Establishment of Vertical Movement Model of Chinese Mainland by Fusion Result of Leveling and GNSS

  Objectives  The leveling and GNSS (global navigation satellite system) results are provided important data for studying the vertical movement in Chinese Mainland. Give full play to the advantages of high precision leveling points and uniform distribution of GNSS points and help improve the reliability of the vertical movement model. In the process of fusion, the lack of coincidence points between leveling and GNSS causes joint adjustment of velocity fusion to fail, a fusion method based on final model is proposed.

  Methods  First, we establish respective vertical movement model by leveling and GNSS with the method of inverse distance to a power. Second, we fuse two types of models by weighted average according to the grid point precision and nearest point principle depending on the distance between grid point and measured point. Aiming at the problem that the weight associated with the distance and the velocity precision affects the final model when inverse distance weighted is applied, a method of multiplying the weight is proposed to determine reasonable weight value for each factor.The vertical movement model of Chinese Mainland is established by using the national first order leveling result, national GNSS geodetic control network and so on. In order to measure the improvement of GNSS results on the vertical movement model, we utilize 20% of the modeling points selected from leveling and GNSS points uniformly to statistics the precision of leveling and fused vertical movement model.

  Results  The results show that the fused vertical movement model has increased by 35.3% in Qinghai Tibet region, 53.6% in other regions of Chinese Mainland and 50.8% in Chinese Mainland. The subsidence of North China Plain and Jiangsu-Shanghai areas are severe, where the velocity of individual areas is up to 100 mm/a, the North-East of China and Tibet areas show a rising trend, and the velocity exceeds 5 mm/a in local area, the vertical movement in other areas is relatively stable.

  Conclusions  Therefore, GNSS results can improve the precision and accuracy of the leveling vertical movement model, which is especially obvious inside the leveling loop. The single-source data vertical movement model is established based on the method of multiplication of two factors, and the fused vertical movement model of Chinese Mainland is established by the method of the result fusion.