The absolute differential positioning is a positioning technique that determines the position of a receiver, usually mobile, based on direct observations to satellites and some (differential) corrections transmitted (in real-time) from another fixed receiver called reference-receiver or base-receiver. A modern version allows the generation of these corrections based on a network of reference stations (receivers) such as the RN-GSP of the CNC. Pseudo-range (satellite-receiver distances) measured by the mobile receiver are corrected based on differential corrections obtained from the base-receiver, and then an absolute (punctual) positioning takes place. These differential corrections improve the accuracy of position determination.
The corrections submitted by the base-receiver can be Pseudo-Range-Corrections (PRC) and Rate of Range Corrections (RRC). These corrections can be determined using the pseudo-range defined on the basis of the codes transmitted by the satellites (DGNSS method -Differential GNSS) or on the basis of measurements performed using the carrier wave (RTK method - Real Time Kinematic). In addition, a specialized service based on a network of GNSS stations, can transmit further corrections, especially those due to the propagation of satellite signals through ionosphere and troposphere.