Grid azimuth is the same as geodetic azimuth only when the point of observation falls on the _______ meridian.

• A. central
• B. Observer's
• C. Greenwich
• D. prime

Answer: (A)

The distance between grid azimuth and geodetic azimuth is the grid convergence angle, which is zero along the projection’s central meridian. In a transverse projection like Transverse Mercator (used by many grid systems), the central meridian is built so that grid north aligns with true north there. Because of this alignment, the angle a line makes with the grid north is the same as the angle it makes with geodetic north exactly on that meridian. Away from the central meridian, the convergence angle is nonzero and the two azimuths differ.

That’s why the correct statement is central meridian. The other options don’t fit because Greenwich or prime meridian aren’t the projection’s central reference for grid north, and the observer’s meridian isn’t the defined reference for grid–geodetic alignment.