China’s BeiDou edging closer to GPS in accuracy
Accuracy of the constellation of third generation BeiDou satellites being built is in the same league with that of GPS
China’s third-generation BeiDou navigation satellite system has been taking shape with eight satellites already coming online and more scheduled to be put into orbit during the second half of the year.
China Satellite Navigation Office director Ran Chengqi told Xinhua that eight satellites were launched in four pairs since last November and were undergoing in-orbit testing and operational evaluations.
Ten more third-generation BeiDou satellites are on China’s hectic launch schedule for the rest of the year. Nine will be catapulted into the medium Earth orbit and another into geostationary orbit.
Eleven more are in the pipeline to enter space in the coming two years to form a constellation of global coverage by 2020, according to Ran.
The new BeiDou satellites emit strong navigation signals, not only to end receivers on Earth, but also to other satellites to coordinate each other’s position and trajectory.
BeiDou’s positioning accuracy is also set to get a big boost to 2.5 to 5 meters, leveraging more satellites in orbits as well as a network of ground augmentation stations throughout China.
The ultimate goal is “centimeter-level accuracy in navigation and positioning” provided an end user has the latest receiver.
The standard accuracy of GPS services is 3.5 to 5 meters. New GPS receiver devices using the L5 frequency launched in 2018 are expected to have a much higher accuracy than before and a device can be pinpointed within 30 centimeters, or just less than one foot, according to the San Jose, California-based semiconductor behemoth Broadcom, which makes mass-market GPS chips.
Since 2000, when the first BeiDou satellite was placed in orbit, 33 others have been launched. BeiDou started guiding civilian users in China and parts of the Asia-Pacific in December 2012, with worldwide coverage planned by 2020.
Aside from traditional mapping and surveying services, BeiDou has already been providing precise navigation services to smartphones, although many Chinese users may have not yet noticed.
“BeiDou B1 and US GPS L1 work on the same frequency band, and many smartphones on the market nowadays are integrated with chips capable of receiving signals from both,” said a technician with Beijing BDStar Co.
The only difference is if a phone has a built-in US-made chip from Broadcom or Qualcomm, the gadget will give high priority to processing GPS navigational signals rather than that from BeiDou.
Chinese cell phones with domestically-developed chips will give priority to BeiDou and such a priority difference does not necessarily mean that GPS and BeiDou are mutually exclusive, as the more navigation signals there are, the more reliable the positioning service gets.
In May, a subsidiary of the state-owned China Electronics Corp based in China’s booming tech hub of Shenzhen launched an open platform of core algorithm and specifications for BeiDou-based navigation chips.
Dish antennae tailor-made for the BeiDou system developed by a Guangzhou-based private navigation technology firm are now fitted on driverless vehicles in trial runs by Alibaba’s logistic arm Cainiao.