Galaxy and Mass Assembly (GAMA): FUV, NUV, ugrizYJHK Petrosian, Kron and
  S\`ersic photometry
  In order to generate credible 0.1-2 {\mu}m SEDs, the GAMA project requires
many Gigabytes of imaging data from a number of instruments to be re-processed
into a standard format. In this paper we discuss the software infrastructure we
use, and create self-consistent ugrizYJHK photometry for all sources within the
GAMA sample. Using UKIDSS and SDSS archive data, we outline the pre-processing
necessary to standardise all images to a common zeropoint, the steps taken to
correct for seeing bias across the dataset, and the creation of Gigapixel-scale
mosaics of the three 4x12 deg GAMA regions in each filter. From these mosaics,
we extract source catalogues for the GAMA regions using elliptical Kron and
Petrosian matched apertures. We also calculate S\'ersic magnitudes for all
galaxies within the GAMA sample using SIGMA, a galaxy component modelling
wrapper for GALFIT 3. We compare the resultant photometry directly, and also
calculate the r band galaxy LF for all photometric datasets to highlight the
uncertainty introduced by the photometric method. We find that (1) Changing the
object detection threshold has a minor effect on the best-fitting Schechter
parameters of the overall population (M* +/- 0.055mag, {\alpha} +/- 0.014,
{\Phi}* +/- 0.0005 h^3 Mpc^{-3}). (2) An offset between datasets that use Kron
or Petrosian photometry regardless of the filter. (3) The decision to use
circular or elliptical apertures causes an offset in M* of 0.20mag. (4) The
best-fitting Schechter parameters from total-magnitude photometric systems
(such as SDSS modelmag or S\'ersic magnitudes) have a steeper faint-end slope
than photometry dependent on Kron or Petrosian magnitudes. (5) Our Universe's
total luminosity density, when calculated using Kron or Petrosian r-band
photometry, is underestimated by at least 15%.
