Earth's magnetic field can be described by components including the vertical intensity (Z) and horizontal intensity (H). By convention, the horizontal component H is always taken as a positive magnitude (it simply measures the strength of the field's horizontal projection), while the sign of the vertical component Z depends on hemisphere: it is positive (pointing downward/into the Earth) in the northern hemisphere and negative (pointing upward/out of the Earth) in the southern hemisphere, consistent with the geomagnetic field behaving approximately like a dipole with field lines emerging from the southern hemisphere and re-entering in the northern hemisphere.