Imagine that you work for a company that is considering setting up a retail store in the area of Hadley, Massachusetts (US). They have ask you to produce a map with potential areas for their consideration. The areas of interest should be flat (less than 3 degrees slope), close to roads for ease of access (less than 150 m from roads) and should fall in the zones allocated by the government to business/industrial areas in the town of Hadley.

This first "site selection" module will show you several issues about working with rasters using the QGIS-GRASS interface, and will solve the raster analysis/modeling part of problem: to find the flat areas (< 3 degrees slope).