Having trouble viewing Land Desktop Contours in Civil 3D? Visit Autodesk’s object enabler assistant web page.
From the AutoCAD Civil 3D 2010 User Documentation…
Opening a Land Desktop Drawing
Land Desktop data is not automatically converted to Civil 3D objects
Geometric data, such as contours, quick sections, grading objects, and curve text, are displayed in AutoCAD Civil 3D as Land Desktop objects. For more information, see the Civil Object Enabler Help
Civil 3D cannot read the LDT Contour data directly
AECExportToAutoCAD Creates Plines with elevations
Using the Object Enabler
The Object Enabler is available on the AutoCAD Civil 3D installation CD and on the Autodesk web site at www.autodesk.com/aecobjenabler.
Drawing Sharing Command Reference in the Civil 3d help file. It lists all the commands such as ExportToAutoCAD2010 and each command’s description.
If you need a specific file version and you are running just AutoCAD there is -AECEXPORTTOAUTOCAD2000 or -AECECPORTTOAUTOCAD2004 or eTransmit with the option to explode AEC objects will give you the same results.
Using -PURGE (the command line version of PURGE) and choosing RegApps option will also clean out unnecessary Registered Applications that may cause stability problems with your drawing.
Thanks to Matt W and R. Robert Bell for their discussion group posts which provided content for this article.