Which statement about meridian convergence corrections in survey practice is NOT true?

• A. The absolute value of meridian convergence is subtracted from the geodetic azimuth if the line is on the east side of the CM.
• B. The absolute value of meridian convergence is subtracted from the grid azimuth if the line is on the west side of the CM.
• C. The absolute value of meridian convergence is added to the true azimuth if the line is on the east side of the CM.
• D. The absolute value of meridian convergence is added to the geodetic azimuth if the line is on the west side of the CM.

Answer: (C)

Meridian convergence is the rotation between grid north (as used on maps and projections) and true/geographic north. Because map grids aren’t perfectly aligned with the Earth’s true north, you must apply a sign-corrected adjustment when converting azimuths between references. The key point is the direction of that rotation depends on whether you’re east or west of the central meridian.

On the east side of the central meridian, grid north lies clockwise from true north.That means a line that has a given true azimuth actually appears with a smaller azimuth when read in grid terms, so you subtract the magnitude of the convergence to obtain the grid or related azimuths. Therefore, adding the convergence to the true azimuth in this situation would be incorrect. For example, with a true azimuth of 45° and a convergence of 2° east of the CM, the grid azimuth should be 43°, not 47°.

The other statements follow the expected sign conventions for the east and west sides, applying subtraction or addition in the appropriate cases to move between true, geodetic, and grid azimuths.