Orthodromic chart

The orthodromic chart is an essential tool in navigation for representing the shortest routes between two points on the Earth’s surface. Unlike the Mercator chart, where constant-bearing routes appear as straight lines, on an orthodromic chart, the straight line corresponds to the shortest path, called an orthodrome or great circle. It is particularly useful for planning long ocean crossings, where minimizing distance saves time and fuel. Orthodromic charts preserve relative distances but distort angles, making them less suitable for following a constant compass course at sea. They are therefore often used in conjunction with Mercator charts to optimize navigation routes.