  The relatively large measured value of $\theta_{13}$ has opened up the
possibility of determining the neutrino mass hierarchy through earth matter
effects. Amongst the current accelerator-based experiments only NOvA has a long
enough baseline to observe earth matter effects. However, NOvA is plagued with
uncertainty on the knowledge of the true value of $\delta_{CP}$, and this could
drastically reduce its sensitivity to the neutrino mass hierarchy. The earth
matter effect on atmospheric neutrinos on the other hand is almost independent
of $\delta_{CP}$. The 50 kton magnetized Iron CALorimeter at the India-based
Neutrino Observatory (ICAL@INO) will be observing atmospheric neutrinos. The
charge identification capability of this detector gives it an edge over others
for mass hierarchy determination through observation of earth matter effects.
We study in detail the neutrino mass hierarchy sensitivity of the data from
this experiment simulated using the Nuance based generator developed for
ICAL@INO and folded with the detector resolutions and efficiencies obtained by
the INO collaboration from a full Geant4-based detector simulation. The data
from ICAL@INO is then combined with simulated data from T2K, NOvA, Double
Chooz, RENO and Daya Bay experiments and a combined sensitivity study to the
mass hierarchy is performed. With 10 years of ICAL@INO data combined with T2K,
NOvA and reactor data, one could get about $2.3\sigma-5.7\sigma$ discovery of
the neutrino mass hierarchy, depending on the true value of $\sin^2\theta_{23}$
[0.4 -- 0.6], $\sin^22\theta_{13}$ [0.08 -- 0.12] and $\delta_{CP}$ [0 --
2$\pi$].
