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Hi all, Not quite sure I'm following either, but I thought it might be useful to give our take on flags and some concrete examples. On 01/11/11 11:14, Lynnes, Christopher S. (GSFC-6102) wrote: > I don't want to speak for Randy, but I know it is quite common in > Level 2 data from the Earth Observing System to have quality > variables where there is a one-to-one match at the pixel level > between a given quality variable and 1 or more data variables. We > see this case in AIRS Level 2 as well as MODIS Level 2 atmospheres On the MODIS data, we produce (level 3) netcdfs with a "l2flags" variable containing the per-pixel flag values and associated CF information from http://cf-pcmdi.llnl.gov/documents/cf-conventions/1.5/ch03s05.html (see bottom of email for an example). This single variable is then associated with and used by many other variables in the file (see below on ancillary variables). However, as I understand it, this part of CF isn't intended to encode "special" values embedded in a data value (e.g. if you have chlorophyll data, but any element with a value of 12345.6789 is actually cloud). > totH2OStd:quality_flags = "Qual_H2O" ; I think this is covered by the ancillary variables element: http://cf-pcmdi.llnl.gov/documents/cf-conventions/1.5/ch03s04.html Admittedly, it's not specific to quality flags, but that's not necessarily an issue (-> a bit more interpretation). Hope that's helpful, or at least leads to further clarifications! Cheers, Mike. ---------------- int l2_flags(time, latitude, longitude) ; l2_flags:_FillValue = 0 ; l2_flags:grid_mapping = "mercator" ; l2_flags:flag_values = 1L, 2L, 256L, 512L, 1024L, 2048L, 4096L, 8192L, 16384L, 32768L, 65536L, 131072L, 262144L, 524288L, 1048576L, 2097152L, 2097153L, 2097156L, 2097160L, 2097168L, 2097184L, 2097216L, 2097280L, 4194304L, 8388608L, 8388612L, 8388616L, 8388624L, 8388640L, 8388672L, 8388736L ; l2_flags:flag_meanings = "LOW_PRESSURE LOW_SUN CASE2_S ABSOA_DUST OOADB SUSPECT COSMETIC COASTLINE PCD_19 PCD_18 PCD_17 PCD_16 PCD_15 PCD_14 PCD_1_13 WATER WHITE_SCATTERER HIGH_GLINT BPAC_ON MEDIUM_GLINT ICE_HAZE CASE2_Y CASE2_ANOM CLOUD LAND TOAVI_INVAL_REC LARS_ON TOAVI_WS TOAVI_CSI TOAVI_BAD TOAVI_BRIGHT" ; l2_flags:flag_masks = 1L, 2L, 256L, 512L, 1024L, 2048L, 4096L, 8192L, 16384L, 32768L, 65536L, 131072L, 262144L, 524288L, 1048576L, 2097152L, 2097153L, 2097156L, 2097160L, 2097168L, 2097184L, 2097216L, 2097280L, 4194304L, 8388608L, 8388612L, 8388616L, 8388624L, 8388640L, 8388672L, 8388736L ; l2_flags:missing_value = 0 ; l2_flags:units_nonstandard = "1" ; -------------------------------------------------------------------------------- Plymouth Marine Laboratory Registered Office: Prospect Place The Hoe Plymouth PL1 3DH Website: www.pml.ac.uk Click here for PML Annual Review Registered Charity No. 1091222 PML is a company limited by guarantee registered in England & Wales company number 4178503 Please think before you print -------------------------------------------------------------------------------- This e-mail, its content and any file attachments are confidential. If you have received this e-mail in error please do not copy, disclose it to any third party or use the contents or attachments in any way. Please notify the sender by replying to this e-mail or e-mail forinfo@xxxxxxxxx and then delete the email without making any copies or using it in any other way. The content of this message may contain personal views which are not the views of Plymouth Marine Laboratory unless specifically stated. You are reminded that e-mail communications are not secure and may contain viruses. Plymouth Marine Laboratory accepts no liability for any loss or damage which may be caused by viruses. --------------------------------------------------------------------------------
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