Description

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Context

The Union Ministry of Home Affairs made a major announcement in December 2024 as part of its annual report for 2023-2024. It stated that the length of India's coastline has expanded from 7,516.6 km to 11,098.8 km, and that it is currently being reviewed.

What is the Coastline Paradox?

Coastlines have fractal-like features, with length increasing with decreasing measurement scales. Lewis Fry Richardson initially identified the Paradox, which was mathematically explained by Benoît Mandelbrot in 1967. Smaller units (for example, water molecules) may theoretically form an indefinitely long coastline.

Geographical Coverage of India’s Coastline

Coastal Boundaries	Bordered by the Bay of Bengal (East), Arabian Sea (West), and Indian Ocean (South).
Coastal States	Gujarat, Maharashtra, Goa, Karnataka, Kerala, Tamil Nadu, Andhra Pradesh, Odisha, West Bengal
Coastal Union Territories	Daman & Diu, Lakshadweep, Puducherry, Andaman & Nicobar Islands

Challenges in Measuring Coastal Length

Coastline Paradox	Identified by Lewis Fry Richardson in the 1950s; shows that coastal length changes with the scale of measurement due to the irregular shape of coastlines.
Fractals	Benoît Mandelbrot (1967) found that coastlines exhibit fractal-like properties, meaning they appear increasingly complex at smaller scales.
Not True Fractals	Coastlines are not pure mathematical fractals but share similar characteristics, complicating accurate measurement.
Ruler Dependency	The measured length depends on the size of the measuring unit (ruler).
Example	A 200-km ruler misses small features, while a 1-km ruler captures detailed curves, making the total coastline appear longer with smaller units.

Why was India’s coastal length increased?

Change in Calculation Method - Previous measurements were based on simple straight-line lengths, but the present methodology employs the fractal method.
This captures every curve and contour, yielding a more precise and extensive shoreline survey.
Change in Scale—The earlier estimate of 7516 km from the 1970s was based on maps depicting India's coastline at a 1:4,500,000 resolution.
The National Hydrographic Office (NHO) and the Survey of India conducted a more recent update measurement using computerized navigation charts at a considerably finer scale of 1:250,000.
Because larger-scale data captures more subtle elements like as bays, inlets, and tiny abnormalities that are smoothed out in smaller-scale data, the length of the map increases.
Updated High Waterlines - To survey the coastline, the Survey of India used NHO-prepared high-water lines based on 2011 data from electronic navigation charts.
The high-water line served as a baseline, and river mouths and creeks were cut off at a predetermined inland threshold.
The coastline length was calculated by adding the peripheral coastline (high-water line) of individual offshore islands.
Inclusion of new islands — Approximately 1,389 islands/islets that were not included in the 1970 survey were added to the list to establish the coastal limits of all Indian states and Union territories.