How Indigenous Indian Technologies Are Helping Aircraft and Trains Navigate Safely Through Dense Fog

India is strengthening its aviation and railway safety infrastructure through indigenous technologies designed to support transport operations during dense fog and other low-visibility conditions. Scientific institutions, government agencies and Indian manufacturers have developed advanced systems that help pilots, air traffic controllers and locomotive drivers operate more safely when visibility deteriorates.

Among these innovations are the Drishti Transmissometer developed by CSIR-National Aerospace Laboratories (CSIR-NAL), the SkyCast atmospheric monitoring system introduced under Mission Mausam, and the Indian Railways’ Kavach automatic train protection system. GPS-based Fog Safety Devices are also helping locomotive pilots identify approaching signals and important railway landmarks when dense fog restricts their view.

These technologies address different operational challenges but share a common objective: improving transport safety by providing accurate information and reducing dependence on direct visual observation. Their development reflects India’s growing expertise in aerospace instrumentation, atmospheric sciences, railway automation and intelligent transport systems.

Drishti: India’s Indigenous Technology for Airport Visibility Monitoring

The Drishti Transmissometer, developed by Bengaluru-based CSIR-National Aerospace Laboratories, is an important achievement in India’s indigenous aviation technology programme. The system measures runway visibility and provides information that helps airport authorities, air traffic controllers and pilots make operational decisions during fog, rain and other conditions that restrict visibility.

Dense fog presents a significant challenge to aviation because aircraft operations depend on accurately determining visibility along airport runways. During approach, landing and departure, pilots require sufficient visual references to maintain safe operations within the limits prescribed for the aircraft, airport and available landing systems.

Drishti addresses this requirement by measuring the transmission of light through the atmosphere. The instrument evaluates how much light is lost over a known distance and uses the measurement to determine atmospheric visibility. This information contributes to the calculation of Runway Visual Range (RVR), an important parameter used in low-visibility airport operations.

The system provides continuous measurements that can support decisions concerning aircraft movements during changing weather conditions. Its ability to deliver objective visibility information is particularly valuable at airports affected by persistent winter fog.

CSIR-NAL developed Drishti as an indigenous alternative to imported runway visibility equipment. The technology has been transferred to Indian industry for manufacturing and deployment, strengthening domestic capabilities in precision optical instrumentation and aviation electronics.

According to official information from CSIR-NAL, more than 175 Drishti units have been installed at civilian and defence airports across India in collaboration with the India Meteorological Department. This deployment demonstrates the practical application of Indian scientific research in safety-critical aviation infrastructure.

SkyCast: Advanced Atmospheric Monitoring for Indian Airports

India introduced another significant aviation technology on 29 May 2026 with the inauguration of SkyCast at Indira Gandhi International Airport in New Delhi. Developed under the Ministry of Earth Sciences’ Mission Mausam initiative, SkyCast brings together several advanced observation instruments to monitor atmospheric conditions affecting airport operations.

Unlike conventional visibility instruments that measure specific atmospheric parameters, SkyCast integrates information from multiple sensors to provide a broader understanding of weather conditions around airports. The system monitors factors associated with fog formation, atmospheric turbulence, wind movement and vertical changes in temperature and moisture.

The installation incorporates a Radar Wind Profiler, Sonic Detection and Ranging equipment, a microwave radiometer, a Ground-based Fog Aerosol Spectrometer and a lidar-based ceilometer. These instruments collect different types of atmospheric information, allowing meteorologists to assess weather conditions across several layers of the lower atmosphere.

The Radar Wind Profiler measures wind speed, direction and atmospheric movement at different heights, while the microwave radiometer provides information about temperature and moisture profiles. The fog aerosol spectrometer examines the characteristics of particles and droplets associated with fog formation, and the ceilometer monitors the vertical structure of clouds and fog layers.

By combining these observations, SkyCast improves the ability of meteorologists to understand how fog develops, changes and dissipates. This information is especially important at airports where rapidly changing visibility conditions can disrupt flight schedules and require adjustments to operational procedures.

The Ministry of Earth Sciences has indicated that SkyCast can support short-range weather forecasting and warnings over periods extending to approximately three hours. Such forecasts can help aviation authorities anticipate deteriorating visibility and prepare for changing weather conditions.

The government has also announced plans to establish another SkyCast facility at Noida International Airport in Jewar, followed by expansion to additional airports.

SkyCast does not enable aircraft to physically see through fog. Its contribution lies in improving atmospheric observations and weather forecasts, allowing pilots, air traffic controllers and airport operators to make better-informed decisions.

