The command CALIBRATE/LONG determines the dispersion relation
for each row of the spectrum. In addition, a bivariate dispersion
relation is computed if the keyword 
is set to
YES, as in:
Midas...> SET/LONG TWODOPT=YES
Midas...> CALIBRATE/LONG
The command CALIBRATE/LONG determines row-by-row
polynomial solutions of degree 
stored in the
table coerbr.tbl and fits a 2-D
polynomial of degree 
to the lines
with entries in columns :X, :Y, and :WAVE of table line.tbl.
The coefficients of the 2D polynomial are stored in
the keyword 
.
The program performs a final oulier rejection which eliminates all
lines with residuals larger than 
pixels (if TOL is
positive). However the minimum number of lines in any given row will be
+2. If this number cannot be obtained, a polynomial
of lower order will be fitted. Three more columns are added to
the table line.tbl:
Note a proper calibration, images should preferably have positive step descriptors and the wavelength should increase from left to right.