ABSTRACT
There are several methods for delineating trade areas: the analog method, the proximal area method, and the gravity models. The analog method is nongeographic, and is often implemented by regression analysis. The proximal area method and the gravity models are geographic approaches, and can benefit from GIS technologies. The analog and the proximal area methods are fairly simple, and are discussed in Section 4.1. The gravity models are the focus of this chapter, and are covered in detail in Section 4.2. Two case studies are presented in Sections 4.3 and 4.4 to illustrate how the two geographic methods (the proximal area method and the gravity models) are implemented in GIS. Case Study 4A draws from traditional business geography but with a fresh angle: instead of the typical retail store analysis, it analyzes the fan bases for two professional baseball teams in Chicago. Case Study 4B demonstrates how the techniques of trade area analysis are used in delineating service areas for public hospitals in Louisiana. Case Study 4A uses Euclidean distances to measure the spatial impedance for simplicity, and thus can be implemented without the Network Analyst module. Case Study 4B uses travel time through the road network and thus relies on several tools in the Network Analyst module. The chapter is concluded with some remarks in Section 4.5.
