Remote Sensing Technology

The Remote Sensing technology has revolutionised monitoring of vegetation, water resources, and subsurface minerals, making exploration faster, cheaper, and more environmentally friendly.

About Remote Sensing Technology

• Remote sensing is the science of acquiring information about Earth’s surface, atmosphere, or objects without physical contact.
• How It Works: It works primarily by measuring reflected or emitted electromagnetic radiation from satellites, aircraft, drones, or ground-based platforms.

Types of Remote Sensing

• Passive: Sensors detect natural energy, usually reflected sunlight (e.g., visible light cameras) or emitted thermal radiation.
• Active: Sensors emit their own energy (e.g., radar or LiDAR) and measure the return signal, enabling operation day/night and through clouds.

Applications of Remote Sensing

• Environmental Monitoring: Tracks deforestation, climate change, glaciers, and biodiversity.
• Agriculture: Precision farming: crop health , soil moisture, pest detection.
  • Chlorophyll content in the vegetation of a specific location; Land surface temperatures of a specific location; Greenhouse gas emissions from rice paddies of a specific location (PYQ:2019)
• Disaster Management: Monitors floods, wildfires, earthquakes.
• Urban Planning & Defense: Land use mapping, infrastructure, surveillance.
• Ocean & Atmosphere: Sea levels, weather forecasting, pollution.

Monitoring Plants and Forests

• Satellites assess plant health using spectral signatures, particularly in visible and near-infrared bands.
• Healthy plants absorb red light for photosynthesis and reflect near-infrared to prevent overheating.
• Normalized Difference Vegetation Index: NDVI quantifies vegetation health, high NDVI indicates vigorous growth; low values signal stress, drought, or disease.
• Applications in India: Forest Survey of India (FSI) uses NDVI for biennial forest cover assessment and monitoring deforestation.

Mapping Water Bodies and Quality

• Remote sensing detects water using optical and radar techniques.
• Normalized Difference Water Index (NDWI) and Modified NDWI (MNDWI) exploit water’s strong absorption in near-infrared and shortwave infrared.
• Synthetic aperture radar (SAR) identifies water as dark areas due to smooth reflection of radio waves; ideal for flood mapping during clouds or storms.
• Recent advancement: NASA-ISRO NISAR satellite (launched July 2025) uses dual-frequency SAR (L-band and S-band).
• Satellites also assess water quality by detecting muddy water or algal blooms via spectral differences.

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Mineral Exploration and Subsurface Mapping

• Remote sensing provides surface clues to underground resources.
• Hyperspectral imaging splits light into hundreds of bands, identifying minerals like copper, gold, and lithium via detailed spectral signatures.
• In India: Used in Rajasthan (e.g., Alwar basin for Cu-mineralization), Jahajpur, and Gadag Schist Belt.

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