Global observation of ocean and sea ice dynamics relies heavily on space altimeters. However, due to their high latitudes, which are less covered by space altimeters, and the ice cover, which hides the sea level, polar oceans are still poorly observed and modeled. The SWOT altimeter significantly increases the density and quality of measurements up to 77° latitude, covering the entire Southern Ocean and a large part of the Arctic Ocean. Still, these observations require a distinction to be made between measurements taken on water and measurements taken on ice. The CNES L3 Unsmoothed 250m v2.0.1 product includes a new flag that identifies the type of surface observed for each pixel, enabling processing tailored to the object under study. Here we present the methodology used to calculate this flag and evaluate the results obtained using space imagery, nadir altimetry and OSI SAF concentration products.