  It is important to explore the diversity of characteristics of low-mass,
low-density planets to understand the nature and evolution of this class of
planets. We present a homogeneous analysis of 12 new and 9 previously published
broadband photometric observations of the Uranus-sized extrasolar planet GJ
3470b, which belongs to the growing sample of sub-Jovian bodies orbiting M
dwarfs. The consistency of our analysis explains some of the discrepancies
between previously published results and provides updated constraints on the
planetary parameters. Our data are also consistent with previous transit
observations of this system. We also provide new spectroscopic measurements of
GJ 3470 from 0.33 to 2.42 $\mu$$m$ to aid our analysis. We find $R_{\star}$ =
0.48$\pm$0.04 $R_{\odot}$, $M_{\star}$ = 0.51$\pm$0.06 $M_{\odot}$, and $T_{\rm
eff}$ = 3652$\pm$50 K for GJ 3470, along with a rotation period of
$20.70\pm{0.15}$ d and an R-band amplitude of 0.01 mag, which is small enough
that current transit measurements should not be strongly affected by stellar
variability. We also present the most precise orbital ephemeris for this
system: T$_{o}$ = 2455983.70472$\pm$0.00021 BJD$_{TDB}$, P =
3.3366487$^{+0.0000043}_{-0.0000033}$ d, and we see no evidence for transit
timing variations greater than 1 minute. Our reported planet to star radius
ratio is 0.07642$\pm$0.00037. The physical parameters of this planet are
$R_{p}$ = 3.88$\pm$0.32 $R_{\oplus}$, and $M_{p}$ = 13.73$\pm$1.61
$M_{\oplus}$. Because of our revised stellar parameters, the planetary radius
we present is smaller than previously reported values. We also perform a second
analysis of the transmission spectrum of the entire ensemble of transit
observations to date, supporting the existence of a H$_{2}$ dominated
atmosphere exhibiting a strong Rayleigh scattering slope.
