Station Definitions¶
Station Definitions control which template is used at each chainage along the alignment. They appear in a grid at the bottom of the Template Editor dialog, below the preview area.
Purpose¶
When a new cross-section is added at a particular station, TunnelCAD looks up the station definitions to find the one whose chainage range contains that station. The matching definition determines which template is automatically assigned to the section. Without station definitions, sections would have no template reference for deviation analysis.
Station Definitions grid¶
The grid contains the following columns:
Column |
Description |
|---|---|
Station From |
Start chainage of the range |
Station To |
End chainage of the range |
Template |
Name of the template to use (dropdown selection) |
Transform To |
Target template for transition (optional) |
Transform Length |
Length in meters over which the transition occurs |
Transform Type |
Type of interpolation: Linear or Cubic |
Adding a station definition¶
Click Add below the station definitions grid. A new row is appended with default values. Edit the Station From and Station To values to define the chainage range, and select a template from the dropdown in the Template column.
Deleting a station definition¶
Select the row to remove and click Delete.
Chainage ranges¶
Station definitions divide the alignment into non-overlapping chainage ranges. Each range maps to one primary template. When a section’s station falls within a range, that range’s template is assigned.
Note
Ranges should be contiguous and non-overlapping. If a station falls outside all defined ranges, no template will be assigned to sections created at that chainage.
A typical setup for a tunnel from chainage 0+000 to 1+200 might look like:
Station From |
Station To |
Template |
|---|---|---|
0.000 |
400.000 |
Standard Section |
400.000 |
600.000 |
Wide Section |
600.000 |
1200.000 |
Standard Section |
Transform types¶
Station definitions support transitions between templates to handle gradual profile changes:
None (no transform)¶
When Transform To is empty and Transform Length is 0, the template is used as-is throughout the entire range. This is the most common configuration – the same profile applies uniformly from Station From to Station To.
Linear¶
When a Transform To template is specified with Transform Type set to Linear, the profile transitions linearly from the primary template to the target template. The Transform Length controls how many meters the transition spans. The interpolation factor increases uniformly from 0% (pure source) to 100% (pure destination).
Cubic¶
When Transform Type is set to Cubic, the transition uses a smoothstep easing curve (3t^2 - 2t^3) instead of a straight line. The profile starts and ends with zero velocity, producing a smoother transition that avoids abrupt changes at the zone boundaries. Cubic is recommended when templates have large shape differences.
How interpolation works¶
The transformation engine interpolates each template line independently. For each line present in both the source and destination templates:
The vertex coordinates (offset and elevation) are blended point-by-point.
Arc bulge values are blended between corresponding vertices.
The line must have the same number of points in both templates.
Lines that exist in only one template, have no geometry, or have different point counts are skipped – they are not included in the interpolated result. Use the Check button in the transformation preview to identify which lines will be interpolated and which will be skipped (see Template Editor).
Tip
Use linear or cubic transforms at geological boundaries or design transitions to avoid sharp discontinuities in the as-designed profile. This produces more realistic volume calculations in the transition zone.
Important
For interpolation to work correctly, corresponding template lines in the source and destination templates must have the same number of points. If a line is skipped due to a point count mismatch, edit the templates so the point counts match.
Station definitions are sorted¶
Internally, station definitions are sorted by their starting chainage. The grid displays them in this order. When the Template Editor applies changes, the list is re-sorted to maintain consistency.
Interaction with cross-sections¶
Station definitions are consulted at the time a cross-section is created. If a station definition is changed after sections have been created, the existing sections retain their original template assignment. To update previously created sections, delete and re-add them, or manually reassign the template.