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The following discussion refers to the Quality Assessment (QA) fields in the MODIS sea ice products. The least significant two bits, 0 and 1, provide information about the general quality of the product, and have a common meaning across all MODIS land products:00 = nominal
The remaining six bits are unique to the sea ice products. The local attribute key describes the setting and meaning of a bit. These are described in the following section.
Note: the following do not apply to Ice Surface Temperature (IST) data.
Bit 3: Flags pixels that were viewed at sensor view angles greater than 45 degrees. If the bit is set to 1 then the observation of that pixel was greater than 45 degrees. Range scan angle is then 45 to 55 degrees. If the bit is set to 0 then the observation was within 45 degrees of nadir. Range of scan angles is 0 to 45 degrees.
Bit 4: Flags occurrences of highly uncertain MODIS band 6 radiance calculations from the MOD02HKM algorithm. If the bit is set to 1 then there was great uncertainty in its calculation. If the bit is set to 0 the uncertainty of calculation is much less.
Bit 2: Flags the occurrence of observations that lie in the viewing azimuth range of 150 to 210 degrees. If the bit is set to 0 then the observation lies in that range. If the bit is set to 1 then it is outside that range.
Bit 3: Flags the occurrence of observations in a cell that fall below the minimal coverage threshold of 20 percentconsidered to be a good observation. If the bit is set to 1 the observation coverage was less than or equal to 20 percent. If the bit is set to 0 the observation coverage was greater than 20 percent.