Sections¶
Cross-sections are the core data in TunnelCAD. A cross-section represents a measured tunnel profile at a specific chainage (station) along the alignment. Together, the collection of cross-sections forms a complete picture of the as-built tunnel geometry, which can be compared against the design template for deviation analysis and volume computation.
What is a cross-section?¶
Each cross-section captures the tunnel profile at a single point along the alignment and carries the following properties:
Station – the chainage (distance along the alignment) where the section is located
Name – a user-assigned identifier (e.g., “Sec 1” or “Sta 0+100”)
Bearing – the surveying bearing of the alignment at that station
Template – the design template assigned to the section, used as the theoretical reference
Insertion Point – the world-coordinate position computed from the alignment engine
Elevation – the alignment elevation at the station
Grade – the longitudinal gradient (%) at the station
Superelevation – cross-fall applied at the station
Line data¶
Each section contains multiple line data entries, one per line definition. Line definitions describe the types of lines measured or designed at each section – for example, an “Excavation” line, a “Final Lining” line, or a “Shotcrete” line. Each line data entry is a polyline: an array of 3D points with optional bulge values to represent arcs.
Note
Line definitions are configured per tunnel. See Line definitions for details on creating and managing them.
Viewing sections¶
Sections are displayed on two canvas tabs:
Sections tab – shows the current section in local coordinates, where X represents the horizontal offset from the alignment axis and Y represents elevation. This is the primary view for inspecting and editing individual profiles.
Alignment tab – shows all sections in world coordinates, positioned along the alignment path. This view provides the overall tunnel context.