Illumination conditions
must be constant through the whole scene

• ILS correction of airborne flight lines must be applied
  • the main reason is that the incident sun light can vary by several percents from start to end of an airborne flight line as the sun height varies
  • another reason is to correct for transient sun light variations
  • this artifact is wavelength-dependent
• Removal of limb brightening must be applied
  • the reason is that the path length increases markedly from vertical viewing to oblique viewing across the flight line
• Atmospheric path radiance must be homogeneous
  • areas affected by haze must be masked out, or "deglinted"
  • if at all possible, areas affected by clouds and their shadows must be masked out.
  • atmospheric adjacency effect must be corrected for, if at all possible, but "deglinting" often achieves a good correction.

Optically deep waters must be available in the image

• This is necessary for calibrating the glint correlations.

• This is absolutely necessary for specifying the deep water radiance Lsw.

• Cyanobacteria tend to move up towards more light in the evening, and then to move down in the morning as illumination becomes too harsh.
• This also depends on wind conditions.
• Passive RS images are taken at a time when solar illumination is maximum.
• This might be the cause of weird results in many atolls like Fakarava and  Tarawa

Sun glints (sea surface clutter) must be totally removed

• Best is to discard images or areas which are too badly affected by sun glint
  • like in case of very oblique viewing towards the sun
• Sun glint and Skyglint can have distinctly different spectral properties
  • sunglint has the spectral properties of direct sun light, i.e. biased towards the yellow region of the solar spectrum
  • skyglint has the spectral properties of the sky light, i.e. usually biased towards the blue region of the solar spectrum for a clear blue sky
• Best deglinting is achieved when the atmosphere is hazy,
  • as this strengthens the correlations among bands from NIR through BLUE regions (Mie scattering).

Resampling
should have been achieved by the nearest neighbor algorithm

Optical properties of water bodies

• must be homogeneous across the scene,
• or this shall show in the output (see the arcachon study case)