Purpose

The purpose of this thorn is to provide a somewhat invariant means of measuring ``waves'' and other geometrical content in the numerically generated spacetime. Specifically, the thorn calculates the complex scalars $\Psi_0$, $\Psi_1$, $\Psi_2$, $\Psi_3$, and $\Psi_4$ with respect to a specified tetrad, and the invariants $I$ and$J$.