Semantic Translation Part 8/8: Round Trip
Often times I may phrase these concepts with examples of CAD to GIS translation, but equally valid is the need for GIS data to be accessible in a CAD format. Many times the same GIS database and spatial tools can be used to manipulate GIS data that is used to build CAD files. Translation between GIS and CAD needs to be bi-directional. ArcGIS tools like the EXPORT TO CAD tool may only be the last tool in a simple or complex model that prepares data to become the most useful expression of GIS data in a CAD file. This GIS data preparation may involve the creation of additional text annotation, symbology definition and the modification of geometric definitions. For example drawing polygons in a CAD file with non-redundant linear network of polylines rather than a closed polygons. Either is valid, but your CAD standards may require one or the other.
Just like you can use database look-up tables to match CAD symbology to GIS attributes you can use database look-up tables and other database concepts like query and CALCULATE to control CAD symbology based on GIS attributes. The ArcGIS-ArcInfo EXPORT TO CAD tool will take field values in specially named columns of the input GIS data and use the information to drive the CAD entity creation; columns like color, layer, thickness, CADType, DOCPath, etc... The EXPORT TO CAD tool can append to existing drawings, output to multiple drawings, overwrite drawings and create CAD entities from all different forms of GIS data.
Taking advantages of these round-trip capabilities your organization can standardize workflows where not only does data flow back and forth to critical applications, it flows more smoothly. Making subtle changes in data constructs or workflow procedures can greatly enhance the ease at which the translation of these spatial languages occurs. Defining, and more importantly implementing a well-defined CAD standard is perhaps the single greatest productivity enhancement step you can make to improve CAD and GIS interoperability. In situations where data flows from one organization or department to another, extra work to define submittal standards may be worth the effort or worth paying extra for.
In the comment section below this or any post I'd love to hear from you and what you would like to discuss in future posts.