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Deep Blue and Polynesian Black...
Deep Blue and Polynesian Black Pearls
Pléiades Neo’s deep blue spectral band improves the performance of water depth estimation, specifically in bathymetry. In the French Polynesian atoll of Arutua, black pearl oyster farming is a significant economic resource. These seafloor maps can provide opportunities for the sustainable management of the Blue economy.
The black-lipped pearl oyster
Sustainable management of black pearl oyster farms
- Black pearl oyster production is French Polynesia's second most valuable economic resource, accounting for over 90% of world production.
- The Arutua atoll, located 368 km north-east of Tahiti, harvested the most cultured pearls in Tahiti in 2021, with 1.7 million pearls.
- Sustainable management of the Arutua lagoon has been implemented since 2017 to control black pearl oyster farming capacity and the health of the atoll.
- The estimation of water depth is necessary to create a geophysical model of the lagoon's bathymetry
- The bathymetric map will make it possible to monitor, develop and adapt the lagoon to decisions relating to sustainable development.
Arutua Atoll
Airbus has developed an advanced satellite image processing algorithm for creating detailed bathymetry maps of coastal areas and coral reef cartography. In this example, we apply it to a Pléiades Neo image captured on September 6, 2022, over the Arutua atoll.
The resulting map delivers depth readings of up to 25m with a resolution of 1.2m, all achieved without the need for external reference data.
The process begins with atmospheric correction and the creation of a clear, haze-free image. Next, water depth is estimated using sophisticated physical or reflectance modelling techniques.
Bathymetric map
While all six spectral bands of Pléiades Neo contribute to the algorithm, the Deep Blue band plays a pivotal role. This valuable information is visually represented using a colour scale.
The Deep Blue band spans between 400 and 450 nanometers, sitting right on the cusp of the visible light spectrum. With minimal water absorption, it enables us to see further into the depths.
Oyster Farm Detection
The water around this atoll provides an ideal environment for both oysters and fish to flourish. As a result, it's essential to safeguard the pearl oysters by housing them in wire mesh baskets suspended on lines.
These lines, visible in the blue band, appear as long, parallel streaks near the pearl farms. Comparing them to the bathymetry map, these oyster lines are typically found at depths ranging from 8 to 10 meters.
Geophysical model of the seabed
A bathymetric map obtained without external reference data.
A bathymetric map with a resolution of 1.20m and a model capable of detecting depths of up to 25m.
Rapid bathymetric data that can be repeated to monitor geomorphological changes in the lagoon.
Blue Economy
Bathymetry enhances the underwater observation capabilities on which other Blue Economy space applications are based:
- Coral reef monitoring
- Sediment dynamics
- Geomorphological changes
- Shallow water vegetation cover
- Hydro-climate
- Monitoring renewable resources
- Food sources for the marine wildlife, including oysters
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