Definition

A system introduced by Marsden early in the nineteenth century for showing the distribution of meteorological DATA on a CHART especially over the OCEANS. A Mercator map projection is used; the world between 90°N and 80°S being divided into Marsden 'squares' each of 10 degrees latitude by 10 degrees longitude. These squares are systematically numbered to indicate position. Each square may be divided into quarter squares, or into 100 one-degree subsquares numbered from 00 to 99 to give the position to the nearest degree.