As reported by Physics.org: China launched two new satellites into space Saturday, state media reported, as it builds a homegrown satellite navigation system to rival the US's Global Positioning System.
A rocket carrying the satellites was launched from the Xichang Satellite Launch Center in southwestern Sichuan province at 8:29 pm (12:29 GMT), the official Xinhua news agency said.
The satellites are the 18th and 19th launched by China as it develops its domestic navigation system Beidou, or Compass. They take the total number launched this year to three.
Beidou is currently centred on the Asia Pacific region but is slated to cover the whole world by 2020.
"The successful launch marks another solid step in building Beidou into a navigation system with global coverage," the satellite launch centre was quoted by Xinhua as saying.
Beidou—named after the Chinese term for the plough or Big Dipper constellation—was announced in 2012, joining the US's GPS, Russia's GLONASS and European Union's Galileo.
The new satellites will be deployed in "testing a new type of navigation signalling and inter-satellite links" as well as providing navigation services, Xinhua said.
The Beidou system is currently used for civilian services such as navigation and messaging, as well as in the transportation and weather forecasting sectors. It also has military applications.
The Beidou system is one of several GPS like systems deployed from various countries around the world. While the US Global Positioning System was the first and most widely used system, the Russian GLONASS system has been operating for several years as well.
The EU is currently deploying their version called the GALILEO system. Japan has deployed the Quazi-Zenith Satellite System (QZSS), a regional tracking system which only covers parts of Asia. India too is deploying a regional navigation satellite system called the (IRNSS).
Tracking devices that use multiple satellite systems have some advantages over individual or dedicated satellite tracking devices, including redundancy and potential higher position accuracy. Providers such as the Swiss u-blox can provide devices that will use multiple satellite systems in order to provide higher accuracy positioning for items like cell-phones that can allow for greater E911 location services.
Satellite systems have been known to go down for periods of time. The Russian GLONASS system suffered a system wide outage in 2014.
In spite of the advantages of using multiple systems, out of concern the FCC in 2014 issued a requirement that all multi-constellation receivers certified for U.S. use ensure that non-GPS constellations were properly licensed in the United States, in spite of the fact that many have been in operation for several years prior to the proclamation.
|A typical Chinese GPS jamming device|
for use in a vehicle. They are illegal to
purchase or use in the USA.
Concerns over interference and potential jamming and 'spoofing' of GPS signals has also prompted the US and the EU to begin deployment of eLoran systems in critical locations throughout the world as a backup to GPS location technology.
The eLoran and GPS systems have come full circle as GPS was designed to provide higher precision location throughout the world by replacing antiquated Loran marine location technology. Now eLoran technology is coming back to potentially rescue the satellite navigation and location technology which has become so critical to daily life throughout the world.