Rail Corridor Drainage Mapping

Drone LiDAR survey through dense vegetation to identify and map surface drainage along 24km of rail corridor


A stretch of over 24km of steep and heavily vegetated slopes above the rail line connecting Sydney and Newcastle were known to include a network of slope drains, which were intended to capture and direct surface water runoff in order to reduce geotechnical instability. The slope drains had never previously been surveyed and so the exact location, extent and condition of the drainage network was unknown to corridor managers. Due to the rugged and remote nature of the area, with some stretches of the rail corridor only accessible by boat, the identification and drainage mapping via conventional means was largely unfeasible.


Diodrone developed a drone-LiDAR solution which would provide the client with a detailed contour map of the rail corridor and any nearby surface drainage. Due to the heavily vegetated nature of the area, the LiDAR survey needed to achieve a relatively high point density to ensure that the presence of any slope drains could be identified in the resulting digital terrain model.

A cross section of the LiDAR point cloud shows the terrain profile and surface drainage mapping even beneath dense vegetation cover
A cross section of the LiDAR point cloud shows the terrain profile even beneath dense vegetation cover.

Topographic survey through dense vegetation while trains were running and without people in the danger zone.

Diodrone surveyed an area of almost 500ha over a period of 8 days in the field, capturing LiDAR and imagery. An 3cm orthophoto of the survey area was produced, to improve on the lower resolution imagery publicly available. The LiDAR survey achieved an average density of 500 points per square metre and an accuracy of 50mm RMSE. Following rigorous ground classification, a digital terrain model (DTM) was developed from which the location and extent of surface drainage was identified. Diodrone extracted surface drainage features from the DTM and prepared a set of detailed contour maps over the 20km+ length of rail corridor.

Corridor managers were able to use the surface drainage mapping to scope and coordinate inspection and subsequent maintenance activities.

Slope drainage mapping from the LiDAR derived Digital Terrain Model
Slope drainage identified from the LiDAR derived Digital Terrain Model