Recently in December 2024, the Union Ministry of Home Affairs reported a significant revision in India’s coastline length.

• The length of the coastline was re-assessed by the National Hydrographic Office (NHO) in coordination with the Survey of India (SoI).
• Previous Length: 7,516 km (as measured in the 1970s).
  Revised Length: 11,098 km (as of 2025) — a 48% increase (~3,582 km).
• Cause: Not physical expansion but technological improvements in mapping resolution and GIS-based measurement.
• The new coastline measurement exercise will now be repeated every 10 years.

Key Reasons for Increase in Coastline Length

• Higher Data Resolution
  • Old maps used a scale of 1:4,500,000 (1 cm = 45 km).
  • New measurement used 1:250,000 scale (1 cm = 2.5 km).
  • Smaller-scale data smooths coastlines; higher resolution captures bends and curves, increasing total measured length.
• GIS-Based Techniques: Transition from manual to GIS software allowed for better mapping of land-water boundaries.
• • GIS tools factor in minute geographical irregularities.

• Inclusion of Previously Missed Islands: Offshore island coastlines were not included earlier due to resolution or manual oversight.
  • Inclusion now adds significantly to the total length.
• Difference due to standardised definitions and data reconciliation among Survey of India, Navy, Coast Guard, and states.
• Excludes riverine islands (e.g., Assam, West Bengal).

Strategic and Administrative Implications

• Coastal Zone Management: CRZ (Coastal Regulation Zone) boundaries may now expand or shift.
  • Planning for habitat conservation, tourism zones, and infrastructure will be affected.
• Disaster and Climate Resilience: Accurate coastline mapping aids in identifying erosion-prone and submergence zones.
  • Helps plan for cyclone buffers, tidal flood defenses, and mangrove regeneration.
• Security and Navigation: Maritime surveillance, Navy, Coast Guard operations rely on exact coastline data.
  • Island mapping is crucial for logistics, strategic outposts, and maritime boundary enforcement.
• Legal and Diplomatic Relevance: While no change in physical territory, recalibration improves claims under UNCLOS for Exclusive Economic Zones (EEZ).
  • Accurate data strengthens India’s Blue Economy and Ocean Diplomacy posture.

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