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Assisted GPS and location-based services
Article By:
van Diggelen, Frank Broadcom Corporation, Santa Clara, California.
Last reviewed:2009
DOI:https://doi.org/10.1036/1097-8542.YB094020
As recently as 2004, the Global Positioning System (GPS) receiver most widely used by the U.S. military was the PLGR (Precision Lightweight GPS Receiver). It is a five-channel receiver that operates on only one of the three GPS frequencies (L1), has a typical start-up time of over a minute, and costs about $2000. The PLGR receives encrypted military signals, is waterproof, and weighs about 1.4 kg (3 lb), making it far more rugged than any modern mobile telephone. But many of those mobile phones today have 12-channel A-GPS (Assisted GPS), which can compute a position within a second and acquire satellite signals that are more than 100 times weaker than can be acquired by the PLGR, and which adds less than $5 to the cost of the phone.
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