The successful planning and implementation of railway station extension projects require precise, comprehensive, and high-resolution spatial data. A Final Location Survey (FLS) forms the foundation of this process, guiding engineering design, structural planning, and construction execution. With the advancement of drone-based survey technologies, particularly the deployment of LiDAR-enabled UAVs, surveys can now achieve unprecedented levels of speed, accuracy, and detail.
This document outlines the methodology, scope, and deliverables of conducting an FLS for a railway station extension project using the DJI Matric 350 RTK (M-350) drone equipped with a high-precision LiDAR sensor (such as Zenmuse L2), along with Differential GPS (DGPS) and Total Station (TS) technologies. The integration of these platforms ensures a robust and reliable dataset for all civil, geometric, and operational design elements.
Survey Objective
The key objective of the Final Location Survey is to enable detailed engineering design for the proposed extension of a railway station through:
- Accurate acquisition of terrain and surface data;
- Finalization of track alignment, horizontal/vertical curves, and gradients;
- Identification of optimal locations for platforms, yards, bridges, and buildings;
- Preparation of Digital Terrain and Elevation Models for earthwork and drainage;
- Support in designing signalling, electrification, and communication infrastructure.
Technology Overview
DJI Matrice 350 RTK (M-350) Drone with LiDAR
The DJI Matrice 350 RTK is a next-generation industrial drone equipped for high-accuracy geospatial surveys. When integrated with Zenmuse L2 LiDAR, it provides dense point cloud data and real-time kinematic positioning.
- Flight Altitude: Typically, 50–100 m AGL, depending on terrain and obstruction.
- LiDAR Sensor: Up to 240,000 points per second with multiple returns, enabling surface penetration through light vegetation.
- RTK GNSS Integration: Delivers centimetre-level position accuracy with real-time correction.
- Camera Integration: RGB data supports generation of high-resolution orthophotos at 2.5 cm GSD.
- Operational Range: Up to 20 km under favourable conditions, ideal for large station yards and adjoining alignments.
- Obstacle Avoidance: Built-in sensors ensure flight safety in complex station environments.
Differential GPS (DGPS)
DGPS is utilized to establish Ground Control Points (GCPs) and Check Points (CPs), serving as reference for geo-referencing the LiDAR data and validating vertical and horizontal accuracy.
- Base and Rover Configuration: Ensures sub-decimetre precision;
- GCPs Deployment: Strategically located throughout the survey area;
- Benchmark Transfer: To ensure continuity with existing survey references.
Total Station (TS)
Total Station survey supports high-precision layout and ground truthing where drone data is insufficient (e.g., under roofed platforms or near vertical structures):
- Measurement Accuracy: Up to 2 mm;
- Applications: Track centreline layout, point and switch location, platform edge marking, and elevation transfer.
Detailed Scope of Survey Work
The comprehensive scope of the Final Location Survey for railway station extension using the M-350 drone with LiDAR includes the following:
Topographical and Feature Mapping
The entire project area will be mapped for both natural and built-up features:
- Trees, electric poles, overhead transmission lines and towers;
- All categories of roads (paved/unpaved), footpaths, and access lanes;
- Rivers, drains, culverts, canals, and other hydrological features;
- Wells, agricultural plots, fences, and plot boundaries;
- Existing railway assets: tracks, signals, OHE, platforms, buildings, water columns, lighting poles, etc.
Surface Elevation Modelling
High-resolution terrain and elevation data products will be created:
- Contours at 10 cm intervals over the full extent of the area;
- Spot Elevation Model on a 5 m × 5 m grid for micro-level gradient analysis;
- Digital Elevation Model (DEM) at 0.5 m resolution for hydrological and structural simulation;
- Digital Terrain Model (DTM) at 1.0 m resolution, used for engineering calculations and earthwork estimates.
Permanent Benchmarking
A permanent benchmark with DGPS-based coordinates shall be established:
- Located within the existing R&D yard or other permanent structure;
- To be used as a reference for all future works in the area;
- Coordinates and elevation certified with backup log sheets and photographs.
Boundary and Pillar Marking
- Plant boundary in possession shall be marked and documented;
- Permanent pillar locations will be geo-referenced and plotted for land-use and encroachment verification.
Track Geometry and Rail Planning
Essential data for alignment, track structure, and operational design will be captured:
- Existing track gauge (e.g., Broad Gauge 1676 mm), rail section (e.g., 60 kg UIC), and sleeper configuration;
- Horizontal and vertical curves, transitions, and super elevation;
- Gradients and elevation differentials between main line and proposed yard;
- Points, crossings, derailing switches, and proposed turnouts with location references.
Bridges, Tunnels, and Station Infrastructure
Mapping and design input for structural components shall include:
- Locations of new or modified bridges, culverts, or underpasses;
- Mapping of platforms, ramps, staircases, shelters, and buildings;
- Determination of station expansion zones, considering operational logistics and safety buffers.
Signalling, Traction, and Communication Systems
- Mapping of existing signalling masts, cabins, and control lines;
- Documentation of OHE poles, masts, feeder lines, and substation locations;
- Space planning for signalling equipment, axle counters, communication ducts, and related services.
Yard Drainage System
The drainage design will be based on elevation models and flow analysis:
- Determination of natural slope and proposed drainage alignments;
- Integration with existing outfall or disposal systems;
- Mapping of sumps, culverts, and catch pits where applicable.
Ortho-Mosaic Image
- Generation of an ortho-mosaic image at 2.5 cm ground sampling distance;
- Used for visual validation, public presentations, and spatial planning overlays.
Data Processing and Accuracy
Post-flight data will be processed using specialized geospatial software (e.g., DJI Terra, Global Mapper, AutoCAD Civil 3D, QGIS):
- Accuracy Standards: Achieving vertical accuracy ≤5 cm and horizontal accuracy ≤3 cm;
- Point Cloud Classification: Ground, vegetation, buildings, rail, and power lines;
- Coordinate Reference System: As per project specification (e.g., WGS84 or local UTM);
- Quality Assurance: Cross-verification with TS and DGPS data to ensure consistency.
Deliverables
Upon completion of the Final Location Survey, the following deliverables will be submitted:
| Deliverable | Format |
| Ortho-mosaic imagery | GeoTIFF, JPEG |
| LiDAR point cloud data | LAS/LAZ |
| Digital Elevation Model (0.5 m) | TIFF, ASCII Grid |
| Digital Terrain Model (1.0 m) | TIFF, DXF |
| Spot Elevation and Contour Maps | PDF, DWG, DXF |
| AutoCAD drawings (alignment, yard, etc.) | DWG, DXF |
| Topographic base maps | PDF, SHP, DWG |
| DGPS Report with benchmark coordinates | |
| Survey Methodology and QA Report | PDF, Excel |
The utilization of the DJI Matrice 350 RTK (M-350) drone with LiDAR capability, combined with DGPS and Total Station, presents a robust and highly accurate solution for conducting the Final Location Survey for a railway station extension. The integration of aerial and ground-based survey techniques ensures full spatial coverage, high data fidelity, and actionable insights for all design and execution stakeholders.
The outputs from this comprehensive survey will serve as the cornerstone for alignment finalization, structural design, yard planning, and infrastructure development—ensuring the railway station extension is built on a foundation of precision and efficiency.
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