“We are trying to revive Geodesy in India”

Maj Gen (Dr) B Nagarajan Professor, Department of Civil Engineering, Indian Institute of Technology (IIT) Kanpur, Kanpur, India

Why is geodesy an indispensable science? How it has evolved over the years?

Geodesy is the science of accurately measuring and understanding the three fundamental properties of the Earth: its geometric shape, its orientation in space, and its gravity field. All of these things have an important effect on our lives, but are always working in the background where most of us don’t notice. It is a science that connects the Earth, oceans and atmospheric systems. Also, for any geospatial application, the most fundamental requirement is the set of coordinates which is provided by the subject of Geodesy. Therefore, even though you are not working in geodesy perse but almost everyone is using geodesy in their daily life.

Though the history of Geodesy started in the Greek Era (625- 195 BC), with contributions from Thales of Miletus, School of Pythagoras and Aristotle, on Trigonometry, Diurnal motion of the Earth and Moon and Sphericity of Earth and possibility of Gravity, it was Eratosthenes (276-195 BC), who determined the size of the earth and also computed the inclination of axis of the earth rotation. That’s why he was rightly called ‘Father of Geodesy’.

After nearly 1500 years, geodesy got a boost through the various mariners like Marco Polo, Columbus, Vasco da Gama and Magellan and from great astronomers and physicists like Copernicus, Kepler, Galileo and Newton. The real revival of the subject at least in India came in the 18th century with the setting up survey organizations in India and beginning of scientific surveys in 1802-with the ‘Great arc’ measurements.

Geodetic & Research Branch (which was earlier called as Great Trigonometric Survey Directorate), of Survey of India, was the only organization carrying out conventional geodesy work for the last two centuries. Unlike rest of the countries in the world, for some inexplicable reasons, the science of Geodesy was treated as restricted and was taught and practiced only in Survey of India in our country, though this subject is the mother of all geosciences. Space based geodetic surveys which can provide two three orders of accuracy better than the conventional surveys have been in vogue for the past three to four decades, but Survey of India has made only a very small improvement in adopting latest techniques mainly due to manpower, budget and other resource constraints.

Now with the importance in geodata increasing, and geospatial technologies becoming the order of the day, even Government of India has felt the necessity of popularizing the subject in the country. The setting up of National Centre for Geodesy is one such attempt in this direction.

What has been the contribution of space geodesy to the growth and evolution of this science?

Space Geodesy has revolutionised the way Geodesists used to observe the earth. Traditional ground surveying techniques, though accurate, require intensive labour and time and also provides limited positional accuracy. On the other hand, the space based geodetic techniques provide measurement accuracy two to three orders better than the conventional methods and has opened up plethora of applications that could not have been thought of few decades ago. Advanced communication and computing facilities have further increased the relevance of employing space geodesy in all scientific applications. With the launch of satellite missions on space Geodesy, studies related to understanding various Earth, atmosphere and ocean system phenomena have got a significant boost. Several global geodetic applications like crustal deformation, post-glacial rebound, and determination of earth’s centre of mass, ice melting, seismic deformation, sea ice melting, volcanic activity, precise satellite orbit determination, earth rotation, land and territory management, and many more are now being studied with the help of space Geodetic observations.

What is the role and mandate of National Centre of Geodesy at IIT Kanpur? Do you have any international collaboration? What is the significance of IGS installation?

The NCG was initially conceived on account of limited education in Geodesy at the national level. Although courses on Surveying and Mapping, Geoinformatics, Remote Sensing/ GIS, etc. are being taught at a few universities, none delve into the fundamentals and advanced concepts in Geodesy.

The primary objective of the NCG is to nucleate and strengthen activities in the area of Geodesy education, capacity building and academic research and development by:

1 Organizing outreach activities: capacity building in Geodesy through regular short and long term training programs; preparing well-trained PG students, development of courses and reference material, and disseminating relevant information in Geodesy.

2 Conducting state-of-the-art research and development activities (academic research, sponsored/consulting) in Geodesy.

3 Acting as the National Resource Centre for extensive support (laboratory, equipment, training, library, SW, etc.) to students and researchers from various universities and institutions and advise state/central government departments on all issues related to Geodesy.

We do have international collaboration. One of our PhD students, Mr. Ropesh Goyal is pursuing joint PhD with Curtin University, Australia and another student, Ms. Sujata Dhar with GFZ Potsdam, Germany. Further, there are various international experts from Germany, Switzerland, USA, Australia, Argentina, Spain, Italy, Austria, and Canada who have been supporting us for establishment of geodetic VLBI in India. We also have the MoUs signed with Curtin University, Australia and NCTU, Taiwan for doctoral joint degree program.

