Convergence correction is a function of:

• A. latitude
• B. central meridian
• C. neither
• D. both a and b

Answer: (D)

Convergence angle in a Transverse Mercator style projection changes with position because grid north is defined by the projection grid, not by true geographic north. The amount you must correct depends on two things: how far you are from the central meridian (the longitude difference) and your latitude. On the central meridian, the convergence is zero; away from it, the grid lines tilt relative to geographic north, and the tilt grows with both the longitude offset and the latitude. A handy takeaway is that the convergence angle roughly follows γ ≈ arctan( tan(Δλ) × sin φ ), showing its dependence on latitude φ and longitude offset Δλ from the central meridian. So convergence correction is a function of both latitude and the central meridian. In practice, you apply this correction when converting between grid bearings and true bearings, adjusting by the angle and its sign depending on direction from the central meridian.