  We generate synthetic HI Galactic plane surveys from spiral galaxy
simulations which include stellar feedback processes. Compared to a model
without feedback we find an increased scale height of HI emission (in better
agreement with observations) and more realistic spatial structure (including
supernova blown bubbles). The synthetic data show HI self-absorption with a
morphology similar to that seen in observations. The density and temperature of
the material responsible for HI self-absorption is consistent with
observationally determined values, and is found to be only weakly dependent on
absorption strength and star formation efficiency.