We all are familiar with International Terrestrial Reference Frame (ITRF), but it is surprising that there is no contribution from India of its realisation. The primary objective of IGS installation at IITK is to contribute to the ITRF realisation and Earth orientation parameter computation. The station is also intended to tie a national datum to the ITRF. It is already included in the Asia- Pacific Reference (APREF) network and will be recommended to be included in IGS list probably by this month end.

We don’t have many geodesists in India – what are the reasons? How do you see the academic scenario of Geodesy in India?

In India, Geodesy has been portrayed as a subject which involves rigorous mathematical understanding and analysis. Due to this, many undergraduate, postgraduate and doctoral students do not prefer to study Geodesy. On the contrary, many such students are fascinated towards the study of Geospatial Science, Geomatics, Geographical Information System, and Remote Sensing. However, Geodesy is the foundation for all geospatial technologies, the mother of all disciplines relevant to Geospatial Science.

It is noticed that many IITs, NITs, reputed government institutions and private universities are known to offer and award Masters and PhD degrees in GIS and Remote Sensing in India. However, Geodesy is not covered in depth at most of these institutions, due to the lack of trained personnel and availability of latest geodetic equipment. This issue has been widely discussed at various forums where experts in the area of Geodesy have emphasized the need to develop adequately trained human resources and standardized course syllabus to expose the subject of Geodesy to the professionals, teachers, and students. To overcome this gap in the area of Geodesy education and research, there is a need for training of the trainers, who would be involved in further training of professionals, researchers, teachers working in the field of Remote Sensing, GIS, and Earth Sciences across the country.

You represent a prestigious technology institute. How do you find the students’ interest in the subject like geodesy given the inclination towards supposedly glamorous streams of technology like computer sciences?

Though geodesy is the fundamental science of the geospatial technology, it is rarely taught in any institution with a degree course on geoinformatics, geomatics or remote sensing. So, this is obviously a new subject for the students joining us at MTech or PhD level. In 2016, we had only one PhD student working in core geodesy. However, slowly the numbers increased and presently, with the establishment of NCG at IIT Kanpur, we have more than 14 PhD students working in physical, geometrical and satellite geodesy.

Obviously, computer science can be seen as a glamourous field, but it should be noted that it is a technology that can be used with geodesy also. Though you cannot escape coding in the geodesy field, it actually depends on the interest of a student that up to what level they would like to use the computer science technology in their geodesy research. For example, our REO, Dr. Ashutosh Tiwari uses deep learning and computer vision in his geodetic applications. He is also a member of IAG working group on Machine learning in geodesy.

To be honest, geodesy is an amalgamation of physics, mathematics and computer science. Since we are trying to revive geodesy in India, it is our duty to promote geodesy and make it interesting for the incoming students.

Key research projects by your Centre.

NCG is presently involved in undertaking and coordinating projects of national importance and of high social relevance. Some of these projects are described in brief:

(i) Project Saptarshi- This project involves realizing the international terrestrial reference frame (ITRF) by setting up a network of Very Long Baseline Interferometry (VLBI) stations in India, co-located with other geodetic techniques like Satellite Laser Ranging (SLR), Doppler Orbitography and Radiopositioning by Satellite (DORIS), Global Navigation Satellite System (GNSS), Gravimeter, Corner reflectors for Interferometric Synthetic Aperture Radar (InSAR) and weather, hydrological and seismic sensors. The aforementioned techniques collect different types of observations, and synergistically provide better accuracy and error identification, leading to establishment of an accurate reference frame. These sensors, however, need to be closely co-located to achieve a robust connection, thereby reaching submm level accuracy in the realization of the ITRF. This project has been taken up as a multi -organisational effort as we need to employ the competencies of several organisations in India. The collaborating organisations are Space Applications Centre, ISRO, Ahmedabad, National Centre for Radio Astrophysicists, Pune and National Physical Laboratory, New Delhi. This project visualises India joining International campaigns involving cutting edge research and also work on our Prime Minister’s vision of Atma-Nirbhar Bharat, in fabricating our own Geodetic VLBI antenna and designing Backend electronics and Correlator required for observation and analysing the VLBI data from extra- galactic sources.

(ii) Indian National Geodetic Reference Frame: NCG is coordinating a project with an aim to establish precise and consistent Indian horizonal, vertical, gravity, and tidal datums. The establishment of the four datums for the country is the need of the hour, which we have collectively termed as Indian National Geodetic Reference Frame (INGReF). After tripartite meeting amongst Survey of India, Department of Science & Technology, and National Centre for Geodesy, a detailed recommendations in this regard have already been submitted to the Government.

