India’s coastline length revised to 11,098.81 km following new methodology

It’s now official. India’s coastline has been recalculated as 11,098.81 km from 7,561.60 km - up by 3,537.21 km or nearly 50 per cent. This is due to a change in the methodology of calculation, according to a circular issued by the Union Shipping Ministry on Tuesday.

The length of India’s coastline, according to the Ministry of Home Affairs, has been 7,561 km since the 1970s. Various government departments have used different figures for the coastline. The issue was examined in 2019, and it was learnt that the Coastal Protection and Development Advisory Committee has been deliberating on this issue since 2010.

The main reason for the deviation in the existing coastline length was the probable variation in scale and calculation method. The length of the coastline calculator in the 1970s might have been computed from then-available records at a scale  of 1:4,500,000 or smaller, whereas the re-verified data has been computed at the scale of 1:250,000. It is understood that the length of the coastline is liable to vary when it is measured from maps of different scales, the circular said.

The larger the scale of the map, the greater the length’s outcome. This is because larger-scale data capture more intricate details like bays, inlets, and minor irregularities that are smoothed out at smaller-scale data, the circular said.

Inclusion of offshore islands and islets 

The length of India’s offshore islands/islets is finalised as 1298 offshore islands/islets (1059 islands and 239 islets) in the reconciliation exercise of the offshore islands. Secondly, the length of offshore islands has been added to the total length of three verified coastlines, which might have been left out in the 1970s coastline length due to scale constraints and conventional/manual measuring methods. Further, the circular said that the peripheral coastline (high-water line) of individual offshore islands has been used to calculate coastline length.

Representatives of coastal states/Union Territories (UTs) deliberated on India’s re-verified coastline in January 2024. The circular said the committee accepted India’s revised coastline length after obtaining concurrence from all coastal states/UTs.

At a meeting in September 2024, under the chairmanship of the Surveyor General of India, it was decided that the probable reasons for the variation between the existing coastline length and the re-verified coastline length must be outlined prior to the publication of the updated length. The circular said that all the stakeholders in the meeting unanimously endorsed this.

Earlier measurements may have relied on simplified straight-line distances, whereas the current approach, using the fractal method, captures every curve and contour, resulting in a more accurate and longer coastline measurement, said a faculty of a large maritime university. It is merely a change in the method of measurement. The actual coastline has not physically increased by 50 per cent overnight, he added.

Length of Coastline of India