美国三维坐标基准现代化新进展

随着空间大地测量技术的发展和对高精度参考系统的迫切需求，美国国家大地测量局（NGS）计划对美国国家空间参考系（NSRS）进行现代化。本文主要介绍了提出并采用板块固定参考框架的理由，并根据NGS的NSRS现代化蓝图阐述了三维坐标基准现代化的基本策略及特点。新的三维坐标基准相比现有的NAD83，主要改进为：①采用了“板块固定”策略，板块参考框架由3个增加至4个；②参考框架实现将主要依靠主动控制点（连续运行基准站），被动控制点仅充当补充和辅助角色；③将提供框架内速度场模型。目前各板块框架板块旋转的欧拉极点和框架内速度场模型还需进一步确定。

Recent progress of the three-dimensional coordinate datum modernization in the United States

With the development of geodetic technology and the increasing demand for high-precision reference system, the National Geodetic Survey(NGS) plans to modernize the National Space Reference System (NSRS). This paper mainly introduces the reason of using plate fixed reference frame, and summarizes the basic strategy and characteristics of the three-dimensional coordinate datum modernization according to the blueprint for 2022. Comparing with the existing NAD83, the new datum is mainly improved as follows: ① Adopting the strategy of “plate fixed”, the number of plate reference frames is increased from 3 to 4. ② The reference frame mainly relies on active control points(CORS), and passive control will be reduced to secondary access. ③ The intra-frame velocity model(IFVM) will be provided. In addition, the Euler pole and IFVM need to be further determined.