Global Navigation Satellite Systems (GNSS) are vital for navigation. This study compared the productivity and accuracy of surveys using different GNSS constellation combinations: GPS-only, GPS+GLONASS, and GPS+GLONASS+Beidou. Instead of costly RTK receivers, an Android phone with Geo++ RINEX and Locus Map Apps served as the receiver. Precise Point Positioning (PPP) was adopted for accurate positioning without a base station. The study was conducted at Nile University Abuja with ten stations, considering various conditions and obstructions. Data collected from the Geo++ RINEX app were analyzed using RTKLIB. Results were evaluated using RTKLIB and Microsoft Excel for position and altitude accuracy. Position readings were generally accurate, while altitude measurements exhibited disparities. When combining GPS, GLONASS, and Beidou constellations, the maximum and minimum numbers of serving satellites were 32 and 26, respectively. The closest altitude reading had a 1-meter difference, while the highest disparity in altitude measurement reached 20.9 meters.
Key words: Global Navigation Satellite Systems (GNSS), GPS, GLONASS, Beidou, Android phone, Geo++ RINEX App, Locus Map App, survey accuracy, GNSS constellation combinations, Precise Point Positioning (PPP), RTK receivers, Nile University Abuja, position accuracy, altitude accuracy, RTKLIB.
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