Spatial interaction models have played an important role in two tasks in the Human Settlements and Services Area. In the Public Facilities Location Task they have been used to represent the locational behavior of establishments and households. In the Urban Change Task they have been used to describe internal migration patterns. In this paper, Waldo Tobler introduces a new spatial interaction model and outlines some of its properties. Variants of the basic model are noted and a computer listing is provided for readers wishing to explore the usefulness of the model as a descriptor of movement patterns
