  The INT/WFC Photometric H-Alpha Survey of the Northern Galactic Plane (IPHAS)
is a 1800 square degrees imaging survey covering Galactic latitudes |b| < 5 deg
and longitudes l = 30 to 215 deg in the r, i and H-alpha filters using the Wide
Field Camera (WFC) on the 2.5-metre Isaac Newton Telescope (INT) in La Palma.
We present the first quality-controlled and globally-calibrated source
catalogue derived from the survey, providing single-epoch photometry for 219
million unique sources across 92% of the footprint. The observations were
carried out between 2003 and 2012 at a median seeing of 1.1 arcsec (sampled at
0.33 arcsec/pixel) and to a mean 5\sigma-depth of 21.2 (r), 20.0 (i) and 20.3
(H-alpha) in the Vega magnitude system. We explain the data reduction and
quality control procedures, describe and test the global re-calibration, and
detail the construction of the new catalogue. We show that the new calibration
is accurate to 0.03 mag (rms) and recommend a series of quality criteria to
select the most reliable data from the catalogue. Finally, we demonstrate the
ability of the catalogue's unique (r-Halpha, r-i) diagram to (1) characterise
stellar populations and extinction regimes towards different Galactic
sightlines and (2) select H-alpha emission-line objects. IPHAS is the first
survey to offer comprehensive CCD photometry of point sources across the
Galactic Plane at visible wavelengths, providing the much-needed counterpart to
recent infrared surveys.
