Rhumbline

In navigation, a rhumb line or loxodrome) is an arc crossing all meridians of longitude at the same angle. It is a path of constant azimuth relative to true north, which can be steered by maintaining a course of fixed bearing. When drift is not a factor, accurate tracking of a rhumb line course is independent of speed. The Mercator projection is a map-making technique designed to represent rhumb l... (Wikipedia)