(1) At each float surfacing all but the first of the position fixes are discarded. (2) The speed is calculated between the surface fix corresponding to the lon/lat information and the previous valid surface fix; since there is no previous valid surface fix for the deployment location the first record is reported after the first full cycle (i.e. the deployment position is not in the file). (3) The time is interpolated between the reported and the previous valid position fix. (4) The position information is NOT interpolated.