Combined topographic and bathymetric survey of the southern facilities of the port of Ajaccio.
Full case study showcasing our methodology for continuously surveying complex areas. [Tetrapods]
Localisation : Port d’Ajaccio – Tino Rossi – Corse
Data Acquisition : Bathymetric LiDAR, photogrammetry
Verification : GNSS + Cross-sectional profiles
Deliverable DSM / DTM / Point Cloud
Resolution : Decimetric for bathymetry
Precision : centimetric
Introduction :
For this case study, we aimed to highlight the two competitive advantages of our methodology:
- The ability to collect data in a complex environment, and in shallow waters (Tetrapods)
- The creation of a continuous digital model, which does not include blind spots between the terrestrial and underwater parts.
1 - LiDAR Bathymetry of the Southern Shell
The southern facilities of the port of Ajaccio consist of a wave-breaking shell. The tetrapods (concrete structures designed to protect port infrastructure against erosion and the destructive effects of waves) are generally very complex to survey using traditional bathymetric methods due to their morphology and the shallow waters in this area.
The conduct of aerial LiDAR bathymetry granted us the ability to generate a digital terrain model of the structure, with sufficient resolution to facilitate a comprehensive inspection of the shell of the structure (gaps, density, and damage).
3D modeling of the terrestrial parts (in red) and the submerged parts (in yellow).
2 - Photogrammetry of the terrestrial installations.
Once the bathymetric survey was completed, we conducted a second survey based on photogrammetry this time. This method allows us to model the emerged parts of the structure with greater precision ( slabs / surfaces / rock fill )
Photogrammetric point cloud of the tetrapods
3 - Classification des points
Our engineers then step in for an important task: the classification of points and the filtering of noise.
This results in a point cloud classified as follows:
- Ground
- Water surface
- Water Bottom
- Vegetation
Combined classified photogrammetric and bathymetric point cloud
4 - Topobathymetric junction of the DEMs.
The two digital terrain models obtained through photogrammetry and bathymetric LiDAR are then combined into a single model, while carefully optimizing the junction areas.
The final data shows a continuous junction between the two parts : terrestrial and underwater.
Continuous topobathymetric DEM – Coloring: Green for terrestrial parts, blue for submerged parts.
Cross-section view and contour lines (Isophyses and Isobaths) of the port of Ajaccio. Cross section profile.
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.
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