  We present a three dimensional extinction map in $r$ band. The map has a
spatial angular resolution, depending on latitude, between 3 -- 9\,arcmin and
covers the entire XSTPS-GAC survey area of over 6,000\,$\rm deg^2$ for Galactic
longitude $\rm 140 \leq$ $l$ $ \leq 220\deg$ and latitude $\rm -40\leq$ $b$ $
\leq 40\deg$. By cross-matching the photometric catalog of the Xuyi Schmidt
Telescope Photometric Survey of the Galactic Anticentre (XSTPS-GAC) with those
of 2MASS and WISE, we have built a multi-band photometric stellar sample of
about 30 million stars and applied spectral energy distribution (SED) fitting
to the sample. By combining photometric data from the optical to the
near-infrared, we are able to break the degeneracy between the intrinsic
stellar colours and the amounts of extinction by dust grains for stars with
high photometric accuracy, and trace the extinction as a function of distance
for low Galactic latitude and thus highly extincted regions. This has allowed
us to derive the best-fit extinction and distance information of more than 13
million stars, which are used to construct the three dimensional extinction
map. We have also applied a Rayleigh-Jeans colour excess (RJCE) method to the
data using the 2MASS and WISE colour $(H-W2)$. The resulting RJCE extinction
map is consistent with the integrated two dimensional map deduced using the
best-fit SED algorithm. However for individual stars, the amounts of extinction
yielded by the RJCE method suffer from larger errors than those given by the
best-fit SED algorithm.
