摘要：This paper is the fourth in a series of publications presenting the process of installation,testing and long-term assessment of the navigational parameters of the Polish DGPS system.This series of publications intends to present – to the general public – the accomplishments of teams of Polish scientists who have been working for years to make the DGPS the main positioning system used in the Polish sea areas.A considerable part of the materials presented in this paper has never been published.The article presents changes in the position accuracy of the Polish DGPS system over 20 years.Both dynamic tests performed on vessels as well as static measurements campaigns were analysed.The publication contains selected results achieved in its installation and testing in 1995–1997 supplemented with the results of studies conducted in the years: 2006,2010,2014,2017.During this period the position accuracy increased from 2–8 m (1996) to approx.1–2 m (2010) due to three reasons: turning – off the Selective Availability (2000),technical modernization of reference stations (2010) and continuous – over many years – reducing GPS signal-in-space pseudorange errors,which results in increased position accuracy in all GPS augmentation systems.
