JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD B.Tech IV REMOTE SENSING AND GIS IN MINING Previous Question Paper (September - 2022 - R18)

Remote sensing data acquisition systems are categorized based on the platform used to carry sensors and the nature of the energy source. These systems are essential for capturing electromagnetic radiation reflected or emitted from the Earth's surface.

The primary data acquisition systems are:

• Spaceborne Systems: Sensors mounted on satellites orbiting the Earth (e.g., Landsat, Sentinel, IRS). These provide repetitive, synoptic coverage of large areas, making them ideal for global or regional monitoring.
• Airborne Systems: Sensors mounted on aircraft, helicopters, or UAVs (drones). These offer high spatial resolution and flexibility in scheduling, suitable for site-specific or high-detail mapping.
• Ground-based Systems: Sensors mounted on tripods, towers, or vehicles (e.g., field spectroradiometers, LiDAR scanners). These provide calibration data and ultra-high resolution measurements for localized studies.

These systems are further classified by their energy source:

• Passive Remote Sensing: Sensors detect naturally available energy, such as reflected sunlight (e.g., optical cameras, multispectral scanners).
• Active Remote Sensing: Sensors emit their own energy pulses and measure the backscatter (e.g., RADAR, LiDAR, SONAR), allowing for data acquisition regardless of lighting conditions or cloud cover.

Key applications of these data acquisition systems include:

• Mineral Exploration: Identifying lithological units and structural features through spectral analysis and thermal mapping.
• Environmental Monitoring: Assessing land degradation, monitoring tailing dams, and tracking vegetation health in mining regions.
• Topographic Mapping: Using LiDAR and photogrammetry for high-precision Digital Elevation Models (DEMs) and volumetric calculations of stockpiles.
• Disaster Management: Monitoring slope stability, land subsidence, and detecting illegal mining activities.
• Land Use/Land Cover Mapping: Classifying surface features to manage mining concessions and reclamation efforts.

Electromagnetic radiation (EMR) is a form of energy that propagates through space as synchronized oscillations of electric and magnetic fields. It travels at the speed of light and does not require a material medium for propagation. The electromagnetic spectrum is the continuous range of all possible frequencies of electromagnetic radiation, extending from extremely short-wavelength gamma rays to extremely long-wavelength radio waves.

The spectrum is typically divided into the following regions: Gamma rays, X-rays, Ultraviolet (UV), Visible light (0.4–0.7 μm), Infrared (Near, Mid, and Thermal), Microwave, and Radio waves. In remote sensing, the visible, infrared, and microwave regions are of primary importance for data acquisition.

The fundamental properties of electromagnetic radiation include:

• Velocity: All EMR travels at the speed of light (c ≈ 3 × 10⁸ m/s) in a vacuum.
• Wavelength (λ): The distance between successive crests of the wave, usually measured in micrometers (μm) or nanometers (nm).
• Frequency (ν): The number of wave cycles passing a fixed point per unit of time, measured in Hertz (Hz).
• Wave-Particle Duality: EMR exhibits wave-like properties (interference, diffraction) and particle-like properties (photons carrying discrete energy packets).
• Relationship: The relationship between velocity, frequency, and wavelength is defined by the equation: c = νλ.
• Energy: The energy (E) of a photon is directly proportional to its frequency, given by E = hν, where h is Planck's constant.