Multispectral Imaging Using Discrete Detectors and Scanning Mirrors (Across-Track Scanner or Whisk Broom Scanner)
Multispectral Imaging: This technique involves capturing images of the Earth's surface using multiple sensors that are sensitive to different wavelengths of electromagnetic radiation. This allows for the identification of various features and materials based on their spectral signatures.
Discrete Detectors: These are individual sensors that are arranged in a linear or array configuration. Each detector is responsible for measuring the radiation within a specific wavelength band.
Scanning Mirrors: These are optical components that are used to deflect the incoming radiation onto the discrete detectors. By moving the mirrors, the sensor can scan across the scene, capturing data from different points.
Across-Track Scanner or Whisk Broom Scanner: This refers to the scanning mechanism where the mirror moves perpendicular to the direction of flight. This allows for the collection of data along a swath, covering a wide area on the ground.
Remote Sensing Terminologies
A. Rotating Mirror
- Definition: A mechanical component in some satellite-based remote sensing systems that rotates to scan the Earth's surface. It directs sunlight onto a sensor, enabling the collection of data over a wide area.
- Purpose: To increase the coverage area of the sensor, allowing for rapid data acquisition.
B. Internal Detectors
- Definition: Sensors within a remote sensing instrument that convert electromagnetic radiation into electrical signals. These signals are then processed to produce images or data.
- Purpose: To capture and measure the intensity of radiation reflected or emitted from the Earth's surface.
C. Instantaneous Field of View (IFOV)
- Definition: The smallest area on the ground that can be resolved by a remote sensing sensor at a given time.
- Purpose: To determine the spatial resolution of the sensor, indicating the level of detail it can capture.
D. Ground Resolution Cell Viewed (GRCV)
- Definition: The area on the ground corresponding to the IFOV of a sensor at a specific altitude.
- Purpose: To measure the size of the smallest distinguishable feature on the Earth's surface.
E. Angular Field of View (AFOV)
- Definition: The angle between the extreme rays of the field of view of a sensor.
- Purpose: To determine the extent of the area that can be observed by the sensor at a given distance.
F. Swath
- Definition: The width of the area on the ground that a sensor can cover in a single pass.
- Purpose: To measure the lateral coverage of the sensor, indicating the efficiency of data collection.
How it works:
- Radiation Collection: The scanning mirror deflects incoming radiation from the Earth's surface onto the array of discrete detectors.
- Spectral Separation: Each detector measures the radiation within its specific wavelength band, capturing information about different materials and features.
- Scanning: The scanning mirror moves across the scene, allowing the sensor to collect data from multiple points.
- Data Processing: The collected data is processed to create multispectral images that can be analyzed to identify and classify features based on their spectral signatures.
Key advantages of this approach:
- High spatial resolution: Can capture detailed images of the Earth's surface.
- Wide swath coverage: Can cover a large area in a single pass.
- Versatility: Can be used for various remote sensing applications, such as land use mapping, vegetation monitoring, and mineral exploration.
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Vineesh V
AISHE and UGC Nodal Officer
Assistant Professor of Geography,
Government College Chittur, Palakkad
https://g.page/vineeshvc
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