Velocity estimation performance of GNSS online services (APPS and AUSPOS)

Before now, the various studies that have been undertaken to investigate the positioning performance of GNSS Online Services have been limited with regard to both time and number of sessions. Within the scope of this study, the accuracy of the velocity models estimated by APPS and AUSPOS are analysed using a wider period. Local ISKI CORS Network stations are used as the subject. To generate true values for an accurate comparison, 129 sessions with BERNESE (v5.2) software were conducted between 2008 and 2019. A linear trend was determined by using least-squares adjustment to obtain true velocity values. To test the reliability of the true velocity values, seasonal, semi-annual and annual oscillation movements have been examined. Additionally, the coherence of the velocity model with the sample data and compliance with the tectonic plate has been investigated. For GNSS Online Services, 34 sessions were carried out over the same timescale, and the velocity model was estimated. AZ-test with a 0.05 significance level was used to examine the performance of APPS and AUSPOS velocity values. As a result, the estimated true velocity model shows high compliance with sample data and the tectonic plate; no seasonal, semi-annual or annual oscillation movements were identified. According to the study's statistical test, the velocity model of APPS solutions performs slightly better than that of AUSPOS. However, both services show high performance in the velocity determination. In summary, the usability of GNSS Online Services in determining velocity has been shown with this study.