  An integrated system of hardware and software allowing precise definition of
arbitrarily oriented magnetic fields up to |B| = 1 {\mu}T within a five-layer
mumetal shield is described. The system is calibrated with reference to
magnetic resonance observed between Zeeman states of the 6S$_{1/2}$ F = 4
$^{133}$Cs ground state. Magnetic field definition over the full 4{\pi} solid
angle is demonstrated, with one-sigma tolerances in magnitude, orientation and
gradient of {\delta}|B| = 0.94 nT, {\delta}{\theta} = 5.9 mrad and
{\delta}$\nabla$ B = 13.0 pT/mm, respectively. This field control is used to
empirically map Mx magnetometer signal amplitude as a function of the static
field (B0) orientation.
