Today's civil engineers rely on satellite navigation and positioning technology to perform surveys and develop topographic maps. One vital tool, real-time kinematic systems, uses a single receiver with mobile units to compare an engineer’s data with the base station. Network RTK extends this to larger areas and involves multiple reference stations and one data processing center. The Continuously Operating Reference Stations network was developed in the United States in the 1990s to provide global navigation satellite system data to support 3D positioning, meteorology, space weather, and geophysical applications. CORS enables users to conduct high-precision positioning combining the network data with their own location information. Currently the United States has 2,400 CORS stations, and there are well established networks in Canada, Japan, and Germany. China began constructing their own CORS, which is called Ground-based Augmentation System or GAS, in 2014 and now has more than 2,000 reference stations across mainland China.

In their new work, “The Development and Performance Assessment of China’s CORS,” published in the Journal of Surveying Engineering, researchers Cheng Liu, Weiguang Gao, Lianjiang Jiang, Fu Zheng, Jun Lu, Hongliang Cai, and Lei Chen provide a comprehensive introduction to GAS. The authors describe its main composition and architecture, detail its performance specifications and format of data products, and lastly evaluate the positioning performance. Learn more about GAS, including an evaluation of the wide-area augmentation service, regional augmentation service, and postprocessing data service in their paper at The abstract is below.


Since 2014, China has embarked on the process of building its own national continuously operating reference system (CORS), called the ground-based augmentation system (GAS), as one of the seven planning services of the BeiDou global navigation satellite system (BDS-3). The performance specifications for GAS were released, and the system has begun to render open services formally in May 2021. This paper involves a comprehensive introduction to GAS, from the aspects of its system composition, reference time system, and coordinate reference frame. The performance specifications and service products of GAS are presented and discussed. Performance tests of GAS services including wide-area and regional real-time augmentation positioning service and postprocessing data service were been carried out. The results show that wide-area real-time augmentation positioning service can realize meter-level to decimeter-level positioning for pseudo-range and carrier-phase positioning, respectively, while for regional real-time service, it can provide centimeter-level positioning within seconds, for postprocessing data service, it can realize millimeter-level positioning in mainland China. Overall, the performance test results of GAS service show that the service performance can well meet the design requirements and indicate the broad application prospects of GAS in the future.

Learn more about China’s CORS and its pros and cons versus the U.S. system: