As a GIS Analyst for the Chesapeake Bay Critical Area Commission (through a contract with the ESRGC), my job primarily involves QC’ing data generated as part of the Chesapeake Bay Critical Area Mapping Project. I often get asked “What is QC?” or “How this that different that QA?” or “I thought QA/QC was one process?” or “When are my county’s maps going to be done…do you really need all this QA/QC?”

QA/QC is actually the combination of 2 project management concepts. Quality assurance (QA) is a predetermined set of processes used to measure and assure the quality of a product or service as it takes place. A set of activities and actions that ensure the product or service will meet the objective is the basis for QA. From the start of the project, QA should be involved. QA is usually the responsibility of the team as a whole, which is helpful due to the varying views of perspective on the project.

Quality control (QC) is the concept of ensuring a product or service meets the customer’s expectations. QC is an activity that verifies that the product/service meets a set of pre-defined standards. The QC process corrects defects and omissions while improving the development process. While identifying weaknesses throughout the process and constantly improving them, the risk of an unsatisfactory end product is lowered. The process of QC should be ongoing to increase consistency and ensure the corrective efforts have produced satisfactory results.

For example, the GIS Analysts at the ESRGC will create wetland and shoreline boundaries.  I then review the boundaries created and note changes from the existing boundaries.  The review points show whether there are increases or losses to the Critical Area in a given county.  After my review is complete, the ESRGC evaluates my review points and makes any changes needed.  Early in the project while QC’ing one of the counties, I noticed there were a huge number of shoreline structures: jetties, groins, bulkheads, and revetments.  The agreed-upon mapping standard had the shoreline simply follow around these structures, but I determined that because there were so many and their size was so significant, they needed to be dealt with in a different way.  In addition, these piles of rocks were being mapped as upland areas, which could become problematic from a legal standpoint.  So as a result of QC, the methodology changed to include our new guidelines (or QA) on shoreline structures which specifically address how bulk heads, revetments, groins, and jetties will be evaluated and incorporated into the shoreline.

A key question is to determine who should be responsible for the QA and QC responsibilities. Should it be an external group or a combination of both sides of the project?  Different situations can require a different approach.  Newer/smaller organizations may want to have an external review to establish credibility and to eliminate as much risk as possible. External QC can provide valuable proficiency and perspective.  However, the funding may not be available for an external QC team.  If this is the case, the person(s) performing the QC needs to be separated from the processing part of the project.

When combined, QA/QC should be considered a series of checks and balances and corrective actions that produce a reliable product that is correct and consistent.