This example highlights one of the fundamental differences between raster and vector capabilities. This situation is used as one of the MFteach Lesson Units and it shows the power of raster based spatial analysis. This is a multiple step process beginning with a map of a road network. Each road is recoded so that each cell of the road represents the distance covered by a standard unit of time based on the speed limit of that road. Major roads like highways have a higer rate of speed than lesser roads.
Unpaved roads have the lowest rate of speed of any road.
These values are encoded into the base map and then just the road network is isolated for analytical purposes. The focus of this exercise in MFteach is to pick a site for development which meets certain travel time conditions. In order to do this, a point is selected as a possible site which might meet these conditions. In a classic vector approach, a buffer ring would be created which extends from the focus point to a specified distance which might be travelled in a fixed period of time. It should also recognize that some areas have no roads and are therefore impassible.