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.