16 Questions
What is the purpose of geometric correction in remote sensing?
To correct geometric distortions from a distorted image.
How are geometric distortions classified?
Internal distortion and external distortion.
What is internal distortion in remote sensing?
It is related to the geometry of the sensor.
What is external distortion in remote sensing?
It is related to the altitude of the sensor or the shape of the object.
What are some of the factors used in the process of geometric correction?
Calibration data of the sensor, measured data of position and attitude, ground control points, atmospheric condition, etc.
What is the primary objective of establishing the relationship between the image coordinate system and the geographic coordinate system?
To achieve geometric correction.
What are the purposes of using geometrically corrected images?
To bring an image into a standard projection, locate points of interest, bring adjacent images into registration, overlay images for change detection, overlay images on a map, co-register images, make accurate measurements, and correct distortion in the imagery.
What are the sources of distortions in geometric correction?
Motion of the platform, motion of the earth, earth curvature, terrain relief, and off-nadir view angle.
What is the process of transforming imagery data from one grid system into another grid system called?
Rectification.
What is the purpose of ground control points (GCPs) in geometric correction?
To provide additional geometric accuracy.
What are the internal distortions in geometric correction due to?
The geometry of the sensor.
What are the products of Landsat dataset that incorporate a Digital Elevation Model (DEM) for topographic accuracy?
The Standard Terrain Correction (L1TP) and Systematic Terrain Correction (L1GT) products.
What is the purpose of overlaying images of the same area from different dates and sensors in geometric correction?
For change detection.
What is the accuracy range found in the geometric correction of Landsat-5 TM imagery using 1:24,000-scale map-derived GCPs?
Root-mean-square (RMS) errors of 0.23 to + 0.93 pixels (+ 7 to + 28 metres).
What is the process of aligning two or more images called?
Registration.
What are the purposes of using ground control points (GCPs) for Standard Terrain Correction (L1TP) correction of Landsat dataset?
To provide geometric accuracy and derived from the GLS2000 data set.
Study Notes
Geometric Correction in Remote Sensing
- Geometric correction is necessary to correct distortions in remote sensing images, ensuring accurate spatial representation.
- Geometric distortions are classified into internal and external distortions.
Types of Distortions
- Internal distortions occur within the sensor, caused by camera lens, scanner, or other instrumental defects.
- External distortions occur due to Earth's curvature, atmospheric refraction, and platform motion.
Geometric Correction Process
- Factors used in geometric correction include image coordinates, ground control points (GCPs), and sensor information.
- Establishing a relationship between image coordinates and geographic coordinates is crucial for accurate geo-referencing.
Objectives and Purposes
- The primary objective of geometric correction is to ensure accurate spatial representation and pixel-to-pixel registration.
- Geometrically corrected images enable accurate change detection, feature extraction, and multi-temporal analysis.
- Geometric correction allows for accurate overlaying of images from different dates and sensors.
Sources of Distortions
- Sources of distortions include platform motion, angular variations, atmospheric refraction, and instrumental defects.
Transforming Imagery Data
- The process of transforming imagery data from one grid system to another is called reprojection.
Ground Control Points (GCPs)
- GCPs are used to establish a relationship between image coordinates and geographic coordinates.
- GCPs are essential for Standard Terrain Correction (L1TP) of Landsat dataset.
Landsat Dataset
- Landsat dataset products incorporate a Digital Elevation Model (DEM) for topographic accuracy, ensuring accurate ortho-rectification.
- The accuracy range in geometric correction of Landsat-5 TM imagery using 1:24,000-scale map-derived GCPs is within 1-2 pixels.
Image Alignment
- The process of aligning two or more images is called image registration.
Purposes of GCPs
- GCPs are used for Standard Terrain Correction (L1TP) correction of Landsat dataset, ensuring accurate geometric correction and ortho-rectification.
This quiz covers the conception of geometric correction, internal/external error, and the process for geometric correction in the context of environmental remote sensing. It discusses the errors and distortions present in remote sensing images acquired from various platforms and sensors.
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