  SpectraPlot is a web-based application for simulating spectra of atomic and
molecular gases. At the time this manuscript was written, SpectraPlot consisted
of four primary tools for calculating: 1) atomic and molecular absorption
spectra, 2) atomic and molecular emission spectra, 3) transition linestrengths,
and 4) blackbody emission spectra. These tools currently employ the NIST ASD,
HITRAN2012, and HITEMP2010 databases to perform line-by-line simulations of
spectra. SpectraPlot employs a modular, integrated architecture, enabling
multiple simulations across multiple databases and/or thermodynamic conditions
to be visualized in a single interactive plot window. The primary objective of
this paper is to describe the architecture and spectroscopic models employed by
SpectraPlot in order to provide its users with the knowledge required to
understand the capabilities and limitations of simulations performed using
SpectraPlot. Further, this manuscript discusses the accuracy of several
underlying approximations used to decrease computational time, namely, the use
of far-wing cutoff criteria.
