# Line definitions

Line definitions describe the types of lines that appear in each cross-section. There are two categories: **measured line definitions** for surveyed data, and **template line definitions** for design profiles. Both are configured per tunnel -- each alignment has its own independent set.

Line definitions are managed in the **Tunnel Settings** dialog, accessible from the ribbon.

## Measured line definitions

Measured line definitions (`TSectionLineDefinition`) describe the types of surveyed lines recorded at each section. Common examples include "Excavation", "Final Lining", and "Shotcrete".

Each measured line definition has the following properties:

| Property | Description |
|---|---|
| **Name** | Identifier for the line type (e.g., "Excavation") |
| **Layer** | CAD layer assignment for display |
| **Color** | Display color of the line |
| **Style** | Section line style, selected from the SectionLineStyleLibrary |
| **Closed** | Whether the polyline is drawn as a closed polygon |
| **Draw** | Whether to render this line on the canvas |
| **Deviation Line** | If checked, this line is used for deviation analysis against the template |

```{note}
Only one measured line should typically be marked as the **Deviation Line**. This is the line compared against the template when computing deviations and generating clearance reports.
```

## Template line definitions

Template line definitions (`TTemplateLineDefinition`) describe the types of theoretical/design profiles. These represent the intended tunnel geometry at each section.

Template line definitions share the same properties as measured line definitions:

| Property | Description |
|---|---|
| **Name** | Identifier for the template line type |
| **Layer** | CAD layer assignment |
| **Color** | Display color |
| **Style** | Section line style from the style library |
| **Closed** | Whether to draw as a closed polygon |
| **Draw** | Whether to render this line |

## How line definitions relate to sections

Each cross-section contains one `TSectionLineData` entry per line definition. This means:

- When you add a new line definition, every existing section gains an empty line data slot for that definition.
- When you add a new section, it automatically gets one line data entry per existing line definition.

The line data itself is a polyline -- an ordered array of 3D points with optional bulge values for arcs.

```{tip}
Plan your line definitions before importing survey data. Having the correct definitions in place ensures that imported points map to the right line types.
```

## Configuring line definitions

1. Open **Tunnel Settings** from the ribbon.
2. Select the **Line Definitions** tab for measured lines, or the **Template Lines** tab for template lines.
3. Add, edit, or remove definitions as needed.
4. Click **OK** to apply.

```{warning}
Removing a line definition deletes all associated line data from every section in the tunnel. This action cannot be undone.
```