一、发展目标与原则
I. Goals and Principles of Development
中国高度重视北斗系统建设，将北斗系统列为国家科技重大专项，支撑国家创新发展战略。
China lays store by the construction of the BDS, ranking it one of its national key technical projects that supports its innovative development strategy.
（一）发展目标
(I) Goals of Development
建设世界一流的卫星导航系统，满足国家安全与经济社会发展需求，为全球用户提供连续、稳定、可靠的服务；发展北斗产业，服务经济社会发展和民生改善；深化国际合作，共享卫星导航发展成果，提高全球卫星导航系统的综合应用效益。
Building a world-class navigation satellite system to meet the needs of the country’s national security as well as economic and social development, and providing continuous, stable and reliable services for global users; developing BDS-related industries to support China’s economic and social development, as well as improvement of people’ s living standards; and enhancing international cooperation to share the fruits of development in the field of satellite navigation, increasing the comprehensive application benefits of Global Navigation Satellite System (GNSS).
（二）发展原则
(II) Principles of Development
中国坚持“自主、开放、兼容、渐进”的原则建设和发展北斗系统。
China upholds the principles of “independence, openness, compatibility and gradualness” in the BDS construction and development.
——自主。坚持自主建设、发展和运行北斗系统，具备向全球用户独立提供卫星导航服务的能力。
– By “independence,” it means to uphold independent construction, development and operation of the BDS, and acquire the capability to independently provide satellite navigation services to global users.
——开放。免费提供公开的卫星导航服务，鼓励开展全方位、多层次、高水平的国际合作与交流。
– By “openness,” it means to provide open satellite navigation services free of charge, and encourage all-scale, multilevel and high-quality international cooperation and exchange.
——兼容。提倡与其他卫星导航系统开展兼容与互操作，鼓励国际合作与交流，致力于为用户提供更好的服务。
– By “compatibility,” it means to enhance BDS compatibility and interoperability with other navigation satellite systems, and encourage international cooperation and exchanges, so as to provide better services to users.
——渐进。分步骤推进北斗系统建设发展，持续提升北斗系统服务性能，不断推动卫星导航产业全面、协调和可持续发展。
– By “gradualness,” it means to carry out the BDS project step by step, enhance BDS service performance, and boost the development of satellite navigation industry in a comprehensive, coordinated and sustainable manner.
二、持续建设和发展北斗系统
II. Development of the BDS
中国始终立足于国情国力，坚持自主创新、分步建设、不断完善北斗系统。
Based on its national conditions, China has independently developed the BDS step by step with constant improvement.
（一）实施“三步走”发展战略
(I) Three-Step Strategy of Development
——第一步，建设北斗一号系统（也称北斗卫星导航试验系统）。1994年，启动北斗一号系统工程建设；2000年，发射2颗地球静止轨道卫星，建成系统并投入使用，采用有源定位体制，为中国用户提供定位、授时、广域差分和短报文通信服务；2003年，发射第三颗地球静止轨道卫星，进一步增强系统性能。
– The first step is to construct the BDS-1 (also known as BeiDou Navigation Satellite Demonstration System). The project was started in 1994, and the system was completed and put into operation in 2000 with the launching of two Geostationary Earth Orbit (GEO) satellites. With an active-positioning scheme, the system provided users in China with positioning, timing, wide-area differential and short message communication services. The third GEO satellite was launched in 2003, which further enhanced the system’s performance.
——第二步，建设北斗二号系统。2004年，启动北斗二号系统工程建设；2012年年底，完成14颗卫星（5颗地球静止轨道卫星、5颗倾斜地球同步轨道卫星和4颗中圆地球轨道卫星）发射组网。北斗二号系统在兼容北斗一号技术体制基础上，增加无源定位体制，为亚太地区用户提供定位、测速、授时、广域差分和短报文通信服务。
– The second step is to construct the BDS-2. The project was started in 2004, and by the end of 2012 a total of 14 satellites – 5 GEO satellites, 5 Inclined Geosynchronous Satellite Orbit (IGSO) satellites and 4 Medium Earth Orbit (MEO) satellites – had been launched to finish the space constellation deployment. Based on a technical scheme which was compatible with the BDS-1, the BDS-2 added the passive-positioning scheme, and provided users in the Asia-Pacific region with positioning, velocity measurement, timing, wide-area differential and short message communication services.
——第三步，建设北斗全球系统。2009年，启动北斗全球系统建设，继承北斗有源服务和无源服务两种技术体制；计划2018年，面向“一带一路”沿线及周边国家提供基本服务；2020年前后，完成35颗卫星发射组网，为全球用户提供服务。
– The third step is to construct the BDS. The project was started in 2009 to inherit the technical schemes of both active and passive services. The goal is to provide basic services to the countries along the Belt and Road and in neighboring regions by 2018, and to complete the constellation deployment with the launching of 35 satellites by 2020 to provide services to global users.
