Podcast
Questions and Answers
What is the leading cause of geometric distortion in vertical aerial photography?
What is the leading cause of geometric distortion in vertical aerial photography?
- Curvature and rotation of the Earth
- Relief displacement (correct)
- Perspective of the sensor optics
- Motion of the scanning system
Why are objects directly below the center of the camera lens affected in aerial photography?
Why are objects directly below the center of the camera lens affected in aerial photography?
- Due to the curvature and rotation of the Earth
- Because they lean away from the center of the photo (correct)
- Because their tops are visible
- Due to platform altitude
What role does terrain relief play in causing geometric distortion?
What role does terrain relief play in causing geometric distortion?
- It influences the motion of the scanning system
- It contributes to geometric distortion (correct)
- It causes objects to lean towards the center of the photo
- It affects platform altitude
In aerial photography, why are objects at the nadir position only showing their tops?
In aerial photography, why are objects at the nadir position only showing their tops?
Which factor influences objects appearing to lean away from the center of an aerial photograph?
Which factor influences objects appearing to lean away from the center of an aerial photograph?
How do framing systems like cameras used for aerial photography capture images?
How do framing systems like cameras used for aerial photography capture images?
What type of distortion results in the compression of image features at points away from the nadir?
What type of distortion results in the compression of image features at points away from the nadir?
Which scanning system distortion causes the sweep of scanning systems to cover an area slightly to the west of each previous scan?
Which scanning system distortion causes the sweep of scanning systems to cover an area slightly to the west of each previous scan?
Which platform type helps alleviate geometric distortions by providing relatively stable orbits?
Which platform type helps alleviate geometric distortions by providing relatively stable orbits?
Which factor influences geometric distortions caused by variations in platform stability?
Which factor influences geometric distortions caused by variations in platform stability?
What causes imagery obtained from satellite multispectral scanners to exhibit skew distortion?
What causes imagery obtained from satellite multispectral scanners to exhibit skew distortion?
How are geometric distortions and positional errors affected by the distance of objects from the center of a photo?
How are geometric distortions and positional errors affected by the distance of objects from the center of a photo?
What is the primary purpose of geometric correction in digital images?
What is the primary purpose of geometric correction in digital images?
Why are raw digital images usually not suitable for direct use as a map base?
Why are raw digital images usually not suitable for direct use as a map base?
Which of the following is NOT a source of geometric distortions in digital images?
Which of the following is NOT a source of geometric distortions in digital images?
What is the role of image data providers in the context of geometric correction?
What is the role of image data providers in the context of geometric correction?
How are systematic distortions typically corrected in digital images?
How are systematic distortions typically corrected in digital images?
What is the key consideration before attempting to make measurements or extract further information from digital images?
What is the key consideration before attempting to make measurements or extract further information from digital images?
What is the purpose of least-squares regression analysis in the context of the given text?
What is the purpose of least-squares regression analysis in the context of the given text?
Which equations are used to interrelate geometrically correct (map) coordinates and distorted-image coordinates?
Which equations are used to interrelate geometrically correct (map) coordinates and distorted-image coordinates?
How are the distorted-image coordinates of any map position estimated?
How are the distorted-image coordinates of any map position estimated?
What does the process of 'resampling' involve in the context of the text?
What does the process of 'resampling' involve in the context of the text?
What determines the intensity value or digital number assigned to a cell in the output matrix during resampling?
What determines the intensity value or digital number assigned to a cell in the output matrix during resampling?
In general, why does a cell in the output matrix not directly overlay a pixel in the input matrix during resampling?
In general, why does a cell in the output matrix not directly overlay a pixel in the input matrix during resampling?
What is the purpose of image registration?
What is the purpose of image registration?
What is the role of feature detection in image registration?
What is the role of feature detection in image registration?
How do area-based methods differ from feature-based methods in feature matching?
How do area-based methods differ from feature-based methods in feature matching?
What does the mapping function do in the image registration process?
What does the mapping function do in the image registration process?
In what manner is a sensed image typically registered in transformation and resampling?
In what manner is a sensed image typically registered in transformation and resampling?
What is the main objective of comparing reference and sensed images with control points in image registration?
What is the main objective of comparing reference and sensed images with control points in image registration?
Study Notes
- Remote sensing images acquired from various platforms/sensors have inherent geometric distortions due to factors like sensor optics, platform motion, altitude, and Earth's curvature.
- Aerial photography systems like cameras can cause relief displacement, where objects away from the camera's center appear distorted in vertical aerial photography.
- Across-track scanning systems exhibit tangential scale distortion compressing features away from the nadir and skew distortion due to the eastward rotation of the Earth.
- Geometric correction is essential to compensate for distortions in raw digital images caused by factors like platform variations, earth curvature, and atmospheric effects.
- Systematic distortions are easily corrected using mathematical formulas and regression analysis to transform distorted-image coordinates into map coordinates.
- Resampling is a process used to determine pixel values in the output matrix from the original image matrix during geometric correction.
- Image registration involves mapping one image onto another using a perfect transformation, including feature detection, matching, designing mapping functions, and transformation/resampling processes.
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Description
Learn about the geometric distortions present in remote sensing images captured through satellite, aircraft, or other sensor platforms. Understand how these distortions affect the representation of Earth's surface in a two-dimensional image.
