  Large photometric surveys with the aim of identifying many Type Ia supernovae
(SNe) at moderate redshift are challenged in separating these SNe from other SN
types. We are motivated to identify Type Ia SNe based only on broadband
photometric information, since spectroscopic determination of the SN type, the
traditional method, requires significant amounts of time on large telescopes.
We consider the possible observables provided by a large synoptic photometry
survey. We examine the optical colors and magnitudes of many SN types from
z=0.1 to z=1.0, using space-based ultraviolet spectra and ground-based optical
spectra to simulate the photometry. We also discuss the evolution of colors
over the SN outburst and the use of host galaxy characteristics to aid in the
identification of Type Ia SNe. We consider magnitudes in both the SDSS
photometric system and in a proposed filter system with logarithmically spaced
bandpasses. We find that photometric information in four bands covering the
entire optical spectrum appears capable of providing identification of Type Ia
SNe based on their colors at a single observed epoch soon after maximum light,
even without independent estimates of the SN redshift. Very blue filters are
extremely helpful, as at moderate redshift they sample the restframe
ultraviolet spectrum where the SN types are very different. We emphasize the
need for further observations of SNe in the restframe ultraviolet to fully
characterize, refine, and improve this method of SN type identification.
