De-biasing the Station Start Time

We study the effect of the bias in the shower front arrival time as measured by the surface detector stations. Using the shower front model of GAP 2006-016, we show that the experimental bias in the detector start time can be properly estimated and corrected for. The correction does not change our angular resolution nor the distributions of the angular distance between the SD and the hybrid reconstruction. On the other hand, it modifies the estimated radius of curvature of the SD events, an important parameter for the mass composition studies.