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GIS basic question types

(Data West Research Agency definition: see GIS glossary.) A GIS can be distinguished by listing the types of questions it can (or should be able to) answer as opposed to being described: a) through formal definitions, and b) through its ability to carry out spatial operations, and linking data sets together with location as the common key. There are five generic questions that a sophisticated GIS can answer:

1 - Location What is at ...? The first of these questions seeks to find out what exists at a particular location described in various ways (e.g., place name, post or zip code, or geographic references).

2 - Situation/Condition Where does it exist? The second question is the converse of the first and requires spatial analysis to answer. Instead of identifying what exists at a given location, a location is found where certain conditions are satisfied (e.g., an unforested section of land of at least 2000 square meters in size, within 100 meters of a road, and with soils suitable for supporting buildings).

3 - Trends What has changed since...? The third question involves both of the first two, and seeks to find the differences within an area over time.

4 - Patterns What spatial patterns exist? The fourth question is more sophisticated; the question is asked to determine whether cancer is a major cause of death among residents near a nuclear power station or how many anomalies there are that don't fit a predetermined pattern and where they are located.

5 - Modeling What if...? The fifth question is posed to determine what happens, for example, if a new road is added to a network, or if a toxic substance seeps into the local groundwater supply. (Answering this type of question requires both geographic as well as other information, and possibly scientific laws.)

GIS glossary

The GIS terms under the entries GIS glossary: a-g and GIS glossary: h-t are condensed and reproduced with permission from "A Practitioner's Guide to GIS Terminology" by Stearns J. Wood. Compiled over 30 years and first published in 1984, the book contains more than 10,000 terms embracing all aspects of geoprocessing and geoanalysis, spatial and network analysis, resource management, facilities management, automated mapping, computer-aided design and drafting, database management systems, open systems connectivity and geographic information system computer technology. Selected terms from geography, cartography, computer science, urban and regional information systems, remote sensing and GPS are also included. See GIS glossary: a-g and GIS glossary: h-t.

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