Effective antenna positioning is critical to achieving satisfactory system performance. GNSS satellite signals and the Fugro correction signals travel by line of sight. If the antenna cannot 'see' enough GNSS satellites, or the selected Fugro correction satellite, even momentarily, the receiver will be unable to generate a position.
Consequently it is important to ensure that not only is the GNSS antenna installed high up on the vessel, in order that it has the best view of the sky, but that it is kept clear of other radiating antennae and does not get 'shadowed' by other equipment.
The following document contains Fugro Satellite Positioning's guidelines on effective Antenna Installation.