A metric is developed providing a quantitative measure of

the two-dimensional spatial coherence of scattered fields. The metric is

based on fitting a function similar to bivariate Gaussian to measured

two-dimensional coherence surfaces. This function provides a robust fit

to the measured data for a range of coherence lengths and surface asymmetries.

Through an eigendecomposition of the bivariate Gaussian

covariance matrix, it is possible to define surface orientation as well as

coherence lengths along the major and minor axes. The metric is applied

to normal-incidence