Geographic Information Systems: An Introduction, 3rd Edition

11.13 Quality Control

Normally, it would be better to control the data during rather than after production. Data can thus be supplied with a “quality guaranty,” and users will be able to assess the data's areas of applications. Control during production presupposes that the producers have established a quality control system. Such a system will contribute to the efficient production of data according to specific requirements and ensure that it is done right the first time. This assumes a product specification or an approved standard for the data sets available. A quality control system includes routines and guidelines that describe working operations, thus preventing errors, attaining the right quality, and ensuring efficient control.

It is well known that geographical data are processed (transformed, etc.) and analyzed several times and by different institutions. Ideally, therefore, each process should be subject to quality control.

A few simple and general rules may help to reduce the problems of inaccuracies:

• Employ verification routines to ensure quality.
• Verify data as early as possible.
• Verify data at several stages of their manipulation.
• Know the nature of the data, be it geometry data or attribute data.
• Be critical in all data uses.
• Apply processing results carefully.
• State inaccuracies associated with results and analyses.

Without control measures, there is no guarantee that specified quality requirements will be met. Checks should certainly be carried out during production, ...