Update README.md

README.md

@@ -16,6 +16,10 @@ tags:
 
 This repo contains the orthoimageries used to colorize point clouds in the [FRACTAL](https://huggingface.co/datasets/IGNF/FRACTAL) semantic segmentation dataset.
 
-They are provided as is, in their original spatial resolution (0.2 m) and band order (near-infrared, red, green, blue).
+They are provided as is, in their original size (50 x 50 m), spatial resolution (0.2 m, i.e. 250 x 250 pixels) and band order (near-infrared, red, green, blue).
 
-They might be used for quick visual inspections of the FRACTAL's point clouds, or for more advanced use such as multimodal (2D-3D) deep learning training.
+They might be used for quick visual inspections of the FRACTAL's point clouds, or for more advanced use such as multimodal (2D-3D) deep learning training.
+
+Note:
+- The files are ordered by filename. Inspecting a single zip archive is therefore not representative of the whole dataset.
+- The band order does not play nice with standard image softwares. Consider reordering band order and disabling the use of transparency in a GIS software like [QGis](https://www.qgis.org/fr/site/).