HYDRO 2016 Paper 8A1
Hans Visser, Dariusz Lapucha, Javier Tegedor, Xianglin Liu, Ole Ørpen, Yahya Memarzadeh
Marinestar offers satellite-based GNSS correction services over the world. An overview of the minimum and maximum number of usable satellites in August 2016 is given: GPS (6-13 satellites), Glonass (4–10 satellites), Beidou (0–13 satellites) and Galileo (0–5 satellites).
Since 2006 Marinestar provides precise orbit and clock corrections for GPS. Glonass was added in 2009 and Beidou in 2014. Galileo will be added when "Early Services" is declared. Improvements in the height accuracy from 20 cm in 2011 to 10 cm in 2016 is shown. Here the G4+ service using all four GNSS constellations with fixed GPS ambiguities is introduced.
A description is given of the PPP-RTK algorithm. GPS satellite hardware delays (UPDs) are measured using an independent network of 110 reference stations. Using another network of 46 reference stations orbit and clock errors are estimated. Improvements are realised by applying the UPDs to GPS and adding Glonass, Beidou and Galileo to the solution. A study on the age of corrections shows that the age can be extended to 10 minutes.
Investigating the minimum elevation mask shows that reducing the mask improves availability and accuracy during ionospheric scintillation and local blockage. For the hydrographic surveyor error sources of G4+ as radio interference, rain, local multipath and antenna type are discussed.
It is shown that G4+ gives standard deviations of 2-3 cm in east and north and 4-5 cm in height. Fixing the ambiguities improves the standard deviations between 10% and 20%.