NoMethodError: undefined method `acts_as_mappable'

[timlentse]

If I use geokit-rails only in activerecord (not rails), i will meet NoMethodError: undefined methodacts_as_mappable' error. Which i totally don't know why? What i expects is just to usegeokit-rails` in no-rails projects(which use activerecord to handle data of mysql), and i just want to enable activerecord has the ability to find by geo.
Do i have misunderstanding of this gem? Any suggestion will be appreciated!