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With the availability of number of commercial software, the manual approaches for quantity surveying are becoming outdated. Within last three decades automated techniques have changed the way estimates are being produced and will continue to change as new software are being developed. The automation of cost estimation facilitates the decision-making and creative thinking by allowing the designer to quickly recall and review issues relevant to the task at hand (Saleh, 1999). Electronic digitizer, which traces drawings and produces a picture of the item being measured, is used for automated quantity takeoffs process. The CAD systems are also capable of generating quantity takeoffs (Cheng & Yang, 2001; Saleh, 1999). Electronic spreadsheets are used for the preparation of pricing sheets. Spreadsheets can quickly perform all mathematical steps for which a quantity estimator spends hours in preparation and checking of calculations. Some of the commercially available estimating software can take the quantities determined either manually, from a CAD file, or with the assistance of digitizers and apply a database of unit prices to calculate the total cost of work.
GIS, a tool that has proliferated within civil engineering in the recent years, is being used to handle various construction project requirements including: cost estimate (Bansal & Pal, 2007; Cheng & Yang, 2001), site layout (Cheng & Connor, 1996), route planning (Cheng & Chang, 2001; Varghese & O’Connor, 1995), integrating information (Bansal & Pal, 2006), construction visualization (Zhong et al., 2004) and scheduling (Bansal & Pal, 2008; Poku & Arditi, 2006).
Cheng and Yang (2001) explored the capabilities of GIS in combination with other software for cost estimation. They developed a GIS based tool called MaterialPlan, to assist planners in quantity takeoffs and assessing materials layout design. MaterialPlan uses GIS in combination with CAD systems to compute quantity takeoff based on the dimensions of the design drawings as well as to generate BOM by using Map/Info and Microsoft Access. The user communicates with the components of the system through a customized interface developed using visual basic application (VBA) and MapBasic. The Open Database Connectivity (ODBC) was also used to write/read the information to/from the associated database.
Bansal and Pal (2007) suggested the use of GIS for cost estimation in a more generalized way by adding new scripts into GIS environment for various cost estimation operations, which allows user to communicate through an interface developed within GIS environment. ArcView, which utilizes the dynamic linkage between the spatial and attribute data, was used for this purpose without ODBC requirement. ArcView has the capability to handle database, thus, study avoid the use of Microsoft Access as suggested in earlier study (Cheng & Yang, 2001).
Cheng and Yang (2001) and Bansal and Pal (2007) used AutoCAD to prepare different data themes, which is a spatial data representation of architectural drawing in GIS. However, the methodology proposed in this study utilizes the ArcGIS to generate the spatial data in place of AutoCAD due to its improved editing capabilities in comparison to ArcView. Therefore, this paper replaces the CAD systems from a GIS based cost estimation methodology. The proposed approach presents a more generalized cost estimation procedure as compare to the earlier study by Bansal and Pal (2007).