Study on the Redefinition of the Senegalese Geodetic Reference Frame Using GNSS PPP Technology

Techniques for establishing geodetic reference frames have evolved considerably with the use of global navigation satellite systems (GNSS) in geodesy through spatial positioning techniques. These techniques have made it possible to replace two-dimensional and local terrestrial reference frames, which were generally established using triangulation or geodetic polygonation techniques, or sometimes by simple astro-geodetic points. This development has therefore made it possible today to modernize most geodetic infrastructures by establishing more consistent three-dimensional reference frames at the global, regional, or national level. However, the technical constraints associated with the resources required to establish such benchmarks using differential GNSS positioning techniques (previously favored or even exclusively used) severely limit the level of modernization, maintenance, densification, and upkeep of geodetic reference frames in developing countries. The simplicity and performance of Precise Point Positioning (PPP) demonstrated in this study prove that this technique can be a real alternative for such geodetic work in these countries. Indeed, the recalculation of Senegalese Geodetic Reference Frame of 2004 (RRS04) carried out in this study based on a GNSS observation campaign over four sessions for sixteen points in the reference frame, in differential mode using the AUSPOS online tool and GAMIT/GLOBK scientific software, and in PPP mode using the CSRS-PPP tool, showed good agreement between the solutions provided by the three tools. The average deviations obtained for the X, Y, and Z components of the different points in the network are less than 2 cm, which is consistent with the accuracies generally associated with these geodetic networks.