DIFFICULT DECISIONS IN LAND USE MODEL CONSTRUCTION

IDENTIFICATION AND DISCUSSION IS CONDUCTED ON DECISIONS WITH RESPECT TO DATA TO BE USED, SCALE AND DETAIL, METHODS OF ESTIMATION AND PROJECTION, AND OTHER ACTIVITIES IN MODEL CONSTRUCTION AND UTILIZATION FOR STUDIES OF URBAN LAND USE. DECISIONS ARE SEPARATED INTO TWO CLASSIFICATIONS' /1/ THOSE HAVING TO DO WITH THE INCLUSION OF NOTIONS ABOUT BEHAVIOR IN MODELS, AND /2/ DECISIONS BEARING ON THE FORMAL STRUCTURES OF THE MODELS. DECISIONS CONCERNING WHERE PLANNING FITS INTO URBAN GROWTH, WHAT ENTITIES ARE ASSUMED TO TAKE ON BEHAVIOR, AND WHAT KINDS OF BEHAVIOR ARE TO BE INCLUDED, ARE EMPHASIZED BECAUSE THEY INTERRELATE WITH DECISIONS ABOUT THE STRUCTURE OF THE MODEL. DECISIONS WITH RESPECT TO ENTITIES THAT TAKE ON BEHAVIOR AND LEVELS OF AGGREGATION INFLUENCE THE METHODS THAT MUST BE USED IN ESTIMATING AND THE NUMBER OF VARIABLES TO BE INCLUDED. DECISIONS RELATED TO THE NATURE OF PROCESSES, AND ESPECIALLY TO SPATIALLY AUTOCORRELATED PROCESSES, INFLUENCE ERRORS OF ESTIMATION, PARTICULARLY ESTIMATES OF THE PROPERTIES OF THE COEFFICIENTS OF THE MODEL. THE DECISIONS AND PROBLEMS DISCUSSED ARE VERY LIMITED ONES WHEN COMPARED TO THE TOTALITY OF KNOWLEDGE AND EXPERIENCE WITH MODEL CONSTRUCTION AND USE. NONE THE LESS, THESE DECISIONS REAPPEAR IN LAND USE MODEL CONSTRUCTION TASKS, AND THEY REQUIRE MORE SYSTEMATIC THOUGHT.