Supreme Court of India directed the Archaeological Survey of India (ASI) to conduct a detailed non-invasive survey of the Gyanvapi mosque in Varanasi, Uttar Pradesh to determine if the mosque was built atop a temple.
Purpose of the Survey
- The petitioners argued that the mosque was built on the foundation of the temple and that there were several Hindu idols and structures hidden inside the mosque.
- The court directed the ASI to form a five-member committee of experts to conduct a comprehensive physical survey of the entire Gyanvapi compound using non-invasive techniques such as ground-penetrating radar (GPR) and carbon dating.
- The survey is expected to reveal whether there are any traces of a temple or other Hindu structures below or within the mosque and to establish the age and origin of the existing structures.
- The court also appointed an observer to monitor and supervise the survey process and report any irregularities or violations.
Non-Invasive Methods in Archaeological Prospecting
- Non-invasive methods are used when investigations are undertaken inside a built structure and no excavation is permitted.
Types of Methods
- Active Methods: Inject energy into the ground and measure the response. The methods provide an estimate of the ground’s material properties, such as density, electrical resistance, and wave velocity.
- Seismic Techniques: Use shock waves to study subsurface structures.
- Electromagnetic Methods: Measure electromagnetic responses after energy injection.
- Passive Methods: Measure existing physical properties.
- Magnetometry: Detect magnetic anomalies caused by buried structures.
- Gravity Surveying: Measure gravitational force variations due to subsurface features.
Ground-Penetrating Radar (GPR)
- ASI will use GPR to produce a 3-D model of buried archaeological features.
- GPR operates by introducing a short radar impulse from a surface antenna and records time and magnitude of return signals from the subsoil.
- Radar beam spreads like a cone, causing reflections before the antenna passes over the object.
- Radar beams spread out in a cone, leading to reflections that may not directly correspond to physical dimensions, creating false images.