${session.getAttribute("locale")} 5 The 'billion galaxy' cosmological HI Large Deep Survey (BiG-CHILDS) 1.5 over half the sky. This survey provides a database of galaxy redshifts, HI gas masses, and galaxy rotation curves that would enable a wide range of science, including fundamental cosmology and studies of Dark Energy. This science requires the next generation of radio arrays, which are being designed under the umbrella of the 'Square Kilometer Array' (SKA) project. We present a science roadmap, extending to 2020 and beyond, that would enable this ambitious survey. We also place this survey in the context of other multi-wavelength surveys.]]> Wed 18 Mar 2015 20:30:50 EST ]]>