26 May 2025
Topic : The Maths of How India’s Coastline Lengthened Without Gaining Land
Relevance : GS Paper 1 Geography
Source : The Hindu
Context :
In December 2024, the Union Ministry of
Home Affairs announced a significant update
to India’s official coastline length, increasing
it from 7,516.6 km (recorded since the 1970s)
to 11,098.8 km. This increase was not due to
any new land acquisition, island annexation,
or natural geological changes like tectonic
shifts. Instead, it was the result of advances
in measurement technology and a deeper
understanding of the nature of coastlines —
a phenomenon explained by the coastline
paradox.
Limitations of Earlier Techniques
- The original 7,516.6 km figure was derived from maps with a coarse scale of 1:4,500,000.
- At such a resolution, many coastal intricacies like estuaries, tidal creeks, sandbars, and smaller islands were missed or generalized.
- Island groups such as the Andaman & Nicobar and Lakshadweep had not been fully mapped or included.
Advances in Technology and Mapping
- The updated measurement used electronic navigation charts with a finer scale of 1:250,000.
- Technologies employed included Geographic Information Systems (GIS), satellite altimetry, LIDAR-GPS mapping, and drone-based imaging.
- The National Hydrographic Office (NHO) and the Survey of India used highwater lines based on 2011 data to define coastal boundaries accurately.
- The updated method accounted for:
- Closing off river mouths and creeks at fixed inland thresholds.
- Including islands exposed at low tide. This higher resolution revealed much more detail along the coast, increasing the total measured length significantly.
The Nature of Coastlines
- Unlike straight lines, coastlines are irregular and jagged, shaped by natural features like river mouths, deltas, and tidal creeks.
- These features cause the coastline to appear different when viewed or measured at different scales.
The Paradox Explained
- Lewis Fry Richardson first identified this paradox in the 1950s; Benoît Mandelbrot later mathematically explored it and introduced the concept of fractals.
- The coastline’s measured length depends on the length of the measuring unit (the “ruler”):
