A navigation experimental survey with real time Differential GPS (RT-DGPS) is described. It was aimed at the precision finding of sample points in forest precedently surveyed with post processing DGPS techniques (PP-DGPS). The practical aspects of navigation, the necessary equipments, some suggestions for the invisible marking of reference points and the use of the metal detector for final precision finding, are illustrated. Four technical schedules study in depth the topics of several possibilities to access differential corrections in real time, and some accuracy indicators for GPS positioning. Further an experimentation related to influence of reflection error of GPS signals (multipath) in forest environment is illustrated and the performance of a GPS receiver of new generation is analysed. Practical suggestions are given on the optimal stay times for precision positioning of points in forest. After about 10 years from the first practical application of this technology in forest surveys, this work underlines and updates the operative technical overview on the use of GPS in this specific field.