Print this pageData Quality and Documentation: What You Don't Know about Your GIS Data Can Come Back to Haunt You
PETERS, DOUGLAS C.
Databases, spreadsheets, and CAD systems have been popular and widely used for storage of engineering and scientific data for many years. Of course, maps and handwritten and printed compilations and analyses of data of all vintages are ubiquitous in our work. Now along comes the enlightening world of GIS (geographic information system) technology that provides us with a means of bringing all our historic, numerical, descriptive, and spatial data together in one coherent and integrated mass to help us derive useful information and knowledge from it all.
Hold on there! What most users and many compilers of GIS databases often forget along the way is that ALL of your data have some inherent limitations embedded in them. Limitations include original scale of maps, measurement and data storage accuracies, the (usually unstated) biases of any given mapmaker or cartographic representation technique, technological limitations of data gathering or reporting methods, surveyor competency, and even such oft forgot things as environmental effects on storage media such as paper or mylar maps. There are so many considerations involved that we may consciously or unconsciously elect to not think about them.
However, such background information must be conscientiously considered and documented to make the most of, or perhaps even to get anything useful out of, your data. The "garbage in, garbage out" effect can be magnified through a GIS, especially because it can add the cachet of spatial respectability to anything output from a computer as a map. This presentation will discuss some of the ways we could unintentionally mess up our GIS spatial analyses by forgetting (or not knowing) the origins of our data and ways to help minimize such internal damage.