（二）北斗系统的基本组成
(II) Main Composition of the BDS
北斗系统由空间段、地面段和用户段三部分组成。
The BDS is mainly comprised of three segments: space segment, ground segment and user segment.
——空间段。北斗系统空间段由若干地球静止轨道卫星、倾斜地球同步轨道卫星和中圆地球轨道卫星三种轨道卫星组成混合导航星座。
– The space segment. The BDS space segment is a hybrid navigation constellation consisting of GEO, IGSO and MEO satellites.
——地面段。北斗系统地面段包括主控站、时间同步/注入站和监测站等若干地面站。
– The ground segment. The BDS ground segment consists of various ground stations, including master control stations, time synchronization/uplink stations, and monitoring stations.
——用户段。北斗系统用户段包括北斗兼容其他卫星导航系统的芯片、模块、天线等基础产品，以及终端产品、应用系统与应用服务等。
– The user segment. The BDS user segment consists of various kinds of BDS basic products, including chips, modules and antennae, as well as terminals, application systems and application services, which are compatible with other systems.
（三）北斗系统的发展特色
(III) Characteristics of the BDS
北斗系统的建设实践，实现了在区域快速形成服务能力、逐步扩展为全球服务的发展路径，丰富了世界卫星导航事业的发展模式。
The BDS development follows a model of developing regional service capacities, then gradually extending the service globally. This practice has enriched the development models for navigation satellite systems worldwide.
北斗系统具有以下特点：一是北斗系统空间段采用三种轨道卫星组成的混合星座，与其他卫星导航系统相比高轨卫星更多，抗遮挡能力强，尤其低纬度地区性能特点更为明显。二是北斗系统提供多个频点的导航信号，能够通过多频信号组合使用等方式提高服务精度。三是北斗系统创新融合了导航与通信能力，具有实时导航、快速定位、精确授时、位置报告和短报文通信服务五大功能。
The BDS possesses the following characteristics: First, its space segment is a hybrid constellation consisting of satellites in three kinds of orbits. In comparison with other navigation satellite systems, the BDS operates more satellites in high orbits to offer better anti-shielding capabilities, which is particularly observable in terms of performance in the low-latitude areas. Second, the BDS provides navigation signals of multiple frequencies, and is able to improve service accuracy by using combined multi-frequency signals. Third, the BDS integrates navigation and communication capabilities for the first time, and has five major functions - real-time navigation, rapid positioning, precise timing, location reporting and short message communication services.
（四）持续提升北斗系统性能
(IV) Improvement of BDS Performance
为满足日益增长的用户需求，北斗系统将加强卫星、原子钟、信号体制等方面的技术研发，探索发展新一代导航定位授时技术，持续提升服务性能。
To meet the increasing user demand, BDS technical research and development in the areas of satellites, atomic clocks and signals will be strengthened, and a new generation of navigation, positioning and timing technologies will be explored to improve service performance.
——提供全球服务。发射新一代导航卫星，研制更高性能的星载原子钟，进一步提高卫星性能与寿命，构建稳定可靠的星间链路；增发更多的导航信号，加强与其他卫星导航系统的兼容与互操作，为全球用户提供更好的服务。
– Providing global services. China will launch new-generation navigation satellites, develop airborne atomic clocks with enhanced performance, further improve the performance and lifetime of satellites, and build more stable and reliable inter-satellite links. It will broadcast additional navigation signals, and enhance the compatibility and interoperability with other navigation satellite systems, so as to provide better services for global users.
——增强服务能力。大力建设地面试验验证系统，实现星地设备全覆盖测试验证；持续建设完善星基和地基增强系统，大幅提高系统服务精度和可靠性；优化位置报告及短报文通信技术体制，扩大用户容量，拓展服务区域。
– Strengthening service capabilities. China will establish a grounded test and validation bed to accomplish the full coverage of tests and validation for space and ground equipment; continue to build and improve satellite based and ground based augmentation systems to substantially enhance BDS service accuracy and reliability; optimize the technical system of location reporting and short message communication to expand user volume and service coverage.
——保持时空基准。北斗系统时间基准（北斗时），溯源于协调世界时，时差信息在导航电文中发播；推动与其他卫星导航系统开展时差监测，提高兼容与互操作。发展基于北斗系统的全球位置标识体系，推动北斗系统坐标框架与其他卫星导航系统的互操作，并不断精化参考框架。
– Maintaining spatio-temporal reference. The BDT is related to the Coordinated Universal Time, and the time bias information is broadcast in the navigation message. China will push forward the clock bias monitoring with other navigation satellite systems, and improve their compatibility and interoperability. It will develop a BDS-based worldwide location identification system, increase the interoperability between BDS coordinate frame and that of other navigation satellite systems, and constantly refine the reference frame.
