The Forward-Fitting method is based on the assumption that the spatial map can be well represented by a small number of elemental  source structures, each of which can be characterized by just a few parameters.  Such structures might be circular, elliptical, or curved elliptical Gaussians (a loop).  Such Gaussians sources can be represented by 4,6, or 7 parameters respectively.

In the Forward-Fitting algorithm, 'pixelized' maps of multiple Gaussian components are created and used to calculate a model modulation profile which is then compared to the observed modulation profile.  The map iteratively evolves into a best-fit image which yields well-quantified parameters. 

The Forward fit algorithm uses the ANNSEC coordinate system internally.


Using the Forward Fit algorithm at the command line:

Select algorithm 

o->set, image_algorithm='forward'

or 'for' or 'hsi_forwardfit'

Object Class 


Extract Object

ff_obj = o->get(/obj,class='hsi_forwardfit') 

Extract the object used in the hsi_image object, o

Parameter Prefix 

ff, e.g.
ff_n_gaussians = o->get(/ff_n_gaussians)
ff_control = o->get(/ff, /control)
ff_info = o-> get(/ff, /info)
ff_all = o->get(/ff)

All parameter names specific to this algorithm have this prefix

Parameter Table 

Forward Fit Object Parameter Table

List and short description of control and info parameters specific to this algorithm