Absolute Calibration of Diffuse Radio Surveys at 45 and 150 MHz
  We use EDGES measurements to determine scale and zero-level corrections to
the diffuse radio surveys by Guzm\'an et al. at $45$ MHz and Landecker &
Wielebinski at $150$ MHz. We find that the Guzm\'an et al. map requires a scale
correction of $1.076 \pm 0.034$ ($2\sigma$) and a zero-level correction of
$-160 \pm 78$ K ($2\sigma$) to best-fit the EDGES data. For the Landecker &
Wielebinski map, the scale correction is $1.112 \pm 0.023$ ($2\sigma$) and the
zero-level correction is $0.7 \pm 6.0$ K ($2\sigma$). The correction
uncertainties are dominated by systematic effects, of which the most
significant are uncertainty in the calibration of the EDGES receivers, antenna
pointing, and tropospheric and ionospheric effects. We propagate the correction
uncertainties to estimate the uncertainties in the corrected maps themselves
and find that the $2\sigma$ uncertainty in the map brightness temperature is in
the range $3.2-7.5\%$ for the Guzm\'an et al. map and $2.1-9.0\%$ for the
Landecker & Wielebinski map, with the largest percent uncertainties occurring
at high Galactic latitudes. The corrected maps could be used to improve
existing diffuse low-frequency radio sky models, which are essential tools in
analyses of cosmological $21$ cm observations, as well as to investigate the
existence of a radio monopole excess above the cosmic microwave background and
known Galactic and extragalactic contributions.
