Abstract: Presented is a method to derive data of ice draft and coverage from acoustic measurements madewith moored Upward Looking Sonars (ULSs), sounding the sea surface remotely from below. The method hasbeen developed on the basis of two-year long time series obtained from four locations in the Weddell Sea. Ittakes into account the variations of sound speed and density which occur between the target and the instrument,the variations of the surface air pressure, and a possible bias of the mean ice draft within the ensonified windowwhich results as the combined effect of beam spreading and skewed ice distributions; ice and open water arediscriminated making use of their specific echo amplitude signatures. The residual total error in the determinedmean ice draft is estimated as 4 cm, compared to an initial error of almost 90 cm in the original uncorrecteddata. Suggestions for further improvement of the instruments are made at the end of the paper.