River mapping using aerial bathymetric LiDAR
A comprehensive case study in a fluvial environment: Bathymetric LiDAR, GNSS Control Survey, and Photogrammetry of the bridge
Localisation : Pont d’Altiani – Corse
Data Acquisition : Bathymetric Lidar + RGB
Verification : GNSS + Cross-sectional profiles
Deliverable DSM / DTM / Point Cloud
Resolution : Decimetric for bathymetry
Precision : centimetric
METHODOLOGY
For this case study, we aimed for a comprehensive comparison in a complex environment that presents challenges related to data post-processing, torrential/fluvial conditions with the presence of waves and silt.
1 - Establishment of a reference base on the site (pivot)
The establishment of a reference base on site helps reduce GNSS errors related to the distance from the base (baseline)
To do this, we used an EMLID RS2+ receiver positioned on a fixed survey nail, calculated over 5 minutes.
This base station will serve as a pivot for correcting the data from our rovers (Drone / GNSS Survey / Flight Trajectories ...)
Establishment of a reference base at the Altiani Bridge site.
2 - GNSS Control Surveys (Topo + Bathy)
Once the base was set up, we conducted surveys using a mobile (GNSS rover Emlid RS3).
Equipped with tilt compensation,Equipped with tilt compensation, this unit facilitates the acquisition of precise points despite a complex environment.
Bare earth points, bathymetric points, and cross-sections were surveyed with this rover, corrected by the base station
Photogrammetric point cloud of the tetrapods
3 - Preparation of the DRONE mission: Bathymetric LiDAR Acquisition
Preparation of the flight plan to maximize the acquisition of bathymetric points despite the presence of a significant obstruction: the bridge.
Preparation of a bathymetric LiDAR mission
4 - Acquisition of Bathymetric LiDAR Data by Drone
Drone flight over the water surface and collection of topo-bathy data
Bathymetric survey by drone at the Altiani Bridge in Corsica
5 - Photogrammetric Survey of the bridge
Photogrammetric survey of the structure to obtain a dense point cloud for 2D drawing.
6- Post-Processing
The data is then post-processed: trajectories, aerotriangulation, photogrammetric reconstruction, and noise filtering (manual and automatic) to create a Digital Terrain Model of the entire site.
Cross-section of the Tavignano upstream of the Altiani Bridge structure. The topographic elements (bare earth and trees) and bathymetric elements (waterline and riverbed) are clearly distinguished.
7 - Photogrammetric Coupling
In order to create a reliable, aesthetic, and comprehensive 3D model, we performed a coupling of photogrammetric and bathymetric data.
Note: This coupling is not necessary for obtaining a complete bathymetric survey; it is only useful in the case of modeling a structure.
Photogrammetry + Bathymetric LiDAR Coupling. The dark blue represents the waterline surveyed, while the light blue indicates the submerged areas
8 - Possible Deliverables
Digital Terrain/Surface or Elevation Models, topographic plan, structure drawing, etc
DTM of the Tavignanu captured by Airborne Bathymetric LiDAR – The Altiani Bridge was removed to allow visualization of the riverbed.
9 – Conclusion
The results of this use case are available for private consultation via video call.
If you would like to know more about LiDAR technology or request a quote for your underwater surveys, feel free to contact us.
English 
Français