GEOMETRIC CORRECTION, RADIOMETRIC CORRECTION, AND NOISE REMOVAL

Geometric Correction, Radiometric Correction, and Noise Removal

1. Geometric Correction refers to the process of adjusting and aligning the geometric properties of an image or object to correct any distortions or irregularities.

• Geometric correction refers to the procedure of aligning and correcting picture data to appropriately depict the Earth's surface.
• This method is crucial for eliminating distortions and inaccuracies associated with image geometry.

Distortions addressed

Sensor-Related Distortions: Corrections for aberrations caused by the imaging sensor, such as lens distortions and spatial misalignments.

Platform-Related Distortions: Platform-Related Distortions refer to corrections made for mistakes resulting from the satellite or aircraft's movement and orientation while capturing images.

Approaches

• Orthorectification is the process of making adjustments to a picture in order to correct for both topographic relief and sensor distortions. This results in the creation of a representation that is accurate in terms of its planimetry.
• Georeferencing involves the process of aligning an image with a coordinate system or map in order to guarantee spatial correctness in relation to real-world places.
• Radiometric Correction refers to the process of adjusting the pixel values in an image to account for variations in sensor sensitivity, atmospheric conditions, and other factors that can affect the accuracy of the image.

• Radiometric correction is the procedure of modifying the image data to precisely represent the actual radiance values of the Earth's surface, while accounting for distortions and discrepancies in the recorded radiometric readings.

Types of Adjustments

• Calibration Adjustments involve making precise corrections for systematic errors and variances in the sensor's response. This is often done by using calibration coefficients and following standardization methods.

• Atmospheric corrections involve compensating for the impact of atmospheric circumstances, such as scattering and absorption, on the measured radiance values.

Methods

1. Dark Subtraction

• Dark Subtraction is a technique used to eliminate the impact of sensor noise by subtracting the dark current or background signal. 

2. Gain and offset correction

• Gain and offset correction involves making modifications to compensate for fluctuations in sensor gain and offset, which can impact the quality of radiometric measurements.

3. Noise Removal

Noise removal is the procedure of detecting and deleting undesired random fluctuations or imperfections in the visual data that may hide or distort the genuine signal.

Types of Noise

• Sensor Noise refers to the stochastic fluctuations caused by the imaging sensor, which can be observed as inconsistencies or anomalies at the pixel level.

• Environmental noise refers to unwanted disturbances in an image caused by external sources, such as interference or environmental conditions, that occur during the process of capturing the image.

Methods

• Filtering Techniques involve the application of algorithms, such as median or Gaussian filters, to reduce noise in an image while retaining important information.
• Statistical Methods: Employing statistical techniques, such as principal component analysis (PCA) or wavelet processing, to distinguish noise from significant signal components.

IMAGE SOURCE (THUMBNAIL)