M/s. Secon-Helica JV has bagged the contract from National High Speed Rail Corporation Limited (NHSRCL) for Final Alignment design including Aerial LiDAR survey and other related works for Mumbai-Nashik-Nagpur High Speed Rail Corridor (about 753 kms. long).
- Contract Package No.: NHSRCL/CO/CA/LIDAR/2020/32
- Name of work: Final Alignment Design Including Aerial LiDAR Survey and other Related Works for Mumbai-Nashik-Nagpur High Speed Rail Corridor (about 753 kms. long).
- Completion period of the Work: 150 days
In September this year, the NHSRCL had invited online open e-tenders for the work Contract: NHSRCL/CO/CA/LIDAR/2020/32.
Scope of work:
According to the tender document, the contractor shall further refine the alignment in the selected alignment corridor by undertaking 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 of interconnected triangles (with a baseline of about 25km) to be established for overall horizontal control with approx. 25 km baseline length throughout the alignment. Secondary Control Network comprising 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 the client.
- 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-Tender update | Image Credit (representational): NHSRCL