Default output to CAD drawings
The Export To CAD tool is preconfigured to generate output that is suitable for most general-purpose applications. By default, ArcGIS feature geometry such as points, lines, and polygons are converted to native CAD geometry types that support and display similar characteristics.
This topic describes the kinds of CAD data the Export To CAD tool generates using the default settings and with no additional fields added to the input features.
Drawing layers
A drawing layer is created and named to match each input feature class or layer, unless otherwise specified with the reserved CAD field named Layer. When the features are added from a map (.mxd) document, the feature layer name in the table of contents is used as the layer name.
Geometry and text
Features are exported to their correct geographic location relative to the x,y, and z coordinates 0,0,0 in the CAD drawing. Geometry types that are native to the target format are generated as described in the following table unless otherwise specified with the reserved CAD field named CADType.
Input feature class | Output DWG/DXF geometry | Output V8 DGN geometry |
|---|---|---|
Point | Point | Zero-length line |
Line | LWPolyline, line, arc, circle, or ellipse | Complex chain, line, arc, or curve |
Polygon | Closed LWPolyline | Complex shape |
Annotation | Text | Text |
Extended output for AutoCAD drawings
Output to DWG formats (version 2007 or higher) includes additional information that extends the native properties of the AutoCAD drawing to support ArcGIS feature class definitions, feature attributes, and a spatial reference. This is nongraphic information that is exported as native DWG xrecords and stored in a standardized framework of DWG object dictionaries. Schemas and encoding structures are defined by the Esri mapping specification for CAD—a CAD-GIS interoperability specification.
ArcGIS for Desktop reads this information and displays the data as subset feature classes, in addition to the standard (hard-coded) CAD feature classes. CAD professionals can edit this information in AutoCAD-based applications with the Esri plug-in ArcGIS for AutoCAD.
Spatial references
The spatial reference of the first input feature class or layer is embedded in the AutoCAD drawing. This information is identical to a projection file. ArcGIS for Desktop recognizes it as a valid spatial reference unless a projection (.prj) file or a universal projection (esri_cad.prj) file exists in the same folder.
Feature class schema
Feature class schema and field definitions are generated for each input feature class. This information is stored at the drawing level as empty (schema-only) feature class definitions. Each feature class definition includes an additional component known as a property filter.
The property filter functions similar to a definition query. ArcGIS for Desktop and ArcGIS for AutoCAD use it to display a collection of geometry as a subset feature class based on one or more DWG properties. The Export To CAD tool defines it as a simple drawing layer filter that specifies the name of the layer generated for the input feature.
For example, if the input feature class is named Parcels, and a drawing layer is generated that is also named Parcels, then the results of the property filter is analogous to a definition query defined with the SQL statement "Layer" = 'PARCELS'.
Feature attributes
Attribute values in the input feature class are exported as DWG xrecords and linked to the appropriate geometry. Field definitions exported with the parent feature class schema provide the mechanism by which an attribute value is identified as a constituent feature attribute. ArcGIS for Desktop displays these values in the feature class's virtual attribute table under their respective field headings.