  Galactic planetary nebula (PN) distances are derived, except in a small
number of cases, through the calibration of statistical properties of PNe. Such
calibrations are limited by the accuracy of individual PN distances which are
obtained with several non-homogeneous methods, each carrying its own set of
liabilities. In this paper we use the physical properties of the PNe in the
Magellanic Clouds, and their accurately known distances, to recalibrate the
Shklovsky/Daub distance technique. Our new calibration is very similar (within
1 percent) of the commonly used distance scale by Cahn et al. (1992), although
there are important differences. We find that neither distance scale works well
for PNe with classic ("butterfly") bipolar morphology, and while the radiation
bounded PN sequences in both the Galactic and the Magellanic Cloud calibration
have similar slopes, the transition from optically thick to optically thin
appears to occur at higher surface brightness and smaller size than that
adopted by Cahn et al. The dispersion in the determination of the scale factor
suggests that PN distances derived by this method are uncertain by at least 30
percent, and that this dispersion cannot be reduced significantly by using
better calibrators. We present a catalog of Galactic PN distances using our
re-calibration which can be used for future applications, and compare the best
individual Galactic PN distances to our new and several other distance scales,
both in the literature and newly recalibrated by us, finding that our scale is
the most reliable to date.
