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Old 07-09-2019, 08:14 AM
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Join Date: Jun 2000
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Huh? Navstar/GPS is the oldest GNSS satellite constellation- the first launch was in 1978, and full coverage was achieved in 1995. GLONASS is slightly newer, but works in essentially the same way as GPS (as do all GNSS systems really), with the main differences being in the technical details of frequencies, etc...

GALILEO is the EU equivalent, and is slightly more accurate with its single-frequency signal- roughly 1 meter accuracy vs. the 3 meter GPS/GLONASS accuracy. Of course all 3 are significantly more accurate when their dual-frequency signals are used.

BEIDOU is the Chinese equivalent, and is more comparable with GPS/GLONASS.

QZSS is a Japanese GPS enhancement for their piece of Asia and the Pacific- receivers using both GPS and QZSS can get 0.1 meter accuracy.