  Baryon acoustic oscillations (BAO), known as one of the largest cosmological
objects, is now recognized as standard cosmological tool to measure geometric
distances via the Alcock-Paczynski effect, by which the observed BAO exhibits
characteristic anisotropies in addition to the redshift distortions. This
implies that once we know the correct distances to the observed BAO, the tip
points of baryon acoustic peaks in the anisotropic correlation function of
galaxies, $\xi(\sigma,\pi)$, can form a great circle (hereafter 2D BAO circle)
in the $\sigma$ and $\pi$ plane, where $\sigma$ and $\pi$ are the separation of
galaxy pair parallel and perpendicular to the line-of-sight, respectively. This
2D BAO circle remains unchanged under the variations of the unknown galaxy bias
and/or coherent motion, while it varies transversely and radially with respect
to the variations of $D_A$ and $H^{-1}$, respectively. Hereby the ratio between
transverse distance $D_A$ and the radial distance $H^{-1}$ reproduces the
intrinsic shape of 2D BAO circle, which is {\it a priori} given by the known
broadband shape of spectra. All BAO peaks of $\xi(\sigma,\pi)$ are precisely
calculated with the improved theoretical model of redshift distortion. We test
this broadband Alcock--Paczynski method using BOSS--like mock catalogues. The
transverse and radial distances are probed in precision of several percentage
fractional errors, and the coherent motion is observed to match with the
fiducial values accurately.
