基于GNSS的CGCS2000数据处理技术综述

An Overview of the CGCS2000 Coordinate Processing Technique Based on GNSS

  • 摘要: 2000国家大地坐标系(CGCS2000)发布后的推广使用不仅涉及大量参心坐标系下的成果转换,同时也涉及基于全球导航卫星系统(Global Navigation Satellite System,GNSS)手段获得的点位坐标的归算。获取GNSS观测数据和将其归算到CGCS2000采用的策略方法不同,如参考站选择原则不同,整网平差前的分区方案不同以及采用不同的方法将位置从当前历元改正到CGCS2000等,将会使最终的CGCS2000系下的坐标差异较大,最大可达到分米级。造成这种结果的原因在于GNSS数据处理的多个环节中依赖数据处理软件操作者的理解,存在人为的选择,换言之,GNSS数据处理缺乏科学的规则为依据。鉴于此,采用一种统计方法,即监督聚类作为参考站选择规则;采用间距分区法进行区域划分;并用板块运动归算方法将当前历元位置改正到CGCS2000。其中基于间距分区方案的站坐标解算精度优于区域划分方案,三维方向的坐标精度优于2 mm。通过以上方案设计,XYZ方向上的速度从0.92、0.72、0.97 mm/a分别降至0.19、0.45、0.32 mm/a,优化和改进了CGCS2000框架维持精度。

     

    Abstract: The CGCS2000 (China Geodetic Coordinate System 2000) was first released on July 1 in 2008. After that, all location-based GNSS (global navigation satellite system) applications are required to be processed and corrected to CGCS2000. As a matter of fact, big differences exist when different implementation strategies or schemes are adopted, such as reference station selection rules, area partition scheme, and different epoch correction methods et al. All of the above-mentioned factors lead to different results. Some of the differences even reach decimeter level. For instance, the coordinate differences based on plate movement correction with velocity field and the quasi-stable adjustment under CGCS2000 may reach decimeter level. The reason why there exists so big differences in coordinate solutions is the fact that the solution depends on a person's different understanding in various choices by the software. In another word, GNSS data processing is lack of detailed guidance from technical standard. In this paper, a statistic method is proposed. Firstly, supervised clustering is proposed as the rule for reference station selection, Secondly a so-called Spacing Zoning method is used for area partition which is a necessary step facing at a large network. And thirdly a plate movement correction method is applied for correcting position from current epoch to epoch 2000. The station coordinate based on the spacing partition scheme is better than that of the regional dividing scheme, and the coordinate precision of the three-dimensional direction is better than 2 mm. Through the reasonable optimization strategy, the root mean squares of the velocity derived in X, Y, Z directions are reduced from 0.92, 0.72, 0.97 mm/a to 0.19, 0.45, 0.32 mm/a respectively. All of these methods used here obviously have improved the CGCS2000 frame maintenance accuracy.

     

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