  Various aspects of cosmology require comprehensive all-sky mapping of the
cosmic web to considerable depths. In order to probe the whole extragalactic
sky beyond 100 Mpc, one must draw on multiwavelength datasets and
state-of-the-art photometric redshift techniques. Here I summarize our
dedicated program that employs the largest photometric all-sky surveys --
2MASS, WISE and SuperCOSMOS -- to obtain accurate redshift estimates of
millions of galaxies. The first outcome of these efforts -- the 2MASS
Photometric Redshift catalog (2MPZ) -- was publicly released in 2013 and
includes almost 1 million galaxies with a median redshift of z~0.1. I discuss
how this catalog was constructed and how it is being used for various
cosmological tests. I also present how combining the WISE mid-infrared survey
with SuperCOSMOS optical data allowed us to push to depths over 1 Gpc on
unprecedented angular scales. These photometric redshift samples, with about 20
million sources in total, provide access to volumes large enough to study
observationally the Copernican Principle of universal homogeneity and isotropy,
as well as to probe various aspects of dark energy and dark matter through
cross-correlations with other data such as the cosmic microwave or gamma-ray
backgrounds. Last but not least, they constitute a test-bed for forthcoming
wide-angle multi-million galaxy samples expected from such instruments as the
SKA, Euclid, or LSST.
