Should we track rankings from the exact business location vs. city center or using geo modifiers?

We recommend tracking your rankings across a geo-grid to understand better how you rank throughout your locality.

The proximity ranking factor makes it so that you will want to track from various points across an area to get a good idea of the keyword coverage area. Checking your rankings at only one point on the map will give you a very poor idea of what is going on with the rankings.

Check out for an example of using a geo-grid.