an inexact model for interpolation. This type of method is based on the gravity model concept and was developed to model potential interaction between masses measured at sample points.
eg: the amount of interaction, in terms of commerce, between the people of two villages is related to the number of people in each village and how close these villages are to each other. More People who are closer together produce a greater total interaction. The interaction at a location far from any village would tend to be zero.