Geographic Information Systems (GIS) and Computer Aided Drawing (CAD) applications are used by many Natural Gas Utilities to maintain information about the facilities in their gas distribution systems. This data is often the same or similar to the information required to build and maintain a hydraulic model of their gas system. This paper will discuss and identify several key issues that should be considered to allow efficient exchange of data between GIS/CAD and modeling applications. A discussion of the difference between GIS and Computer Aided Drawing (CAD) applications will be presented. Common generic exchange file formats will be described for each application type. Data related topics such as coordinate systems, facility identification and separation, pipe size designation, connectivity, customer load allocation, regulator and gate station handling, inclusion of valves, and the use of operating data will be discussed along with common issues associated with each topic. Although focused primarily on building models for distribution system applications, the topics in this discussion apply to all piping systems types.
Modern electronic mapping and drawing systems began to spawn during the 1980's. Computer-Aided-Drafting (CAD) systems began to be used by natural gas operators to map their facilities in the early part of the decade. Systems such as AutoCad (1982) and MicroStation (1985) were PC based applications that provided simple two dimensional functions suitable for drawing and mapping line work. This technology allowed utility operators to move from purely paper based record systems to electronic based systems. Later in the decade, Automated Mapping / Facilities Management (AM/FM) systems began to appear. At the time, these systems were often referred to as "smart maps" and were the predecessors to what we know as GIS now. These systems merged CAD and database technology allowing mapping and facility data to be maintained by the same application. During this time systems were available from vendors such as Intergraph, McDonald-Douglas, and IBM. These platforms were expensive, often required specialized hardware to operate, and thus had a limited user base. Towards the end of the decade, Geographic Information Systems (GIS) began to be applied to utility network type systems. Prior to this time, GIS was mainly used in traditional natural resource fields, such as forest and wildlife management. GIS was largely used to manage area type features, such as tree species or soil type in a defined area. These systems relied heavily on area geometry like polygons to manage and identify the physical features that they worked with. Managing linear features, like roads and utility networks was not well supported by these systems in the beginning. AM/FM and GIS systems were similar, but with not so well defined differences. AM/FM systems were generally based on a graphics or mapping system that connected to a separate database to access facility data. The graphics data and attribute data were kept separately. GIS systems were generally based on a database system that used a graphics system to display or map the various geographic features contained in the database.