The NOAA AVHRR/3 reader enables VISAT to import NOAA AVHRR/3 HRPT and AVHRR/3 LAC Level-1b data products.
Note: The AVHRR/3 reader is implemented in line with the "NOAA KLM User's Guide" (http://www.ncdc.noaa.gov/oa/pod-guide/ncdc/docs/klm/index.htm) and is capable of reading data products in version v2 to v4.
Note: A good source for AVHRR/3 data products is http://www.class.noaa.gov/
While AVHRR pixel data is read into memory it is calibrated on the fly. Scan lines with calibration errors are detected and corresponding sample values are set to a special no-data-value. Visat will excludes those no-data-values from pixels statistics and displays them in a separate image overlay.
The AVHRR/3 reader supports data products from the NOAA -15, -16, -17, and -18, as well as from the NOAA-N' satellites. The following features characterize the reader:
From Format version 4, which is produced since 25 January 2006 (see http://www.osdpd.noaa.gov/PSB/PPP/notices/notice_files/jan2506.html),
the product contains the CLAVR-x (Clouds from AVHRR
Extended cloud mask) cloud band. A draft of the CLAVR-x cloud mask
theoretical basis document can be found at
The reader has been tested with products obtained from the NOAA CLASS server which conforms to the format version 2 used for the NOAA -15, -16 and -17 satellites. Recently, NOAA has changed to the new version 3 format. The AVHRR/3 reader for BEAM already supports both existing 10-bit packed format versions. AVHRR/3 data products can optionally have an Archive Retrieval System (ARS) Header Record. If this header is present, it is automatically detected by the reader. In particular, the AVHRR/3 reader implementation has the following features: