Positioning and navigation systems constitutes important systems of most military platforms. GNSS-receivers provides accurate position, velocity and time estimates in many scenarios. However, in urban environments, where the satellite signals are subjected to radio wave propagation effects such as multipath propagation, attenuation from buildings and diffraction, the accuracy and availability may be insufficient. Furthermore, GNSSreceivers are susceptible towards jamming and spoofing attacks, which are expected to occur in future conflicts. The report describes how GNSS-receivers can achieve a higher robustness, through detection of jamming and spoofing attacks and through the use of multi-constellation receivers. Collaborative navigation can also provide substantial benefits for smaller platforms that operate in GNSS-challenged environments. Platforms that are equipped with advanced PNT-systems can yield substantial improvements in particular for smaller platforms that utilize less advanced PNT-systems.