MODIS Sea Ice Quality Assessment Fields

MOD29 and MYD29
MOD29P1D and MOD29P1N

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
01 = abnormal
10 = cloudy
11 = invalid

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.

MOD29 and MYD29

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.

MOD29P1D and MOD29P1N

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.