The need for high accuracy PNT in challenging environments has become obvious and, henceforth, mandatory for many applications. Currently, an accuracy target of 1 m in an urban environment seems a realistic achievement with multi-GNSS PPP or RTK capabilities. A significant R&D effort is ongoing to reach this target in operational products, using carrier phase positioning (PPP and RTK) and European institutions are actively taking their part in this effort.
In most hybrid PNT systems, GNSS is rightly considered the primary source of high-accuracy positioning, including in urban environments. Hence, current techniques and R&D efforts rely on GNSS as the primary source of high accuracy for both absolute and relative positioning.