Image Data Function Record - GOES Satellite Hunt
Image Data Function Record
This header describes the physical meaning of the Image included in the LRIT File. It may contain calibration data depending on the image type.
Table 8 - Image Data Function Record Fields
The Data field is consisted by several map values in
key := value format with some special meanings.
|$HALFTONE||Specifies a Halftone Grayscale Data.|
|$DISCRETE||Specifies a Discrete Type that each value has a specific meaning|
|$OVERLAY||Specifies a Overlay Data|
|_NAME||Name of the image|
|_UNIT||Unit used for the data|
|a number||A map to defined values|
This is usually used for marking overlays or calibration data. One great example to explain is a thermal infrared channel that has a map for each pixel value to it’s corresponding temperature. In this case, there will be a $HALFTONE field defined with the number of bits that are relative to the map, a _UNIT field with the type of unit, for example Degrees Kelvin, and then several
number := number maps representing each value. For example:
$HALFTONE:=8 _NAME:=Calibrated Infrared _UNIT:=Degree Kelvin 0:=330 1:=329.5 2:=329 3:=328.5 4:=328 5:=327.5 6:=327 7:=326.5 8:=326 9:=325.5 10:=325 11:=324.5 12:=324 13:=323.5 (...)
A pixel with value 11 mean its temperature is 324.5 Degrees Kelvin.