Near-infrared extinction with discretised stellar colours
  Several methods exist to convert near-infrared (NIR) stellar observations
into extinction maps. We present a new method based on NIR multiband
observations. The method uses a discretised version of the distribution of
intrinsic stellar colours. A number of variations of the basic method are
tested, and the results are compared to NICER calculations. When photometric
errors are large, the results are close to those of NICER method but some
advantages can be seen when the distribution of intrinsic colours cannot be
described well with a single covariance matrix. A priori information about
relative column density variations at sub-beam scales can result in a
significant increase in accuracy. The results may be further improved by
considering the magnitude dependence of the intrinsic colours. Thus, the new
methods are useful mostly when photometric errors are small, the distribution
of intrinsic colours is well known, or one has prior knowledge of the
small-scale structures.
