عنوان مقاله [English]
Since many sophisticated Global Navigation Satellite System (GNSS) applications require satellite precise ephemeris (orbit and clock products), in recent years, many organizations have been responsible to provide users with information on GNSS. With the advent of these products, a positioning method known as Precise Point Positioning (PPP) was introduced. This technique is based on only using the observations of one receiver. Therefore, it is possible to determine the position using the observation of code and phase. In the last decade, due to the advent of this technique, achieving high accuracy, the need of only one receiver instead of differential observations, as well as reducing the cost of operation is possible by users for scientific and commercial research. This technique makes it possible to determine the position with a precision of centimetres to decimetres for static and kinematic applications. According to the results presented in the review of two case studies, comparison of estimated results with the actual values provides centimeters-level accuracy. For this reason, these services can be used to access the position components using PPP. In this research, the accuracy of the PPP method has been evaluated. The observations of four stations have been used globally. The collected data is processed using online services and open source software. Finally, the relevant results have been carefully examined. Based on the results presented in the first part and comparison with the final characteristics of the known points in the study area, on average, a difference of 3 mm has been reported when using 24 hours of observation. Considering the set of observations related to ten points in six-time intervals, the accuracies provided for the X, Y and Z coordinate components in the first period are 42, 31 and 20 mm, respectively and in the sixth period, the values of 9, 11 and 7 mm are reported.