天顶对流层产品发布时间分辨率的确定

IGS分析中心发布的天顶对流层产品（zenith tropospheric delay，ZTD）的时间分辨率为5 min、1 h和2 h，高时间分辨率ZTD产品能有效提高相关应用精度并拓展应用领域，但ZTD产品发布的时间分辨率作为数据资源属性缺乏规范化研究。鉴于此，首先利用历元差分和区间拟合研究ZTD产品的时变统计特征，其次利用L-S频谱分析法分析ZTD短周期特性，同时结合奇异值分解法研究不同时间分辨率ZTD数据矩阵的奇异值比特征。通过多种方法计算结果的比较，ZTD产品发布的合理时间分辨率建议为30 min。

Determining Reasonable Time Resolution of Zenith Tropospheric Delay Products

The tropospheric delay is an important GNSS error source. To reduce this error, the zenith tropospheric delay (ZTD,with 5 min, 1 h, and 2 h time resolution) produced by IGS analysis centers is widely used for satellite navigation andpositioning. However, the reasonable or normalized time resolution of ZTD product treated as one data resource is lacking in theoretical and experimental research. On one hand, high time resolution can improve the modeling accuracy of related applications. On the other hand, it could lead to both large redundant data for storage and time consuming for processing when modeling accuracy approaches nominal accuracy. Thus, the reasonable time resolution of ZTD should be investigated by understanding the advantages and disadvantages. Firstly, this paper analyzed the variation of the ZTD in detail using the epoch-differenced method and interval fitting method. Secondly, the periodicity of the 5-min ZTD was analyzed using L-S spectrum analysis. Then, the singular value decomposition algorithm was employed to extract the singular value ratio of ZTD data matrix with different time resolution and determine the reasonable time resolution of the ZTD products. Finally, it was suggested that the reasonable time resolution is normalized by 30 minutes. The results can also be used as reference for the international GNSS service(IGS).