Discrete Detectors and Scanning mirrors Across the track scanner Whisk broom scanner.

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.

Warm regards.
..
Vineesh V
AISHE and UGC Nodal Officer
Assistant Professor of Geography,
Government College Chittur, Palakkad
https://g.page/vineeshvc

Comments

Atmospheric Window

The atmospheric window in remote sensing refers to specific wavelength ranges within the electromagnetic spectrum that can pass through the Earth's atmosphere relatively unimpeded. These windows are crucial for remote sensing applications because they allow us to observe the Earth's surface and atmosphere without significant interference from the atmosphere's constituents. Key facts and concepts about atmospheric windows: Visible and Near-Infrared (VNIR) window: This window encompasses wavelengths from approximately 0. 4 to 1. 0 micrometers. It is ideal for observing vegetation, water bodies, and land cover types. Shortwave Infrared (SWIR) window: This window covers wavelengths from approximately 1. 0 to 3. 0 micrometers. It is particularly useful for detecting minerals, water content, and vegetation health. Mid-Infrared (MIR) window: This window spans wavelengths from approximately 3. 0 to 8. 0 micrometers. It is valuable for identifying various materials, incl...

Platforms in Remote Sensing

In remote sensing, a platform is the physical structure or vehicle that carries a sensor (camera, scanner, radar, etc.) to observe and collect information about the Earth's surface. Platforms are classified mainly by their altitude and mobility : Ground-Based Platforms Definition : Sensors mounted on the Earth's surface or very close to it. Examples : Tripods, towers, ground vehicles, handheld instruments. Applications : Calibration and validation of satellite data Detailed local studies (e.g., soil properties, vegetation health, air quality) Strength : High spatial detail but limited coverage. Airborne Platforms Definition : Sensors carried by aircraft, balloons, or drones (UAVs). Altitude : A few hundred meters to ~20 km. Examples : Airplanes with multispectral scanners UAVs with high-resolution cameras or LiDAR High-altitude balloons (stratospheric platforms) Applications : Local-to-regional mapping ...

History of GIS

1. 1832 - Early Spatial Analysis in Epidemiology: - Charles Picquet creates a map in Paris detailing cholera deaths per 1,000 inhabitants. - Utilizes halftone color gradients for visual representation. 2. 1854 - John Snow's Cholera Outbreak Analysis: - Epidemiologist John Snow identifies cholera outbreak source in London using spatial analysis. - Maps casualties' residences and nearby water sources to pinpoint the outbreak's origin. 3. Early 20th Century - Photozincography and Layered Mapping: - Photozincography development allows maps to be split into layers for vegetation, water, etc. - Introduction of layers, later a key feature in GIS, for separate printing plates. 4. Mid-20th Century - Computer Facilitation of Cartography: - Waldo Tobler's 1959 publication details using computers for cartography. - Computer hardware development, driven by nuclear weapon research, leads to broader mapping applications by early 1960s. 5. 1960 - Canada Geograph...

Scattering

History of GIS

The history of Geographic Information Systems (GIS) is rooted in early efforts to understand spatial relationships and patterns, long before the advent of digital computers. While modern GIS emerged in the mid-20th century with advances in computing, its conceptual foundations lie in cartography, spatial analysis, and thematic mapping. Early Roots of Spatial Analysis (Pre-1960s) One of the earliest documented applications of spatial analysis dates back to 1832 , when Charles Picquet , a French geographer and cartographer, produced a cholera mortality map of Paris. In his report Rapport sur la marche et les effets du choléra dans Paris et le département de la Seine , Picquet used graduated color shading to represent cholera deaths per 1,000 inhabitants across 48 districts. This work is widely regarded as an early example of choropleth mapping and thematic cartography applied to epidemiology. A landmark moment in the history of spatial analysis occurred in 1854 , when John Snow inv...

Vineesh V, Geography

Search This Blog