Feature Goal Breakdown Interconnection Project Constraints Materials Construction Reservoirs Conflicts Costs O&M Cost Construction Time ROW Costs UPRR NDOT Permits ROW 404 Permits Business Impacts NEPA Residential Impacts Emergency Access Residential Access Socioeconomic Impacts The decision matrix breakdown desirable result for all applications? Depending on the network, a significant number of potential routes may be possible. Depending on the specific network problem being considered, a single best solution may not be the most feasible or useful. For example, the third best route from a cost perspective may be the best when considered from a maintenance or environmental perspective. Decision makers often like to consider multiple options before coming to a final decision on the selected route, especially for significant and large diameter pipelines. For these reasons, modelers typically generate more than just the default “best” route. Selecting more than one default route using ArcGIS Network Analyst can be done both manually and programmatically. This article summarizes the use of ArcObjects and Visual Basic for Applications (VBA) to develop a custom application for pipeline alignment optimization that can identify a number of potential routes and list and rank these routes for further analysis in an automated fashion. The application extracts project-specific information, including segment weights and costs from a Microsoft Excel spreadsheet, and imports them as attributes to a pipe network www.esri.com bines the associated costs for each segment. Engineering, environmental, and socioeconomic factors are considered in the decision matrix. Each segment is given a score on each of these factors along with the relative weights between these criteria. The weighted score for both weight and cost is calculated for each segment. The lower the value assigned to the segment, the more desirable the segment would be for the pipeline corridor. Engineering considerations include land uses, terrain, materials, constructability, rightof-way acquisition, crossings and conflicts, soils, geology, length, and operation and maintenance. Environmental considerations include land use, visual and physical impacts, National Environmental Policy Act (NEPA), permits (for departments of transportation or local and regional agencies, or for Section 404 [permits issued pursuant to Section 404 of the Clean Water Act, which regulates the discharge of dredged, excavated, or fill material in wetlands, streams, rivers, and other U.S. waters]), and site conditions. Socioeconomic considerations include business and residential impacts, agency consider- feature class composed of individual pipe segments. The application loops through the potential corridors to list a predetermined number of potential routes. A feature class listing these corridors is generated and displayed. The application then exports the output back to Microsoft Excel and ranks the corridors according to their total weight (summation of weights for the comprising segments) and costs and generates a graph illustrating all the generated corridors in a triaxial chart for quick analysis of the potential routes. This application uses a pipe segments feature class in which the segment IDs are stored as integers in a field named SgID. It also uses a decision matrix, a two-dimensional table listing all segments available between origin and destination points and their scores for each criteria and subcriteria included in the analysis. The decision matrix is created in Microsoft Excel. Decision makers and stakeholders use Excel when developing project priorities, defining project design criteria, assigning relative weights to criterion, and assigning a score for each segment for each criterion. This is a preprocessing tool that aggregates all factors into two numbers— weight and cost. Weight combines all segment weighted scores on all criteria, while cost com- Segments shape le ArcGIS Segment ID Decision matrix Microsoft Excel Segment weight Segment cost Segments shape le ArcGIS The process for importing segment weights and costs Continued on page 34 ArcUser Spring 2010 33