FIMR has been utilizing the Radarsat-1 ScanSAR data inoperational sea ice monitoring for several years. The surfacescattering dominates the backscattering at C-band, but itis still possible to estimate ice thickness based on this surfaceroughness visible in SAR data in some areas of the Baltic Sea,because typical Baltic Sea drift ice becomes more and moredeformed as it gets older and thicker, i.e. there is correlationbetween Baltic Sea ice surface roughness and thickness.For ship navigation in the Baltic Sea ice ridging is anotherimportant ice parameter, in addition to ice thickness. However,it is impossible to detect single ridges from our operationalSAR data, Radarsat-1 ScanSAR Wide images in 100 mresolution. One ice parameter closely related to ridging is theequivalent deformed ice thickness (Tdef ). The total (mean overan area) ice thickness (T) is the sum of the level ice thickness(Tlev) and equivalent deformed ice thickness:T = Tlev + Tdef . (1)In this paper we study estimating of Tdef from our operationalRadarsat-1 data, and also make some comparisons to Electromagneticinduction (EM) based ice thickness measurements.