(iii) Observatory for upcoming NISAR mission: NCG is involved in a project which aims to establish an observatory for calibration/validation and deformation monitoring using images from the upcoming NASA ISRO NISAR mission.

(iv) An IGS station has been set up with the policy of ‘open data centre’ to initiate all kinds of application research in the field of Geodesy using GNSS data.

What is the status of Indian National Geodetic Infrastructure? What is the way forward?

Geodetic infrastructure of a country implies establishment of the precise national horizontal, vertical, gravity and tidal datums. In India, organisations have claimed that we do have well established datums but in our brainstorming meeting on “Indian Geodetic Infrastructure: current status and a way forward” it has been unanimously agreed that those datums were established with the best available data during those times and all of which do not meet the present accuracy requirements, and they are not consistent among themselves. Moreover, no information about these datums is available in the public domain for the use by various stakeholders. In such a scenario, the major aim of geospatial policy, i.e., collection of consistent geospatial data without duplication is hard to achieve.

Since establishing the precise and consistent geodetic infrastructure is of national importance, it is inevitable to bring in different stakeholders (Government, academia, research organisation, industry) to realise the same. Recently, we conducted a tripartite meeting among NCG, DST and Survey of India and have provided some recommendations that include formation of three working groups one each for Horizontal datum, gravity and vertical datum, and tidal datum. There will be one apex body to monitor and coordinate the activities of these three working groups.

NCG would be very happy to coordinate this project of national importance. In fact, one of our students, Mr. Ropesh Goyal, has already developed a gravimetric geoid model for the whole of the mainland India and is proactive in conceiving the ideas for the definition and realisation of IRNSS based Indian geodetic reference frame. There are a few new PhD students also who are working in this domain. Now is the crucial time for a collaborative effort among various organisations to develop our national reference frame. We hope DST may be working on the realisation of the recommendations emerged from the brainstorming session and the tripartite meeting as a way forward to the Indian Geodetic Infrastructure.

You had a long association with the Survey of India. Do you think the organization has evolved vis-à-vis the fast-evolving technology and demanding users’ needs?

Being India’s National mapping agency, Survey of India prepares maps for the whole country. The organization is making efforts to keep pace with the international mapping agencies. However, the growth requires significant jumps in terms of technology awareness, adoption and application to keep pace with the fast-evolving technology. In my opinion, Survey of India is far from absorbing the new technologies. Though there can be several reasons, main reason is that they need sufficient trained manpower and financial resources. This requires training of the SoI personnel on the use of advanced geodetic instruments, and the relevant science and application. Today, there are umpteen number of applications which require the use of geospatial data and maps. User needs can better be fulfilled with the adoption of advanced geodetic techniques and technologies in mapping.

With one of the objectives of NCG to organise outreach activities, we have signed an MoU with Survey of India to conduct different short- and long-term courses for the training of Survey of India’s personnel. We have already conducted a course on Geodesy for senior level officials of Survey of India and have planned another course for surveying officers to be conducted in December 2021.

Thoughts on the Geospatial policy

The new geospatial policy is very thoughtful. It will be very productive and supportive for the geospatial industry and other stakeholders in India, and are likely to be the game-changer in the long run. We also feel that the availability of comprehensive, highly accurate, granular and constantly updated Geospatial Data will significantly benefit diverse sectors of economy.

However, one should note that the geospatial data collection and preparation of maps follow the survey principle of ‘whole to part’. Few decades back, the horizontal coordinates of a point on the surface of the earth were usually referred to Great Trigonometric Survey (GTS) station coordinates and the heights to the Indian Mean Sea level (IMSL) datum. With the introduction of spacebased technologies and modern survey techniques, the required accuracy of point positions and contour heights have increased several folds. For maintaining the consistency and avoiding the duplication, it is a welcome step that SoI topographic database will be accessible to the public. As per policy itself, the individuals can collect data of any high-resolution and accuracy, but it is also mentioned that the spatial accuracy of the sharable topographic database shall be one meter for horizontal or planimetry and three meters for vertical or elevation.

Moreover, it is welcoming step that any individual can process any geospatial data, but there exists no standard operating procedure. In such a scenario, these guidelines may not provide the consistency of the national database and hence, cannot avoid the need of duplication. As per the plottable error defined by SoI and the present accuracy availability (3m horizontal and 1 m vertical) we cannot even contribute towards the consistent mapping of the country at 1:10000 scale (plottable error=2.5 m) with heterogenous data collected by several individuals/ industries and collated by one organisation. No doubt, it can be useful in mapping the entire country at relatively smaller scale, but which is not the need of the hour.

Therefore, to meet the vision of the new geospatial policy, we should start working on a consistent National geodetic infrastructure with a long-term goal of IRNSS based Indian National Geodetic Reference Frame.