Assessing the performance of Vienna Mapping Functions 3 for GNSS stations in Indonesia using Precise Point Positioning

Abstract

Abstract. Tropospheric delay is one of the major error sources for space geodetic techniques, such as the Global Navigation Satellite Systems (GNSS). Mapping functions are used to scale the delay from zenith direction to the elevation angle of the signal. Several mapping functions have already been published, including the Global Mapping Functions (GMF) and Vienna Mapping Functions 1 (VMF1). Recently, a refined version of VMF1, VMF3, was released. The tropospheric gradients GRAD were also determined using the same data set as VMF3. This study aims to test the performance of VMF3 on GNSS observations in Indonesia, using observations from 21 stations of the permanent GNSS network in Indonesia, InaCORS. Data processing was carried out using Precise Point Positioning in Bernese GNSS Software, version 5.2 for the year 2014. Station coordinates were estimated daily, while the zenith wet delays were estimated every 30 min and tropospheric gradients were estimated hourly. A similar processing scheme was carried out using GMF and VMF1. Generally, the results from VMF3 agree very well with the results from GMF and VMF1, although small biases can be found, especially for the height component. Based on the repeatability, while there is no significant difference for the latitude and longitude, there are slight improvements for the height, particularly compared to GMF. The estimated gradients tend to fluctuate more compared to gradients from GRAD. The correlation coefficients between the estimated gradients and those from GRAD are small, with the largest being 0.65 at site CUKE.

Evaluation of Zenith Tropospheric Delay Derived from Ray-Traced VMF3 Product over the West African Region Using GNSS Observations

“…For the PPP technique, ZTD is estimated using the GNSS observation equation of the ionosphere-free linear code and phase combinations and all needed ancillary information as follows [38,48]:…”

“…e Vienna Mapping Function (VMF) service (https://vmf.geo.tuwien.ac.at/) provides both gridded and sitewise ray-traced VMF1 and VMF3 tropospheric products as open-access data for global and more than 500 IGS stations users. ey are generated based on raytraced delays at 3°elevation using NWP model data spanning 2001 to 2010 from the European Centre for Medium-Range Weather Forecasts (ECMWF) ERA-40 and ERA-Interim reanalysis data, respectively [38]. ey are provided every 6 hours daily at four epochs (00, 06, 12, and 18 UT) and at 23 h UT the next day [51].…”

“…e results showed that the VMF1-FC model outperformed the GPT2 and GPT2w models and recommended its implementation in real-time GNSS applications for modelling tropospheric delays. Putri et al [38] assessed the performance of VMF3-mapping function for GNSS stations in Indonesia using PPP. Compared to VMF1 mapping function and Global Mapping Function (GMF), the results showed comparable performance for the VMF3 and VMF1 mapping functions.…”

Regression models for predicting daily IGS zenith tropospheric delays in West Africa: Implication for GNSS meteorology and positioning applications

“…The VMF service (https://vmf.geo.tuwien.ac.at/) provides both gridded and site-wise ray-traced VMF1 and VMF3 tropospheric products as open access data for global and more than 500 IGS site users. They are generated based on ray-traced delays at 3 elevation using NWM data spanning 2001-2010 from the ECMWF ERA-40 and ERA-Interim re-analysis, respectively (Putri et al, 2020); and are provided every 6 h daily at four epochs (00, 06, 12 and 18 UT) and 23 h UT the next day . VMF3 is the successor of VMF1 realized on both 1 Â 1 and 5 Â 5 global grids (Landskron & Böhm, 2018).…”