PPP-derived tropospheric ZWD augmentation from local CORS network tested on bridge monitoring points

This paper developed the tropospheric correction augmented PPP for the purpose of bridge displacement monitoring. ZWD is estimated from undifferenced observations collected by UK CORS, and further applied to augment PPP client for displacement at the bridge surveying points. Coordinate time series obtained by GPS DD are treated as the true bridge displacement, which is used to assess the standard and CORS ZWD augmented PPP solutions obtained by varying cutoff angles. The experimental results reveal that the displacement precision of standard PPP severely depends on the satellite geometry. Meanwhile, the CORS ZWD augmented PPP results are less affected. The RMSE of improved PPP time series in the vertical component drops by 12%, 49% and 66% for the 5°, 10° and 15° cutoff angle cases, respectively. CORS ZWD augmented PPP can improve the monitoring precision and eliminate irregular displacement time series due to poor satellite geometry.