National Center for Geographic Information and Analysis

This paper is a part of Research Initiative 10, "Spatio-Temporal Reasoning in GIS," of the U.S. National Center for Geographic Information and Analysis (NCGIA). 

This report contains two papers, plus supplementary material. The first paper develops and presents the formal mathematical definitions of the 9-intersection; it is under consideration by a journal at the time of this writing. The second paper reports of cognitive testing, based on the mathematical model presented in the first paper. It contains the complete set of stimuli used in Mark and Egenhofer’s experimental work up to January 1994.