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CAD2GIS: What's New, What Works

by Mike on February 3, 2014

CAD2GIS is the process of converting CAD design files to GIS data. I find this to be the most effective method to convert facilities CAD data to GIS. 
In the drive to get facilities built as economically as possible, the best opportunity to obtain surveyed as-built data is often missed.  Later efforts by facilities maintenance staff to obtain that data in a GIS format are often hampered or avoided altogether due to the cost. The following methodology allows for a simple and effective method to do both, with the owner reaping the benefits.
Since there are many ways to resolve this issue, some background helps us determine what works best for each particular organization: communities, corporate campuses, hospitals, universities, manufacturing facilities, airports, and more.
Anyone who wants to has to do more work with less time to get better results AND understands the data from both sides of the fence: one being data producers, the other being data maintainers.
It’s a pretty high fence.
  • How many engineers/land surveyors/developers/contractors had GIS classes in college?  How many of those were in-depth about digital workflow optimization?
  • How many GIS professionals have experience in CAD/design/field layout considerations?
  • Even more to the point, Autodesk has the lion’s share of the CAD market, as Esri does for the GIS market.  CAD by far has the advantage over GIS in developing design files that communicate how things get built, but GIS has the same advantage over CAD in organizing, querying and maintaining data on what has been built.
  • Data producers are all about getting things built and into the ground – and they typically leave when the task is completed and go on to the next site; data maintainers are the people who take over operation after construction and stick around for the next 20 to 40 years or so. They may work for the same overall organization, but even I am surprised after all these years how completely divergent their management and budget streams can be.
So, you can begin to see the landscape.
In the dim past (say, circa 1994) Autodesk and Esri cooperatively produced a hybrid product called ArcCAD, which used some GIS data tools inside AutoCAD. However, the two sides went their own ways long ago. Now Autodesk uses FDO to view and edit certain types of GIS data inside AutoCAD; and Esri uses CAD Interoperability inside ArcGIS, as well as ArcGIS for AutoCAD inside AutoCAD to do similar things. The ever-changing proprietary technology prevents either one from using the best of each, in my opinion. Using the two together requires a constant juggling of versions on both sides, as well as versions of operating systems, database versions, database drivers, and even internet browser versions.
In my experience, having migrated data on over $2 billion in assets in the last couple of decades, the best solution is to greatly reduce the conversion time and effort to translate data from each format (CAD and GIS) to the other, and to be able to do it on demand in the least amount of time and effort at any point needed thereafter. This goal is best accomplished using a combination of basic import export tasks available in each format, along with a set of procedures tailored over time to make the process as interactive and quality-controlled as possible.

 Well begun is half done - Aristotle

 Begin with the end in mind – Covey’s Second Habit

What works is using AutoCAD’s Map platform to export and import shapefiles, offer export from AutoCAD (where attributes stored as Object Data can also be utilized and converted from the source), as well as import back into AutoCAD, with symbology intact. 
At this point, I know there are subject matter experts with specialization in one or more of the platforms who will argue that the time and money spent on refining other more sophisticated technology created in the Esri/Autodesk labs is far superior, but hear me out.  I’ve been using the same technique for almost 20 years now, for a variety of vertical industries and clients: corporate campuses, utility networks, manufacturing plants, and the first international airport in the U.S. post-911.  In doing so, I’ve worked with the CAD standards and versions of dozens of vendors, third-parties, and in-house target systems.
The cost savings here derive from two significant sources: Time savings (from vastly reduced training time), and Dollar savings from vastly reduced software maintenance issues. 
Oddly enough, even though shapefiles are no longer a recommended or supported format, by using them we can get the full value from our data on both the export and import side. We also haven’t had to change procedures for a dozen years and almost as many software versions, including CAD, GIS, sde, browsers, operating systems, and databases. Some of the more specialized “built in” systems in both Autodesk and Esri platforms can be interrupted by an incompatibility from any one of these co-dependent software versions changing.
The advantages of using BOTH AutoCAD Map Object Data and Esri Shapefiles together stem from using seamless, coordinate-based features with embedded Object Data (no need to juggle attached or linked data in other formats or files), and the ease with which proper native symbolization and modeling can be maintained on both sides. 

Using AutoCAD Map, and specifically using object data, provides the capability to store attribute data on lines, and allows us to design tables for individual and multiple layers and entity types, project data, metadata and feature class attributes.
There are special situations that may call for a more specialized methodology of managing and transporting data between CAD and GIS. The best solution is dependent on existing data, the background and expertise of vendors, and the organizational goals for the implementation, among other things. The methodology described above is targeted towards the 99% of facilities having data beginning in the Autodesk design world, and the 90% of those who can benefit from at least two-dimensional GIS map interactivity. 
For those fortunate enough to be ready for three-dimensional BIM solutions, they will still find value in this methodology for the 90% of future viewers and users who will best be served by automation of two-dimensional maps, anyway.
In future blogs, we will delve into some real-life examples, a brief paragraph about State Plane Coordinate Systems, and the productivity boost this methodology receives from using AutoCAD’s Object Class definitions. I look forward to your questions and feedback!