Geokit plus Rails 3.1.1，lat和lon问题。

I am using geokit-rails3 gem to find products in all colleges within range of particular college. A college has_many products and a product belong to college, there is another category model which has_many products and product belongs_to category. But when I try to find college from database on basis of addess using geokit it tell me lat coloumn is missing in my table. I am using geokit-rails3 gem to find products i