Our Quality Assurance process consists of three sequential steps. These are illustrated above on a site detail scan dating back to 2002. We converted it to CAD in 2016. Each panel from left to right corresponds to one of the three QA steps below.
- SCAN INSPECTION – Review source scan to understand and assess the contents of the original drawing. Research marginal data.
- OVERLAY COMPARISON – Methodically toggle on and off the overlaid CAD and image, then check and tag each item individually.
- CAD CORRECTIONS – Correct the CAD data by addressing each tag instruction. Verify all discovered errors were corrected.
The first step consists of reviewing the original source data to understand the contents of the drawing. Of course, this is also done by the technician doing the initial CAD conversion work, but this step adds a second set of eyes looking at the data. This ensures nothing is missed or misunderstood. During this step we usually discover items that are not entirely clear, either the image is somewhat obscured or dimensions simply do not add-up. We call these items “marginal data”. The team collectively decides what the barely legible word should be or how to solve the dilemma of incorrect dimensions. Either way, the end result is a CAD file that is as free of errors as humanly possible. If any item cannot be safely converted to CAD, then it is tagged with a red rectangle and identified as “illegible” to the client.
The second step consists of running though the CAD file contents, one CAD object at a time, to compare it to the underlying scanned image. This superposition plus our software’s ability to very easily toggle the overlay on and off, allows the QA reviewer to determine the accuracy, completeness and correctness of the CAD data. Once verified, the individual item is tagged by a single click, which creates a temporary black background rectangle that identifies the CAD item as “checked and passed”. This assures no object is missed and eliminates repetitive and unnecessary double checking.
Finally, the last step includes the actual corrections to the CAD data. By using the tags embedded in the file, our CAD technicians move though the contents very quickly and perform any corrections as identified by the QA manager. These may range from simple layer changes and correcting typos or misspellings to more substantial redrafting tasks, if needed. Occasionally, discovering an incorrect dimension triggers a substantial edit operation that may affect a large portion of the drawing. In fact, an error discovered in one drawing sometimes affects several other drawings, which we correct as well. An example of this is a dimensional error discovered in a multi-level building, where all upper floor plans must be edited to maintain correct “stacking” from floor to floor.