The accuracy obtained by processing the GPS observations is important in several applications. This research, using the three different techniques for processing GNSS/CORS stations to illustrate the variation in coordinates of some GNSS/CORS stations on each month at two different years using the GPS observations.
In this research, we obtained the GPS observations of five stations for one day in every month over 24 months. We tried to have the same day of each month, but there were some problems in the observation of these stations, which led to the replacement of the day in some months. The differences of coordinates between every two successive months in 2018 and 2019 at all IGS stations when using the SECTOR tool at SOPAC technique are within 5 mm. But when using TBC and CSRS-PPP techniques we detected that the differences in coordinates between every two successive months for IGS stations in 2018 are not the same as in 2019. By fixing the coordinates obtained by the SOPAC technique and compared to other techniques, in TBC the common months between two years, which gives a high difference for all IGS stations coordinates are July, August, October, November, March, and December. But when using CSRS-PPP, the difference in IGS coordinates in 2018 differs from 2019 for all months.