Autodesk CIVIL3D - CIVILDESIGNCOMP 2007 SLM CD User Manual page 15

Types of Surface Data
Surfaces can be built from a combination of many different types of data:
• Boundaries
• Breaklines
• Contours
• DEM files (Digital Elevation Models)
• Drawing Objects
• Point Files
• Point Groups
• Point Survey Queries
• Figure Survey Queries
Boundaries
A boundary is a closed polygon that limits the triangulation of a surface.
Boundary Types:
• Outer
o Defines the outer boundary of a surface
o Triangles outside of this boundary are removed
• Show
o Displays the triangles inside the boundary
o
Can be used inside of a Hide boundary
• Hide
o Removes triangles inside of the boundary
o Creates a hole in the surface
o Can be used for building footprints to keep contours from crossing through them
• Data Clip
o Keeps data outside this boundary from being added to the surface
o
Must be added before other surface data or moved up in priority in the surface definition
o Useful for limiting the size of large datasets
Non-destructive breakline boundaries
Outer, Show and Hide boundaries have the option to be created as non-destructive breaklines. When this
option is enabled it trims the TIN lines at the boundary. When it is not used it erases all the TIN lines that
touch the boundary.
This can be a good option if you have good surface data on each side of the boundary as it will cut a clean
and straight boundary through the surface. However, if this option is used on an outer boundary where all of
Lesson: Building Surfaces from Survey Data
Chapter: Building a Survey Quality Surface
157