  Large scale simulations of two-dimensional bidisperse granular fluids allow
us to determine spatial correlations of slow particles via the four-point
structure factor $S_4(q,t)$. Both cases, elastic ($\varepsilon=1$) as well as
inelastic ($\varepsilon < 1$) collisions, are studied. As the fluid approaches
structural arrest, i.e. for packing fractions in the range $0.6 \le \phi \le
0.805$, scaling is shown to hold: $S_4(q,t)/\chi_4(t)=s(q\xi(t))$. Both the
dynamic susceptibility, $\chi_4(\tau_{\alpha})$, as well as the dynamic
correlation length, $\xi(\tau_{\alpha})$, evaluated at the $\alpha$ relaxation
time, $\tau_{\alpha}$, can be fitted to a power law divergence at a critical
packing fraction. The measured $\xi(\tau_{\alpha})$ widely exceeds the largest
one previously observed for hard sphere 3d fluids. The number of particles in a
slow cluster and the correlation length are related by a robust power law,
$\chi_4(\tau_{\alpha}) \approx\xi^{d-p}(\tau_{\alpha})$, with an exponent
$d-p\approx 1.6$. This scaling is remarkably independent of $\varepsilon$, even
though the strength of the dynamical heterogeneity increases dramatically as
$\varepsilon$ grows.