How Aircraft Navigate and Land During Dense Fog

Modern aircraft use several navigation and landing technologies that allow them to operate when external visibility becomes severely restricted. These include satellite navigation, onboard instruments, ground-based radio navigation equipment and advanced instrument landing systems.

An Instrument Landing System (ILS) provides guidance that helps pilots maintain the correct horizontal alignment and vertical descent path while approaching a runway. The system transmits radio signals that aircraft instruments interpret to guide the approach.

Airports equipped with suitable Category II or Category III landing facilities can support operations in lower visibility conditions, subject to the certification and capabilities of the aircraft, crew, airport and associated equipment.

Advanced aircraft may also use automatic landing systems that follow instrument guidance during the final stages of an approach. These systems reduce dependence on visual references, although specific visibility requirements and operational restrictions continue to apply.

Indian technologies such as Drishti and SkyCast complement these capabilities by providing accurate information about runway visibility and atmospheric conditions. Drishti measures visibility, while SkyCast supports weather observation and forecasting.

The distinction is important because safe operations during dense fog require both navigation capability and reliable weather information. An aircraft may possess advanced landing equipment, but its operation must still comply with the weather limits and safety requirements applicable to that flight.

India’s indigenous contribution through Drishti and SkyCast strengthens the information infrastructure supporting these established aviation technologies.

Kavach: India’s Indigenous Automatic Train Protection System

Indian Railways has developed Kavach, an indigenous Automatic Train Protection system designed to prevent accidents arising from unsafe train movements, including passing signals at danger and exceeding authorised speeds. The system was developed by the Research Designs and Standards Organisation (RDSO) in collaboration with Indian industry.

Kavach is particularly relevant during dense fog because reduced visibility can make it difficult for locomotive pilots to observe railway signals and other trackside indications from a sufficient distance.

The system uses a combination of radio communication, electronic equipment, track-mounted RFID tags and railway signalling information to monitor train movements. It determines important operating parameters and communicates relevant information to equipment installed inside the locomotive.

The onboard display provides the locomotive pilot with information about signal aspects, permitted speeds and movement authority. This allows the driver to receive essential operational information even when distant signals are difficult to see through fog.

Kavach also provides an automatic safety function. When a train approaches a dangerous operating condition and the locomotive pilot does not take the required corrective action, the system can intervene by applying the brakes.

This capability distinguishes Kavach from equipment that merely provides warnings or navigation information. It acts as a protective system capable of automatically responding to certain unsafe situations.

The Ministry of Railways has been progressively expanding Kavach across the Indian railway network. According to an official assessment released in February 2026, implementation had extended across more than 2,200 route kilometres, with the Kavach 4.0 version covering more than 1,300 route kilometres across five railway zones.

The continued expansion of Kavach represents an important step towards strengthening India’s railway safety infrastructure through domestic engineering and advanced electronic systems.

Kavach 4.0 Strengthens Railway Safety and Automation

Kavach 4.0 represents an improved version of India’s indigenous automatic train protection technology, incorporating refinements intended to strengthen system performance, reliability and operational integration.

The system operates through communication between equipment installed along railway tracks, signalling infrastructure and electronic systems mounted on locomotives. This allows trains to receive movement-related information without relying exclusively on visual observation of trackside signals.

The technology is designed to support safe train operation by monitoring authorised movement and intervening when necessary. Its effectiveness depends on the integration of onboard equipment with the railway signalling network and associated communication infrastructure.

The development of Kavach 4.0 also involves specialised Indian manufacturers supplying electronic components, radio communication equipment, control systems and other technical infrastructure.

This industrial participation has helped create domestic capabilities in railway automation, embedded electronics, communication systems and safety-critical engineering.

As Kavach deployment expands, its role in protecting train movements will become increasingly important, particularly on heavily used routes where signalling, speed management and traffic density require reliable automatic safeguards.

During dense fog, the availability of in-cab signalling information and automatic braking protection can help address some of the challenges created by poor visibility. However, the system must operate alongside established railway signalling arrangements and prescribed operating procedures.

GPS-Based Fog Safety Devices Assist Locomotive Pilots

Alongside Kavach, Indian Railways has introduced GPS-based Fog Safety Devices to support train operations during periods of restricted visibility.

These portable electronic devices use satellite positioning and stored railway route information to alert locomotive pilots when trains approach important trackside locations.

