A system for showing the distribution of meteorological data on a chart, especially over the oceans; using a Mercator map projection, the world between 80øN and 70øS latitudes is divided into Marsden “squares, each of 10ø latitude by 10ø longitude and 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.
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