As promised in my previous column, this is the first in a series of GIS case studies in real estate. The GIS application is residential brokerage. Using a GIS to more efficiently purchase a home is almost always the initial idea that people have when thinking about GIS in real estate. And, indeed, GIS technology is well suited to this task, especially when photographs of the interiors and exteriors of candidate properties can be displayed.

A typical session is envisioned as follows. One or more potential home buyers sit in front of a broker's terminal and specify the type of dwelling of interest vis-a-vis price range, number of bedrooms, detached or zero-lot-line, proximity to certain schools, etc. The broker applies the criteria to a multiple listing service (MLS) database. The homes fulfilling the criteria appear as correctly located symbols on a street map on the broker's terminal screen. MLS information about each home (e.g., asking price, date first listed, square footage) is listed next to each location. Other geographic features of interest are also mapped, such as schools, parks, shopping centers, and bus lines. Different sets of criteria, MLS information, and/or geographic features are quickly processed, until the home buyers have a promising set of properties to actually visit.

The time savings for brokers and the home buyers are potentially huge. Not surprisingly, many entrepreneurs have developed such systems. Most function in this way: Selection criteria are entered into a broker's PC, which are then submitted by modem to an MLS' mainframe database. Records satisfying the criteria are downloaded back to the PC. The records are address-matched (using GIS software on the PC) to a TIGER, GDT, ETAK, or other street file (also resident on the PC). Textual, numeric, symbolic, and geographic information are displayed at the user's request, utilizing GIS software and customized programs. The displays can then be sent to a printer, plotter, or other output device. Frequently, the MLS records used in the GIS application are also sent to a report writing module which prepares standard documents of interest to brokers and home buyers, e.g., a Comparative Market Analysis (CMA).

Despite the potential benefits, few such systems are actually in use. Multiple listing services and the brokers using their databases tend to be conservative about adopting hi-tech tools, and especially about increasing their operating expenses. Widespread use of GIS in residential brokerage will come about only when pioneering multiple listing services and brokers demonstrate substantial increases in their productivity, competitive positioning, and gross revenues�thereby forcing everyone else to board the train.