ESDU 88025 gives data and methods of analysis for deriving true airspeed, Mach number, pressure height and ambient air temperature from registered values of total pressure and temperature, and static pressure. The methods apply for Mach numbers between approximately 4 and 10 and for heights up to 65 km (210 000 ft). Such air data are of particular importance where they are used to control an air-breathing propulsion unit. The assumptions and limitations of the methods are clearly stated and explained, and a worked example illustrates the use of graphs and tables for the properties of equilibrium air behind a normal shock which are then used with the Rankine-Hugoniot relationships to derive the required data. ESDUpac A8825 gives as three random access ASCII files on disc a more extensive range of properties than those presented graphically.