Drishti for Fog Monitoring

By: Staff Reporter
Reduced winter visibility due to fog can be a major deterrent to transport operations. The indigenously developed Drishti-transmissometers installed at Indian airports have successfully managed to overcome this challenge.
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During winter, fog reduces visibility in most parts of central, northern and eastern India. Heavy fog takes a toll of rail, road and air traffic, causing delays and cancellations of flights and trains. Pilots have to land at airports with visibility as low as 50 m, risking accidents.


Drishti-transmissometer a visibility measuring device, developed indigenously by the Council of Scientific and Industrial Research (CSIR)-National Aerospace Laboratory (NAL), enables aircraft landing in very low visibility.


Developed through an MoU signed between the CSIR-NAL, Bangalore, and India Meteorological Department (IMD) on June 22, 2011, this sophisticated instrument can assess the runway visual range, which is a critical parameter for safe landing and takeoff of aircraft in poor visibility.


Drishti-Transmissometer is indigenously designed and developed by CSIR-NAL to cover the wide span of lowest to highest visibility (<25 to >2000 meters) aiding pilots for safe landing and take-off. This cost-effective product is a mandatory system required at all airports as per International Civil Aviation Organisation (ICAO) and World Meteorological Organisation (WMO) norms. The system is extremely robust with high mean time between failures. Drishti is  empowered with a web enabled health monitoring system remotely operated from any location in the country. It is also possible to remotely access the data as also other maintenance issues, which serves as important features of this state-of-the-art system. Servicing has been made user friendly and cost-effective by modular electronics and virtual instrumentation concepts in the design. Drishti needs almost zero maintenance and has, so far, delivered the most accurate results.

Drishti is operational at the Choudhary Charan Singh International Airport, Lucknow, from 2010 onwards, and the Netaji Subhash Chandra Bose International Airport, Kolkata from 2012 onwards. At Indira Gandhi International Airport (IGI), Delhi, 13 Drishti systems are operational on its three runways, which was installed in a phased manner from 2011. In all, 27 Drishti systems are currently functional at 10 international airports. Another 12 Drishti-transmissometers are in the process of being installed. The IMD, working in tandem with the MoES has already requisitioned for Drishti-transmissometers to be placed in 60 out of 70 Indian airports.


Drishti is indigenisation of a technology which had been the exclusive domain of a few developed countries so far. Priced at one-third of an imported system, Drishti shall not only lead to substantial savings in foreign exchange, but shall also make the country self reliant in the field of front-end technology.


The official website of the IGI Airport, New Delhi quotes an analysis by the Ministry of Civil Aviation which found that flight diversions at the airport reduced by around 36 per cent despite longer durations of low visibility in the 2015-16 winter. Flight diversions decreased to 45 between December 1 and January 5, from 71 during the corresponding period in the 2014-15 winter. This was despite an increase in the total duration of low visibility periods at the airport. The reduction also happened at a time when the airport witnessed total closure due to zero visibility for almost 30 hours as against 15 hours during the corresponding period last winter. Flight cancellations during the low visibility period were also reduced by about 53 per cent (from 83 last winter to 39 this season). It showed that the overall flight operations at the airport also increased during the low visibility period this winter by nearly 67 per cent from 2,808 aircraft movements (both take-off and landing) last winter to 4,683 in the current season.

Future plans

At the moment, plans are afoot to install Drishti in all civilian airports in the country, as per a memorandum of understanding (MoU) signed in 2014 between the IMD and CSIR-NAL.


Drishti will also be installed at airports run by the Indian Navy and Indian Air Force (IAF). Tata Power SED also intends to install 54 systems in 18 airfields of IAF under an airfield infrastructure modernisation programme. Mini Drishti systems have also been developed to help the Indian Railways and those living in hilly terrain. Mini Drishti systems are proposed to be installed in various places to help the Indian Army in the fog season.


Besides transmissometers, CSIR-NAL have also developed the Drishti-automated weather monitoring system. Two such systems have been installed at IGI airport, Delhi for field testing and have been successfully functioning since the last six months. This system, which costs just 1/5th of an imported system, is a mandatory requirement at airports.


CSIR-NAL has also developed the Drishti-forward scatter meter for helipads, which shall soon undergo field testing. The Mini Drishti and mini-weather monitoring systems are also ready for deployment at the highways.


The indigenously developed Drishti-transmissometer meant to assess visibility levels is proving a boon for pilots who can now land aircraft safely during conditions of highly reduced visibility. Similar Drishti systems developed for road and rail traffic will help a great deal in ensuring risk-free winter transport, particularly in hilly terrain prone to foggy weather.

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