2000国家大地控制网的构建和它的技术进步

Establishment of 2000 National Geodetic Control Network of China and It's Technological Progress

“2000国家大地控制网”是国家大地测量的重大科学工程项目。它主要包括建立2000国家GPS大地控制网,2000国家重力基本网,以及前者与国家天文大地网的联合平差等,以实现国家3维地心坐标系统的坐标框架。这个项目的主要特点有:①涉及多个学科,如经典和空间大地测量学、天文测量学、重力测量学、近代数据处理理论和技术等;②处理的数据量大、种类多,如2000国家GPS大地控制网有2600多个测点,46000多条独立基线,天文大地网与2000国家GPS大地控制网联合平差所需解算的未知数多达15万个;处理的数据几乎包含了三角测量、导线测量、天文测量、重力测量和GPS测量等各类测量的成果;③所处理数据的施测时间跨度长,如2000国家GPS大地控制网中三个子网的施测时间各不相同,前后从1988年到2000年历时12年,而天文大地网的施测时间是在上一世纪的50至70年代;④处理数据所覆盖的国土面积大,2000国家GPS大地控制网及天文大地网覆盖了我国整个大陆及部分沿海岛屿,而2000国家重力基本网则扩展到香港、澳门以及南沙等地区;⑤处理数据需顾及的因素多,如需分析近70年来我国大陆板块运动、板内运动、局部地壳运动和新旧大地测量基准、新旧天文系统、和不同历元对上述这些大地测量观测数据的影响及其统一归算。本项目的主要技术创新点有以下四个方面:①首次将我国不同部门、不同时期施测的多个平面(2维)和高程(1维)分离的大地控制网通过空间大地测量和数据处理技术,科学的整合为全国统一的整体的国家3维大地控制网,将原来大地测量中所采用分离的几何与物理参数,进行了科学的统一的整合;②首次将我国非地心大地坐标框架整体的科学的转换为地心大地坐标框架;③首次将我国大地坐标框架的地心坐标精度由±5 m提高15倍,达到了±0.3 m;将我国重力基本点的精度由±25×10-8ms-2提高近4倍,达到了±7×10-8ms-2;④首次将海量数据由原来采用的最小二乘平差经典数据处理技术提高为最小二乘平差,抗差估计和方差分量估计相结合的现代数据处理技术,提高了成果的精度和可靠性。

2000＇ National Geodetic Control Network of China is an important fundamental scientific engineering project in China. It consists of three parts which are establishment of 2000 National GPS Geodetic Network, its combination adjustment with national astro-geodetic network and 2000 National Gravity Fundamental network. There are five characteristics in the project：① various kinds of scientific branches involved, for example classical geodesy, space geodesy, physical geodesy, astronomy, modern data processing and computer science etc. ②large amount and different sorts data to be processed, ex. 2 600 GPS points, 46 000 geodetic baselines, 259 gravity points, nearly 50 000 geodetic points and 150 000 unknown variables in the combination adjustment of national astro-geodetic network and 2000 national GPS geodetic network.③Long time span of the observed data in these geodetic networks, such as 12 years span of GPS observation data in 2000 national GPS geodetic network, and the national astro-geodetic network was completed almost 30 years ago. ④Large area covered by these geodetic networks, ex. the 2000 national GPS geodetic network and national astro-geodetic network cover most lands and islands of China, while 2000 national gravity fundamental network extends from main land to Hong Kong, Macao and Nansha islands. ⑤Many factors have to be taken into consideration in the data processing, e.g. the influence of crust movement, internal plate movement, and regional deformation on the geodetic data in the networks, the changes of geodetic datum, astronomy constants and epoch effect on the data reduction and processing of the networks. The major innovation of this project is in 3 parts： ①Horizontal and vertical dimensions in national astro-geodetic network were separated from each other. After the combination adjustment with national 2000 GPS geodetic network a unified geocentric 3D coordinates for it was obtained. ②To improve accuracy of geodetic coordinate frame 15 times which is from ±5 m to ±0.3 m and4 times of gravity points which is from ±25×10^-8 ms^-2 to ±7× 10^-8 ms^-2.③ To improve processing technique from classic least-square method to which is combination with least-square, robust estimation and variance component evaluation. The accuracy and reliability of results are enhanced.