Paul Bartsch of the Spatial Tips site shares some tips on working with CADD data to make it more “GIS friendly”.
The transition between CADD and GIS can be difficult but if you follow these five simple steps, it shouldn’t be very painful.
- Use Polylines instead of discontinuous lines. For example, when drawing a waterline, don’t break the line until it actually “breaks” in the real world (valve or point of connection to building).
- Stick to layering standards. I prefer that all the CADD data received conform to National CADD Standards. We’ve noticed that even within these standards there is room left for interpretation… so in my opinion even a set of national standards must be narrowed down so that layers can be decided upon between the CADD departments/ consultants and the GIS department. A data dictionary or document of some type should then be created detailing the equivalence of specific CADD layers to specific GIS feature classes.
- Use Object Data. Object Data is relatively simple to setup in AutoCAD and makes the transformation from CADD to GIS very efficient. Object Data can be exported from AutoCAD as attributes of the feature (fields within the exported shapefile). Object Data should be used in place of text annotation whenever possible. Feature linked annotation may then be created from the Object Data for use in the printed product.
- Use a known coordinate system. The standard for digital submitals to my department is NAD83 – California State Plane, and if elevations are included they must be NAVD88.
- XREF’s should be bound, and each physical sheet should have its own CADD file. Files should be named according to a descriptive naming convention which allows the user to recognize sheet number and design designation without ever opening the file. Since each physical sheet will have it’s own CADD file, it’s helpful to turn off or completely purge unused layers from the drawing rather than using only the viewport layer controls.
