  We propose a simple algorithm to locate the "corner" of an L-curve, a
function often used to select the regularisation parameter for the solution of
ill-posed inverse problems. The algorithm involves the Menger curvature of a
circumcircle and the golden section search method. It efficiently finds the
regularisation parameter value corresponding to the maximum positive curvature
region of the L-curve. The algorithm is applied to some commonly available test
problems and compared to the typical way of locating the l-curve corner by
means of its analytical curvature. The application of the algorithm to the data
processing of an electrical resistance tomography experiment on thin conductive
films is also reported.
