Very interesting article in the latest "Inside GNSS" magazine.
Researchers in Australia are checking out Single Frequency L5 RTK.
Let me give some background. 12 GPS 2F satellites are in orbit broadcasting in the L5 frequency. 12 means interesting but not quite useful for GPS location here in the United States. But it seem the world is well ahead of the US. The L5 frequency is broadcast by Galileo (12 satellites to date), the Quazi-Zenith Satellite System (3) and Indian Regional Navigation Satellite System (7). 34 satellites makes a very useful system.
Galileo satellites are in some what similar to GPS orbits, but the real advantage comes from QZSS AND IRNSS which are SBAS (Space Based Augmentation Systems) which broadcast their own corrections).
QZSS is a Japanese system. The 3 satellites are in geosynchronous orbits at 135å¡ guaranteeing a satellite over Japan at any one time. Since Australia is due South from Japan they serve there equally well.
IRNSS is an Indian system with 3 geostationary satellites are 32.5å¡, 83å¡ (mid longitude of India) and 129.5å¡. The other 4 are geosynchronous orbits, 2 each at 55å¡ and 112å¡.
GPS L1 RTK is improved by including L1 ranging from the L1 correction signals from 1 or 2 WAAS (SBAS) satellites with brodcast corrections.
What the Australians are testing is a single frequency L5 only receiver using GPS and Galileo L5 only plus ranging from as many of the 10 geostationary or geosynchronous satellites as possible. I estimate a minimum of 4 or 5 at all times. Using the 4 galaxies they are getting almost instantaneous "Integer Ambiguity" fixes with a single frequency.
The bottom line is RTK from low cost single frequency receivers not only under canopy but possibly inside buildings.
Doing the math it appears that two of the geosynchronous satellites from IRNSS are well positioned to also be used in Japan.
I have little information on any well organized plans for the US to launch or do anything similar at this time.
Paul in PA
