Definitions for "Grid north"
Central meridian of referred mapping projection.
is the direction that all topographic maps are aligned with. It's purpose is to adjust for the difference, when transferring the curvature of the Earth to a two dimensional plane. True North and grid north and so close, they are considered the same direction.
Bearings taken from the grid lines on maps and charts. The grid lines vary from exactly true north-south on most maps due to curvature of the earth's surface.