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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.
| Name | Type | Description |
|---|---|---|
| Data | string | Data |
Table 8 - Image Data Function Record Fields
The Data field is consisted by several map values in key := value format with some special meanings.
| Key | Description |
|---|---|
| $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.