Using ASC files

ASC files are elevation text files provided by IGN France and downloadable for free. You can use this elevation data to generate elevation textures to use in your soils that match the real world.

Each ASC file is a tile of 1000 x 1000 values of elevation.

ASC files come in 3 possible precisions 1 meter, 5 meters and 25 meters.

Which means that two neighbour values inside the tile will be spaced by either 1m, 5m or 25m where we do not have the value, and an average between neighbouring values will be done. So 1 file of a 5m precision departement will cover a square tile of 5 x 1000m = 5 km by 5 km.

Contrary to what may seem logical, it is not always advisable to use 1m precision files. These files are created based on satellite images, which means at a 1m precision you will be able to detect the buildings, trees etc. These are not details that you want to translate as terrain elevation in NDunes, this is why we advise the use of 5m precision files.

Let's try it with a concrete case :

Automatically, an elevation texture named asc_merge_455_6775_3000_3000_height.tif is generated, along with a text file with the same name. These files are located in your working directory next to your soil document, and automatically set as elevation texture, so we get this result in the soil view.

Let's analyse the generated texture :

Once your elevation texture is correct, you can use the node graphs to generate your other soil channels (color, flow etc) using the Graph editor. This is the process automatically done in the Blueprints to generate a complete primary soil from the ASC files covering the OpenStreetMap zone.