Step Arguments
==============

The ``adaptive_trace_model`` step has the following step-specific arguments:

``--fit_threshold`` (float, default=10.0)
  Signal threshold value for attempting a spline fit, specified as the number of
  standard deviations from the overall mean for the image. This parameter controls
  whether a spline fit is attempted for a given spectral region (slit or slice).
  Higher values will create spline models for fewer slices; lower values will attempt
  to fit more slices. If set to 0, all slices will be fit.

``--oversample`` (float, default=1.0)
  Use the trace model to oversample the data by this factor.  If the value is 1.0,
  the only change to the datamodel is to attach a spectral trace image, in the
  ``trace_model`` attribute.  If any other value is specified, the input flux, error,
  and variance images are replaced with interpolated data oversampled onto a new pixel
  grid.

``--slope_limit`` (float, default=0.1)
  Slope limit for using the spline model to compute the trace.  This parameter is used to
  distinguish between bright, compact sources for which the spline model is appropriate and
  faint, diffuse sources for which it is not.
  For compact sources (high slope), the spline models are saved in the output trace model
  and are used to compute the oversampled flux if oversampling is performed.
  For diffuse sources (low slope), a linear interpolation is used in oversampling.
  Set the slope limit to lower values to use the spline model for fainter sources.
  If set to zero, the spline model will always be used.

``--psf_optimal`` boolean(default=False)
  If set to True, the values for ``fit_threshold`` and ``slope_limit`` are ignored and
  the spline models are fit and used for all data.  Also, residual differences from
  the spline model are not interpolated and added to the spline fits in oversampling.
  This option is generally only appropriate for simple, isolated point sources.

``--save_intermediate_results`` boolean(default=False)
  If set to True, additional image models are saved to disk for inspection, containing the full
  spline model, the spline model as used for compact sources, the linearly interpolated
  data, and the residual flux model.  The saved files will have suffix
  ``spline_full``, ``spline_used``, ``linear_interp``, and ``spline_residual``,
  respectively.  The linear interpolation and residual flux files are saved only
  if oversampling was performed.