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 deg ^ { 2 } for Galactic longitude 140 \leq l \leq 220 \deg and latitude -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 - W 2 ) .
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 .