  We present the data reduction pipeline for the Hi-GAL survey. Hi-GAL is a key
project of the Herschel satellite which is mapping the inner part of the
Galactic plane (|l| <= 70\cdot and |b| <= 1\cdot), using 2 PACS and 3 SPIRE
frequency bands, from 70{\mu}m to 500{\mu}m. Our pipeline relies only partially
on the Herschel Interactive Standard Environment (HIPE) and features several
newly developed routines to perform data reduction, including accurate data
culling, noise estimation and minimum variance map-making, the latter performed
with the ROMAGAL algorithm, a deep modification of the ROMA code already tested
on cosmological surveys. We discuss in depth the properties of the Hi-GAL
Science Demonstration Phase (SDP) data.
