For all scenes, there is an obvious incidence angle effect
that can be seen in the HH images. The tone is brighter at the
near-range portion of the scene. There is no obvious effect of
incidence angle visible in the ice concentration estimation. This
indicates that the CNN model is able to model the incidence angle
effect very well. Banding caused by a SAR defect in the HV
image causes a slight overestimation of the ice concentration
in the middle left of the water region for 110725 and 110811.
Regions with less strong banding are successfully modeled, as
the right part of the water regions in all three images has clean
estimation of 0% ice concentration. The banding might be the
cause of the overestimation at low-ice-concentration areas in
Fig. 4. Melting causes the appearance of ice in the SAR image
to become similar to water. At this time of year, the darker
regions in the top left and middle left parts of scene 110811 are very likely to have water on the surface. The uniform dark
regions in the HH image can be easily misinterpreted as water in
automatic SAR image analysis methods and are similarly usually
mistaken for ice of low concentration by passive microwave
ice concentration retrieval algorithms [26], [33]. Those regions
are labeled by CNN with intermediate ice concentration levels.
In comparison, the ASI data indicate ice concentration that is
very low, whereas the image analysis is between the two.