Which statement is TRUE concerning a Mercator projection?

The Mercator projection is a cylindrical map projection where the meridians (lines of longitude) are represented as equally spaced vertical lines. This characteristic leads to a significant distortion of size and distance, especially as one moves away from the equator.

The statement that the length of the meridians is increased to provide for equal expansion in all directions is true. In a Mercator projection, to maintain the angle (or shape) of geographical features, the scale increases as one moves toward the poles, which causes areas farther from the equator to appear much larger than they actually are. This design allows navigators to plot straight-line courses easily, as compass bearings remain true.

In contrast, the other statements related to the projection contain inaccuracies. Degrees of longitude do not decrease in length as latitude increases; instead, they remain constant in terms of angular measurement but the physical distances they represent do change due to the projection's nature. Additionally, the mileage between the meridians does not necessarily increase as the latitude increases in a conventional sense; instead, the distortion from the projection creates the impression that distances are larger in higher latitudes.

Understanding these attributes of the Mercator projection is essential for mariners and cartographers as it impacts navigation and map reading