Mapping India

S. ARNEJA

Interview with Dr. Prithvish Nag, Surveyor-General of India

The Great Arc Expedition, or the Great Trigonometrical Survey (GTS) of India, that was led by Col. William Lambton two centuries ago, laid the foundation for a remarkable institution, the Survey of India (SoI). It is the oldest Indian scientific institution. Dr. Prithvish Nag, Surveyor-General of India, responds to a set of questions sent to him by Science Correspondent R. Ramachandran with regard to the premier mapping agency's achievements, its ongoing tasks, the techniques and tools it uses and its prospects.

How do you assess the achievements of the Survey of India in the last two centuries, compared to similar agencies elsewhere in the world?

The Great Trigonometrical Survey of India commenced on April 10, 1802. This laid the foundation of scientific geodesy that provided an incomparable framework of precise geodetic control points and enabled our topographical and cadastral maps to be based on inch perfect surveys. The Survey of India was in existence since January 1, 1767 in the form of the Bengal Surveys. The three presidencies of Bengal, Madras and Bombay were amalgamated in 1815, and in 1877, the three branches of the Trigonometrical, Topographical and Revenue Surveys were amalgamated to form the Survey of India.

During the early years, we were on a par with, and at few places even above, other mapping agencies of the world. But with the passage of time, the paucity of funds, lack of human resources and inadequate technological skills made us lag behind. But with the setting up of the India Survey Committee in 1904-05, the department again put itself on wheels and proved itself in many fields of surveying and mapping. After Independence, mapping at the Survey of India - as elsewhere in the world - was revolutionised with the introduction of new techniques... The SoI's responsibilities increased manifold owing to a sudden spurt of developmental activities in the newly independent country. Between 1951 and 1956, almost 70 per cent of the staff were employed in survey work for developmental projects such as hydroelectric projects and for geophysical studies for natural resources. The SoI switched over to the metric system in 1956-57.

With developments taking place in other parts of the world in the field of surveying and mapping, we have incorporated state-of-the-art technologies in our work. The revolution called computer was adopted in the 1970s, space geodesy in the early 1980s, digital cartographic techniques in 1987-88 and GPS (global positioning system) in the 1990s. The SoI is keeping abreast with all the modern techniques available, and we are second to none. We are the first country to complete mapping on 1:50,000 scale by 1985 after starting the process in 1957.

What were the unique features of the methods and techniques employed by Col. Lambton and later by Sir George Everest that have stood the test of time and have become part of cartography the world over?

Col. William Lambton and Sir George Everest were great geodesists. They did not make any major contribution to the theory of geodesy as a science but they introduced important innovations in practical procedures in the field, which have stood the test of time and have become part of cartography the world over. These are, 1. Spacing of triangulation into definite chain as bars of grid iron; 2. Observation of astronomical azimuth from circumpolar stars; 3. Laying down of distant stations by the ray-trace method, and 4. Deduction of astronomical arcs by simultaneous observation of identical stars with similar instruments at either ends of the triangle. Though the science of geodesy has developed since their days, the principles that they enunciated, the methods they evolved, cannot be too well known to working surveyors, especially to those who follow them in India.

Sir George Everest introduced measurements on a reference frame now known as the Everest Spheroid. We still use the same datum for topographic maps. What kind of improvements have been made in defining this datum? For instance, how well does this cover the Indian region and its neighbourhood?

The Everest Spheroid is still being used in India and adjacent countries. It is being used as such, with no major changes incorporated. It is well suited and covers the Indian sub-continent but on a global frame it does not fit.

What kind of instruments, records, documents and diaries of historical and archival value, particularly from a history of science perspective, does the SoI have from that period? And what is being done to preserve them?

We have old field books, journals, maps, memoirs and letters which have been lodged with the National Archives of India, New Delhi, and can be accessed there particularly from a history of science perspective. The material that is preserved at the NAI, and some that is available with the department, are being digitised to preserve them for posterity. Instruments of that period survive, and these are preserved in the Survey Museum in Dehra Dun.

The grave of Lambton in Hinganghat in Maharashtra and the estate of Everest near Mussoorie were reported to be in a state of neglect. Has the SoI tried to restore and preserve them as heritage sites?

