Marsden square

Marsden square mapping or Marsden squares is a system that divides a chart of the world with latitude-longitude gridlines (e.g. plate carrée projection, Mercator or other) between 80°N and 70°S latitudes (or 90°N and 80°S: refer chart at Ocean Teacher’s Ocean Geography page) into grid cells of 10° latitude by 10° longitude, each with a unique, numeric identifier.