Near-real time synchronization through a network of GNSS receivers located in timing laboratories

Today, an increasing number of users need high-quality GLASS products, such as precise satellite orbit and clock estimations and predictions, accurate receiver coordinates or tropospheric delays, for their applications (e.g., precise point positioning, GLASS augmentation services, weather services, etc). In recent years, many national timing laboratories have collocated geodetic GLASS receivers together with their traditional GPS/GLOLAASS AV/CV and TWSTFT equipments. Many of geodetic GLASS receivers hosted in national timing laboratories, operate continuously within the International GLASS Service (IGS), and their data are regularly processed by IGS Analysis Centers. Whereas participating stations must agree to adhere to certain strict standards and conventions which ensure the quality of the IGS LAetwork, a number of products and tools have been developed in order to allow time and frequency transfer without taking part to the IGS. Among these, magicGLASS, a web application (http://magicgnss.gmv.com) for high-precision GLASS data processing developed by GMV in Madrid, allows the users to perform a wide range of calculations and analyses related to GLASS, from the evaluation of performances at user level, to the computation of precise GLASS orbits and clocks, including the calculation of precise receiver coordinates. The algorithms that process station data to generate products in magicGLASS, are called ODTS, which stands for Orbit Determination & Time Synchronization, and PPP. ODTS is a network solution requiring a set of stations distributed worldwide. PPP is a single-station solution (although several stations can be processed together for convenience). The advantages of a network solution compared to PPP are that the estimates of each station can benefit from the measures of all stations being in principle more robust and precise. Starting from promising results achieved in recent works, in this paper we want to investigate a possible network solution, sim- lar to the IGS analysis center solutions, that can be easily managed by a network of timing centers to solve in a unique system all the clock differences (besides other quantities), to understand the feasibility and the advantages of this approach in time and frequency transfer. In particular, thanks to the automation of the ODTS process, the possibility to use magicGLASS as a tool for the near-real time synchronization of atomic clocks and time scales worldwide distributed with a latency of at least 30 minutes, is evaluated. Furthermore, the near-real time synchronization capabilities of the ODTS network solution are compared to PPP solutions provided by magicGLASS and other tools, as well as to IGS products and estimates generated by the traditional time and frequency transfer techniques.