4 km AVHRR Pathfinder Quality Assurance

Several quality assurance steps are conducted to insure the integrity of the data provided here. These steps are conducted routinely during the processing and transfer stages of the system. Note that these steps are aimed primarily at assuring items like file integrity and availability, not at the accuracy of the derived sea surface temperature (SST) values. That type of quality control is integral to the Pathfinder processing through derivation of parameters like the overall quality flag and quality mask values, as well as post-processing studies being carried out to test the satellite SSTs against in situ observations.

The steps to insure file integrity are as follows:

1. Perform checksumming during transfer between RSMAS and NODC, and between systems at NODC as files are moved on to the operational server at data.nodc.noaa.gov. This step insures the files are not corrupted during transfers between computer systems.
2. Generate browse images for every file in the dataset. This process verifies the file format integrity for every file by accessing the file and reading data from it. The browse images (for 1985-2006) are available at http://data.nodc.noaa.gov/pathfinder/Version5.0/browse_images. Note that the browse imagery for interim 2007-2009 is currently available at: http://data.nodc.noaa.gov/pathfinder/Version5.0_interim/browse_images.
3. Compute and verify counts of files in each directory structure to insure no files are missing. The counts results are updated hourly and are available here:
   • Browse Graphic Counts Table
   • Data Directory Counts Table
4. Compute and verify the volumes of each directory to insure reasonable data volumes are present. The results are updated hourly and are available here:
   • Browse Graphic Volume Table
   • Data Directory Volume Table
5. Visually inspect every browse image for gross errors, unusual features, etc. This check reveals obvious errors or processing problems.