Saturday, 28 August 2021

Notes: SAR - distortions

continued from: SAR Basics

 Distortions:

  • Foreshortening,
  • Layover,
  • Shadow


Foreshortening: 

  • mountain appear as if leaning towards the sensor 
  • sensor facing slope foreshortened in image
  • decreases with increasing look angle


Layover: 

  • top of the mountain imaged before the base
  • mountain top overlain on ground ahead of the mountain
  • decrease with increased look angle


Shadow: 

  • area behind the mountain
  • increases when the angle is large


Speckle Effect: grainy appearance: salt and pepper - due to the result of interference from the many scattering echoes


___


Geocoding and RTC processing:

  1. Read in data
  2. Apply precise orbit files
  3. Radiometric Calibration
  4. Multilooking (optional)
  5. Speckle filter (optional)
  6. Radiometric terrain flattening
  7. Geocoding / geometric terrain correction
  8. Linear to decibel conversion (optional)
  9. write data in desired format



The above contents has been the attempt to prepare the excerpt from the book " The SAR Handbook" Ch-2 while trying to learn. The chapter has the very minute details and information for every avid individual interested in SAR. The contents
written above does not fully capture the whole chapter for sure.





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