Geography Reference
In-Depth Information
Measure of Quality Assurance
One of the values of a GIS is its capability to combine different types of information that have the same
geographic base. For example a user might need a map displaying a single variable derived from a
combination of soil type, bedrock type, and depth to bedrock. An important aspect of the defining
information of a report combining these three variables is the confidence one can place in the accuracy of
the resultant information. Each of the constituent individual variables is stored in the database and each
has its own characteristics of precision and accuracy—measured in terms of geographic coordinates and the
values of the variable. Therefore, just as the values of the three individual variables are combined to produce
a single variable, the precision and accuracy attributes of these variables should be combined—according
to appropriate numerical techniques—determine the accuracy of the final result. Statements of accuracy
should be included as part of the resultant report.
The process of assessing accuracy is not always easy, nor are the results always encouraging. For
example, in a study done by the Australian Commonwealth Scientific Industrial Research Organization
a number of years ago, involving three variables, an analysis was made of the output. When particular
points on the Earth's surface were picked out and “ground truthed,” it was found that at least one of the
constituent variables was incorrect more than 60 percent of the time. The implications for the accuracy of
the combined report are obvious.
Frankly, the lack of sufficient quality reporting of derived products is a major shortcoming of all
commercial GIS software.
The Decision Maker-Product Interface
The act of a decision maker sitting down at a computer terminal is one that cuts out virtually all the
“people buffers” between the decision maker and the computer. Many decision makers will not want
to spend the time necessary to either learn or operate the software. There is also a certain element of
justified fear involved for even the ablest individual in doing something new with others looking on.
A person familiar with the product (including the assumptions underlying it and other products that
might be useful to the decision makers) should be present when the product is used. People charged with
making decisions have a way of asking questions no one thought they would ask. Anyone who presumes
to provide them with new information in new forms had better be ready.
The person charged with the responsibility of understanding and explaining a document is also in an
ideal position to recommend changes in the document's structure or information content based on
conversation with the users of the product. The dissemination of a product containing information is very
much a two-way street and relies on user feedback for its successful continuation.
Often, user needs are not correctly perceived by product designers. Further, user needs change.
These and many other factors suggest that a continuing dialogue between the providers and users of
information products must exist.
It may be that, instead of having a person assigned to a particular set of products as the interface between
the decision maker and the product, personnel will be assigned as liaisons to various departments using
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