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Radiometric balancing

     Radiometric processing

     Radiometric processing (balancing) means a set of adjustments that compensate for visual effects such as hot spots, lens vignetting and mismatches between adjacent mosaic images.
     Overall appearance and quality of the final orthophoto must be a realistic representation of the true likeness of the ground at the time of capture. Also, radiometric balancing ensures homogenous representation over an entire processing area.

     The effects of hot spot and vignetting are caused by:

     • Perspective angle of the camera sensor
     • Time of the day for the flight mission
     • Sun position during the flight mission
     • Inadequate camera filters for environmental conditions (this can accentuate the effects)

     Other effects of mismatching between images are caused by:

     • Alternative flight directions for the 2 consecutive strips
     • Different time of the day for flight missions
     • Different periods of the week/month/year for flight missions of the same processing area
     • Different atmospheric conditions during multiple flight of the same area

A very important aspect in the radiometric ballancing process is the quality of initial images. That's why, image raw data processing is an very important process. Image burnout or dark shadows (saturation), colour bleeding, rainbow effects are detrimental to the final radiometric accuracy of orthophoto. Saturation of images, for instance, can't be undone!

Example of initial images - assembled table:

Example of radiometric processed images - assembled table: