  GLEAM, the GaLactic and Extragalactic All-sky MWA survey, is a survey of the
entire radio sky south of declination +25 deg at frequencies between 72 and 231
MHz, made with the Murchison Widefield Array (MWA) using a drift scan method
that makes efficient use of the MWA's very large field-of-view. We present the
observation details, imaging strategies and theoretical sensitivity for GLEAM.
The survey ran for two years, the first year using 40 kHz frequency resolution
and 0.5 s time resolution; the second year using 10 kHz frequency resolution
and 2 s time resolution. The resulting image resolution and sensitivity depends
on observing frequency, sky pointing and image weighting scheme. At 154 MHz the
image resolution is approximately 2.5 x 2.2/cos(DEC+26.7) arcmin with
sensitivity to structures up to ~10 deg in angular size. We provide tables to
calculate the expected thermal noise for GLEAM mosaics depending on pointing
and frequency and discuss limitations to achieving theoretical noise in Stokes
I images. We discuss challenges, and their solutions, that arise for GLEAM
including ionospheric effects on source positions and linearly polarised
emission, and the instrumental polarisation effects inherent to the MWA's
primary beam.
