15:23 Monday April 29, 2002. To estimate the uncertainties in ray tracing results due to variability of the ocean medium, we need to rum Michael's ray-tracing program with different sound-speed profiles. We only have one which goes as deep as 3000 m; the others stop at about 1000 m. So, we need to extend them deeper by some sort of extrapolation. Toby suggests making a "guess" at the variation of the temperature and salinity, and then calculating the speed of sound as a function of depth. This should not be too off the wall since the main dependence at greater depths in on the depth (pressure) itself.