Show Navigation | Hide Navigation

How Import from CAD (Conversion) works

Release 9.2
Last modified April 2, 2008
E-mail This Topic Printable Version Give Us Feedback

The purpose of IMPORT to CAD is to establish a staging geodatabase of highly normalized tables and feature classes for the purpose of assembling geoprocessing models and scripts to perform complex data mining of CAD data. For simple viewing and importing of CAD data, it can be easier to use a CAD file as a feature source without using Import CAD. The advantages to Import CAD include multiple document input, the handling of AutoCAD extended entity data, more extensive support for Microstation user data, better geometric data support, access to text properties, and document properties.

When one or more CAD drawing files are imported using the Import CAD geoprocessing function, a geodatabase feature dataset is created to store a series of tables and feature classes that reformats the CAD data into predefined highly normalized tables and feature classes. This staging geodatabase feature dataset is an optimized representation of the CAD drawing file(s) as a geodatabase. Converting CAD drawings into a geodatabase facilitates further data translation in ArcGIS using other geoprocessing tools.

CAD drawing translation

The process of converting CAD drawings into geodatabase feature classes is a multistep process made possible by other geoprocessing tools and the geoprocessing framework of ArcGIS. It is profitable to consider the task of moving data from one or more CAD drawings into a geodatabase feature class as a pulling rather than pushing operation. By conceptualizing the process as starting with an existing geodatabase feature class with its own particular table schema, CAD translation becomes a process of defining what candidates in the staging geodatabase feature classes will qualify as new target features.

There is not always a one-to-one correspondence between CAD objects in a drawing file and GIS features. It is therefore often necessary to aggregate or split objects during the translation process to obtain the necessary candidate objects. For example, oftentimes the information necessary to construct the target GIS feature may come from two different CAD objects in the drawing file. With the case of extended attribution of CAD objects, the relationships between objects and their extended attributes can be rather complex. Using the Pivot Table tool, for example, can build a new table from an existing table. Where the various column values can become column headings in the process of building a new table where a combination of values define a new table. The use of Pivot Table will often be the first step for extracting AutoCAD Xdata or cell attributes in Microstation or block attributes in from AutoCAD data.

The concept of Spatial aggregation would be a linear GIS feature that has been represented in a CAD drawing file as a line entity and a corresponding text entity near that line that describes the identity of the line. The text entity functions as a form of attribution that will be a column value in the target geodatabase feature class. Before the two objects can be considered a viable candidate for the linear feature and its identity attribute, one must perform a type of spatial join linking the two CAD candidate objects into a single object (i.e., the Identity_analysis tool), which can then be appended to the target geodatabase feature class.

The translation process may include several of these data manipulation and database modification functions in a geoprocessing script or ModelBuilder model that has as its final step the creation or appending of data to a geodatabase feature class. Leveraging the geoprocessing framework, sophisticated translation tasks can be saved and reused, thus automating the process for future translations.

Import CAD's output schema

Supported CAD drawing files

Several CAD formats can be processed by Import CAD. Supported CAD drawing files include:

Please visit the Feedback page to comment or give suggestions on ArcGIS Desktop Help.
Copyright © Environmental Systems Research Institute, Inc.