  Understanding diffuse Galactic radio emission is interesting both in its own
right and for minimizing foreground contamination of cosmological measurements.
Cosmic Microwave Background experiments have focused on frequencies > 10 GHz,
whereas 21 cm tomography of the high redshift universe will mainly focus on <
0.2 GHz, for which less is currently known about Galactic emission. Motivated
by this, we present a global sky model derived from all publicly available
total power large-area radio surveys, digitized with optical character
recognition when necessary and compiled into a uniform format, as well as the
new Villa Elisa data extending the 1.4 GHz map to the entire sky. We quantify
statistical and systematic uncertainties in these surveys by comparing them
with various global multi-frequency model fits. We find that a principal
component based model with only three components can fit the 11 most accurate
data sets (at 10, 22, 45 & 408 MHz and 1.4, 2.3, 23, 33, 41, 61, 94 GHz) to an
accuracy around 1%-10% depending on frequency and sky region. Both our data
compilation and our software returning a predicted all-sky map at any frequency
from 10 MHz to 100 GHz are publicly available at
http://space.mit.edu/home/angelica/gsm .

Astrophysics