The estate of Everest near Mussoorie, called the Park Estate, is in a state of neglect. It was in the hands of a private owner but now it has been acquired by the Garhwal Mandal Vikas Nigam of the Government of Uttaranchal. The SoI and the Uttaranchal government are exploring the possibility of preserving this heritage site. As for Lambton's tomb near Nagpur, it has not been identified accurately. Once we are sure, steps will be taken to preserve it.

As an offshoot of the Great Arc Expedition, the Himalayas were shown to be the highest mountain ranges in the world and Mount Everest (earlier known as Peak XV) was determined to be the highest peak. In 1954 the Survey of India determined the height to be 29,002 feet. In recent times this height has been revised downwards by other agencies. Can you comment on the improved techniques of measuring heights that are now available?

As far as the SoI is concerned, the height of Mount Everest is still 29,002 feet; it has not been revised. The techniques used by Lambton and Everest to measure the height of mountain ranges have changed but the accuracy of the improved techniques is still not hundred per cent.

There is criticism that topographic maps of sufficiently large scale are not accessible for civilian use. In the present digital age, when digitised maps of other regions of the world are available freely, the lack of such maps in India hampers development. Why are we lagging behind here, even though India set the pace for mapping in the world?

As for digitised topographical maps of a sufficiently large scale for other countries being available for civilian use, I have my apprehensions. But we are not lagging behind. Within certain government policies and norms, digital maps are being prepared and will be available for general use by 2004 - hopefully.

Last year the first digital map of the Gujarat region was released. What is the progress on that front, and how long do you think it will take to release digital maps in 1:50 K and 1:25 K for the entire country?

The Gujarat Digital Map was released last year. There were a few hiccups with the government policy on security. These have been cleared, and hopefully we will be able to provide digital maps for the entire country by 2004.

What is the status of the National Spatial Data Infrastructure (NSDI)?

The SoI has the longest known tradition of systematic collection of scientific spatial data. Today digitisation has greatly facilitated the management of this data. The NSDI is developing and maintaining a standard digital collection of the data, and from the data it is to develop common solutions for discovery, access and use in response to the needs of diverse user-groups.

What are your views on creating a separate agency for defence-related applications and uses of the SoI's cartographic maps?

There exists a separate Defence Survey Unit that caters to the needs of the defence forces. The SoI and the defence wing are in close association and these survey units build up from the data for their own precise requirements.

What kind of policy is being evolved for the special needs of developmental projects, particularly in the private sector with GIS-related applications, in topographic maps of even higher resolution?

The SoI is evolving a policy to develop a digital cartography base on 1:250 K, 1:50 K and 1:25 K that will cater to the needs of various GIS applications and for the quick updating of topographical maps on large scales on which the user can add on.

The SoI has been constrained by inadequate budgetary support in terms of Plan funds to undertake new projects and revise maps that have become outdated.

The Department has been constrained by inadequate budgetary support in terms of Plan funds, but adequate provision has now been made in the Tenth Five Year Plan.

How is the exercise of producing maps for civilian use on the GPS reference frame of WGS-84 going? Is it an expensive proposition?

No, it is not expensive at all. We are not resurveying the entire country on the WGS-84 reference frame. Since we already have the source data for the entire country on the Everest Spheroid, we are coming up with transformation parameters that will accurately and inexpensively help us convert the Everest Spheroid to the WGS-84 reference frame.

What products are the SoI planning to release for civilian use and for developmental projects?

The SoI is planning to release several value-added products. These include special purpose maps such as those of trekking routes, antique maps, town planning maps and Assembly constituency maps (also in digital form); thematic maps that meet specific needs such as census operations, soil management and education, and a digital cartography database on various scales on which the user will be able to build on for specific requirements.

How does the SoI plan to overcome the problem of shortage of skilled manpower?

There is an acute shortage of skilled manpower owing to the government's policy with regard to recruitment. We are trying to overcome this by using the skilled workforce of similar agencies by means of strategic partnerships with them.

Do you feel that aspects of geodesy and cartography should be introduced as subjects at the school and college levels now that spatial data is of vital importance in today's information-driven economy?

Aspects of geodesy and cartography are already taught in schools and in a few universities, but I recommend the inclusion of these subjects in the regular curriculum.

How do you see the future of the SoI?

Very good and very bright, with many more productive years ahead in the service of the nation.