Real-Time Tropospheric Delay Estimation Using GPS/Galileo Observations and NAVCAST Products

Precise estimation of real-time zenith tropospheric delay (RT-ZTD) is critical for real-time atmospheric sounding applications. Recently, the NAVCAST real-time service has been launched, which provides GPS/Galileo precise satellite orbit and clock corrections. This study aims to assess the precision of real-time zenith tropospheric delay obtained through the real-time GPS/Galileo precise point positioning (RT-PPP) solution. GPS/Galileo observations, spanning three successive days, from a number of globally distributed reference stations are first acquired and processed in the real-time mode using the NAVCAST real-time products. The RT-ZTD is then estimated and compared with the center for orbit determination in Europe (CODE) rapid tropospheric product counterpart. It is shown that the RT-ZTD estimates are in good agreement with the CODE counterparts with a maximum standard deviation (STD) of 22.2 mm. The addition of Galileo observations improves the precision of the RT-ZTD estimates by about 25% in comparison with the GPS-only solution.