Context:
Advances in remote-sensing technology have transformed how scientists monitor vegetation, water resources, and mineral deposits. Using satellites and advanced sensors, Earth’s surface can now be analysed with high spatial and spectral precision, aiding environmental management and resource planning.
Key Highlights:
- Scientific Principle
- Remote sensing studies reflected or emitted electromagnetic energy from Earth’s surface.
- Each material has a unique spectral signature, enabling identification of its composition and condition.
- Vegetation & Crop Monitoring
- Healthy plants reflect more near-infrared (NIR) light and absorb visible red light.
- Normalized Difference Vegetation Index (NDVI) uses this contrast to assess plant health and stress.
- Declining NIR reflection indicates water stress, disease, or nutrient deficiency.
- Mapping Water Resources
- Water reflects green light, aiding surface water detection.
- NDWI and Modified NDWI map water bodies using green and shortwave infrared bands.
- Synthetic Aperture Radar (SAR) can detect water through clouds and at night, with calm water appearing black in radar imagery.
- Minerals, Oil & Gas Detection
- Hyperspectral sensors analyse hundreds of narrow spectral bands to:
- Identify specific minerals
- Map alteration zones
- Detect oil and gas micro-seepage via subtle soil and vegetation changes
- Satellite imagery helps geologists identify anticlines and sedimentary basins, favourable for hydrocarbon accumulation.
- Groundwater Assessment
- The GRACE mission (2002–2017) of NASA tracked changes in Earth’s gravity to measure groundwater depletion.
- Data revealed alarming groundwater loss in North India, informing water policy and resource planning.
Relevant Prelims Points:
- Remote Sensing: Data collection without physical contact.
- Spectral Signature: Unique EM reflection pattern of materials.
- NDVI / NDWI: Indices for vegetation and water mapping.
- SAR: Radar-based imaging effective in all weather conditions.
Relevant Mains Points:
- Science & Technology: Enables data-driven environmental monitoring.
- Environment & Ecology: Supports forest conservation, drought assessment, and water security.
- Indian Geography: Enhances mineral exploration and groundwater management.
- Governance: Informs disaster management, agriculture planning, and climate adaptation.
- Way Forward:
- Integrate satellite data with ground-based validation.
- Strengthen indigenous remote-sensing capabilities.
- Use real-time monitoring for sustainable resource governance.
UPSC Relevance:
- GS 3: Science & technology, environment
- GS 1: Physical and resource geography
- Prelims: Remote sensing applications, satellite missions