What is LiDAR Technique?
Context in Current Affairs: The Indian Railways is to use LiDAR technique to conduct ground survey for the Delhi Varanasi High Speed Rail corridor. LiDAR is Light Detection and Ranging technique.
What is the plan?
The Indian Railways is to use the LiDAR technique mounted on a helicopter. This is being done after its success in the Mumbai Ahmedabad bullet train project for the first time.
The technique uses a combination of GPS data, laser data, flight parameters to give an accurate survey.
The length of the Delhi Varanasi corridor is about 800 kilometres and the alignment of stations is to be decided based on the survey and in consultation with the government. The corridor is to connect the national capital territory with major cities such as Agra, Lucknow, Mathura, Prayagraj, Raebareli, Etawah, Bhadohi, Ayodhya and Varanasi.
Technology provides high quality data in very short interval of time. This data is usually used in projects related to landslides, roads, surface transport, Canal, irrigation and city planning.
- It is a remote sensing method that uses light in the form of pulsed laser to measure available distances in the earth. The light pulses in the system generate three-dimensional information about the shape of the earth and its surface characteristics. A LiDAR instrument consists of a scanner, laser and a GPS receiver. Helicopters and aeroplanes are the most commonly used platforms to acquire LiDAR data.
- There are two types of LiDAR namely topographic and Bathymetric. The topographic LiDAR uses infrared laser to map the land. On the other hand, the bathymetric LiDAR uses water penetrating green light and measures river bed elevations and sea floors.
- The wavelengths used in the technology is between 10 micrometres which lies in the infrared region and 250 nanometres which lies in the ultraviolet region.
- The scattering effects used in the technology are Raman scattering, Rayleigh scattering, Mie scattering.
- The technology measures the amplitude changes or the changes in the phase of the reflected light to form the shape of the structure on the earth surface.