It is time to get technical. Recently were shared an update about gathering drone footage and satellite images to improve accuracy of our algal mat predictive mapping tool. Well, here is more!
These are images of Lédano Cove – The Trieux river (FR)
Our satellite images are provided by the Planet company that allows us to see changes of the earth and make better decision. The Planet constellation provides daily satellite data to help the users to understand the physical world and take action. The advantage of these images is that they have a spatial resolution of about 3 m with a daily repeatability. The latest generation sensor has 8 bands (compared to 4 before), 5 of which are interoperable with Sentinel-2, with an atmospheric correction. This makes it possible to calculate vegetation indices and to develop applications on the ocean allowing vegetation indices to be calculated and applications to be developed over the ocean. However, unlike the free sentinel-2 images, these are paid for with a minimum order of 4500 Euros (about 0.053 Euros per hectare). To process these images a new methodology has been developed based on a fuzzy classification. Three indices were calculated upstream NDVI, NDTI and NDWI2 . On one or more reference images, we select the set of pixels containing only green algae.
Next steps will be to apply the method to other planet images, and to other patterns such as saltmarsh, seagrass, and to classify other substrates such as sand and mud, to the planet images acquired on English sites and to adapt the method to Sentinel-2 images.