Gravitational Distance from major cities

Discussion created by amcinturff on May 23, 2011
Latest reply on Jun 1, 2011 by tomdilts
I am trying to create a raster for the US such that every point is influenced by its distance to every major city (about 210 cities total). Imagine each city is a massive object exerting a force on each point in the raster. The closer the city, the greater its force on the raster point; the larger the city, the greater its force on the raster point. Every raster point should be influenced by every city in this manner.

Inverse distance weighting doesn't do the trick, as points between large and small cities get an intermediate rather than an additive value - for example, points around Phoenix have higher values than those around LA, a bigger city, because LA is surrounded by smaller cities and Phoenix is not. I want all those little cities around LA to further increase the values of the surrounding raster points, not decrease them.

My idea to do this would be to make an inverse distance weighted raster for every single city and then combine them, but there must be an easier way. Please respond with any ideas or examples, I could use the help.