A method is described for calculating indices of sea ice distribution from digital data distributed by the National Snow and Ice Data Centre, Colorado, USA. Data consist of an image of the Antarctic, made up of 312x332 pixels, each having a dimension of 25x25km, for every day in the year. Primary data of the distance of sea ice from CEMP sites, the northerly position of the sea ice edge, and the percentage ice cover in subareas, are entered into the CCAMLR database. Indices of ice cover are calculated from these primary data. The techniques used are validated against alternative known data.