Update model_structure.md

added description for VegetationLayer

docs/src/model_structure.md

@@ -14,3 +14,4 @@ The following components and resources make up the model:
 
 - `LandscapeLayer`: This layer holds a grid of cells. Each cell is referenced by geo-coordinates. The georeferenced data contained in the `Model` folder are used to determine which cell is accessible (i.e., within the perimeter) and inaccessible (i.e., outside the perimeter).
 
+- `VegetationLayer`: This raster layer consists of a collection of pixels representing the vegetation on the surface of the park, based on the calculated NDVI. This high-resolution vegetation map was created using QGIS processing and then exported to a raster file. The georeferenced data enable agents in the simulation to effectively determine which areas in the park are suitable for food production. The associated data are located in the file mars_ndvi_raster.geojson in the Resources/ folder.