  We show that the statistical error, $\sigma_{\tau}$, in estimating the
optical depth, $\tau$, due to microlensing is substantially higher than the
naive Poisson estimate: $\sigma_{\tau} = \sqrt{\eta / N} \tau$, where $N$ is
the number of detections and $1.65 \leq \eta \lsim 3$. We construct a
``microlensing map'' using an observationally well-constrained barred bulge
model and compare this with a map based on a spherical bulge model. The result
indicates a significant differences in the distribution of optical depths. If
the optical depths are determined over a wide range of positions around the
Galactic center, one could make a rudimentary determination of the geometry of
the mass distribution of the Galactic bulge by observing $\sim 200$ events.
About 800 events are required to determine the relative contributions to the
event rate by bulge and disk Machos.
