The Mercator chart has been used for navigational purposes for nearly four hundred years. Before Kramer devised his chart in 1569 navigators generally used a chart based on the simple cylindrical projection. The Cylindrical Orthomorphic projection devised by Kramer (or Mercator, as he is commonly called) revolutionized navigation and from that time has been the standard navigational chart for marine use. It was to be expected that, when the time came, air navigators would copy and perhaps modify the technique of the seaman. This was done, and today air navigators continue to use the Mercator chart. In many ways, however, it is not an ideal chart; it is now time to depart from this tradition and to use charts more suitable for air navigation. That this is possible has been shown by experimental flying in the Royal Air Force and by other countries, notably the United States and Canada.