PPP doesn’t utilise ground stations, and to achieve cm accuracy, you need to utilise phase information and solve the ambiguity problem 1mm accuracy almost cert

PPP doesn’t utilise ground stations, and to achieve cm accuracy, you need to utilise phase information and solve the ambiguity problem 1mm accuracy almost certainly relies on ionosphere and troposphere observations at high temporal and spatial frequency. The process of post processing is essentially correct, but there is a point at which the ionosphere solution won’t get better without an increase in density of observations