High Precision ZTD Model for the Chinese Southeast Region Using ERA5 Reanalysis Data

Improving the accuracy of troposphere Zenith Total Delay (ZTD) is essential in Global Navigation Satellite System (GNSS). In this study, a high precision ZTD model for Chinese Southeast region is constructed by the ERA5 reanalysis data, considering the relationship between ZTD and elevation mainly shows a negative exponential form and the ZTD at a certain elevation has a significant periodicity. Therefore, combining the periodicity of ZTD at the Mean Sea Level (MSL) with the elevation normalization factor, the ZTD of test stations can be acquired by restoring the grid ZTD to the same elevation with test stations. The ZTD derived from the static PPP (Precise Point Positioning) solutions in 2022 of CMONOC (Crustal Movement Observation Network of China) was used as the reference value to measure the accuracy of the model, and the error RMS (Root Mean Square) of the test stations was in the range of 1.73 cm ~ 5.12 cm, and the MAE (Mean Absolute Error) was in the range of 1.40 cm ~ 4.33 cm. The total error RMS is 3.39 cm and the MAE is 2.53 cm. This model fully takes the variability of ZTD with elevation in different latitude and longitude regions into account, and can meet the troposphere delay correction needs of regional GNSS navigation and positioning.