We present an algorithm ( mead , for ‘ Mapping Extinction Against Distance ’ ) which will determine intrinsic ( r ^ { \prime } - i ^ { \prime } ) colour , extinction , and distance for early-A to K4 stars extracted from the IPHAS r ^ { \prime } / i ^ { \prime } / { H } \alpha photometric database .
These data can be binned up to map extinction in three dimensions across the northern Galactic Plane .
The large size of the IPHAS database ( \sim 200 million unique objects ) , the accuracy of the digital photometry it contains and its faint limiting magnitude ( r ^ { \prime } \sim 20 ) allow extinction to be mapped with fine angular ( \sim 10 arcmin ) and distance ( \sim 0.1 kpc ) resolution to distances of up to 10 kpc , outside the Solar Circle .
High reddening within the Solar Circle on occasion brings this range down to \sim 2 kpc .
The resolution achieved , both in angle and depth , greatly exceeds that of previous empirical 3D extinction maps , enabling the structure of the Galactic Plane to be studied in increased detail . mead accounts for the effect of the survey magnitude limits , photometric errors , unresolved ISM substructure , and binarity .
The impact of metallicity variations , within the range typical of the Galactic disc is small .
The accuracy and reliability of mead are tested through the use of simulated photometry created with Monte-Carlo sampling techniques .
The success of this algorithm is demonstrated on a selection of fields and the results are compared to the literature .