during the last two decades precise point positioning ppp has been given a growing interest from the gnss community until it recently becomes the most famous technique in a wide range of the scientific researches. the ppp is a promising positioning approach capable of achieving sub-centimetre horizontal and few centimeters vertical accuracy using a gnss receiver along with precise orbits and clocks; and modelling of some special errors zumberge et al. 1997; kouba and héroux 2001; seepersad and bisnath 2014 although ppp is an easy cost-effective and high-accuracy positioning method it still suffers a long convergence time which prevents the use of ppp in high-accuracy real-time gnss positioning applications. the convergence period can be defined as the time the solution took for the coordinates or the ambiguities reach a specific accuracy or a steady state then no leaving it. with continuous modernization of multi-gnss systems there is a potential and an urgent need to improve the performance of the real-time ppp in two elements: the convergence time and accuracy. the objective of the phd research is to reduce the convergence time of multi-gnss real-time ppp.