The band information for the GVAR Sounder is provided in Appendix B, Satellite Information.
McIDAS Programmer's Manual
Version 2003
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GVAR Sounder areas are decoded from Block 11 data. The GVAR Sounder decoder reads the Block 11 holding areas, which contain blocks of type 32 (20 hex), type 35 (23 hex) and others. These blocks are documented in OGE, sections 3.3.7.2 and 3.3.7.3.
Navigation and calibration data is read from type 32 blocks, which are sounder documentation blocks. Sensor data is read from type 35 blocks, which are sounder scan data blocks. After the sensor data is read, it is reformatted and placed in the sounder image area.
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The band information for the GVAR Sounder is provided in Appendix B, Satellite Information. |
The GVAR Sounder produces data for a given spatial location in 18 IR spectral bands and one visible band. The number of bands in the sounder data must match the value in word 14 of the directory block. Word 19 designates the band map. All sounder data fields are 13 bits placed in 2-byte (16-bit) fields. Each data point in a scan data block has 23 bands of data. The data points correspond to a geographic area 11 pixels west-east and 4 pixels north-south. For each image line, the decoder produces 11 sets of 23 interleaved fields of data.
Bands 20-23 of this data are not displayable; they hold the latitude and longitude of the first 19 bands. The latitude and longitudes are 32-bit values. Since the actual sounder data is 16 bits, the latitude and longitude values must be split in half to store them in the area structure.
Band 20 holds the two most significant bytes of the latitude; band 21 holds the two least significant bytes. Band 22 holds the two most significant bytes of the longitude; band 23 holds the two least significant bytes.
If the latitude and longitude values are not requested, the band list section will contain 20 bytes total with 19 bytes used.
These latitude and longitude values are in the Gould floating point format. See OGE, section 3.5.4. For example, if the latitude of a data point is 100.1640625, the hex representation is 42642A00; band 20 holds 4264, and band 21 holds 2A00.
This package does not provide any code for using these latitudes and longitudes; they are included only for reference purposes.
The four sounder detectors are numbered 1, 2, 3, and 4. Each data block line contains information from only one detector. The documentation block contains a field indicating which detector was used for the current line.
The line prefix contains a 4-byte validity code and a documentation region, which is described in the table below. The remainder of the line consists of the interleaved sounder data.
| Documentation region | Bytes | OGE table |
|---|---|---|
|
If the value in word 49 of the area directory is 216, the first 180 words of the Sounder Auxiliary Data block have been inserted here. |
Navigation blocks contain 640 words. Unless otherwise noted, words are twos complement binary integers. Navigation information comes from Block 11 records, type 32. Bytes designated R*4 in the OGE Tables are in Gould format in the holding areas. They must be scaled and then converted to integer, or converted to Real on the machine doing the decoding, scaled as designated below, and then converted to integer.
If the latitude and longitude values are not requested, the band list section will contain 20 bytes total with 19 bytes used.
Because the word allocation information for the sounder navigation block is nearly identical to that for the imager, it is not repeated here. Only the words with a different description are shown below. That difference is usually the OGE table number and/or byte numbers.
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