The LD6 GNSS heading direction is computed from Ant 1 to Ant 2, with the accuracy of the solution largely determined by the distance (or baseline) between both antennas. The larger the baseline, the better the heading precision will be. VERIPOS recommend a minimum baseline of two metres.
Assuming the antennas are mounted along the vessel Fwd/Aft centreline, with Ant 2 being the furthest forward antenna, a small correction would be required to calibrate the Heading to the True Vessel Heading.
Note: If the main and primary antennas are installed perpendicular to vessel North, with Ant 1 at the Starboard side and the Ant 2 at the Port side, a correction of around +/-90° would be needed in Quantum to align the GNSS heading to vessel North.