Basically, within PPP, code and phase measurements of single static or kinematic receivers are used to estimate an independent solution of three-dimensional position coordinates, receiver clock estimates and tropospheric parameters with the aid of externally provided precise orbit and clock information instead of using the imprecise navigation data broadcast by the satellites themselves. Since 2010, researchers at the Institute of Geodesy, Working Group Navigation, have been working on a PPP software, called PPPsoft, with ambiguity resolution and fixing. This software package has been used in various funded projects. Related Projects: UPIC, POScity, PPPserve, RT-PPP, RA-PPP After achieving outstanding results (see the dissertation of Katrin Huber), the work was continued for single-frequency PPP and low-cost GNSS receivers for special applications like RPAS (remotely piloted aircraft systems) where a continuous data link cannot be guaranteed but high precision and/or accuracy is required.