  We present an empirical method which measures the distance to a Type Ia
supernova (SN Ia) with a precision of ~ 10% from a single night's data. This
method measures the supernova's age and luminosity/light-curve parameter from a
spectrum, and the extinction and distance from an apparent magnitude and color.
We are able to verify the precision of this method from error propagation
calculations, Monte Carlo simulations of well-sampled SNe Ia, and the Hubble
diagram of scarcely observed supernovae. With the reduction in telescope time
needed, this method is three to four times more efficient for measuring
cosmological parameters than conventional light-curve based distance estimates.
