The provided Matlab code allows for fitting an ellipse to given data points with the additional prior knowledge that the center of the ellipse is located on a given line. The usage of this constraint in a new global convergent one-dimensional search problem ("Tunneling") improves the fitting accuracy compared to other ellipse fitting methods.
You can find more details on the theoretical background of the presented algorithm here:
http://doi.org/10.1007/s10851-015-0584-x
If you use the code please cite our paper:
Waibel, P; Matthes, J.; Gröll, L; Constrained Ellipse Fitting with Center on a Line; Journal of Mathematical Imaging and Vision; November 2015, Volume 53, Issue 3, pp 364-382