Radiometric corrections
Convert relative digital-number to at-sensor radiance
| Raw spectral signature (digital numbers) | Physical unit of measurement spectral signature (spectral radiance [watts/m2.μm]) |
Conversion to at-sensor radiance is needed in pre-processing if the image is to be used for:
- Calculation of biophysical variable is required (e.g. temperature, absorption)
- Multi-date mapping of biophysical variables
- Using field measured spectral-signature libraries to process data
Converts relative sensor measurement (digital-numbers) to an absolute physical unit of measurement AT THE SENSOR: (e.g. spectral radiance [watts/m2.μm] ).
Conversion equation is established for each band(λ) pre-launch and in some cases updated post-launch: At-sensor spectral radiance λ = [gain λ * DN λ] + offset λ
