, all 9 launches since December 1995 have occurred in the last month of the year... read more

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Innovation: The International GNSS Service: Any Questions? (PDF)

January 1, 2007 - By

Innovation: The International GNSS Service: Any Questions? (PDF) By Angelyn W. Moore Published: January 2007 GPS World In this month’s column, Angelyn Moore, the IGS Central Bureau’s deputy director, overviews the organization’s service, history, and future, demonstrating that the IGS is a model of scientific collaboration of which not just the GNSS community but the whole world should be proud.—Richard... read more

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Update: GNSS Accuracy: Lies, Damn Lies, and Statistics

January 1, 2007 - By

This update to a seminal article first published here in 1998 explains how statistical methods can create many different position accuracy measures. As the driving forces of positioning and navigation change from survey and precision guidance to location-based services, E911, and so on, some accuracy measures have fallen out of common usage, while others have blossomed. The analysis changes further when the constellation expands to ombinations of GPS, SBAS, Galileo, and GLONASS. Software scripts, provided online, help bridge the gap between theory and reality. read more

This article is tagged with , and posted in GNSS