I am trying to filter the best quality nLw using the l2_flags in the Aqua/MODIS L2_LAC files.  The Ocean Level-2 Data Products document (http://oceancolor.gsfc.nasa.gov/DOCS/Ocean_Level-2_Data_Products.pdf) indicates that the l2_flags is INT32 and has the bit setting described in Table 3 on p. 9.  In looking at a sample granule, A2003303180500.L2_LAC, the range of the integers is [-2147483648, 679510848].  To use the l2_flags, should I convert it to UINT32 first, then go in and extract each bit according to the definitions shown in the Ocean Level-2 Data Products document?  According to the bit definitions, the best quality pixels would have bit 1 to 29 set to 0 and bit 32 set to 1.  Am I correct?

Regards,
Justin

Justin,

You are right. You may use SeaDAS's Read & Profileo function to help
you better understand those L2 flag use.

Function -> Read & Profile -> Pixel bit data display + cursor motion

If you wish to write an IDL program, SeaDAS's 'sdp_read_bit_dsp.pro'
is your good reference.

Long