I am attempting to analyze coastal landscape change. I have two DEMs from significant post-storm periods for my study area. I would like to produce a simple DEM of difference using the Minus tool. My DEMs are from 2016 and 2014, if I want to see how much change occurred from 2014 to 2016 would I use 2016 DEM for Input 1 or 2?
Sometimes it is easier to look into ArcGIS help: http://desktop.arcgis.com/en/arcmap/10.3/tools/spatial-analyst-toolbox/minus.htm
You can see, that it is Raster1 - Raster2.
So difference between 2014 and 2016 is Raster1(2014) - Raster2(2016). Which would be 0 in same areas. Negative in areas that are higher in 2016 and positive in areas where 2014 is higher.