¥LCT schema in use today have one
central idea: proper motions of features in 2 successive images - whether G-band filtergrams, Ha images, or photospheric magnetograms - separated in time by Dt are found by maximizing a cross-correlation
function, or minimizing an error function between sub-regions of the images. The concept is generally attributed to November & Simon
(1988).
¥The FLCT method (which we developed) is
similar. For each pixel, we:
Ðmultiply each of the 2 images to be
correlated by a Gaussian, of width s, centered
at that pixel; crop the resulting altered images 1 and 2 by chopping the insignficant parts of the
images;
Ðcompute the cross-correlation function
between the two cropped images using standard Fast Fourier Transform (FFT) techniques;
Ðuse cubic-convolution interpolation to
find the shifts in x and y that maximize the cross-correlation function to one of two precisions (chosen by the user), either 0.1 or
0.02 pixel; and
Ðuse the shifts in x and y and Dt between images to find the intensity features' apparent motion along the
solar surface.