  Vector meson photoproduction offers the opportunity to image target nuclei.
The two-dimensional Fourier transform $d\sigma_{\rm coherent}/dt$ of coherent
vector meson photoproduction gives the two-dimensional distribution of
interaction sites in the target. Since vector meson photoproduction occurs, at
lowest order, via two-gluon exchange, this is sensitive to gluon shadowing. We
present an analysis of $\pi^+\pi^-$ photoproduction using data from the STAR
detector and a study of $d\sigma_{\rm coherent}/dt$, with an emphasis on
probing the nuclear shape and its systematic uncertainties.
