  An updated model for the synchrotron and inverse Compton emission from a
population of high energy electrons of the Crab Nebula is used to reproduce the
measured spectral energy distribution from radio to high energy gamma-rays. By
comparing the predicted inverse Compton component with recent Fermi
measurements of the nebula's emission, it is possible to determine the average
magnetic field in the nebula and to derive the underlying electron energy
distribution. The model calculation can then be used to cross calibrate the
Fermi observations with ground based air shower measurements. The resulting
energy calibration factors are derived and can be used for combining broad
energy measurements taken with Fermi in conjunction with ground based
measurements.
