Variations of the sodium layer altitude and atom density profile induce errors on laser-guide-star (LGS) adaptive
optics systems. These errors must be mitigated by (i), optimizing the LGS wavefront sensor (WFS) and the
centroiding algorithm, and (ii), by adding a high-pass filter on the LGS path and a low-bandwidth
natural-guide-star WFS. In the context of the ESO E-ELT project, five centroiding algorithms, namely the centre-of-gravity
(CoG), the weighted CoG, the matched filter, the quad-cell and the correlation, have been evaluated in closedloop
on the University of Victoria LGS wavefront sensing test bed. Each centroiding algorithm performance is
compared for a central versus side-launch laser, different fields of view, pixel sampling, and LGS flux.