Observed polarization position angle of Sgr A* at 492 GHz, compared with prior data from Aitken et al. (2000), Bower et al. (2003, 2005), the mean of Macquart et al. (2006), and Marrone et al. (2006a, 2007). The polarization position angles of the data from Macquart et al. (2006) were unwrapped by −180°. We overplot the mean fitted intrinsic polarization position angle the and rotation measure by Marrone et al. (2007), and the updated fit including our measurement at 492 GHz. Gray curves show 50 independent random realizations which characterize our fitting errors. We note that our fitting error is not well-defined, because our observations did not include the XY and YX cross correlations. We omit error bars due to the crowded data points. However, we note that the scattering of data points due to actually observed time variations (e.g. Bower et al. 2005; Marrone et al. 2006a, 2007), is more significant than the measurement errors. Therefore, the data we present in this figure are adequate for providing the sense of uncertainty in rotation measure. The same arguments are relevant to Fig. 10.