National High-Speed Railway Corporation Limited (NHSRCL) has launched LiDAR (Light Detection and Ranging Survey) survey for the Mumbai-Hyderabad High Speed Rail project to speed up and improve the future train journey of Mumbaikars. Mumbai-Nagpur, Mumbai-Ahmedabad, and now Mumbai-Hyderabad.
- A Detailed Project Report (DPR) is being prepared for the Mumbai-Pune-Hyderabad bullet train (approximately 650 km) for which an aerial LiDAR survey has been started.
- The aircraft, equipped with state-of-the-art aerial lidar and imagery sensors, made its maiden flight from Pune and started gathering information related to the ground survey.
- The detailed information will be collected in 3-4 months as against the process that usually takes 12-18 months.
- It will also include information on various terrains, hills, rivers along the proposed route.
- A 100-megapixel camera is used for laser data, GPS data, and actual photographs to provide accurate survey data.
- Work is underway to prepare DPR for Mumbai-Hyderabad and Mumbai-Nagpur bullet train projects.
- NHSRCL has been entrusted to prepare the Detailed Project Reports for seven (7) High Speed Rail Corridors and LiDAR survey technique will be used for ground survey in all the corridors.
In January this year, Monarch Surveyors & Engineering Consultants Pvt. Ltd. bagged the contract from National High Speed Rail Corporation Ltd. (NHSRCL) for the work Final Alignment design including Aerial LiDAR survey and other related works for Mumbai-Hyderabad High Speed Rail Corridor.
- Tender No.: NHSRCL/CO/CA/LIDAR/2020/38
- Name of work: Final Alignment design including Aerial LiDAR survey and other related works for Mumbai-Hyderabad High Speed Rail Corridor.
According to the tender document, the scope of work includes:
Scope for Final Alignment Report: Detailed Final Location Survey and Studies with final alignment design:
The contractor shall further refine the alignment in the selected alignment corridor by undertaking a detailed Final Location Survey using Aerial LiDAR technology along with establishment of Ground Control Network, Pillar fixing, Hydrological Survey (wherever required) and final alignment design (horizontal as well as vertical). For doing this, the contractor shall undertake the following:
Aerial LiDAR & Imagery Survey:
The contractor will undertake Aerial LiDAR Survey complemented by Aerial Imagery in a corridor width of 300 m (150 m on either side) around the proposed alignment. Detailed Specifications are provided in TOR and Broadly the work will involve the Following:
- Collection & paper study of existing alignment reports, data, drawing, documents, ground control points etc;
- Ground Control Survey to be undertaken as follows:
- Carrying out reconnaissance survey of the project area for identifying the Control Points locations for carrying out DGPS survey and preparing a plan of a grid network of Control Points on SOI topo-sheets/satellite imagery.
- Survey of India Benchmarks to be located during the above reconnaissance survey. These benchmarks shall be tested for stability and the same shall be reported to the client. The entire horizontal and vertical control shall be linked to the approved stable Benchmarks for conversion of LiDAR data to MSL.
- Master Control Network comprising interconnected triangles (with baseline of about 25km) to be established for overall horizontal control with approx. 25 km baseline length throughout the alignment. Secondary Control Network consisting of interconnected triangles weaved with the Master control network to be established with a baseline length of approx. 3-5 km throughout the alignment. Target LiDAR points to be established at an interval of approx. 5 km within the final alignment. To densify Horizontal Control Network, the GNSS triangulation method should be adopted and processing of data for network adjustment should be done to achieve an accuracy of at least 1:100,000 in horizontal.
- Establishment of vertical control referenced to SoI MSL Permanent Benchmarks to be undertaken by double tertiary leveling along the entire route by connecting target points.The threshold limit for levelling loop closure accuracy should be 12√K mm, where K is circuit length in km.
- Monumentation of Master and Secondary Control Points shall be undertaken if required in consultation with client as per Section 3.3.2
- Applying to DGCA/Ministry of Defence for flying permissions as per DGCA guidelines and procedures along with adherence to all security stipulations issued by Ministry of Defence in the issue of the permit. NHSRCL will provide the necessary support.
- The contractor will mobilize an aircraft/helicopter to site fitted with state of art Aerial LiDAR and Imagery sensors (equipment as per minimum specification mentioned in Annexure 3) after due security inspection as per MoD stipulations.
- Preparation of flight plan for the Area of Interest.
- Acquiring and pre-processing LiDAR data and digital imagery with LiDAR collected at a point density of 10 points per sq m with FHA (Fundamental Horizontal Accuracy) of 10 cm and FVA (Fundamental Vertical Accuracy) of 10 cm both at 95% confidence interval level. Imagery is to be taken at a resolution of 10 cm GSD.
- Pre-processing data to be referenced to MSL with SoI permanent benchmarks.
- Ground survey/Hydrological survey using traditional methods such as Echo Sounders etc along areas such as river crossings etc where Aerial LiDAR data needs to be complemented, including the following:
- 4 km (2 km on each side of centerline) along all river crossings with river cross-sections soundings (or alternate acceptable method) taken at centerline and then at every 500 m distance along upstream and downstream of the river and upto 50 m beyond high bank.
- The DEM generated from this data shall be suitably merged with the LiDAR DEM in consultation with the client.
Source: NHSRCL-Update | Image Credit (representational): NHSRCL