planblue's DiveRay mounted on a autonomous underwater vehicle, floating in Hemmoor Lake. Image: planblue

After almost a year of work within the MtecPla Project, it was finally time for a field test. Planblue took the DiveRay, our underwater satellite monitoring system, to a lake in northern Germany called Hemmoor. The goal was to determine whether we could detect and identify prepared sediment plastic mixtures in natural conditions. Since we had already tested the system under controlled laboratory conditions imitating a natural setting, we were optimistic – but of course in the field conditions are always different to a laboratory environment.

Chief Technical Officer and Diver Guy Rigot pulling the remotely operating vehicle past the landing stage. Image: planblue

The Kreidesee Hemmoor near Cuxhaven is clear and the dive base offers perfect conditions to test underwater systems. Together with scientists of the German Research Center for Artificial Intelligence (DFKI), we mounted the planblue DiveRay with its hyperspectral camera on DFKI's autonomous underwater vehicle (AUV) "Dagon", which was operated in a hybrid remote mode for this purpose. The modular hardware housing for the combined unit was specially constructed by our partner Kurt Synowzik Werkzeug u. Maschinenbau (KSW), who built a strong and effective housing which is waterproof, allows light to optimally reach the camera and weighs very little.

Trays with the plastic samples on the bottom of the lake. Image: planblue

For the experiments in the Kreidesee, divers positioned various plastic samples provided by the Institute of Biomaterials and biomolecular systems of the University of Stuttgart (and removed them from the lake afterwards of course). The samples consisted of the most commonly used and found plastics in the world: PP, HDPE, LDPE, PS, PET, Nylon and PVC. These are, for example, used in the production of disposable cups and plates, trash bags, water bottles, fish nets and packaging. The samples were a variety of colors and sizes, embedded in trays with quartz sand.

We weren’t only testing whether our underwater system could detect clean, new plastic. Some samples were degraded beforehand. One set of plastics were exposed to sunlight for one week (in the controlled environment of a climate chamber). The other was placed in a lake for six weeks to develop a biofilm on their surface.

Development Engineer Nils Öhlmann, CTO Guy Rigot, and Mechanical Systems Engineer Hédi Bokri examing software readouts. Image: planblue

Over the three days, we performed multiple tests. The aim was to detect the samples, to record the condition of the plastic, and to couple the results with georeferenced data. As a result, we had both the AUV with DiveRay scan the plastic, as well as a diver with the DiveRay.

plablue's DiveRay mounted on a remotely operating vehicle, scanning plastic in Hemmoor Lake. Image: planblue

The information obtained from the dives is visualized stitched maps which can be color coded to show the plastic. These are comprehensible even without expert knowledge. We are extremely pleased that the field tests not only satisfied our expectations, but also showed that our technology works reliably in the field. The next step is a trip to the Dominican Republic to scan plastic in the ocean.