In a transverse Mercator projection, the mapping angle varies with which of the following?

In a transverse Mercator projection, the mapping angle, also known as the angle of distortion, varies primarily with latitude. This projection is designed to minimize distortion along a central meridian, where the scale is true. As you move away from the central meridian towards higher latitudes, the projection increasingly distorts distances, areas, and angles.

The transverse Mercator projection is particularly effective for regions that are elongated in the north-south direction, as it preserves angles over small areas but introduces distortions as one moves away from the central meridian. Therefore, while longitude plays a role in determining positioning along the projection, it is the latitude that fundamentally influences the variations in the mapping angle and associated distortions in the projection.

Thus, the correct option indicates that the mapping angle varies specifically with latitude, reflecting the nature of distortion inherent in this type of projection.