Problems in Synthetic Aperture Radar (SAR) Image

There are a number of reasons of disturbance in the performance of the SAR system and degradation in the quality of SAR image. Some of the reasons are nonlinearities of the SAR subsystem that damage the ability of the system resolution. Noise is one frequently seen problem in SAR images whose major source is image acquisition. Other sources of noise introduction are the position of sensor and velocity errors that result in geometric distortion in the SAR image. Major occurring problems in the SAR image are discussed in Table 1.

Table 1 Real problems in SAR images

Real effects on

SAR images (Problems)

Major sources






Geometric distortion

·    Change in position: movement variation and changes in platform attitude (high and low frequencies) cause distortion due to the platform of spaceborne or airborne.

·    Rotation of earth, topographic effect and curvature cause distortion due to earth.

·    Deviation in sensor mechanism and viewing geometry: panoramic effect causes distortion due to the sensor.

·    Refraction and turbulence cause distortion due to the atmosphere.

·    Time-variations or drift and clock synchronicity cause distortion due to measuring instruments.



System nonlinear effects

·    Amplitude error and phase error degrades the system impulse response function (IRF).

·    Thermal noise damages the dynamic range of the system.

·    Quantisation error, bit error noise and system nonlinearities damage the azimuth resolution and dynamic range of IRF.



Range migration

·    Linear drift because of elliptical orbit and earth rotation.

·    The appearance of hyperbola shaped reflection as target move towards the synthetic aperture.

·    Curvature depends on range compressed response due to which SAR handles the two-dimensional space-variant problem.

·    High velocities of airplanes and satellite-borne SAR system.




Speckle Noise effects

·    SAR images are shaped by the constant interaction of the transmitted high-frequency radar waves with target areas. This constant interaction causes random constructive and destructive nosiness that result in salt and pepper noise all over the image. This noise scatters all around the image and suffers from the speckle noise effects and degrades the quality of the SAR image. It is a granular pattern noise that inherently exists in the SAR image.

·    The existence of numerous elemental scatterers with an arbitrary distribution within a resolution cell.

Read more: 
Applications for Synthetic Aperture Radar (SAR)

Different Types of SAR | Strip mapping Mode SAR | Spotlight Mode SAR | Inverse SAR (ISAR)

Radar Categorization Based on Antenna Size | RAR (Real Aperture Radar) | SAR (Synthetic Aperture Radar)

Radar | Types of Radar | Active Radar | Passive Radar

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                For more image processing topics refer:
Problems in Synthetic Aperture Radar (SAR) Image Problems in Synthetic Aperture Radar (SAR) Image Reviewed by IPR on January 31, 2022 Rating: 5

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