Abstract: This study made comprehensive comparison of sea ice concentration derived from ship observations, optical and passive microwave images. Seven types of SIC derived from AMSR-E images and MODIS images were compared with RSO at 27 sample points between 2002 and 2007. The correlation between SIC derived from synchronous data observed at the same spatial scale had higher correlation coefficients than the others, whereas SICs observed at different times and scales displayed large inconsistencies. The correlation between SIC derived from data observed at the same spatial scale but at different times were affected by the spatial resolution. The RSO had considerably large differences with the PSO, the subjectivity in e visual estimation, weather conditions, quality of the image classification, and extraction method all attribute to their differences. Although the pseudo ship observation extraction method is helpful to generate large number of samples at the sea ice edges, error propagation must be controlled in the extraction process.