Compressor performance changes, day to day, with changes in the ambient pressure and temperature. Woolenweber shows the change in performance of a turbocharger compressor when the inlet temperature varies between 70 and 100 deg F. In the case of aircraft compressors, inlet pressure and temperature also change with altitude and airspeed. The presentation of different performance for every combination of inlet temperature and pressure would be unmanageable but it is possible to collapse it all onto a single map, which is applicable to a wide range of inlet conditions, using dimensional analysis. In dimensional analysis individual quantities such as rotor speed, mass flow and delivery pressure are each grouped with other relevant quantities in such a way that the groups have no dimensions but still have a physical meaning. For example rotor speed formula_1, inlet temperature formula_2, compressor diameter formula_3 and gas properties formula_4 and formula_5 are grouped together as dimensionless formula_6 which is equivalent to the blade mach number.