This README explains (briefly) how to use the MATLAB scripts
in this package (EUV_GEN_PREPROC.zip) to generate LBCC and IIT factors for
EUV image data. This package is for advanced users only.
If one is using STEREO-A/B 195 and AIA 193 data, it is
recommended to use the provided precomputed pre-processing
data at [www.predsci.com/chd].
For each script mentioned below, several parameters need to be
set and the data is assumed to be in hdf4 format and organized
as described in the EUV2CHM README file. Refer to the
script documentation to set the parameters.
To generate LBCC factors:
1) Use get_EUV_annuli_histograms.m to extract radial histogram information from a set of
EUV images. The results are saved in a .mat file.
2) Run get_LBCC_factors.m which loads the .mat file from (1) and generates the
LBCC factors for the set of images. The results are stored in a .mat file.
To generate IIT factors:
1) Compute the LBCC factors using the above method for use
in pre-processing the data before computing IIT factors (optional).
2) Run get_EUV_histograms.m to extract latitude-limited histograms for each instrument.
The histograms are stored in a .mat file.
3) Run get_IIT_factors.m which loads the .mat file above and computes the IIT factors.
The results are stored in a .mat file.
For additional help, the following is a list of each
of the included scripts and its function:
get_LBCC_factors.m Script to generate limb-brightening correction curve
transformation factors using histogram data generated
from get_EUV_annuli_histograms.m.
get_EUV_annuli_histograms.m Script to extract latitude-limited data histograms from EUV
line-of-sight images for discrete radial bins.
get_IIT_factors.m Script to generate inter-instrument transformation factors using
histogram data generated from get_EUV_histograms.m.
get_EUV_histograms.m Script to extract latitude-limited data histograms from EUV
line-of-sight images. The script allows the application of
limb-brightening correction to the images before taking the histograms.
get_annuli_mex.c C MEX function to perform data selection for latitude limit and mu bounds.
The C code is much faster than performing the selection in MATLAB.
To compile, run "mex get_annuli_mex.c".
get_analytic_limb_brightening_curve.m Function to compute line-of-sight emission integrals over radial mu values,
assuming spherically-symmetric hydrostatic equilibrium, given a
temperature in Kelvin and the solar mean coronal radius R0.
The result can be used to generate an analytic LBCC [F(mu)/F(mu=1)].
get_lat.m Function to take in B0 and central meridian angles,
as well as the x and y vectors defining the line-of-sight of the sun,
as well as the mean coronal radius R0, and return a latitude map.
get_mumap.m Function to take in x and y vectors defining
line-of-sight disk scales (in units of solar radii),
and the solar mean coronal radius R0, and returns a 2D weight map (mu).
hist_shift_sse_alpha_x.m Function which computes the SSE between a reference histogram
and that of applying the transformation I'=alpha*I+x.
hist_shift_sse.m Function which computes the SSE between a reference histogram
and that of applying the transformation I'=I+shift.
optimize_hist_transform_alpha_x_naive.m Performs a low-res brute-force optimization
for I'=alpha*I+x. For use in cases where fminsearch() fails.
optimize_hist_shift_naive.m Performs a low-res brute-force optimization
for I'=I + shift. For use in cases where searching() fails.
For further assistance, feel free to contact caplanr@predsci.com.