Monarch Surveyors & Engineering Consultants bags contract for Aerial LiDAR Survey for Rangpo to Gangtok Railway line in Sikkim

RITES has issued a Letter of Acceptance (LoA) to M/s. Monarch Surveyors & Engineering Consultants Pvt. Ltd, for Aerial LiDAR Survey and other works for Rangpo to Gangtok Railway line in the State of Sikkim.

  • Name of work: Aerial LiDAR Survey and other works for Rangpo to Gangtok Railway line in the State of Sikkim  
  • Accepted Contract Amount: Approx. 1.65 Crore 
  • Work Completion Period (in days): 150 Days 

In March this year, the RITES invited a tender for Tender Number: RITES/RP/T and S/RANGPO TO GANGTOK/FLS/SURVEY

Scope of Aerial LiDAR Survey:

 Clearances for Flying:

  • The contractor is responsible to obtain necessary clearances from Director General of Civil Aviation, Ministry of Defence, Government of India as per DGCA CAR Section 3 Air Transport Series F Part I Issue I, 12th October 2010 (Refer Section 6 – Aerial Photography/Geophysical Surveys and Annexure E) and other agencies as may be required to complete the job of flying over the AOI, acquire LiDAR and digital camera data etc. 
  • The client would provide necessary documentation; however, getting clearance would be the entirely the responsibility of the contractor. 
  • There are chances that alignment may change at any stage of the project. 
  • The contractor would need to plan accordingly.

Flight Planning:

  • The flight path shall cover the study area completely including enough cross flight lines to eliminate shadowing and allow for proper quality control. 
  • Flight line overlap should be 20% or greater, as required, to ensure that there are no data gaps between the usable portions of the swaths. 
  • Data collections in high relief terrain should have greater overlap.
  • Any data with gaps between the geometrically usable portions of the swaths will be rejected.
  • The contractor shall generally avoid missions during inclement weather which have been known to degrade the accuracy of laser return data. 
  • The contractor must document mission date, time, flight altitude, airspeed, scan angle, scan rate, laser pulse rates, and other information deemed pertinent.

Sensor Calibration:

  • The contractor must provide a calibration certificate of the sensor issued by the manufacturer. 
  • In addition, the contractor must submit evidence that the total LiDAR system was calibrated prior to current project initiation, for the purposes of identifying and correcting systematic errors. 
  • Proper system calibration requires repetitive over-flight of terrain features of known and documented size and elevation using flight paths similar to those that will be used in the Aol.

Ground Control Survey: 

  • The contractor must use appropriate ground control to achieve required deliverables as listed above. 
  • During data collection, two DGPS base stations will simultaneously be used during the mission. 
  • Inter- distance between two base stations should not exceed 25km.


  • The raw LiDAR data should be assembled for clipping, filtering, and processing.
  • The elevation data may then be examined and compared to known values and control.
  • Because of the reflective nature of light, it is common for errors to be recorded because of the reflectivity, or lack there of, from surfaces within the project area. 
  • Though a few points within each mission are indeed identified as discrepant, it is an insignificant percentage (usually less than 5%) that should be removed from the data.

Post – Processing:

  • The contractor will provide high – resolution, high – accuracy, “bare – earth” ground elevation data at regular spacing (DEM), irregular spacing with mass points and break – lines (DTM), and the elevation data of all top surfaces (DSM).
  • To restrict data to ground elevations only, the contractor must remove elevation points on bridges, buildings, and other structures and on vegetation, from the LIDAR – derived data. 
  • In addition to randomly spaced LIDAR points, before and after removal of data associated with structures and vegetation, the contractor must produce a bare – earth DEM.
  • The contractor must use Triangular Irregular Network (TIN) linear interpolation procedures, including break lines, when validating the vertical accuracy of the data models.

Quality Control/Quality Assurance:

  • Tender for Aerial LiDAR Survey and other works for Rangpo to Gangtok Railway line in the State of Sikkim Quality Control/Quality Assurance (QC/QA) of the LIDAR and/or LiDAR derived data will be the responsibility of the contractor. 
  • This QC/QA process shall include reviews of flight alignments and completeness of supporting data (e.g., cross sections, profiles). 
  • The client may perform additional QC/QA testing.

About RITES Limited:

  • RITES Limited is a Miniratna (Category -I) Schedule ‘A’ Public Sector Enterprise and a leading player in the transport consultancy and engineering sector in India, having  diversified services and geographical reach. 
  • The company has experience spanning 47 years and has undertaken projects in over 55 countries across Asia, Africa, South America, and Middle East region. 
  • RITES Limited is the only export arm of Indian Railways for providing rolling stock overseas (other than Thailand, Malaysia and Indonesia).

Source: RITES-Tender Update | Image Credit (representational): MoR

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