Related WorkTo be more specific, the schedule update involves comparing as-built data from a construction site with the as-planned model, calculation of the actual progress of each ongoing activity, and updating and reflecting the start and finish dates for each activity and providing critical schedule information (Kiziltas and Akinci 2005). Most previous studies on automating some of the schedule update processes have focused on calculation and measurement of actual progress of each ongoing activity through use of state of- the-art sensors, such as RFID sensors, digital cameras, and laser scanners. Chin et al. (2008) proposed a method of measuring progress by attaching RFID tags to individual steel components and associating them with components in a 4D computer-aided design (CAD) model. In this approach, the RFID tags are scanned by the operator when the steel components are installed to enable identification of the construction activities pertaining to them. When the tags are scanned, the weight is checked by identifying the weights of the components associated with the relevant tags in the schedule-related 4D CAD model. The actual progress is measuredby adding up the weights of the tagged components by date. Then the construction progress is measured by comparing the total measured weight to the total planned weight. When the RFID system is used, the data analysis can be conducted in this manner, but this method does not readily lend itself to automation of the data collection, which limits its functionality. Thus, methods using a digital camera or laser scanner to improve the efficiency of the processes of data collection and analysis have recently been proposed.