4.6 What Other GNSS Are There Beyond GPS?

This chapter has been devoted to GPS: the way it operates, the types of errors it’s liable to make, and how its accuracy issues can be resolved. However, as we touched on earlier, “GPS” properly refers to the U.S. NAVSTAR GPS. Other countries have developed (or are in the process of developing) their own versions of GPS or GPS augmentation systems, presumably so as not to be completely dependent on U.S. technology. There are other full constellations of GPS-style satellites being developed and put into orbit, and numerous other enhancement systems either in operation or in the planning stage all around the globe.

GLONASS was the name of the USSR’s counterpart to GPS and operated in a similar fashion. The GLONASS equivalent to the C/A code operated at horizontal accuracies of about 100 meters (or better) with an equivalent of the P code for more accurate use. GLONASS consisted of a full constellation of satellites with an orbital setup similar to GPS. By 2001, however, there were only a few GLONASS satellites in operation. In recent years Russia has renewed its GLONASS program, and by the end of 2011 a full operational constellation was in place, and there are plans to launch additional satellites in the near future. In 2007, Russia announced that the civilian signal from GLONASS would be made freely available for use, and at the time of writing GLONASS accuracy was reported to be approximately 5 meters.

Galileo is the European Union’s version of GPS. When it’s completed, it will have a constellation of 30 satellites and operate in a similar fashion to GPS. The first of the GIOVE (Galileo In Orbit Validation Element) satellites was launched in 2005, and since then the program has continued to develop (at the time of writing it was projected to be completed by 2019). Galileo promises four different types of signals, including information available to civilians as well as restricted signals. Also in development is China’s version of GPS, Compass (also referred to as Beidou-2), which is also projected to have a full constellation of satellites. The first Compass satellite was launched in 2007, and at the time of writing the system is expected to be servicing the Asia/Pacific region by 2013, and in service globally by 2020.

Other Satellite Based Augmentation Systems have been developed across the world to operate like WAAS but to function in regions outside of North America. EGNOS (European Geostationary Navigation Overlay System) is sponsored by the European Union, and provides improved accuracy of GPS throughout most of Europe. EGNOS functions the same way WAAS does—a series of base stations throughout Europe monitor GPS satellite data, calculate corrections, then transmit these corrections to geostationary EGNOS satellites over Europe, which in turn broadcast this data to Earth. An EGNOS-enabled receiver is necessary to utilize this correction data, and the system is capable of accuracies of about 1.5 meters. Japan also operates its own SBAS, known as MSAS (Multifunctional Satellite Augmentation System), which covers Japan and portions of the Pacific Rim. MSAS operates in a similar way to WAAS and EGNOS, but it covers a different region of the world and uses just two satellites to provide coverage.

Many other GPS enhancement systems exist or are in development throughout the world, including the following:

• Beidou—an SBAS operating in China
• GAGAN—an SBAS in development for India
• IRNSS—an Indian satellite navigation system, consisting of seven satellites, currently in development
• QZSS—an expanded SBAS based in Japan, currently in development