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Abstract

We present a detailed methodology for extracting the full set of
Newman-Penrose Weyl scalars from numerically generated spacetimes without
requiring a tetrad that is completely orthonormal or perfectly aligned to the
principal null directions. We also describe an extrapolation technique for
computing the Weyl scalars' contribution at asymptotic null infinity in
post-processing. These methods have continued to be used to produce $\Psi_4$
and $h$ waveforms for the Simulating eXtreme Spacetimes Waveform Catalog and
now have been expanded to produce the entire set of Weyl scalars. These new
waveform quantities are critical for the future of gravitational wave astronomy
in order to understand the finite-amplitude gauge differences that can occur in
numerical waveforms. We also present a new analysis of the accuracy of
waveforms produced by the Spectral Einstein Code. While ultimately we expect
Cauchy Characteristic Extraction to yield more accurate waveforms, the
extraction techniques described here are far easier to implement and have
already proven to be a viable way to produce production-level waveforms that
can meet the demands of current gravitational-wave detectors.