It is worth mentioning that, in the differential
procedure there is an extra communication between
the reference and the mobile receiver
through a terrestrial radio-navigation system (very
high frequency––VHF system) in order to transfer
different kind of corrections (e.g., meteorological
etc.) from the reference to the mobile stations. This
results to a considerable improvement of the determination
accuracy of the position vector. The
differential procedure is today a more powerful
tool for applications related to combination procedures
of GPS especially with geographic information
systems (GIS). Moreover, absolute
Fig. 1. The parts of the GPS. positioning accuracies better than one meter, can