It is proposed that units of length called nautical spans, chains and feet—and defined respectively to be 60, 1/60 and 1/6,000 nautical miles in length—be adopted internationally for use in weather-service and aeronautical operations. It is also proposed that the mandatory reporting levels for upper air charts he at intervals of one nautical mile of barometric altitude.

These proposed units have been selected to provide close numerical correspondences with associated sexagesimal measures of angular position and time; they are shown to interrelate values for time, horizontal angular and linear positions speeds, accelerations, and vertical barometric and geometric positions as closely as possible within our current knowledge of the earth and atmosphere. The kinds of practical advantages which would accrue from the adoption of such geodetically and aerodetically derived units of length in characteristically world-wide weather-service and aeronautical operations are also indicated.

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