1. IGIC CAD/GIS Integration Workgroup Update
Michael Condre, GISP

2. CAD/GIS Integration Workgroup
Members:
Charlene Avey
Perry Cloyd
Mike Condre
Mike Cranfill
Chelly Gracy
Nate Hunt
Steve Leatherman
Jennifer McMillan
Eric Meyer
Tim Smith
David Surina
Theresa Thompson
Jayson Troughton
Jason Tuck
Leane Welsh
Joyce West
Robert N. Wilkinson
Phil Worrall

3. CAD/GIS Integration Workgroup
The Workgroup is developing a set of
data standards,
database templates,
and policy documents
to support existing best-practices, integrated with commonly-used software, to facilitate private industry and local government data exchange.

4. CAD/GIS Integration Workgroup
Use of these templates will streamline the electronic exchange of CAD-based engineering design data submitted to local governments for direct integration into a local government's GIS.

5. CAD/GIS Integration Workgroup
Philosophical Assumptions:
“CAD-to-GIS” means AutoCAD Civil(Map) to ESRI feature classes most of the time
We will bring our particular “field” experiences to bear in recommending attributes
We will begin from existing standards, where available
SDSFIE
Hag-Tag
IU CAD Standards
Others

6. CAD/GIS Integration Workgroup
The Workgroup will
publish a summary of all critical layers necessary to address in the CAD-to-GIS process,
provide a schema and specifications for AutoCAD and ESRI data exchange,
and examples of existing local government policy documents to support this effort.

7. CAD/GIS Integration Workgroup
Coordinate System and Projections
 Data should be created on a known projected coordinate system along with a known horizontal datum that align the known coordinate system grids with the ellipsoids. The recommendation would be for NAD 83 State Plane, using US Survey Feet units.
MetaData
“Industry Standard” per philosophical assumptions
AutoCAD Map 3D currently supports two standards for geospatial metadata: the FGDC CSDGM Standard and ISO

8. CAD/GIS Integration Workgroup
Topological structure
 Objects should be created using a topological structure such that vertices are snapped and line segments follow a consistent, logical direction.
Continuous edges should be represented by polylines.
Adjacent features of a common theme generally should not have gaps or overlaps unless that is their “true” spatial relationship.

9. CAD/GIS Integration Workgroup
Topological structure (continued)
Polygonal areas should be represented by closed polylines or MPolygon objects.
Point objects may be points or blocks, but if blocks are used they should have symmetrically-placed insertion points so that they may be easily scaled without losing their “true” coordinate value.

10. CAD/GIS Integration Workgroup
Layers, colors, linetypes
Typically, colors and linetypes should be defined as “ByLayer” so that these properties may be adapted as needed by end users for cartographic communication and specific end uses. Layers should uniquely discriminate between object classes, and should be “plain English” descriptions of the object. We would discourage against using layer names to carry information that would be better stored as Object Data tables. Although end users will of course use additional layer names for specific end uses, it is understood that this imposes a separate need for translation to other platforms and uses.

11. CAD/GIS Integration Workgroup
Other properties
Other CAD-based object properties such as explicit lineweight, linetype scale, etc. are typically used for cartographic communication purposes and are not a mandatory part of the Object Classification, however, those properties can be stored without specifying explicit property values so that those values may be transferred from CAD to GIS when useful.

12. CAD/GIS Integration Workgroup
Object Data
Object Data tables as offered in AutoCAD’s Civil3D product provide a consistent method for storing and transporting tabular data that is fairly equivalent to attribute data in GIS, especially as in ESRI shapefiles and geodatabase feature classes.
Object Data can store tabular data on lines, polylines, and polygons as well as on simple points and more complex blocks whereas AutoCAD’s traditional block attributes work on blocks only. However, block attributes in conjunction with Link Template definitions are still a more efficient methodology for linking CAD objects to external, relational databases such as Access or SQL.

13. CAD/GIS Integration Workgroup
Feature Classes (Object Classes)
The new process is based primarily on Object Classes in AutoCAD Map. From the Autodesk Help Files:
Object classification helps organize and select objects in your drawings.
Object classification organizes objects in your drawing based on the real-world features that they represent, for example, roads or manholes. When you create an object using object classification, the object automatically has properties and values assigned to it based on its object classification. In addition, you can find or select all objects in an object class.

14. CAD/GIS Integration Workgroup
Object classification definitions include
A name assigned to the object (sanitary_manhole, street_centerline, etc.)
The entity type of the object (line, polyline, block symbol, text, etc.)
The graphic properties of the object (layer, color, linetype, etc.)
The descriptive attributes of the object (block attributes, Object Data, or linked database records)

15. CAD/GIS Integration Workgroup
 The definitions are stored in an XML file format, which also requires a CAD template file (DWT) to hold layer and block definitions. These files can be used to efficiently and effectively transfer the standard both internally between users and task sessions, as well as to external agencies and vendors for digital submittals.

16. CAD/GIS Integration Workgroup
Using Object Classes (formerly known as “Feature Classes”) in AutoCAD ensures that there is a data structure on the CAD side that is very equivalent on the GIS side, which also uses “feature classes” to associate and define geographic, cartographic, and attribute data properties of both real-world objects and imaginary ones such as cadastral parcels, zoning boundaries, etc.

17. CAD/GIS Integration Workgroup
Having common definitions on each “side” of the CAD/GIS data structure equation lets us make “one-for-one” exports, imports, and even round-tripping of data with a minimal amount of pre- or post-processing time and effort.
Subject, of course, to typical shapefile limitations of arc “aliasing” and 8-character field-name constraints.

18. CAD/GIS Integration Workgroup
Next Steps:
XML generation
CAD Templates
Instructional documents / downloadable web content
Road Show / publication
Your Feedback, ongoing improvements and Success Stories 
Thanks!