China has launched another two satellites as part of its Beidou satellite navigation system.
A rocket left the Xichang Satellite Launch Center in southwest China's Sichuan Province on Saturday night with the 18th and 19th satellites to be deployed.
Beidou is currently centered on the Asia Pacific region but is expected to cover the entire globe by 2020.
"The successful launch marks another solid step in building Beidou into a navigation system with global coverage," the satellite launch center said.
Beidou — named after the Chinese term for the Big Dipper, or plough, group of stars — was up and running in 2012, joining the United States' GPS, Russia's GLONASS and European Union's Galileo systems.
The project began in 1994, but it was not until 2000 that the first satellite was launched. By 2012, a regional network had taken shape, with the system providing navigation and short message services in China and several other Asian countries.
The plan is for 35 navigation satellites to be operational by 2020.
The new satellites will be deployed in "testing a new type of navigation signalling and inter-satellite links" as well as providing navigation services, the center said.
The Beidou system is currently used for civilian services such as navigation and messaging, as well as in transport and weather forecasting. It also has military applications.
Xie Jun, the project's chief engineer, said the latest satellites are designed to be "trail blazers" as the system expands.
"We have deployed a new type of signal format for the 'twin sats', which enable us to double the data exchanged between satellites within the same period of time. That means a faster and better service," Xie said.
Inter-satellite links will allow Beidou satellites to connect with their GPS and GLONASS counterparts. "The compatibility edge allows clients to use GPS data for corrections in positioning in order to improve service accuracy and convenience," Xie said.
"Though we started late, the Beidou system can now almost rival any foreign counterparts in terms of general performance. In fact, we might even have a little edge in the fields of regional enhanced services, positioning reports and short message services," he said.
Xie said 98 percent of the new satellites' components were made in China.
"When we first started the Beidou project, China was not at the time technologically equipped to manufacture much-needed items of technical sophistication, so we had to buy them from other countries," he said.
Scientists have gradually substituted foreign parts with domestic ones, Xie said.
