AVHRR US Scaling

  1. Equations for scaling and unscaling values.
           scaled = actual * scale + offset
           actual = (scaled - offset) / scale
    
  2. Values to be scaled are stored in signed data types, except unsigned byte.
  3. Satellite zenith angles are truncated to the range -90 to 90.
  4. Relative azimuth angles are stored as absolute values.
  5. For byte scaling, valid reflectance values are 0 to 63; valid radiace values are 0 to 333; and valid thermal values are 203 to 330. Values below these ranges are set to zero in the output image and values above these ranges are set to 255 in the output image.
  6. NDVI values are not actually implemented in the scaling coding and are listed in the these tables only for reference.
    
                         Field        Actual     Valid
                     --------------------------------------
                     SatZen:       -180 to 180   -90 to  90
                     SolZen:          0 to 180     0 to 180
                     RelAz:        -180 to 180     0 to 180
                     Reflectance:     0 to 100     0 to 100  (byte: 0 to 63)
                     Radiance:        0 to 540     0 to 540  (byte: 0 to 333)
                     Thermal:       160 to 340     0 to 340  (byte: 203 to 330)
                     NDVI:           -1 to   1    -1 to   1
    
    
    
                 |         BYTE                          |         16BIT
        Field    |  scale offset min/max        Field    |  scale offset min/max
    ------------------------------------    ------------------------------------
    SatZen:      |  1.0     90.0   0/180    SatZen:      | 10.0     0.0  -900/ 900
    SolZen:      |  1.0      0.0   0/180    SolZen:      | 10.0     0.0     0/1800
    RelAz:       |  1.0      0.0   0/180    RelAz:       | 10.0     0.0     0/1800
    Reflectance: |  4.0      0.0   0/252    Reflectance: | 10.0     0.0     0/1000
    Radiance:    |  0.766    0.0   0/255    Radiance:    | 10.0     0.0     0/5400
    Thermal:     |  2.000 -405.0   1/255    Thermal:     | 10.0     0.0  1600/3400
    NDVI:        |100.0    100.0   0/200    NDVI:        |100.0   100.0     0/ 200
    
    
    
                 |         32BIT                          |         REAL            
        Field    |  scale offset min/max        Field     |  scale offset min/max   
    ------------------------------------     ------------------------------------
    SatZen:      |   10.0    0.0  -900/ 900  SatZen:      |   1.0    0.0  -90/ 90
    SolZen:      |   10.0    0.0     0/1800  SolZen:      |   1.0    0.0    0/180 
    RelAz:       |   10.0    0.0     0/1800  RelAz:       |   1.0    0.0    0/180 
    Reflectance: |   10.0    0.0     0/1000  Reflectance: |   1.0    0.0    0/100 
    Radiance:    |   10.0    0.0     0/5400  Radiance:    |   1.0    0.0    0/540 
    Thermal:     |   10.0    0.0  1600/3400  Thermal:     |   1.0    0.0  160/340 
    NDVI:        |  100.0  100.0     0/ 200  NDVI:        | 100.0  100.0    0/200