McIDAS Programmer's Manual
Version 2015

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GVAR Block 11

The GVAR Block 11 holding areas contain data for sounder images. This data is not easily accessed. A decoder must reformat the raw Block 11 data and place it in the sounder image, where it is available for analysis and display.

GVAR Block 11 directory block

Word Value Description

11

1 or 2

number of bytes per element, depending on the element size of the band; a holding area cannot contain both 1- and 2-byte data

14

1

number of bands in the image

19

 

block type filter; positions of set bits correspond to the block types requested; the least significant bit is the rightmost bit; the value 787968 translates to 0c0600 hex with bits set in positions 20, 19, 11 and 10

25-32

RT BK11 BYT1

normal entry; ASCII

49

40

length of the data block line prefix documentation,
in bytes

50

0

length of the data block line prefix calibration,
in bytes

51

0

length of the data block line prefix band list, in bytes

52

BK11

image source type; 4 bytes ASCII

53

RAW

calibration type; 4 bytes ASCII

GVAR Block 11 data block

GVAR transmits 22 types of Block 11 data. This can be 6-, 8- or 10-bit data. The user can specify any type to be stored in a single holding area. Control fields in the line prefix or the first portion of the data (called the SAD ID) are used by postprocesses, such as the sounder decoder, to determine the block type. Each data block line consists of a single Block 11 sector, or block. All blocks are 8040 bytes. Refer to the OGE, sections 3.3.7 - 3.3.7.14 for a description of the contents of each block type.

The 10-bit data is formatted as follows, with x representing a data bit and the rest being zero-filled after shifting.

| 0 | x | x | x | x | x | x | x | x | x | x | 0 | 0 | 0 | 0 | 0 |

The 8-bit data is formatted as follows:

| x | x | x | x | x | x | x | x |

The 6-bit data is formatted as follows:

| 0 | 0 | x | x | x | x | x | x |

The line prefix for Block 11 contains a 4-byte validity code. Its documentation region is 40 bytes, consisting of the following:

Documentation region Bytes OGE table

block header CRC; this field is overwritten in the mainframe by a 2-byte counter and is used to check sequencing of the data flow

2

3-5

year, day and time from Block 0

8

3-6

block header

30

3-5

The rest of the Block 11 line consists of up to 8040 bytes of data, depending on block type.

Bytes 17-24 contain the time the block was sent from the ground station.


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