Before revision: 300px | Spitfire's grid compass,Type P8 No 100366D A grid compassCAA Advisory circular known as well as grid steering compass, is a navigational instrument that provides a reference direction (relative to north) in the horizontal plane and allows setting a course (horizontal angle respect to this point), by means of a lockable rotating limb and then, follow that course with a simple sight, by keeping the cross axle within the grid's parallel lines.
After revision: A grid compassCAA Advisory circular known as well as grid steering compass, is a navigational instrument that provides a reference direction (relative to north) in the horizontal plane and allows setting a course (horizontal angle respect to this point), by means of a lockable rotating limb and then, follow that course with a simple sight, by keeping the cross axle within the grid's parallel lines.