Explainer / Joint hydrographic survey

Indian Navy’s Sandhayak-class ship INS Jamuna will carry out detailed hydrographic surveys and several shore-based survey activities over the two-month deployment period in Sri Lanka, officials have said.

Commanded by Captain H.A. Hardas, hydrographic survey ship INS Jamuna reached Colombo on February 6.

The ship has been deployed to Sri Lanka based on a mutual agreement to carry out a joint hydrographic survey off the south-west coast of Sri Lanka.

“Over the two-month deployment period, the ship will carry out detailed hydrographic surveys and several shore-based survey activities,” an Indian Navy statement said.

Sri Lankan Navy personnel will embark on the ship during the conduct of the joint survey. Additionally, they will also be provided “hands-on survey training during every operational turnaround in port”, it added.

What is hydrography?

Hydrography is the branch of applied sciences that deals with the measurement and description of the physical features of oceans, seas, coastal areas, lakes and rivers, as well as with the prediction of their change over time, for the primary purpose of safety of navigation and in support of all other marine activities, including economic development, security and defence, scientific research and environmental protection.

In addition to supporting safe and efficient navigation of ships, hydrography underpins almost every other activity associated with the sea, including…

* Resource exploitation (fishing, minerals)

* Environmental protection and management

* Maritime boundary delimitation

* National marine spatial data infrastructure

* Recreational boating

* Maritime defence and security

* Tsunami flood and inundation modelling

* Coastal zone management

* Tourism

* Marine science

What is the significance of hydrographic survey?

In the past, many artisanal shelters and fishing ports were built at convenient locations, with no particular attention paid to such environmental factors as wave heights, sudden changes in water depths, uncharted reefs, currents, tidal streams, seaweed and mobile beaches (sand drift).

Many of the structures were subsequently expanded and, in countless cases around the world, many of the problems that used to be considered minor have now developed into major ones, with some shelters, for example, fouling up with seaweed or silting up

(shelter mouth facing the wrong direction) or just being inaccessible in rough weather (reefs too close to entrance channel).

A hydrographic survey, also known as a bathymetric survey, is therefore essential if the correct design decisions are to be made right from the project inception stage to ensure that the landing is easy to use and free of major maintenance problems under all conditions.

Hydrographic surveys are required for a wide variety of purposes, ranging from simple reconnaissance (at project formulation, for instance) to payment for work carried out underwater, such as dredging or reclamation.

The results from a hydrographic survey are normally plotted to produce a bathymetric

contour map, which is a plan of the depth of the sea bed arranged in such a manner as to show lines of equal depth from the coastline.

International Hydrographic Organisation

The International Hydrographic Organisation (IHO) is an intergovernmental organisation  that works to ensure all the world’s seas, oceans and navigable waters are surveyed and charted. Established in 1921, it coordinates the activities of national hydrographic offices and promotes uniformity in nautical charts and documents. It issues survey best practices, provides guidelines to maximise the use of hydrographic survey data and develops hydrographic capabilities in member states.

Since 2005, the IHO celebrates World Hydrography Day on June 21. The aim is to give suitable publicity to its work at all levels and of increasing the coverage of hydrographic information on a global basis, and urges all states to work with that organisation to promote safe navigation, especially in the areas of international navigation, ports and where there are vulnerable or protected marine areas.

Hydrography surveys in India

The Indian Naval Hydrographic Department (INHD) functions under the Chief Hydrographer to the government of India. The department, being the nodal agency for hydrographic surveys and nautical charting in India, has a very well-established organisational set-up.

The INHD has eight indigenously built modern survey ships including one Catamaran Hull Survey Vessel (CHSV) fitted with state-of-the-art surveying equipment and a well established National Institute of Hydrography, which is recognised as the Centre for Imparting Training in Hydrography for Southeast Asia by the IHO.

Surveys are conducted in strict compliance with the IHO standards for hydrographic surveying. The department also pioneered in making official Electronic Navigational Charts (ENCs) for Indian waters. INHD is committed to capacity building in the Southeast Asian region and conducts training to personnel from countries in the region and some of the African nations. The department has also signed MoU with various countries for surveying their waters as part of international cooperation.

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