Laser transit anemometry (LTA) systems find many practical applications where the statistical variability noise produced by wall flare light limits signal detection. Under these conditions, non-linear threshold-detection and pulse-centre-estimation, along with cross-correlation processing, is superior to either photon correlation or to classical pulse pair timing. We have developed a photon-limited pulse-centre estimation discriminator and demonstrated the efficiency of this with cross-correlation processing in recent unseeded back-scatter wind tunnel tests with the new SDL LTA system. This paper introduces ideas concerning cross-correlation of non-linearly discriminated LTA signals, some effects of correlator parameters on the measurement of turbulence, and supportive experimental results from steady transonic flow.