I have recently flown aerials for our township. Our arborist wants me to do a Tree Canopy Assessment. There is a free toolbox to download. I had to acquire spatial analyst to use the toolbox. I've never worked anywhere that was willing to pay for SA, so I'm a bit out of touch with these things. In the toolbox, the input raster must contain 7 categories it says. This is where I'm stuck and can't find much in the ESRI help. I've only ever used rasters (aerials) for viewing, never manipulating or extracting data. How to I create these categories in the raster. Please forgive my ignorance, never had to so never learned it.