[Esip-infoquality] A different perspective on quality from GODAE

Leptoukh, Gregory G. (GSFC-6102) gregory.g.leptoukh at nasa.gov
Tue Jun 7 08:35:00 EDT 2011

I would argue that this is an "assimilation-biased" perspective on data quality. Assimilation systems are known to be very sensitive to outliers, so for assimilation system is better to have just few data points but be sure that they are not outliers. On the contrary, if you monitor ash transport, you want to have an image with the best coverage, where a human eye can 'filter" outliers easily. 

-----Original Message-----
From: esip-infoquality-bounces at lists.esipfed.org [mailto:esip-infoquality-bounces at lists.esipfed.org] On Behalf Of Lynnes, Christopher S. (GSFC-6102)
Sent: Tuesday, June 07, 2011 8:19 AM
To: esip-infoquality at lists.esipfed.org
Subject: [Esip-infoquality] A different perspective on quality from GODAE

Interesting...GODAE kind of equates quality level with processing level:  http://www.godae.org/Data-definition.html.  

I guess there may be some truth to that, in that you discard more and more suspect values as you go up the processing level chain:
L0 = raw data, keep everything
L1B = probably keep everything, but flag suspect quality based on calibration
L2 = discard individual pixels where retrievals are impossible or (sometimes) where they are highly suspect
L3 = (usually) do not include suspect pixels in grid averages
L4 = use only the best retrievals for assimilation

Of course, most levels carry exceptions:
L0 = delete packets with incorrect timestamps or apparent bit-level corruption 
L2 = keep only values that pass strict quality control (e.g., AIRS CO2)
L3 = keep all retrievals (MODIS Image_Optical_Depth)
Christopher Lynnes     
Goddard Earth Sciences Data and Information Center, NASA/GSFC

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