  The Galactic magnetic field, locally observed to be on the order of a few
$\mu$G, is sufficiently strong to induce deflections in the arrival directions
of ultra-high energy cosmic rays. We present a method that establishes measures
of self-consistency for hypothesis sets comprised of cosmic magnetic field
models and ultra-high energy cosmic ray composition and source distributions.
The method uses two independent procedures to compare the backtracked velocity
vectors outside the magnetic field model to the distribution of backtracked
velocity directions of many isotropic observations with the same primary
energies. This allows for an estimate of the statistical consistency between
the observed data and simulated isotropic observations. Inconsistency with the
isotropic expectation of source correlation in both procedures is interpreted
as the hypothesis set providing a self-consistent description of GMF and UHECR
properties for the cosmic ray observations.
