Determine Tectonic Motion Velocities of Some Vietnam CORSs Computed from PPP Coordinates When Using IGS and CNES Products

Precise point positioning method (PPP) is increasingly popular in determining crustal displacement. The PPP should have precise products of the GNSS satellite orbit and clock correction. Currently there are several different Analysis Centers (AC) that offer this product such as the Center for Orbit Determination in Europe (CODE), the Center National d'Etudes Spatiales (CNES), the International GNSS Service (IGS). In principle, PPP using different products will give different positioning results. To calculate the tectonic motion velocity of some continuously operating reference stations (CORSs) in Vietnam in the period of 2019–2021, we use a precise point positioning method with 2 different products of IGS and CNES. The RMS of coordinate deviation between the two options is (3.2, 5.7, 9.1)mm in the North, East, and Up components. However, when calculating the velocity of the North component, the value of CNES is always about 2/3 smaller than IGS. While the difference in velocity of the East and Up components is within the allowable limits.Through comparison, the calculation results of tectonic velocities from IGS are more consistent with the results of previous studies despite different data sources and processing methods.