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RTCM Version 3, initially released in February 2004, [5] is the current and continually evolving version of the RTCM standard. In contrast to 2.3, version 3.x uses a variable-length message format and a single 24-bit cyclic redundancy check (CRC) on the entire message as opposed to a 6-bit parity for every 30-bit word.
The system is an expansion of the previous Maritime Differential GPS (MDGPS), which the Coast Guard began in the late 1980s and completed in March 1999. MDGPS covered only coastal waters, the Great Lakes, and the Mississippi River inland waterways, while NDGPS expands this to include complete coverage of the continental United States. [ 18 ]
StarFire is a wide-area differential GPS developed by John Deere's NavCom and precision farming groups. StarFire broadcasts additional "correction information" over satellite L-band frequencies around the world, allowing a StarFire-equipped receiver to produce position measurements accurate to well under one meter, with typical accuracy over a 24-hour period being under 4.5 cm. StarFire is ...
Decca position coordinates were directly displayed by four decometers and these were plotted on a conventional chart that had been over-printed with Decca lattices. The Decca Navigator System was a hyperbolic radio navigation system that allowed ships and aircraft to determine their position by using radio signals from a dedicated system of ...
The local-area augmentation system (LAAS) is an all-weather aircraft landing system based on real-time differential correction of the GPS signal. Local reference receivers located around the airport send data to a central location at the airport.
This is done by resolving the number of cycles in which the signal is transmitted and received by the receiver. This can be accomplished by using a combination of differential GPS (DGPS) correction data, transmitting GPS signal phase information, and ambiguity resolution techniques via statistical tests, possibly with processing in real time.
Similar service is provided in North America by the Wide Area Augmentation System (WAAS), in Russia by the System for Differential Corrections and Monitoring (SDCM), and in Asia, by Japan's Multi-functional Satellite Augmentation System (MSAS) and India's GPS-aided GEO augmented navigation (GAGAN).