The equipment provides advance information about signals, level crossings, permanent speed restrictions and other designated railway landmarks. As the train approaches a stored location, the device generates visual or audible alerts to inform the locomotive pilot.

This capability becomes especially valuable during winter fog, when railway signals and trackside structures may remain invisible until the locomotive reaches a relatively short distance from them.

By receiving advance warnings, locomotive pilots can anticipate approaching locations and prepare to comply with applicable operating instructions.

The Ministry of Railways confirmed in March 2026 that 29,848 GPS-based Fog Safety Devices were available across Indian Railways as of 31 January 2026.

The extensive availability of these devices reflects the importance of supporting train crews during seasonal low-visibility conditions, particularly across northern India.

Fog Safety Devices differ from Kavach in their operating functions. They primarily provide location-based information and alerts, while Kavach is designed to provide automatic train protection and braking intervention under specified conditions.

The two systems therefore serve complementary purposes. Fog Safety Devices improve situational awareness, while Kavach adds an electronic safety mechanism that can intervene when certain operational limits are violated.

Why Dense Fog Creates Challenges for Aircraft and Trains

Fog forms when tiny water droplets remain suspended close to the Earth’s surface, reducing the distance over which objects can be seen clearly.

These droplets scatter and absorb light, making distant objects difficult to distinguish. The degree of visibility reduction depends on the concentration, size and distribution of the suspended droplets.

For aircraft, dense fog can limit the visibility of runway markings, approach lights and other references used during landing and take-off. Although modern aircraft possess sophisticated instruments, airport operations must still remain within approved visibility limits.

For railway operations, fog can make signals, curves, level crossings and other trackside features difficult to identify from a distance. This can increase operational complexity and require additional precautions.

The challenges differ because aircraft and trains operate within distinct environments and follow different navigation principles.

Aircraft rely on a combination of onboard instruments, satellite navigation, air traffic control and ground-based navigation facilities. Trains move along fixed tracks but must respond to signalling instructions, speed restrictions and conditions affecting the railway network.

The technologies developed in India address these challenges through specialised methods suited to each mode of transport.

Drishti measures runway visibility, SkyCast monitors atmospheric conditions, Kavach protects train movements, and Fog Safety Devices provide advance location-based warnings.

Although none of these systems eliminates fog, each improves the information or protection available during adverse weather conditions.

Advanced Sensors Reduce Dependence on Human Vision

A common feature of modern transport safety technologies is their ability to obtain essential information without depending entirely on direct human observation.

Optical instruments such as Drishti can measure atmospheric transparency more consistently than subjective visual estimates. SkyCast adds information from radar, acoustic sensors, microwave instruments and lidar equipment to build a more comprehensive picture of weather conditions.

On the railways, satellite positioning and electronic communication allow onboard equipment to identify approaching landmarks and receive signalling information even when those locations are obscured by fog.

These capabilities demonstrate how different scientific principles can address similar operational difficulties.

Aviation weather instruments primarily measure environmental conditions, while railway protection equipment determines movement-related information and can support automatic safety responses.

The effectiveness of these systems depends on accurate sensors, reliable communication, appropriate calibration and regular maintenance. Their information must also be integrated into established operational procedures.

The growing use of such technologies reflects a broader transition towards intelligent transport infrastructure in which electronic systems continuously support human decision-making.

Indian Research Institutions Drive Transport Technology Development

The development of indigenous fog-safety technologies demonstrates the contribution of India’s scientific institutions to practical infrastructure requirements.

CSIR-National Aerospace Laboratories has played an important role through its work on precision instrumentation and the development of Drishti. Its efforts have enabled Indian industry to manufacture equipment previously associated with specialised imported aviation technologies.

The Ministry of Earth Sciences and its associated organisations have contributed to advanced atmospheric observation through programmes such as Mission Mausam and the introduction of SkyCast.

In the railway sector, RDSO has worked with Indian manufacturers to develop Kavach and integrate advanced electronic safety systems into railway operations.

These institutions bring together expertise in optical engineering, atmospheric physics, electronic communication, embedded software, control systems and industrial manufacturing.

The successful deployment of their technologies demonstrates the importance of sustained scientific research and collaboration between public institutions and domestic industry.

Such partnerships also create opportunities for Indian companies to develop specialised components, manufacture advanced equipment and provide long-term technical support.

Indigenous Manufacturing Strengthens Technological Self-Reliance

The development of Drishti, Kavach and associated transport safety equipment supports India’s broader objective of building domestic capabilities in strategically important technologies.

