  We reconsider calibration of statistical distance scales for planetary
nebulae, examining precision and systematic error for various distance methods
used as well as the scales themselves. A different calibration strategy, one
based on precise trigonometric parallaxes by Harris et al. (2007; some improved
by Benedict et al. 2009), is presented. Most statistical scales have an overall
scale error; in addition, all four tested show dependence of distance ratio
[scale/actual] on nebular radius. However, the H-alpha scale of Frew (2008;
slightly revised in Frew et al. 2014) has only a small radius dependence at
large R and overall is consistent with these parallaxes. Some methods used for
calibration have systematic errors, and the extinction method is found to be
mostly unreliable. Comparison of Hipparcos parallaxes for a few large
planetaries with our "best estimate" distances for those confirms the
overestimation of 2.5 found by Harris et al. for PHL 932. We suggest a possible
connection with the smaller overestimation found by Melis et al. (2014) when
testing Hipparcos parallaxes for some of the Pleiades.

Solar and Stellar Astrophysics