Radiometric Resolution

The radiometric resolution specifies how well the differences in brightness in an image can be perceived; this is measured through the number of the grey value levels. The maximum number of values is defined by the number of bits (binary numbers). An 8-bit representation has 256 grey values, a 16 bits (ERS Satellites) representation 65.536 grey values.

The finer or the higher the radiometric resolution is, the better small differences in reflected and emitted energy can be measured, and the larger the generated data amount will be (compare with the image on the right).

The advantage of additional differentiation is rather small - when comparing LANDSAT-MSS (6 bits) and TM (8 bits) the improvement is a marginal 2-3%.

Radiometric resolution depends on the wavelengths and the type of the system. Resolutions of different satellite systems:

  • LANDSAT-MSS (from LANDSAT 1-3): 6 bits (64 grey values)
  • IRS-LISS I-III: 7 bits (128 grey values)
  • LANDSAT-TM (from LANDSAT 4-5) & SPOT-HRV: 8 bits (256 grey values)
  • LANDSAT-ETM & ETM+ (from LANDSAT 6-7): 9 bits (only 8 bits will be transmitted)
  • IRS-LISS IV: 10 bits (only 7 bits will be transferred)
  • IKONOS & QuickBird: 11 bits (Löffler et al. 2005).