What is the primary projection used on most maritime charts?

The primary projection used on most maritime charts is the Mercator Projection. This projection is particularly favored for its ability to represent lines of constant course, known as rhumb lines, as straight lines. This characteristic makes it highly useful for navigation, as it allows mariners to plot a course on a chart without dealing with complex calculations for angle changes. The scale on the Mercator Projection is consistent along any given latitude, which simplifies navigation even further, enabling navigators to easily measure distances and angles.

The Mercator Projection does distort areas, particularly as one moves away from the equator, but this distortion is an acceptable trade-off for the navigation ease it offers. Most nautical charts are designed for practical use, focusing on navigation rather than representing true land masses or areas accurately.

Other projections, such as the Lambert Conformal Projection or the Transverse Mercator Projection, are used in different contexts and applications, like for aeronautical charts or regional maps, but the Mercator Projection is distinctively recognized in maritime navigation for its practicality. The Stereographic Projection is primarily used for polar regions and does not serve the same purposes in maritime navigation as effectively as the Mercator does.