When an AutoCAD Civil 3D project is created, an initial set of empty or near-empty files is created in the project database.
Data is added to these files as you add drawings and data to the project.
Each time a surface, alignment, pipe network, or view frame group project object is created, a corresponding .c3dData file is created. The .c3dData file creates a reference to the appropriate object in its source drawing. When the object is modified in the source drawing, the .c3dData file enables modifications to be reflected in any consumer drawings.
This file contains the project’s point geometry. The points contained in the file are listed in the project’s Points list in the Prospector tree. This file is not checked in and out directly as project drawing files are; it is checked in and out indirectly when users use point access control commands.
This file contains access control information about the points in PointsGeometry.mdb, including the status (checked-in, checked-out, or protected) of individual points.
This file represents the project survey database. For more information, see Survey Database.