Interference Between Direct and Reflected Rays, Including the Effect of the Velocity Profile This figure (graphed with pxmas1.m) shows our best attempt to fit the observed signal strength variation (black curve) with a model for interference between the direct ray and the ray reflected once from the surface. Using the tidal stage (upper green curve) to calculate the path difference gives the red theoretical curve, agreeing with the data (black) only in general trends, but not in detail. The current velocity is shown in the lower green curve. Using this data, and assuming that the vertical current profile follows the y^1/6 law, the blue theoretical curve is calculated. Agreement with the data is improved, but still not exact.