Conclusions and Recommendations

As an integrated approach to managing and analyzing map and attribute data, geographic information systems are becoming increasingly common. GIS applications begin with a spatial question and proceed to a data collection phase during which both map and attribute data are collected. The initial spatial question drives the data collection and the model-building process. In the analysis phase which follows, both map and attribute data are manipulated via the analytical tools provided by the GIS software.

While the review of both database and map analysis were separated for purposes of discussion, they are closely linked in practice. Indeed, the power of GIS-based investigations comes largely from the ability to simultaneously access and process both map and attribute data. The tools presented in this paper for performing these analyses are commonly used and represent broad categories of functionality. However, this discussion does not constitute a complete or comprehensive listing of GIS tools.

The increasing influence and use of GIS can be largely attributed to its ability to support decision making. Toward this end, a GIS needs reliable data and must be able to analyze and synthesize this data quickly. For the GIS to reach its full potential it must be soundly implemented. This implementation must consider database development and the accuracy and the long-term maintenance of data sets.

Needs assessment is perhaps the most important step of GIS implementation. Discussions about systems requirements, an understanding of who are the users and what they demand of the system, and an evaluation of the educational and training needs of users are all part of needs assessment. This process can ensure that proper data sets are collected, that all users understand the technology and its role within the organization, and that proper analyses and output can be generated. After a consensus of the needs is established, education, training, and data compilation (i.e., acquiring and digitizing proper data sets) can begin.

During the data acquisition stage, special attention must be paid to data accuracy, quality, and scale. Most data collected for a GIS comes from published maps. The scale of these maps relates to the relative spatial accuracy or precision of the data they contain. The degree of accuracy needed depends on the type of application. In defining minor watersheds for a county, locations specified to +/- 40 feet is well within acceptable limits because 40 feet is relatively insignificant for that particular analysis. However, in parcel mapping, where property lines need to be defined, a more accurate map at a larger scale with more accurate and precise data would probably be needed. Users must also be cognizant of errors generated in the measurement, encoding, and classifying of data.

Collection and creation of the data to be stored in the database is typically one of the largest expenditures in implementing a GIS. For this reason, data must be as reliable and accurate as possible. Complete documentation of all databases is important to assure the integrity of the data, the reliability of subsequent analyses, and the ability to maintain the system over time. A commitment must be made to maintain these databases. Remember that the utility of GIS is a direct function of the data contained within the system. Only dedicated care of the database can ensure that database manipulations and spatial analysis will produce results of the highest order.

Suggested References

Aronoff, S. 1989. Geographic Information Systems: A management perspective. WDL Publications, Ottawa, Canada. 294 p.

Berry, J. K. 1987. Fundamental operations in computer-assisted map analysis. Int. J. of Geographic Info. Systems 1:119-136.

Berry, J. K. 1989. Beyond mapping: Spatial data analysis. pp. 10-16. In The GIS Sourcebook. GIS World, Inc., Ft. Collins, CO. 180 p.

Dangermond, J. 1986. The software toolbox approach to meeting the user's need for GIS analysis. pp. 66-75. In Geographic Information Systems Workshop Proceedings, Atlanta, GA, April 1-4, 1986. Am. Soc. for Photogrammetry and Remote Sensing, Falls Church, VA. 426 p.

Goodchild, M. F. 1987. Towards an enumeration and classification of GIS functions. Volume II. pp. 67-78. In International Geographic Information Systems (IGIS) Symposium: The Research Agenda Proceedings, Arlington, VA, November 15-18, 1987. National Aeronautics and Space Administration, Washington,DC.

Rhind, D. 1989. Why GIS? Arc News, Environmental Systems Research Institute, Redlands, CA. 11(3):28-29.

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