Discussion of “Building Project Model Support for Automated Labor Monitoring” by R. Sacks, R. Navon, and E. Goldschmidt

Abstract

The critical-path method (CPM), commonly used for building project planning and control in practice, falls short of resource and space considerations. Consequently, seasoned site managers have been informally relying on judgment, intuition, and experience to mentally coordinate the resource and work space requirements with the use of CPM produced bar-chart schedules. The authors presented a product/process integrated and object oriented model (referred to as the “building project model” in the paper) in an effort to seamlessly blend space, resource, time, activity, and building elements into a generic method for managing building projects. The state-of-the art in product/process integrated modeling consists of 4D modeling (i.e., 3D CAD plus time) (Koo and Fischer 2000), CAD integrated simulation modeling (AbouRizk and Mather 2000), and virtual reality enhanced simulation modeling (Kamat and Martinez 2001). At present, the requirement of abundant, consistent, and accurate data has been recognized by many as a major challenge in advancing research and application of process/product integrated modeling in construction. Hence, what indeed makes the authors’ “building project model” outstanding is its companion global positioning system (GPS) for automated collection of construction operations data. The GPSbased system described in the paper was able to achieve the accuracy of “arm’s length” (i.e., 1–2 m) for fixing locations within a building environment. The authors made an important point that by following certain rules, the GPS-collected raw data could be postprocessed into resource operations data at the “activity” level or even a more refined “basic element” level (e.g., the time a worker spent on a particular column and an adjacent wall on one floor, respectively). With 20 years of development, the current stand-alone GPS can provide positions with accuracy of around 10 m. The positioning accuracy of 1 to 2 m can be achieved with the technology of differencing GPS (DGPS), which uses a second GPS receiver located at a fixed known point and applies differential corrections to the observations from a mobile receiver. The existing civilian GPS technologies appear to provide the key to overcoming the “data” obstacle and making sophisticated models work in a building environment. This may represent a significant