Heliborne Geophysical Survey System – Garuda Vasudha

Republic Day Spl

The Garuda Vasudha is an advanced Light Helicopter of Geological Survey of India equipped with Heliborne Geophysical Survey System (HGSS). It is a ‘Dhruv’ category helicopter that has been indigenously built by HAL and the HGSS comprising four aerogeophysical sensors, namelyTime Domain Electromagnetic, Magnetic, Spectrometric and Gravimetric alongwith Data Acquisition Systems, have been procured from M/s Pico Envirotec Inc., Canada. The installation and integration of the sensor system has been carried out at HAL. The total cost of the HGSS is about Rs. 63 crores. The state-of-the-art HGSS will bolster the probing prowess of aerogeophysical surveys for locating concealed and deep seated mineral deposits of the country. This is going to be used for second-generation multisensor aerogeophysical survey by the Remote Sensing and Aerial Survey (RSAS) Division of Geological Survey of India.

A brief description of the surveys/sensors is:

Time-domain Electromagnetic (TDEM): This sensor by virtue of its greater penetrability is capable of detecting mineral presence from depths upto 300 meters in various geological terrains. This is one of the most widely used electromagnetic techniques in mineral exploration, particularly for conducting minerals like base metal sulphides, etc. The TDEM system (PTHEM) is developed by Pico Envirotec, Canada.

Magnetic: It is very much useful in delineating geological structures, determination of depth to the basement rocks and identifying basic and ultrabasic rocks, mineral deposits rich in magnetic minerals. This is a CS-3 magnetometer developed by Scintrex, Canada.

Spectrometric: It is useful in locating atomic mineral deposits and delineation of formational boundaries. The Spectrometer (AGRS) is developed by Pico Envirotec, Canada.

Gravity: This survey is effective in delineating sedimentary basins hosting coal and hydrocarbons as well as high-density mineral deposits such as chromium, manganese, barytes, etc. The Gravimeter GT-1A is developed by Gravimetric Technologies, Russia.

The surveys by the sophisticated HGSS will be conducted using two different configurations employing (a) Spectro -- TDEM – Mag (the last two sensors fitted on a loop suspended from the helicopter) and (b) Gravity – Mag (the latter fitted on a towed bird suspended from the helicopter) depending on the requirement.

RSAS, with its headquarters at Bangalore, has been engaged in the planning and execution of multi-sensor airborne geophysical surveys, acquisition of aerogeophysical data and their processing, interpretation and identification of aerogeophysical anomalies. The interpreted aerogeophysical data is integrated with remote sensing and ground geological data on GIS platform.  The integrated data with identified and prioritized blocks is taken for ground follow-up/evaluation by geological, geochemical and ground geophysical surveys and finally exploration by drilling is taken up in potential / target areas of mineralisation. 

While aerogeophysical survey in India commenced in 1967 with the help of other agencies, RSAS has been acquiring data since 1986 using its own de Havilland Twin Otter aircraft equipped with Twin Otter Airborne Survey System (TOASS) comprising magnetic, electromagnetic and radiometric sensors, which was upgraded with the state-of-the-art technology in the year 2000. Some salient achievements of TOASS conducted by RSAS, GSI so far are:

·         Through subsequent intensive ground follow-up and drilling under the first two projects alone, at least 35 base metal prospects were identified.

·         An image map of aeromagnetic anomalies of Peninsular India (between lat. 8° and 25° N) in collaboration with NGRI was prepared.

·         Kimberlite Clan Rocks (KCR) bodies (host for diamond) were located in Narayanpet-Raichur block and Ibrahimpur area in parts of Andhra Pradesh & Karnataka, Basna, Jamnadi, Chandkuri in Chhattisgarh and Sakri, Masankura and Dumrapur areas in Odisha.

·         Collaborative programme between RSAS and Central Ground Water Board, South-Western Region, Bangalore on evaluation of ground water prospect in hard rock terrain in parts of Tumkur district, Karnataka using aeromagnetic and remote sensing data interpretation yielded encouraging results in recognizing mega- and meso-scale lineaments correlated with deep aquifer systems.

            Heliborne survey operation has certain added benefits over the aerogeophysical survey using aircraft. These are: a) low ground clearance, tight line flying in any terrain; b) can replace or minimize ground follow-up; c) slower flying rates (higher data density); d) able to operate in remote areas and rugged terrain (no runway required); e) able to keep the sensors very close to the ground with under slung, and f) able to produce high-resolution data.

            These will lead to better and more accurate interpretation for targeting and modeling of mineral deposits within the Obvious Geological Potential Area of around 5.71 million sq km in India, identified earlier by GSI.

Courtesy: Press Information Bureau (pib.nic.in)