Assessing IGS Network and Free Web-based Online GPS Services Accuracy with Session-duration Variation

Mohammed M.A. Ghollam1, *, Essam M. Fawaz1, Mohamed A. Elshewy1, Mostafa H. A. Mohamed1
1 Civil Engineering Department, Faculty of Engineering, Al-Azhar University, Cairo, Egypt

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© 2024 The Author(s). Published by Bentham Open.

open-access license: This is an open access article distributed under the terms of the Creative Commons Attribution 4.0 International Public License (CC-BY 4.0), a copy of which is available at: This license permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

* Address correspondence to this author at the Department of Civil Engineering, Faculty of Engineering, Al-Azhar University, Cairo, Egypt; E-mail:



The objective of this research was to evaluate online Post-Processing Services (PPSs) and Global Navigation Satellite Systems (GNSS) software in order to determine the significance of space geodesy techniques in assessing accurate coordinates for mega projects worldwide.


Principally, literature in the field of space geodesy techniques was assembled and scrutinized. Trimble R4 was utilized to observe 4 ground surfaces (i.e., asphalt, grass, sand and concrete), in Al-Azhar University, throughout 5 Session-Durations “SD” (i.e., 1, 2, 3, 4 and 5 hr.). The observed results were processed by TBC (i.e., It utilizes the International GNSS Service “IGS” network) and by 3 online services (i.e., Trimble Center Point RTX, AUSPOS and CSRS-PPP). Results were obtained, contrasted, and analyzed.


The IGS results were compared in terms of SD, where it was clear that, regardless of surface type, SD has an insignificant influence on Easting, as Northing, but has an influence on elevation accuracy, especially for the 2hr-SD. In addition, the 3 online software services were contrasted against IGS results in terms of the different SDs, where it was clear that, regardless of the surface type, AUSPOS, CSRS-PPP and Trimble-RTX accuracies were arranged in ascending order, the 3hr-SD achieved accurate Easting so as Northing; while IGS 5hr-SD provided optimal elevation accuracy.


Accordingly, the research recommended that GNSS users make informed decisions according to the accuracy requirements due to time constraints while establishing data processing strategies to designate strengths and weaknesses of processing and to optimize GNSS data processing applications.

Keywords: IGS network, AUSPOS, CSRS-PPP, Trimble-RTX, Online processing services, GNSS.