I'm trying to use the modeler in QGIS to calculate the NDVI on a raster image. The model is the one below:
In the "NDVI Calculator" algorithm I have set the parameters like this.
The model is working and I get a raster, but NDVI values are completely different from the result obtained with the standard raster calculator (the one that opens from the QGIS toolbar).
Could anyone help me to set it up properly?
Here is a screenshot showing differences between the result with the raster calculator and the modeler. Differences are relevant for the soil pixels, which are mostly negative or 0 for the output of the raster calculator (correct!) and positive (more than 1) for the modeler (wrong!)