"Let's Look at the Map [Digital Data]"

The following text is Gil Castle's final draft of the real estate column appearing in Business Geographics, March/April 1995

Copyright © 1995 GIS World, Inc.

This is the second in a series of columns on real estate information sources. The topic this time is digital data. I will define the topic, delineate the many types of digital data, and conclude with data sources.

As used here, digital data refers to maps-e.g., zip code zones, census tracts, streets, individual buildings-displayed on a computer monitor or printer. Everything on each map is defined by one or more longitude-latitude coordinates, state plane coordinates, or cartographic coordinate system. Without becoming too technical, such maps are vector files, in contrast to aerial photographs, satellite images, and other raster files (which will be discussed in a future column).

Innumerable types of digital data exist. Anything that can appear on a map can be digitized. In real estate, the most frequently used digital files are these:

Other files that are employed less frequently (because they are not conveniently available, are too expensive, and/or are not easily interpreted by users) include the following:

Digital files that are only now beginning to become available but which will be extensively used by real estate professionals are the locational coordinates of individual properties plus comprehensive attribute information on square footage, acreage, number of stories, year built, type and quality of construction, ownership, assessed valuation of land and improvements, asking price (if any), selling price in previous transactions, and similar information published by select government agencies and other real estate data vendors.

Sources of data can be as diverse as the types of data. Broadly speaking, real estate professionals acquire their digital files in these ways:

In the near term, real estate professionals will acquire data in the above order; that is, buying data from the GIS software vendor will be the most frequent approach, followed by purchases directly from data vendors, and so on. Within a year or so "data stores" will begin popping up in cities around the nation for one-stop shopping of whatever data one needs in a given geographic area. Shortly thereafter, as data becomes more and more of a commodity, data catalogs will begin arriving in the mail much like the catalogs of MacWarehouse®, Egghead Software®, and other discount computer supply houses.