Aviation instrumentation and railway protection systems require high levels of reliability because their performance directly influences operational safety.

Developing these technologies domestically allows Indian institutions and manufacturers to acquire expertise in design, testing, manufacturing, certification and maintenance.

Indigenous production can also improve access to technical support and facilitate future improvements based on the country’s specific operational requirements.

For the aviation sector, these capabilities are relevant to precision optical instruments, weather-monitoring equipment and advanced electronic systems.

For Indian Railways, the development of Kavach has encouraged domestic expertise in signalling technology, electronic control systems, radio communication and railway automation.

The technologies also provide opportunities for Indian manufacturers to develop products that meet demanding safety and performance requirements.

As deployment increases, the associated manufacturing and maintenance activities can contribute to a stronger domestic ecosystem for advanced transport technologies.

Strengthening India’s Transport Infrastructure for Challenging Weather

India’s climatic diversity creates significant operational demands for its transport infrastructure. Dense winter fog affects northern airports and railway corridors, while heavy rainfall, thunderstorms and other weather events create additional challenges in different regions.

The development of indigenous monitoring and protection systems helps transport operators respond to these conditions with better information and stronger safety mechanisms.

Drishti provides reliable runway visibility measurements, while SkyCast improves the monitoring and forecasting of atmospheric conditions affecting airports.

Kavach supports train safety through electronic monitoring and automatic intervention, while GPS-based Fog Safety Devices help locomotive pilots anticipate approaching railway signals and landmarks.

These technologies work within broader operational frameworks that include established safety procedures, trained personnel and supporting infrastructure.

Their wider deployment can improve transport reliability and strengthen the ability of airports and railways to manage adverse weather conditions.

The continued advancement of Indian research and engineering capabilities will also support the development of more sophisticated transport technologies suited to the country’s growing infrastructure requirements.

India Advances Towards Safer and More Intelligent Transport Systems

India’s indigenous fog-safety technologies demonstrate how scientific innovation can address practical challenges affecting millions of travellers.

The Drishti Transmissometer has strengthened runway visibility monitoring at civilian and defence airports, while SkyCast has introduced advanced atmospheric observation capabilities. Indian Railways’ Kavach system adds automatic protection against unsafe train movements, and GPS-based Fog Safety Devices provide important location-based information during low-visibility operations.

These developments reflect progress across different areas of Indian engineering, including aerospace instrumentation, meteorology, electronic communication and railway automation.

Their importance extends beyond fog-related operations because the underlying technologies contribute to the modernisation of aviation and railway infrastructure throughout the country.

As India continues expanding its transport networks, the development and deployment of indigenous safety technologies will remain essential to improving operational reliability, strengthening domestic technological expertise and supporting safer journeys.

The combined progress of Indian research institutions, public agencies and manufacturers demonstrates the country’s growing ability to develop advanced transport solutions suited to its own geographical, climatic and operational requirements.

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References

1. CSIR-National Aerospace Laboratories – Aerospace Electronics and Systems Division

Official information on the indigenous Drishti Transmissometer, its development, technology transfer and deployment across Indian civilian and defence airports.

https://nal.res.in/en/current-research/aerospace-electronics-and-systems-division-ald

2. Ministry of Earth Sciences – Inauguration of SkyCast at Indira Gandhi International Airport

Press Information Bureau, 29 May 2026.

Official government announcement covering SkyCast’s advanced atmospheric monitoring instruments, fog observation capabilities and plans for deployment at additional airports.

https://www.pib.gov.in/PressReleasePage.aspx?PRID=2266638

3. Ministry of Railways – Kavach and Artificial Intelligence Strengthening Railway Safety

Press Information Bureau, 6 February 2026.

Official assessment of Kavach deployment, automatic train protection capabilities and the role of advanced technologies in railway safety.

https://www.pib.gov.in/PressReleasePage.aspx?PRID=2224380

4. Ministry of Railways – GPS-Based Fog Safety Devices

Press Information Bureau, 13 March 2026.

Official confirmation of the availability of 29,848 GPS-based Fog Safety Devices and measures to improve railway operations during restricted visibility.

https://www.pib.gov.in/PressReleasePage.aspx?PRID=2239700

5. Ministry of Railways – Indigenous Kavach Automatic Train Protection System

Press Information Bureau, 23 March 2022.

Official information on the development of Kavach and its role in strengthening train safety during adverse weather.

https://www.pib.gov.in/PressReleasePage.aspx?PRID=1808641

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