Convert NCSU campus CAD file into a geographic file with a geodatabase

Problem

The North Carolina State University (NCSU) requests to convert its campus layout CAD file into a geographic format with a geodatabase which essentially comprise of the landmarks and features of the campus. The CAD file has coordinates in the cartesian format which GIS capabilities, such as buffering and topology, cannot be performed. Transforming it into a geographic format will be advantageous for the future management of campus buildings and facilities.

Analysis Procedure

To address the client’s future need, the CAD file will undergo a transformation from x-y coordinates to latitude-longitude coordinates using a technique called georeferencing. The CAD file came with its own datasets which also needed to be converted into a geodatabase. Specifically, the six features to be converted: Existing and Future Buildings, Streets, Sidewalks, Lakes, Rocky Branch Creek and Athletic Fields. The CAD drawing was done in 2005, however, the reference information to be used in the transformation was in 1999. Thus, care must be taken to select appropriate control points on the CAD drawing used for the transformation. This is done in ArcPro 2.4.

An important first step, the data frame must have the correct projection defined using ArcMap. Then the reference layer, the orthophotograph, had to be loaded. The CAD file could only have at most two control points to prevent skewing of the drawing. The CAD drawing should be adjusted as close to the size and orientation as the orthophotograph by scaling, shifting and rotating. This should yield better georeferencing result. Now that the CAD drawing has geographic coordinates, the CAD data layers should also be converted into a geodatabase. On close inspection, 4 features were prominently displayed in both CAD polylines and CAD polygons. Toggling data revealed that buildings, streets, sidewalks, creeks and athletic fields were better represented in CAD polylines, while Lakes were better represented in CAD Polygons. Clearly, the streets, sidewalks and creeks were straight conversion from CAD polylines features to ArcGIS line features. And the Lakes were straight conversion from CAD polygon features to ArcGIS polygon features. The Existing and Future buildings polylines required an additional step of merging before they got converted, together with Athletic Fields features, into polygon features.

Workflow Diagram

Application and Reflection

The AutoCAD is popular in its use among engineers, surveyors, and architects. It is just a static drawing and cannot perform spatial analysis unlike ArcGIS. However, when used together, the two software complement each other. This is because the CAD drawings are usually used for onsite application which means geographic coordinates will be needed for those drawings.

Problem Description Utility companies need to maintain the pipes and integrity of underground tunnels. The pipes could be carrying electrical network, gas, or water. The structure and properties of the pipes are housed in AutoCAD drawings and need to have spatial information attached to them to enable engineers to locate and repair them as necessary.

Data Needed Utility companies such as Duke Energy kept such data proprietary and cannot be available publicly in order to protect their assets.

Analysis Procedures The AutoCAD pipelines are georeferenced to be used in digital map applications. The districts and counties where assets are, are subdivided into grids to enable quick retrieval of documents, pinpoint the damage and deploy resources on-site. These grid polygons are also georeferenced to establish geographic coordinates and highlighted on digital maps. Digital drawings and maps are portable, easy to access and allow data retrieval on the go, especially when dealing with natural disasters and emergencies for the utility companies.