where PS⊥=I−(USUST) is the orthogonal projector onto the noise subspace, r and e are position and orientation vectors, respectively. This cost function is zero when g(r, e) corresponds to one of the true source locations and orientations, r = rdipi and e = edi, i = 1, ..., p. An advantage over least-squares estimation is that each source is found in turn, rather than searching simultaneously for all sources.
